Stéphanie Cantiniaux

Marianne Vaugoyeau

Danièle Robert

Christine Horrelou-Pitek

Julien Mancini

Tatiana Witjas

Jean-Philippe Azulay
email: jean-philippe.azulay@ap-hm.fr

Comparative analysis of gait and speech in Parkinson's disease: hypokinetic or dysrhythmic disorders?

Keywords: Parkinson's disease, Locomotion, Speech, Deep Brain Stimulation

Gait and speech are automatic motor activities which are frequently impaired in Parkinson's disease (PD). Obvious clinical similarities exist between these disorders but were never investigated. We propose to determine whether there exist any common features in PD between spatiotemporal gait disorders and temporal speech disorders.

Gait and speech were analyzed on eleven PP undergoing deep-brain-stimulation of the subthalamic-nucleus (STN-DBS) and eleven control subjects (CS) under 3 conditions of velocity (natural, slow and speed). The patients were tested with and without L-Dopa and stimulator ON or OFF. Locomotor parameters were recorded using an optoelectronic system. Speech parameters were recorded with a headphone while subjects were reading a short paragraph.

The results confirmed that PP walk and read more slowly than controls. Patient's difficulties in modulating walking and speech velocities seem to be due mainly to an inability to internally control the step length and the interpause-speech duration ISD. STN-DBS and levodopa increased patients' walking velocity by increasing the step length.

STN-DBS and levodopa had no effect on speech velocity but restored the patients' ability to modulate the ISD. The walking cadence and speech index of rythmicity (SPIR) tended to be lower in patients and were not significantly improved by STN-DBS or levodopa. Speech and walking velocity as well as ISD and step length were correlated in both groups. Negative correlations between SPIR and walking cadence were observed in both groups Similar fundamental hypokinetic impairment and probably a similar rhythmic factor affected similarly the patients' speech and gait. These results suggest a similar physiopathological process in both walking and speaking dysfunction.

Introduction

Basal ganglia dysfunction leads to the lack of automatic execution of learned motor sequences [START_REF] Marsden | The mysterious motor function of the basal ganglia: the Robert Wartenberg Lecture[END_REF] and to the development of Parkinsonian motor symptoms [START_REF] Lee | Clinical observations on the rate of progression of idiopathic parkinsonism[END_REF], including changes in gait and speech.

Gait disorders in PD [START_REF] Hoehn | Parkinsonism: onset, progression and mortality[END_REF], constitute one of the main factors affecting patients' independence and quality of life [START_REF] Koplas | Quality of life and Parkinson's disease[END_REF]. PP walk slower, with shorter step length and a compensatory increased walking cadence [START_REF] Blin | A new method of quantitative analysis of parkinsonian gait: report of 6 patients[END_REF], Morris et al., 1994a, b). Levodopa improves spatiotemporal parameters such as walking velocity and step length, but not temporal parameters such as step time, swing time and walking cadence [START_REF] Azulay | Automatic motion analysis of gait in patients with Parkinson disease: effects of levodopa and visual stimulations[END_REF][START_REF] Blin | A new method of quantitative analysis of parkinsonian gait: report of 6 patients[END_REF][START_REF] Pedersen | Effects of withdrawal of antiparkinson medication on gait and clinical score in the Parkinson patient[END_REF]. Studies have shown that Sub-Thalamic-Nucleus Deep Brain Stimulation (STN-DBS) improves walking velocity by increasing the step length without affecting the walking cadence [START_REF] Faist | Effect of bilateral subthalamic nucleus stimulation on gait in Parkinson's disease[END_REF][START_REF] Lubik | Gait analysis in patients with advanced Parkinson disease: different or additive effects on gait induced by levodopa and chronic STN stimulation[END_REF] while a modulation of cadence has been reported by others [START_REF] Stolze | Effects of bilateral subthalamic nucleus stimulation on parkinsonian gait[END_REF].

Approximately 70% of PP experience speech difficulties attributed to bradykinetic and hypokinetic articulatory movements, orofacial hypomimy, rigidity and rest tremor [START_REF] Hartelius | Speech and swallowing symptoms associated with Parkinson's disease and multiple sclerosis: a survey[END_REF].

PPs' speech timing deficits seem to have some points in common with their spatiotemporal gait deficits. Speech velocity often decreases in PP [START_REF] Canter | Speech Characteristics of Patients with Parkinson's Disease: I. Intensity, Pitch, and Duration[END_REF][START_REF] Metter | Clinical and acoustical variability in hypokinetic dysarthria[END_REF] just like walking velocity. The interpauses speech duration (ISD) is usually shortened in PP [START_REF] Forrest | Kinematic, acoustic, and perceptual analyses of connected speech produced by parkinsonian and normal geriatric adults[END_REF][START_REF] Hammen | Speech and pause characteristics following speech rate reduction in hypokinetic dysarthria[END_REF], in line with the step length.

PP are subject to dysprosody, and show less variability in the fundamental frequency and intensity and more speech velocity and pausing abnormalities than control subjects (CS) [START_REF] Canter | Speech Characteristics of Patients with Parkinson's Disease: I. Intensity, Pitch, and Duration[END_REF][START_REF] Harel | Variability in fundamental frequency during speech in prodromal and incipient Parkinson's disease: a longitudinal case study[END_REF][START_REF] Kegl | Articulatory consequences of Parkinson's disease: perspectives from two modalities[END_REF] . Dysfluent behavior has also been described in PP [START_REF] Benke | Repetitive speech phenomena in Parkinson's disease[END_REF], consisting mainly of repetitive speech phenomena involving the repetition of syllables, words or phrases. [START_REF] Skodda | Speech rate and rhythm in Parkinson's disease[END_REF] reported that during a standardized reading task, the speech velocity of PP accelerates more strongly while speaking and the total number of pauses decreases significantly, which indicates that their speech rhythm and timing organization processes are impaired. Physicians often have the feeling that paroxystic speech velocity accelerations develop in line with gait festinations and dysrhythmic pauses and that repetitive speech phenomenon such as stuttering, iterations and palilalia are somewhat comparable to freezing of gait. Few studies have focused on the effects of levodopa on speech timing parameters. Levodopa does not improve speech velocity [START_REF] Wolfe | Speech changes in Parkinson's disease during treatment with L-dopa[END_REF] or stuttering [START_REF] Anderson | Developmental stuttering and Parkinson's disease: the effects of levodopa treatment[END_REF][START_REF] Benke | Repetitive speech phenomena in Parkinson's disease[END_REF]. Speech dysfluencies may be due to an increase or a decrease in the dopamine levels present in the brain Two studies have shown that selective left-side STN-DBS may have negative effects on prosody [START_REF] Santens | Lateralized effects of subthalamic nucleus stimulation on different aspects of speech in Parkinson's disease[END_REF][START_REF] Wang | The effect of unilateral electrostimulation of the subthalamic nucleus on respiratory/phonatory subsystems of speech production in Parkinson's disease--a preliminary report[END_REF], but the quantitative effects of STN-DBS on specific temporal speech parameters have never been assessed.

Our aim was to compare gait and speech patterns of PP and CS, and to analyse the patients' responses to levodopa and STN-DBS. Another aim was to determine whether there exist any correlations between the spatiotemporal gait and temporal speech parameters with a view to establishing whether, in line with what occurs with gait, hypokinesia may be mainly responsible for these patients' speech timing disorders and whether accelerated timing strategies may be used as compensatory mechanisms.

II. MATERIAL AND METHODS

Subjects

Eleven PP, 7 males and 4 females (mean age 64.5) and 11 age-matched CS, 7 males and 4 females (mean age 66.3) with no neurological history took part in these experiments after giving their informed consent. The project was approved by the local ethical committee.

All the PP had undergone bilateral STN-DBS and were stable when the study was conducted.

PP and controls with any other disorder possibly affecting their walking or speaking abilities were excluded from the study.

PPs' level of functional disability was determined on the Unified Parkinson's Disease Rating Scale (UPDRS) motor and axial scores in four treatment conditions (OFF and ON states of STN-DBS and levodopa). The patients' characteristics are given in Table 1.

Test procedure

Gait and speech recordings were conducted in the four treatment conditions, always in the same order. Gait recordings were run always just before speech recordings.

1. PP were tested in the OFF STN-DBS state at least 12 hours after undergoing STN-DBS treatment and in the OFF levodopa state at least 12 hours after their last dose of dopaminergic treatment (DT) (OFF/OFF) 2. the PP were tested in the ON STN-DBS state at least 1 hour after undergoing STN-DBS treatment and in the ON levodopa state at the peak effect of a suprathreshold dose of levodopa (ON/ON).

3. the PP were tested in the ON STN-DBS state at least 12 hours after undergoing STN-DBS treatment and in the OFF levodopa state at least 12 hours after taking their last DT dose (ON/OFF).

4. the PP were tested in the OFF STN-DBS state at least 3 hours after undergoing STN-DBS treatment and in the ON levodopa state at the peak effect of a suprathreshold dose of levodopa (OFF/ON).

The gait and speech recordings were conducted just once on the CS.

Gait recordings 3.1 Tasks

Subjects were instructed to walk on level ground at their natural speed (NS), slowest as compared with the first task (SS) and as fast as possible without running (FS).

Experimental recordings

Kinematic analysis was performed with the ELITE TV image processing system [START_REF] Ferrigno | ELITE: a digital dedicated hardware system for movement analysis via real-time TV signal processing[END_REF]. 22 reflective markers 1 cm in diameter were taped onto the subjects' skin at specific symmetrical anatomical points. The recordings were taken with 6 TV cameras at a sampling rate of 100 Hz.

Gait parameters

Based on the kinematic recording, temporal and spatial gait parameters were measured during each trial: walking velocity (m/s), step length (mm) and walking cadence (step/min).

Speech recordings 4.1 Tasks

Subjects had to read a short printed text at their natural speed (NS), slowest as compared with the natural condition (SS) and as fast as possible (FS).

Experimental recordings

Subjects were seated in a quiet room. Temporal acoustic recordings obtained via a headphone were analyzed using the Prosody R software program, which is part of the Software Environment for Speech Analysis and Evaluation (SESANE R ).

Speech parameters

Based on the acoustic data the following parameters were measured at each trial:

-Speech velocity (syllables/second) -Interpause speech duration (ISD in seconds): It corresponds to the time interval between two pauses. It was determined by tallying the duration occurring between two pauses.

-Speech Index of Rhythmicity (SPIR): this is an index to evaluate speech rhythmicity in the same way as the walking cadence. As the alternation between pauses and speech gives rhythm to speech just as the alternation between steps and double foot support phases gives rhythm to gait, SPIR corresponds the number of speech interpauses per minute.

Statistical procedure

Because of the small size and the non normal distribution of our samples, all the tests applied were non parametric tests. For each subject and condition, all variables have been averaged over the three trials. In the OFF/OFF situation, two PP were unable to walk.

Nevertheless, we have used the data of these patients in the other conditions of treatment. The statistics given are medians and interquartiles.

Differences between CS and PP were tested with a Mann-Whitney U test. The task effect in each group and the treatment effect in the PP group were analyzed with a Friedman ANOVA. In order to isolate statistical differences when the hypothesis of differences was verified we have realised a multiple comparison procedures (post-hoc tests) using a Student-Newman-Keuls (SNK) test. The correlations between gait and speech parameters were tested with a Spearman test.

RESULTS

Gait analysis 1.1 Effects of PD

In order to assess the effects of PD on gait parameters, the gait characteristics of PP in the OFF/OFF state of treatment were compared with those of the CS.

Whatever experimental situations, gait velocity of PP was slower than that of CS (T (1.18)=61, p<0.05; T (1.18)=62, p<0.05 and T (1.18)=58, p<0.05 in conditions NS, SS and FS, respectively); the mean step length was shorter (T (1.18)=57, p<0.01; T (1.18)=59, p<0.01 and T(1.18)=59, p<0.01 in conditions NS, SS and FS, respectively); whatever the experimental task the cadence was similar in both groups.

Effects of treatment

The gait characteristics of PP in each mode of treatment are given in figure 1.

a. Walking Velocity

The statistical analysis revealed a global effect of the treatment on walking velocity in all experimental condition (chi²=9.41, p<0.01; chi²=17.93, p<0.001 and chi²=15, p<0.01 for NS, SS, and FS respectively). Walking velocity increased similarly with levodopa, DBS and combination of both compared with the complete OFF state.

b. Step Length

In the NS condition, we showed a significant global effect of treatment on step length (chi²=15.27, p=0.002). Statistical analysis showed a significant increase of the step length in the ON/ON state of treatment in comparison with the other states. The SNK post hoc analysis revealed a significant decrease of the step length in the OFF/OFF state of treatment as compared with the ON/OFF and OFF/ON states of treatment. No significant differences were observed between OFF/ON and ON/OFF states, indicating that levodopa and DBS similarly improved step length and that the combination of both therapies had an additional effect.

In SS and FS, we showed a significant global effect of treatment on step length (chi²=15.8, p=0.001 and chi²=11.8, p<0.01, for SS and FS respectively). The step length was significantly shorter in the OFF/OFF state than in the other. No significant differences were observed between the states OFF/ON, ON/OFF or ON/ON.

c. Walking cadence

In the NS and SS conditions, the walking cadence did not differ significantly between all states of treatment. In the SS condition, a significant overall effect of treatment was observed (chi²=8.33, p<0.05). The multiple comparisons revealed that the walking cadence was significantly lower in the OFF/OFF state of treatment than in the other.

INSERT FIGURE 1 ABOUT HERE

1.3 Task effect a. Walking velocity A significant effect of task was observed in CS (chi 2 =22, p<0.001) and in treated PP (chi²=22, p<0.001; chi²=20, p<0.001 and chi²=18.2, p<0.001 in the OFF/ON, ON/OFF and ON/ON states, respectively): The walking velocity increased significantly between SS and FS. Without treatment a significant effect of task was also observed in PP (chi²=12.67, p<0.001) but interestingly, no significant difference was found between NS and FS, indicating that PP were unable to increase significantly their velocity.

b. Step length

A significant effect of task on step length was observed in CS (chi²=22, p<0.001) and in treated PP, whatever the treatment the step length increased significantly between the SS and the FS condition (chi²=22, p<0.001; chi²=16.8, p<0.001 and chi²=14.6, p<0.001 in the OFF/ON, ON/OFF and ON/ON states, respectively). In untreated PP a significant effect of task was also observed (chi²=11.56, p=0.001), but no significant difference was found to exist between NS and FS conditions. c. Walking cadence A significant effect of task was observed in CS (chi²=16.55, p<0.001) and in treated PP (chi²=16.22, p<0.001; chi²=22, p<0.001; chi²=18.2, p<0.001 and chi²=20, p<0.001 for OFF/OFF, OFF/ON, ON/OFF and ON/ON states of treatment, respectively). The walking cadence increased significantly between SS, NS and FS.

INSERT FIGURE 2 ABOUT HERE

Speech analysis 2.1 Effects of Parkinson's Disease

During NS and SS tasks, speech velocity did not differ significantly between the two groups. In the FS task the speech velocity was significantly lower in PP (T=93.5, p<0.05).

In the NS task, ISDs' values were similar in both groups. In the SS task, ISD's value of PP was significantly longer than that of CS (T=160.5, p<0.05); whereas in the FS task, the ISD of PP was significantly shorter than that of CS (T=91, p<0.05).

In NS and FS tasks, the SPIR did not differ significantly between the two groups. In the SS task, the SPIR values of PP were significantly lower than those of CS (T=93, p<0.05).

Effects of treatment

In order to assess the effects of treatment, speech performances of PP were compared depending on the treatment undergone. The speech performances of PP are given in figure 3. a. Speech velocity Whatever the experimental condition, no significant differences were observed between the four states of treatment.

b. ISD

Concerning the ISD, the Friedman's ANOVA showed significant differences between the four states of treatment during NS (chi 2 =9.275, p<0.05) and FS condition (chi 2 =1.175, p<0.01) but not during SS condition. ISD increased significantly with levodopa, DBS and combination of both therapies as compared with the complete OFF state.

c. SPIR

The SPIR did not differ significantly between any of the states of treatment during NS and SS conditions. During FS condition, the statistical analysis showed the existence of a significant overall effect of treatment on SPIR (chi 2 =8.46, p<0.05) which were significantly higher in the OFF/OFF state of treatment than in the other states.

INSERT FIGURE 3 ABOUT HERE 2.3 Task effects a. Speech velocity

A significant effect of task on speech velocity was observed in CS (chi 2 =16.545, p<0.01) and in treated PP (chi²=14.727, p<0.01; chi²=20.182, p<0.001 and chi²=14.364, p<0.01 in the OFF/ON, ON/OFF and ON/ON states, respectively): the speech velocity increased significantly between the SS and the FS condition. A significant effect of task was also observed in the OFF/OFF PP (chi²=17.636, p<0.01): speech velocity increased significantly between NS and FS condition, but not between SS and NS conditions. b. ISD A significant effect of task on ISD was found in CS (chi 2 =13.273, p<0.01) and in treated PP (chi²=10.093, p<0.01; chi²=8.727, p<0.05 and chi²=13.273, p<0.01 in the OFF/ON, ON/OFF and ON/ON states, respectively): the ISD increased significantly between the SS and FS condition. It is worth noting that the increase of the ISD between NS and FS was only significant in the ON/ON state of treatment. In PP in the OFF/OFF state of treatment, no significant differences were detected.

c. SPIR

A significant effect of task on SPIR was observed in CS (chi 2 =8.909, p<0.001): the SPIR values decreased significantly in this group between SS and NS and between NS and FS.

No significant effects of task on SPIR were detected in PP.

INSERT FIGURE 4 ABOUT HERE

Correlations between gait and speech parameters

In order to measure the strength of association between gait and speech parameters we have used the Spearman's coefficient of correlation. We have correlated gait velocity with speech velocity, walking cadence with SPIR and step length with ISD. We have brought together all the velocity of tasks executions.

Statistical correlations between walking velocity and speech velocity

Significant correlations were found to exist between walking and speech velocities in CS (r=0.84, p<0.001), in PP in the OFF/OFF (r=0.717, p<0.001), in the ON/OFF (r=0.505, p<0.01), and in the OFF/ON states of treatment (r=0.4325, p<0.05) but not in the ON/ON sate.

Correlations between step length and ISD

A significant correlation was found to exist between step length and ISD in CS (r=0.609, p<0.001), in PP in the ON/OFF (r=0.486, p<0.01) and ON/ON (r=0.421, p<0.05) state of treatment. No statistical correlations were observed in the OFF/OFF and OFF/ON states of treatment.

Correlations between walking cadence and SPIR

A significant negative correlation was found between walking cadence and SPIR in CS (r=-0.702, p<0.001) in PP in the OFF/OFF (r=-0.418, p<0.05) and in the OFF/ON state of treatment (r=-0.438, p<0.05), but not in PP in the ON/OFF or ON/ON states of treatment.

DISCUSSION:

Our results demonstrate large similarities between the gait's pattern and speech's involvement in PD and in their responses to STN-DBS and levodopa treatment

Gait and speech impairments in PD

The spatiotemporal gait disorders observed in PD are in line with those previously described: without treatment, walking velocity and step length of PP are decreased while walking cadence is not significantly different [START_REF] Azulay | Automatic motion analysis of gait in patients with Parkinson disease: effects of levodopa and visual stimulations[END_REF]Morris et al., 1994b;[START_REF] Sofuwa | Quantitative gait analysis in Parkinson's disease: comparison with a healthy control group[END_REF].Neither walking velocity nor step length increased when the untreated patients were asked to walk as fast as possible, suggesting that they were unable to regulate their step length on the basis of internal control mechanisms. Oppositely, the patients' internal walking cadence regulation process seems to be preserved, since their walking cadence increased significantly between SS and NS and between NS and FS. This fundamental hypokinetic deficit has previously been described by Morris et al. (1994b).

The results of the speech analysis brought to light the existence of speech timing disorders showing some analogies with the gait impairments. Without any treatment, PP tended to speak more slowly than the CS, their ISD often tended to decrease in comparison with the control values, in parallel with the decreasing step length. The SPIR showed some similarities with the walking cadence, since it was equal to the control values at NS and FS.

Few data are available to compare our results, [START_REF] Canter | Speech Characteristics of Patients with Parkinson's Disease: I. Intensity, Pitch, and Duration[END_REF] and [START_REF] Metter | Clinical and acoustical variability in hypokinetic dysarthria[END_REF] observed changing speech velocities in PP. The ISD has often been reported to be shorter in PP than in CS during both reading and spontaneous speech [START_REF] Forrest | Kinematic, acoustic, and perceptual analyses of connected speech produced by parkinsonian and normal geriatric adults[END_REF][START_REF] Hammen | Speech and pause characteristics following speech rate reduction in hypokinetic dysarthria[END_REF]. The speech velocity also changes with the co-existence of bradylalia and tachylalia [START_REF] Gentil | Parkinsonian dysarthria][END_REF]. The present results show in addition that the speech velocity of PP without treatment did not differ between SS and NS, and that their ISD remained unchanged under all the experimental conditions. In line with the changes observed in their walking patterns, PP therefore have some difficulty in modulating their speech velocities because they are no longer able to internally control the ISD. However, the internal speech rhythm regulation processes seem to be also impaired, since the SPIR remained unchanged at NS and FS condition.

Effect of levodopa and STN-DBS on gait and speech deficits

As regards the patients' responses to treatment, their walking velocities were greatly improved by both STN-DBS and levodopa, probably due to an increase in the step length, whereas the walking cadence remained unchanged in NS and FS. In all tasks, no significant difference between STN-DBS and levodopa was observed, but a cumulative effect was observed in the NS condition. Two previous studies show that STN-DBS, like levodopa, improves walking velocity by increasing step length without changing walking cadence [START_REF] Faist | Effect of bilateral subthalamic nucleus stimulation on gait in Parkinson's disease[END_REF][START_REF] Lubik | Gait analysis in patients with advanced Parkinson disease: different or additive effects on gait induced by levodopa and chronic STN stimulation[END_REF]. These findings suggest that STN-DBS may involve the same action mechanisms as levodopa via the dopaminergic basal ganglia loop while the cadence, which is a rhythmic parameter, is probably regulated by a non dopaminergic structure.

Levodopa and STN-DBS had no effect on the patients' speech velocity but increased the ISD. Combined treatment restored the patients' ability to modulate their ISD. The ISD therefore seems to be the main clinical manifestation of speech akinesia, since this parameter is regulated by the dopaminergic basal ganglia loop. The effects of treatment on the SPIR were often not significant. This finding probably means that in the case of both speech and gait, the rhythm is regulated by a non dopaminergic structure.

Gait and speech deficits in PD: a common feature?

This is the first time that correlations have been made between gait and speech parameters in PD. In CS and PP undergoing no treatment or under STN-DBS treatment alone, a significant correlation was found between walking velocity and speech velocity. In other words, CS and PP who walk faster also speak faster. This outcome seems to be modified by levodopa.

A significant positive correlation between step length and ISD was also found. This confirms that step length and ISD decrease are clinical manifestations of both gait and speech akinesia, that they are both responsive to levodopa and STN-DBS and that just as akinesia is the main gait deficit, speech akinesia may be the main speech deficit in PD. The negative correlation between walking cadence and SPIR in CS underlines the different strategies used to modulated gait and speech velocity: to walk faster, CS increase the number of steps they make, whereas to speak faster, they decrease the number of speech interpauses and pauses. This result suggests that the SPIR is a good index to analyse speech rhythmicity, just as the walking cadence is a good index to analyse gait rhythmicity. In PD, a similar phenomenon was observed only under levodopa suggesting that walking cadence and SPIR are regulated by different non dopaminergic structures and that rhythmic perturbations do not always affect speech and gait concurrently, but that they may occur earlier in speech, where a two-fold deficit occurs due to the patients' inability to internally regulate either the number of pauses or the ISD.

Conclusions:

As recently suggested by [START_REF] Moreau | Oral festination in Parkinson's disease: biomechanical analysis and correlation with festination and freezing of gait[END_REF], who established that oral festinations were correlated with gait festinations in PP, the present results underline several common features between gait and speech troubles in PD. The decrease in PPs' walking velocity and speech velocity result from a decrease in step length and ISD: these akinetic parameters, which are strongly correlated, are regulated by the dopaminergic basal ganglia loop. Walking cadence and SPIR, which are the rhythmic gait and speech parameters, do not seem to be regulated by a non dopaminergic structure.

Experimental studies on animals have shown that the PPN of the MLR [START_REF] Aziz | The role of descending basal ganglia connections to the brain stem in parkinsonian akinesia[END_REF] is involved in the regulation of the locomotor rhythm (Garcia-Rill and Skinner, 1988).

On the basis of our results, we propose an equivalent model for the regulation of the spatial and rhythmic parameters of gait and the temporal and rhythmic parameters of speech (figure 5). Further studies are required to confirm such hypothesis and determine what structures are involved.

INSERT FIGURE 5 Step/min

Walking Velocity

Step Length Step length regulation

Walking cadence regulation

Interspeech duration regulation

Speech Rhythm regulation

FIGURE 1 :

 1 FIGURE 1: Task effect on gait parameters: From top to the bottom, medians and quartiles of

FIGURE 2 :

 2 FIGURE 2: Treatment effect on gait parameters: Medians and quartiles of walking velocity,

FIGURE 3 :

 3 FIGURE 3: Task effects on speech parameters : Medians and quartiles of speech velocity,

FIGURE 4 :

 4 FIGURE 4: Treatment effects on speech parameters : Medians and quartiles of speech

FIGURE 5 :

 5 FIGURE 5: Model for the regulation of the spatial and rhythmic parameters of gait (left) and

  Figure 2

Table 1 FIGURE CAPTIONS:TABLE 1 :

 11 Medical characteristics of the 11 Parkinsonian patients: sex, age and disease duration, UPDRS part III and axial scores, effect of L-Dopa and STN in % iof the OFF/OFF score, in 4 states of treatment performed at the time of testing. The axial score was the sum of items numbers 18, 19, 22, 27, 28, 29 and 30 in the motor UPDRS score.

	ABOUT HERE

Acknowledgements:

We are grateful to all the subjects who participated in this study and to Dr Jessica Anderson-Blanc for revising the English manuscript.


Oksala Nkj

; Melkas

; Oksala

PhD ; Hietanen

; Kaste

MD, PhD; Karhunen Pj

Docent, MD Niku Oksala
email: niku.oksala@tuubi1.net

COGNITIVE IMPAIRMENT PREDICTS POSTSTROKE DEATH IN LONG-TERM FOLLOW UP

Keywords: ischemic stroke, outcome, neuropsychology Word count: 2682, References: 62, Tables: 2, Figures: 1

Background: Poststroke global cognitive decline and dementia have been related to poor long term survival. Whether deficits in specific cognitive domains are associated with long term survival in ischemic stroke patients is not known in detail. Methods: Consecutive acute stroke patients subjected to comprehensive neuropsychological evaluation were included in the study (N=409) and followed-up up to 12 years. Results: In Kaplan-Meier analysis, impairments in following cognitive domains predicted poor poststroke survival (estimated years): executive functions (48.2%) (5.8 vs. 10.1 years, p<0.0001), memory (59.9%) (6.8 vs. 9.3 years, p=0.009), language (28.9%) (5.3 vs. 8.6 years, p=0.004), and visuospatial/constructional abilities (55.2%) (5.6 vs. 10.1 years, p<0.0001). Low MMSE ≤25 (30.5%) (4.4 vs. 9.3 years, p<0.0001), low education (<6 years) (31.8%) (6.4 vs. 8.2 years, p=0.003) and poor modified Rankin score (39.9%) (3.9 vs. 9.7 years, p<0.0001) were also related to poor survival. In Cox regression proportional hazards analyses including age, sex and years of education as covariates, deficits in executive functions (HR 1.59, p<0.0001), memory (HR 1.31, p=0.042), language (HR 1.33, p=0.036) and visuospatial/constructional abilities (HR 1.82, p<0.0001), were significant predictors of poor poststroke survival. Of these, executive functions (HR 1.33, p=0.040) as well as visuospatial/constructional abilities (HR 1.53, p=0.004) remained as significant predictors after addition of MMSE≤25 and poor modified Rankin score as covariates.

Furthermore, cognitive impairment no dementia (CIND) was also an independent predictor of poor poststroke survival (HR 1.63, p=0.0123). Conclusions: In patients with ischemic stroke, cognitive impairment particularly in executive functions, and visuospatial/constructional abilities relate to poor survival.

INTRODUCTION

Poststroke cognitive impairment is frequent -up to 65 to 78% of patients demonstrate cognitive decline [START_REF] Tatemichi | Cognitive impairment after stroke: frequency, patterns, and relationship to functional abilities[END_REF][START_REF] Pohjasvaara | Correlates of dependent living 3 months after ischemic stroke[END_REF] and 25 to 31% of patients demonstrate poststroke dementia [START_REF] Pohjasvaara | Clinical determinants of poststroke dementia[END_REF][START_REF] Desmond | Mortality in patients with dementia after ischemic stroke[END_REF][START_REF] Tatemichi | Dementia after stroke is a predictor of long-term survival[END_REF][START_REF] Barba | Previous and incident dementia as risk factors for mortality in stroke patients[END_REF][START_REF] Henon | Influence of prestroke dementia on early and delayed mortality in stroke patients[END_REF].

Further ischemic stroke is an important factor predicting long-term survival [START_REF] Staals | Differences in long-term survival in two lacunar stroke types: a 15-year follow-up study in 782 cerebral infarct patients[END_REF].

Global measures of cognition e.g. Mini Mental Status Examination (MMSE) [START_REF] Patel | Cognitive impairment after stroke: clinical determinants and its associations with long-term stroke outcomes[END_REF][START_REF] Friedman | Atrial fibrillation after stroke in the elderly[END_REF][START_REF] House | Mortality at 12 and 24 months after stroke may be associated with depressive symptoms at 1 month[END_REF][START_REF] Friedman | Predictors of survival after cerebral infarction: importance of cardiac factors[END_REF] and similar short mental status tests [START_REF] Woo | Factors influencing long-term survival and disability among three-month stroke survivors[END_REF] have been related to a poor survival in poststroke follow-up studies. Similarly poststroke dementia has been related to a poor survival [START_REF] Desmond | Mortality in patients with dementia after ischemic stroke[END_REF][START_REF] Tatemichi | Dementia after stroke is a predictor of long-term survival[END_REF][START_REF] Barba | Previous and incident dementia as risk factors for mortality in stroke patients[END_REF][START_REF] Henon | Influence of prestroke dementia on early and delayed mortality in stroke patients[END_REF][START_REF] Melkas | Poststroke dementia predicting survival in longterm follow-up: influence of prestroke cognitive decline and previous stroke[END_REF].

Poststroke cognitive impairment consists of decline in various cognitive domains such as memory, language, visuospatial and constructional abilities [START_REF] Tatemichi | Cognitive impairment after stroke: frequency, patterns, and relationship to functional abilities[END_REF][START_REF] Bowler | Cognition in stroke[END_REF] and also in executive function [START_REF] Glosser | Disorders in executive control functions among aphasic and other brain-damaged patients[END_REF][START_REF] Sala | Autobiographical recollection and frontal damage[END_REF]. However, the role of these specific cognitive impairments on poststroke long-term survival has not been studied in detail. Moreover, it is not known whether a milder cognitive impairment short of dementia is relevant for poststroke survival.

The aim of our study was to detail the effect of different cognitive deficits as well as cognitive impairment no dementia (CIND) on poststroke survival controlling for main covariates in a large well defined ischemic stroke cohort followed up to 12 years. We hypothesized that cognitive impairment would be related to impaired poststroke survival.

METHODS

Patients

The Helsinki Stroke Aging Memory (SAM) cohort comprised a consecutive series of all Finnish (caucasian) patients with suspected stroke admitted to Helsinki University Central Hospital (n=1622) between 1 December 1993 and 30 March 1995, as described in detail previously [START_REF] Oksala | Smoking and the platelet fibrinogen receptor glycoprotein IIb/IIIA PlA1/A2 polymorphism interact in the risk of lacunar stroke and midterm survival[END_REF][START_REF] Pohjasvaara | Comparison of stroke features and disability in daily life in patients with ischemic stroke aged 55 to 70 and 71 to 85 years[END_REF][START_REF] Oksala | Long-term survival after ischemic stroke in postmenopausal women is affected by an interaction between smoking and genetic variation in nitric oxide synthases[END_REF]. Patients aged 55-85 years living in Helsinki were included. Patients without ischemic stroke (n=175), presenting with intracerebral (n=229) or subarachnoid hemorrhage (n=69) were excluded. A total of 642 patients fulfilled the inclusion criteria and were invited to a baseline visit 3 months later. Of these, 71 died (11.1%) before the 3month follow-up, 82 refused (12.8%) and 3 were lost (0.5%) due to undefined causes.

Finally, 486 (85.1%; 246 men, 240 women) of the living patients were included in the final cohort [START_REF] Mantyla | Magnetic resonance imaging white matter hyperintensities and mechanism of ischemic stroke[END_REF]. Of these 409 (84.2%) participated in neuropsychological examination.

Patients with severe aphasia and thus unable to participate neuropsychological examination were excluded together with those with severe sight or hearing disabilities, or reduced level of consciousness.

The study was approved by the Ethics committee of the Department of Clinical Neurosciences, Helsinki University Central Hospital, Finland. The study was explained to the patients, and informed consent was obtained.

Clinical evaluation

A detailed medical and neurological history was taken [START_REF] Pohjasvaara | Comparison of stroke features and disability in daily life in patients with ischemic stroke aged 55 to 70 and 71 to 85 years[END_REF]. In the basic cohort of 486 patients, there were 388 (79.8%) patients with first-ever and 98 patients (20.2%) with recurrent stroke. Exclusion of those with recurrent stroke did not have any effect on study results and therefore the final study was conducted including recurrent stroke patients. Stroke severity was assessed using modified Rankin score at 3 months [START_REF] Van Swieten | Interobserver agreement for the assessment of handicap in stroke patients[END_REF].

Neuropsychological analyses

A comprehensive neuropsychological assessment was administered three months after the index stroke as detailed before [START_REF] Pohjasvaara | Clinical determinants of poststroke dementia[END_REF][START_REF] Jokinen | Medial temporal lobe atrophy and memory deficits in elderly stroke patients[END_REF][START_REF] Jokinen | Cognitive profile of subcortical ischaemic vascular disease[END_REF]. There were no statistically significant dfferences in gender, age, education, MMSE or modified Rankin score between these and the original 486 subjects.

In brief, global cognitive function was measured with the Mini-Mental State Examination [START_REF] Weiner | Albuminuria, Cognitive Functioning, and White Matter Hyperintensities in Homebound Elders[END_REF]. Score ≤25 indicated cognitive impairment. Executive functions including attention were evaluated with the Trail making test [START_REF] Reitan | Validity of the Trail Making Test as an indicator of organic brain damage[END_REF], the Stroop color naming test [START_REF] Macleod | Half a century of research on the Stroop effect: an integrative review[END_REF] and the Digit span subtest of the Wechsler Memory Scale [START_REF] Wechsler | A standardized memory scale for clinical use[END_REF], the modified Wisconsin Card Sorting Test and the verbal fluency test [START_REF] Lezak | Neuropsychological assessment[END_REF]. Data was available in 365 and missing in 44 subjects (10.8%). The assessment of memory functions included the Logical memory and Visual reproduction subtests of the Wechsler Memory Scale-revised [START_REF] Wechsler | Wechsler memory scale-revised manual[END_REF] as well as the Fuld Object Memory Evaluation [START_REF] Fuld | Fuld object memory evaluation[END_REF]. Data was available in 379 and was missing in 30 subjects (7.3%). Language was evaluated with the short version of the Token test [START_REF] Renzi | Normative data and screening power of a shortened version of the Token test[END_REF] the Boston naming test [START_REF] Borod | Normative data on the Boston Diagnostic Aphasia Examination, Parietal Lobe Battery and the Boston Naming Test[END_REF] and the verbal fluency test [START_REF] Lezak | Neuropsychological assessment[END_REF]. Moreover, overall evaluation of speech functions was based on the Boston Diagnostic Aphasia Examination [START_REF] Laine | Adaption of the Boston Diagnostic Aphasia Examination and the Boston Naming Test into Finnish[END_REF]. Data was available in 395 and missing in 14 subjects (3.4%). Visuospatial and constructional abilities were assessed with the Block design subtest of the Wechsler Adult Intelligence Scale-revised [36], the clock test (recognizing and setting time), and by copying a triangle, a flag, a 3-dimentional cube, and a Greek cross [START_REF] Christensen | s Neuropsychological Investigation: Text[END_REF]. Data was available in 391 and missing in 18 subjects (4.4%). Abnormality (impaired vs. not impaired) in each domain was judged with the use of normative data from a random healthy Finnish population (2 SD or, if more than one test was used, 1 SD below the level of the norm on several tests indicated abnormality) [START_REF] Ylikoski | White matter changes in healthy elderly persons correlate with attention and speed of mental processing[END_REF]. The normal values were evaluated in different age groups.

Cognitive

RESULTS

Characteristics of the study sample

The basic demographics of the cohort are as follows: age 71.2 ± 7.7 years; female sex 49.4%; MMSE≤25 28.6%; poor modified Rankin score 39.9%.

The demographics with respect to presence of deficits in cognitive domains are presented in table 1. Patients with executive, language or visuospatial/constructional deficit (p<0.0001) were older than those without it. Women were overpresented in patients with language (p=0.009) or visuospatial/constructional deficits (p=0.004). Low education was more prevalent in patients with deficits in executive functions (p=0.019), memory (p=0.023), language (p=0.017) and visuospatial/constructional abilities (p=0.002). Poor modified Rankin score was significantly more prevalent in those with any of the cognitive deficits (p<0.0001) (Table 1). MMSE≤25 was frequent in all patients with deficits in any of cognitive domains (p<0.0001) (Table 1).

The cognitive deficits were highly interrelated: 77.3% of patients with executive deficit had also a deficit in visuospatial/constructional abilities, and 73.9% had a memory deficit. On the other hand, the least frequent combination was executive and language deficit (30.1%).

The effect of cognitive impairment on survival

In Kaplan-Meier log-rank analysis, deficits in executive functions (n=176, 48.2%) (5.8, CI 4.7-7.0 vs. 10.1, CI 8.7-11.4 years, p<0.0001), memory (n=227, 59.9%) (6.8, CI 5.3-8.3 vs. 9.3, CI 7.9-10.7 years, p=0.009), language (n=114, 28.9%) (5.3, CI 3.8-6.9 vs. 8.6, CI 7.7-9.4 years, p=0.004) and visuospatial/constructional abilities (n=216, 55.2%) (5.6, CI 4.6-6.7 vs. 10.1, CI 8.5-11.7 years, p<0.0001) predicted poor survival (Figure 1). .0001), and poor modified Rankin score (n=194, 39.9%) (3.9, CI 4.2-5.6 vs. 9.7, CI 8.5-10.9 years, p<0.0001) predicted poor poststroke survival (Figure 1).

To account for potential confounders, and to estimate the predictive value of different factors, a multivariate Cox regression proportional hazards analysis utilizing two models (Table 2) was used. In Cox proportional hazards regression analysis (Model 1, including age, sex and years of education), deficits in executive functions (HR 1.65, CI 1.27-2.13, p<.001), memory (HR 1.31, CI 1.01-1.70, p=0.042), language (HR 1.33, CI 1.02-1.73, p=0.036) and visuospatial/constructional abilities (HR 1.82, CI 1.40-2.36, p<0.0001) were significant predictors of poor poststroke survival (Table 2). Deficits in executive functions (HR 1.38, CI 1.05-1.81, p=0.021) and visuospatial/constructional abilities (HR 1.53, CI 1.14-2.04, p=0.004) remained as significant predictors after addition of MMSE≤25 and poor modified Rankin score as covariates (Model 2) (Table 2). MMSE≤25 (HR 1. 32-1.46) and poor modified Rankin score (HR 1.54-1.61) predicted poor survival in all the models.

To further explore the role of cognitive impairment we analyzed the effect of cognitive impairment no dementia (CIND) on poststroke survival. In this population (n=284), CIND (n=212, 74.6%) (7.9, CI 7.4-8.5 vs. 9.7, CI 8.8-10.6, p=0.003) was a predictor of poor poststroke survival (Figure 2) when compared to patients with no cognitive impairment in any of the assessed domains. In Cox proportional hazard regression analysis with age, sex and years of education as covariates, CIND remained an independent predictor of survival (HR 1.63, CI 1.12-2.39, p=0.012).

The association of neuropsychological domains and causes of death

Of all the deaths (n=347), 30.5% were attributable to cardiac causes, 33.7% due to brain related causes (bleeding, infarct, dementia), 14.0% due to cancer, 4.3% due to infectious causes, 3.9% due to traumatic causes and 12.5% due to other causes. In the present study, proportion of patients with deficits in different cognitive domains varied between 29-60%, the lowest proportion found in language and the highest in memory. Studies on the effect of cognitive domains on poststroke survival are limited. Deficits in domains like verbal, visuomotor and memory performance and reaction time have previously been associated with shortened survival at general population level [START_REF] Shipley | Cognition and all-cause mortality across the entire adult age range: health and lifestyle survey[END_REF][START_REF] Portin | Cognitive impairment and the 10-year survival probability of a normal 62-year-old population[END_REF].

According to

Prestroke [START_REF] Barba | Previous and incident dementia as risk factors for mortality in stroke patients[END_REF][START_REF] Henon | Influence of prestroke dementia on early and delayed mortality in stroke patients[END_REF], any poststroke [START_REF] Desmond | Mortality in patients with dementia after ischemic stroke[END_REF][START_REF] Tatemichi | Dementia after stroke is a predictor of long-term survival[END_REF][START_REF] Barba | Previous and incident dementia as risk factors for mortality in stroke patients[END_REF] and new-onset poststroke [START_REF] Henon | Influence of prestroke dementia on early and delayed mortality in stroke patients[END_REF] dementia has been consistently related to poor survival. This is in line with our finding of the association of global MMSE with survival. In a population based study 3 months after stroke [START_REF] Patel | Cognitive impairment after stroke: clinical determinants and its associations with long-term stroke outcomes[END_REF], the proportion of cognitively impaired subjects (MMSE<25) was found to be 38% which is considerably higher than in the present study of hospitalized patients. However, similar prevalence was detected in a study of hospitalized patients [START_REF] House | Mortality at 12 and 24 months after stroke may be associated with depressive symptoms at 1 month[END_REF]. We consider our cohort representative of hospitalized stroke patients. Our cohort with up to 12 year follow up showed significant effect of low MMSE on long-term survival. In line with our results, cognitive impairment as measured by MMSE was associated with impaired survival up to 4 year follow-up [START_REF] Patel | Cognitive impairment after stroke: clinical determinants and its associations with long-term stroke outcomes[END_REF][START_REF] Friedman | Atrial fibrillation after stroke in the elderly[END_REF][START_REF] House | Mortality at 12 and 24 months after stroke may be associated with depressive symptoms at 1 month[END_REF][START_REF] Friedman | Predictors of survival after cerebral infarction: importance of cardiac factors[END_REF]. However, two short 1 year studies demonstrate that MMSE is not an independent predictor of survival [START_REF] Thommessen | Predictors of outcome of rehabilitation of elderly stroke patients in a geriatric ward[END_REF][START_REF] Altieri | SPASE-I: a multicenter observational study on pharmacological treatment of acute stroke in the elderly. The Italian Study of Pharmacological Treatment of Acute Stroke in the Elderly Group[END_REF]. A single study utilizing short 10 item mental status questionnaire showed that cognitive impairment is an independent predictor of 6 year survival [START_REF] Wang | Predictors of survival among elders suffering strokes in Taiwan: observation from a nationally representative sample[END_REF] In a previous study [START_REF] Moulin | The Besancon Stroke Registry: an acute stroke registry of 2,500 consecutive patients[END_REF] severe aphasia was independently associated with poor survival which is in line with our finding of the association of deficit in language domain and As far as we know, our study is thus far the largest poststroke cohort with a long follow up and a detailed neuropsychological examination. It is also the only study controlling for main covariates including severity of stroke. The present study showed that impairment in major cognitive domains relates to poor poststroke survival. When controlling for the effect of global cognitive decline (MMSE≤25) and severity of stroke only executive functions as well as visuospatial and constructional abilities remained as independent correlates of poor survival. Executive functions, including planning, initiation, sequencing and monitoring of complex goal-directed behaviour, heavily rely on the integrity of the prefrontal cortices and their connecting pathways with the subcortical structures [START_REF] Royall | Executive control function: a review of its promise and challenges for clinical research. A report from the Committee on Research of the American Neuropsychiatric Association[END_REF]. The frontal lobe functional system is also involved with visuospatial and constructional abilities which require intact attention and organisational skills together with the more posteriorly-mediated visuoperceptual functions.

Cerebral small vessel disease is reflected by white matter lesions seen in MRI [START_REF] Inzitari | Leukoaraiosis: an independent risk factor for stroke?[END_REF][START_REF] Inzitari | Risk of rapid global functional decline in elderly patients with severe cerebral age-related white matter changes: the LADIS study[END_REF],

which have also been related to recurrent stroke [START_REF] Fu | Extent of white matter lesions is related to acute subcortical infarcts and predicts further stroke risk in patients with first ever ischaemic stroke[END_REF][START_REF] Pantoni | The significance of cerebral white matter abnormalities 100 years after Binswanger's report. A review[END_REF][START_REF] Kuller | White matter grade and ventricular volume on brain MRI as markers of longevity in the cardiovascular health study[END_REF][START_REF] Briley | Does leukoaraiosis predict morbidity and mortality?[END_REF][START_REF] Inzitari | Vascular deaths in elderly neurological patients with leukoaraiosis[END_REF] and poor survival mostly due to cardiovascular causes [START_REF] Fu | Extent of white matter lesions is related to acute subcortical infarcts and predicts further stroke risk in patients with first ever ischaemic stroke[END_REF][START_REF] Kuller | White matter grade and ventricular volume on brain MRI as markers of longevity in the cardiovascular health study[END_REF][START_REF] Kerber | Increased risk of death in community-dwelling older people with white matter hyperintensities on MRI[END_REF]. White matter lesions on the other hand associate with general cognitive function and with global functional decline [START_REF] Inzitari | Risk of rapid global functional decline in elderly patients with severe cerebral age-related white matter changes: the LADIS study[END_REF] and executive dysfunction related with frontal lobe system [START_REF] Inzitari | Risk of rapid global functional decline in elderly patients with severe cerebral age-related white matter changes: the LADIS study[END_REF][START_REF] Van Der Flier | Small vessel disease and general cognitive function in nondisabled elderly: the LADIS study[END_REF][START_REF] O'sullivan | Diffusion tensor MRI correlates with executive dysfunction in patients with ischaemic leukoaraiosis[END_REF][START_REF] Carey | Subcortical lacunes are associated with executive dysfunction in cognitively normal elderly[END_REF][START_REF] Tullberg | White matter lesions impair frontal lobe function regardless of their location[END_REF]. We have previously demonstrated the association of white matter lesions and cognitive deficits in the present cohort [START_REF] Jokinen | White matter hyperintensities as a predictor of neuropsychological deficits post-stroke[END_REF]. In addition, recently, we have demonstrated in the present cohort that of the patients 28% had mild, 18% had moderate and 54% had severe white matter lesions and that severe lesions predicted poor poststroke survival [START_REF] Oksala | Age-related white matter changes predict stroke death in long-term follow up[END_REF].

Together these results suggest that there may be a complex interplay of cerebral small vessel pathology and a related disruption of the frontal lobe functional system behind impaired poststroke survival.

A potential weakness of our study is the possibility of selection bias, as the cohort was formed three months after the index stroke. This may limit generalization of the results. Therefore, we retrospectively obtained additional data on stroke-related deaths in Helsinki University Hospital district during the collection of the cohort from an independent organization (Statistics Finland). In this retrospective data, up to 64 percent of stroke related deaths occurred in women. While the proportions of both sexes in the present study were equal, this suggests that some women may have died before hospital assessment at 3 months. Due to exclusion of patients, the true survival rate may be underestimated. In addition, since patients with severe aphasia could not be assessed with comprehensive neuropsychological examination, there is a possibility for survival bias since these patients are prone to impaired survival resulting in underestimation of the effect of language. Strengths of our study are that the cohort is a consecutive one, and that the neuropsychological and clinical characteristics of the patients were strictly evaluated, and also that the severity of stroke at admission was quantitated according to the modified Rankin score. Also, the survival data is comprehensive with negligible amount of unresolved deaths.

In summary, cognitive impairment already at less severe stages without dementia is related to poor long-term survival poststroke. Deficits in executive functions and visuospatial and constructional abilities, in particular, predict poor outcome independently of global cognitive decline and severity of stroke.

Table 1. The association of cognitive deficits with demographic and clinical parameters (Stroke Aging Memory-cohort).

Executive

Memory Language Visuospatial

  impairment without dementia, i.e. cognitive impairment no dementia (CIND) [39] was defined as cognitive impairment in any of the above mentioned domains after the exclusion of patients with dementia. Of the patients with MMSE≤25 (n=138), 94/138 (68.1%) had dementia at the 3 month follow-up. Further, of these 62/94 (66.0%) had had a prestroke cognitive decline. Assessment of prestroke cognitive decline involved interviews with the patient and a knowledgeable informant, using structured questions. Dementia was defined according to Diagnostic and Statistical Manual of Mental Disorders 3 rd edition criteria. From the basic cohort of 486 patients, we first excluded those who had not been tested for dementia (n=35, 7.2%) and those who had dementia (n=115, 23.7%). Further we investigated whether patients had impairment in any of the assessed domains. 52 patients were excluded at this point because of missing values in the assessed domains, at the same time as none of the existing values indicated impairment. Finally, there were 212 patients with CIND and 72 patients with no cognitive impairment. Survival data and causes of death Long-term survival data and causes of death at 21 September 2006 were obtained from Statistics Finland. The mean (+-SD) follow up time was 7.5 ± 4.0 years with a range between 0.3 and 12.8 years. Statistical analysis SPSS/WIN (version 12.0, SPSS Inc) software was used. Chi-Square test was used to test dichotomous variables and Student's t-test to test continuous variables. The effect of different neuropsychological domains (executive functions, memory, language and visuospatial/constructional abilities), CIND and copredictors such as global cognitive function i.e. MMSE (MMSE≤25), education (low education <6 years), and poor modified Rankin score (3-5 vs. 0-2) on long-term survival were first analyzed using Kaplan-Meier log rank analysis. The median estimated years of survival are presented. The cumulative hazard function was also used and according to these analyses, the proportional hazards assumption was met for each parameter included in further models. In Cox-regression proportional hazards survival analysis, in the forced entry model (Model 1) only the demographic background variables were used as covariates (age, sex, years of education). Another model (Model 2) was constructed adding MMSE≤25 and poor modified Rankin score (3-5 vs. 0-2) as clinical covariates. Statistical significance was set at p<.05.

Furthermore

  .003), MMSE ≤25 (n=138, 30.5%) (4.4, CI 3.7-5.1 vs. 9.3, CI 8.3-10.4 years, p<0

  Kaplan-Meier log rank test, the probability of dying due to cardiac causes alone showed no association with deficits in any of the cognitive domains. Death due to brain related causes on the other hand was more likely in those with deficits in executive functions (p=0.019), language (p=0.001), visuospatial/constructional abilities (p<0.0001). No associations between cognitive domains and infectious, traumatic or other causes of death were found. DISCUSSION The present study showed that poor poststroke survival relates to deficits in cognitive functions, i.e. executive, memory, visuospatial/constructional functions and language. Global cognitive impairment was also related to poor survival. Deficits in executive and visuospatial/constructional functions remained as independent predictors after controlling for global cognitive impairment and severity of stroke. Furthermore, cognitive impairment no dementia (CIND) was indepdendently related to poor poststroke survival. These findings on CIND are in line with previous studies [39-41].

  survival. In earlier studies, CIND has been related to impaired survival in studies of community based populations where stroke has not been regarded [39-41]. Our results of CIND, a potentially reversible condition, as an independent predictor of poor poststroke survival in a specified poststroke population is of clinical significance. Recognition of CIND might alert the clinicians to schedule more strict and accurate poststroke follow-up.

Figure 1 .

 1 Figure 1. The effect of different cognitive deficits (groups with given deficits are

Figure 1 .

 1 Figure 1.

ACKNOWLEDGEMENTS AND FUNDING PAGE

This study was supported by grants from the Maire Taponen Foundation; the Paavo Nurmi Foundation; The Finnish Angiologic Association; the Medical Council of the Academy of Finland (Helsinki); the Clinical Research Institute, Helsinki University Central Hospital; the Yrjö Jahnsson Foundation (Helsinki); the Finnish Cultural Foundation and the Elli and Elvi Oksanen Fund of the Pirkanmaa Fund under the auspices of the Finnish Cultural Foundation (Tampere); the Medical Research Fund of Tampere University Hospital; the Finnish Medical Foundation; and the Finnish Foundation for Cardiovascular Research (Helsinki). We thank Ms. Elli Ada Olivia Oksala and Statistics Finland for their expert assistance in the data collection.


M. D Enrico Alfonsi
email: enrico.alfonsi@mondino.it

M. D Ilaria Maria Merlo

M. Sc Michela Ponzio

Ph. D Cristina Montomoli

Ph. D Cristina Tassorelli

M. D Caterina Biancardi

M. D Alessandro Lozza

M. D Emilia Martignoni

Fondazione S Maugeri

An electrophysiological approach to the diagnosis of neurogenic dysphagia; implications for botulinum toxin treatment

Keywords:

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Traditionally, deglutition has been described as a series of four phases that relate to the passage of the bolus through specific anatomic structures: oral preparatory, oral, pharyngeal, and oesophageal.

The physiology of swallowing implies the interaction of sensory and motor functions and the interaction of voluntary and involuntary aspects. Recent studies suggest that swallowing is best understood as a single behaviour with four components that must act in an integrated manner if swallow success has to be achieved; these studies have also underlined the importance of sensation and of sensory-motor integration. [START_REF] Cichero | Applied Anatomy and physiology of the normal swallow[END_REF] Dysphagia, impairment in swallowing, is a frequent symptom in patients with many different neurological disorders, which can further complicate their clinical management, and adversely affect their quality of life and their outcome. Epidemiological studies have found that clinical dysphagia is present in up to a third of patients with stroke and in 50% of patients with Parkinson's Disease (PD). [START_REF] Hamdy | Explaining oropharyngeal dysphagia after unilateral hemispheric stroke[END_REF][START_REF] Pfeiffer | Gastrointestinal function in Parkinson's disease[END_REF] Objective studies of swallowing in PD have shown an even higher frequency of swallowing abnormalities than subjective survey studies. Several investigators have reported abnormalities on modified barium swallow test in 75 to 97% of PD patients tested. [START_REF] Logemann | Editorial: dysphagia in parkinsonism[END_REF][START_REF] Stroudley | Radiological assessment of dysphagia in Parkinson's disease[END_REF][START_REF] Bird | Asymptomatic swallowing disorders in elderly patients with Parkinson's disease: a description of findings on clinical examination and videofluoroscopy in sixteen patients[END_REF] Although any one phase of swallowing can be involved, dysphagia due to incomplete relaxation and defective opening of the upper esophageal sphincter (UES) is a frequent abnormality in these patients. [START_REF] Pfeiffer | Gastrointestinal function in Parkinson's disease[END_REF][START_REF] Schenider | Treatment of dysfunction of the cricopharyngeal muscle with botulinum A toxin: introduction of a new, noninvasive method[END_REF][START_REF] Haapaniemi | Botulinum toxin in the treatment of cricopharyngeal dysphagia. Review of the use of botulinum in treating proximal dysphagia[END_REF][START_REF] Ahsan | Botulinum toxin injection of the cricopharyngeus muscle for the treatment of dysphagia[END_REF][START_REF] Blitzer | Botulinum Toxin: Basic Science and Clinical Uses in Otolaryngology[END_REF][START_REF] Restivo | Botulinum toxin for cricopharyngeal dysfunction in Parkinson's disease[END_REF][START_REF] Merlo | Not paralysis, but dystonia causes stridor in multiple system atrophy[END_REF][START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF] UES opening is a complex interaction between neural control and biomechanical events related to adjacent structures. Patients with UES dysfunction have difficulty passing the bolus into the esophagus. This results in hypopharyngeal retention with consequent aspiration of food or liquid into the airways. [START_REF] Cichero | Applied Anatomy and physiology of the normal swallow[END_REF] The use of botulinum toxin (BTX) has recently been expanding to encompass neurogenic dysphagia. Although no data from blinded randomized trials are available on the effect of BTX, several case series studies have shown the efficacy of BTX injection into the cricopharyngeal (CP) muscle (the main component of the UES), but yet some patients do not respond to BTX treatment, [START_REF] Schenider | Treatment of dysfunction of the cricopharyngeal muscle with botulinum A toxin: introduction of a new, noninvasive method[END_REF][START_REF] Haapaniemi | Botulinum toxin in the treatment of cricopharyngeal dysphagia. Review of the use of botulinum in treating proximal dysphagia[END_REF][START_REF] Ahsan | Botulinum toxin injection of the cricopharyngeus muscle for the treatment of dysphagia[END_REF][START_REF] Blitzer | Botulinum Toxin: Basic Science and Clinical Uses in Otolaryngology[END_REF] and reliable markers predicting BTX treatment response are lacking.

At present, videofluoroscopic swallowing study or fiberoptic endoscopic evaluation of swallowing are the mainstay of the diagnosis and clinical assessment of dysphagia. They can evaluate the anatomy and physiology of the swallowing process, assess swallowing safety, identify patterns of impaired swallowing and their consequences, confirm the patient's symptoms, and assess the efficacy of compensatory manoeuvres, or rehabilitation procedures. However, neither videofluoroscopy nor endoscopy can provide information about the pathophysiological process underlying the observed abnormality of the CP muscle. They cannot distinguish between insufficient opening from inadequate relaxation due to altered neurophysiologic control of the muscle tone, and that from stenosing fibrosis, or from other organic cause, when there is no abnormality of the lumen outline.

Electrophysiological investigations of oropharyngeal swallowing can detect CP muscle abnormalities during swallowing; they can characterize the dysfunction of CP muscle relaxation, as well as other abnormalities of the propulsive oral phase, of the interval between the oral and the pharyngeal phases, and of the duration of the pharyngeal phase of swallowing. [START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF][START_REF] Ertekin | An electrophysiological investigation of deglutition in man[END_REF] In this study of patients with clinical dysphagia, and incomplete relaxation with defective opening of the UES our aims were: 1) to assess the efficacy of BTX injection into the CP muscle when absence of its inhibitory pause is observed on electromyography (EMG); and 2) to find out if our electrophysiological investigation could predict the efficacy of BTX, and discriminate responders from non-responders to the treatment, based on the association of CP dysfunction with other electrophysiological abnormalities of the oropharyngeal phase of swallowing.

MATERIAL AND METHODS

Population

The main characteristics of our patients are summarized in table 1. We studied 34 patients with clinical dysphagia, and incomplete relaxation and defective opening of the UES confirmed by EMG evaluation. None of our patients had a Zenker's diverticulum at the endoscopic investigation of the pharyngeal and esophageal tracts.

Patients with PD were all examined during the "on" phase of the levodopa response cycle. We decided to study PD patients in the "on" phase because we wanted to assess the entity of swallowing problems in the real life context. These patients were advised to take their L-dopa therapy in a way to provide maximum protection during meal time, as L-dopa should reduce oral and pharyngeal swallowing impairment as well as enhance upper extremities function.

Patients with stroke were examined between 12 and 17 months after onset of disease, when all stroke symptoms had stabilized.

Dysphagia severity was assessed based on the patient's subjective complaint or problem and quantified with a simple rating scale, the dysphagia severity score (DSS). [START_REF] Merlo | Not paralysis, but dystonia causes stridor in multiple system atrophy[END_REF][START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF] Briefly, DSS is graded as follows: 0 (absence of dysphagia), when there are not subjective difficulties in the swallowing of liquids or solids; 1 (mild to moderate dysphagia), when the patient experiences a feeling of something getting stuck while swallowing, or has to cough during or after swallowing, or has to cut food finely and to avoid certain difficult-to-particulate foods, or has to swallow liquids in small sips; 2 (severe dysphagia), when serious nutritional problems are present with need of a feeding tube. The main advantages of this scale reside in its utility in the clinical assessment of the level of swallowing safety, and in the fact that its 3 well separated levels make it highly specific for detecting changes after interventions. We considered as responders those patients in whom a reduction of at least 1 degree in DSS was observed.

Electrophysiological studies

The method applied was described previously. [START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF][START_REF] Ertekin | An electrophysiological investigation of deglutition in man[END_REF] For the investigation, an electromyograph Keypoint Medtronic (Skovlunde, Denmark) was used. Simultaneous electrokinesiographic recording from 3 channels was performed (fig. 1). The first channel recorded the EMG activity of suprahyoid/submental muscles (a muscle complex consisting of the mylohyoid, the genioglossus, and the ventral belly of the digastric) using two surface electrodes applied to the skin over the suprahyoid region at an interelectrode distance of 30 mm. This activity marks the beginning of the propulsive action of the tongue in the oral phase of swallowing and continues throughout the pharyngeal phase of swallowing. [START_REF] Logemann | Evaluation and treatment of swallowing disorders[END_REF] The second channel recorded the EMG activity of the CP muscle using a coaxial needle-electrode inserted through the skin at the level of the cricoid cartilage, 1.5 cm posterior to its palpable lateral border, in the posteromedial direction. At rest, this muscle shows tonic activity related to its function as a muscular sphincter, since it is a major contributor to the functional area known as the upper esophageal sphincter (UES); such EMG activity disappears completely (inhibitory pause), for a brief time, during the hypopharyngeal phase of swallowing.

Opening of the UES was defined as the EMG inhibitory pause of CP muscle when the EMG signal amplitude was below 50 µV.

EMG signals from both, first and second channels were bandpass filtered between 100 Hz and 2 kHz and then rectified. The third channel recorded the mechanogram obtained from a piezoelectric transducer detecting the deformations produced by pharyngolaryngeal structures during the pharyngeal phase of swallowing. In particular, the transducer marks the time of elevationretroflection, and return to the rest position of the epiglottis. This transducer consisted of a rectangular strip with a triangular rubber button in the centre of the strip applied to the skin over the cricothyroid membrane, and kept in place by adhesive tape wrapped around the neck. It showed a linear force-to-signal ratio for forces ranging from 0.1 to 300 g; its signals were bandpass filtered between 0.01 and 30 Hz. For each channel the signal sampling rate was 20 kHz.

Each patient was examined while seated with the head in a natural position, and had to swallow a small volume of water (3 ml) introduced into his/her mouth with a disposable syringe without needle.

We analysed the following electrophysiological measures: Signals were triggered when signal amplitude of suprahyoid/submental muscle EMG activity was equal to or greater than 50 μV. Recordings obtained from ten successive swallowing acts were stored and the average value of each electrophysiological measure was evaluated.

Since all patients initially presented with absence of CP muscle inhibition, they all received a BTX injection into the CP muscle. This procedure was carried out while monitoring the EMG activity of the muscle using a needle electrode-cannula with the characteristics of a monopolar electrode. This electrode was inserted in the neck at the level of the cricoid cartilage in the same way described above; a surface electrode (reference electrode) was applied ipsilaterally over the middle line of the clavicle. In each patient 15 units of BTX (BOTOX®, Allergan), diluted 5.0 units/0.1ml, were injected into the CP muscle of one side (stroke patients received the injection on the paretic side).

We performed unilateral injection because injecting bilaterally could have increased the risk of aspiration. In fact, not only is BTX effecting CP muscle relaxation during the hypo-pharyngeal phase of swallowing. BTX is also reducing CP muscle resting tone. The loss of CP muscle sphincterial function would increase the risk of food reflux from the oesophagus, with consequent post-deglutition aspiration into the airways.Furthermore, we chose the unilateral injection because the treatment with BTX into the CP muscle exposes to objective risks of contamination of nearby muscles involved in laryngeal and vocal cord motility. Diffusion of the toxin to such muscles could paralyse them and bilateral injection could lead to greater severity of the side-effects due to the diffusion of the drug, with serious consequences for the patient.

In each patient, both clinical and electrophysiological evaluations were repeated 2 months after treatment. Clinical and electrophysiological procedures at baseline and after BTX treatment were performed in a blind manner by two different investigators, one performing the clinical assessments while the other the electrophysiological studies; the two-month assessments were performed without knowledge of preceding BTX injection.

Statistical analyses

Analyses were performed using Stata version 10 (Stata Corp, College Station, Tex).

Student's t-test, Mann-Whitney U-test, or Fisher exact test was used to compare the clinical, electrophysiological, and demographic differences between responders and non-responders. To compare DSS before and after treatment, we used extended McNemar test. For all analyses, the significance level was set at p = 0.05. Electrophysiological measures were compared at baseline, and cut-off levels for each measure were identified on the graphical analysis (they represent the extreme non-outlier points in the box plots) in order to establish "warning values" that could be used to predict responders or non-responders to BTX treatment. Using the presence of a 'warning value' as a diagnostic test, able to detect the nonresponse to the BTX, we calculated the positive predictive value (PPV), that is the probability for a subject to be a non-responder given that he is test-positive, i.e. he has a 'warning value' at baseline.

In the same way, we calculated the negative predictive value (NPV), that is the probability for a subject to be a responder given that he is test-negative, i.e. he does not have a 'warning value' at baseline.

Ethics

The research protocol was approved by the Ethics Committee of our Institute. All patients gave written informed consent to all the procedures of the study.

RESULTS

Patients' characteristics and changes in DSS after BTX treatment are summarized in table 1.

Responder and non-responder patients were homogeneous in relation to age, gender, and DSS (table 2).

Following the electrophysiological procedures used and the dose of BTX injected into the CP muscle, we did not observe any worsening of dysphagia or any other side effects, like vocal cord dysfunction, in any of our patients, neither did any patient complain of other problems.

Two months after BTX treatment, 50% of patients had a significant improvement of dysphagia (lower DSS, p<0.001) (table 2). In these patients, the electrophysiological study showed the normal pause of the EMG activity of the CP muscle (fig. 1). None of the responders with severe dysphagia (DSS: 2) became symptom-free ( DSS: 0). Eleven patients showed a DSS improvement from1 to 0, and 6 patients from 2 to 1. On the other hand, the remaining 50% of patients did not show any significant change in dysphagia severity (table 2). In 13 of these patients the electrophysiological study showed a pause of the EMG activity of the CP muscle, whereas in the other 4 patients the absence of EMG pause of the CP muscle persisted as before treatment.

Table 3 summarises the median values and interquartile ranges of the electrophysiological measures at baseline and two months after BTX treatment. Since all our patients presented with complete absence of CP muscle inhibition, we did not have any CPEMG-ID value at baseline. After treatment, we observed recovery of this measure in both groups; although we obtained a larger increase for responders than for non-responders, the median CPEMG-ID was not significantly different between the two groups (p = 0.105).

The SHEMG-D at baseline was significantly longer in the non-responder than in the responder group (p = 0.005); the same trend was present after treatment and the difference between the responder and the non-responder group was statistically relevant (p = 0.04).

The median LPM-D at baseline was similar in both groups (p = 0.480) but after treatment a sharper median decrease was observed in the responders compared to the non-responders (p<0.001).

The median value of I-SHEMG-LPM was significantly higher in the non-responder group, both at baseline (p<0.001) and after treatment (p<0.001).

The descriptive analysis of the electrophysiological measures at baseline showed significant differences between the responders and the non-responders for two measures: SHEMG-D and I-SHEMG-LPM. The graphical analysis of the distribution of SHEMG-D and I-SHEMG-LPM at baseline highlighted the following 'warning values': less than 1,000 ms and more than 1,680 ms for SHEMG-D; and more than 300 ms for I-SHEMG-LPM (fig. 2).

We observed that the frequency of patients with 'warning values' at baseline for both measures, SHEMG-D and I-SHEMG-LPM, was significantly higher in the non-responders than in the responders (88.2% and 64.7% vs. 0% and 5.9%, p<0.001). The same result was observed after treatment: the frequency of patients with 'warning values' for both measures, SHEMG-D and I-SHEMG-LPM, was significantly higher in the non-responders than in the responders (82.4% and 70.6% vs.5.9% and 5.9%, p<0.001).

The PPV for SHEMG-D was 100.0%; the PPV for I-SHEMG-LPM was 91.7%; the PPV for SHEMG-D plus I-SHEMG-LPM was 94.1%. The NPV for SHEMG-D was 89.5%, the NPV for I-SHEMG-LPM was 72.7%; the NPV for SHEMG-D plus I-SHEMG-LPM was 94.1%.

DISCUSSION

In this study we examined the efficacy of BTX treatment in patients with symptomatic dysphagia when absence of CP muscle relaxation was present alone or in association with other abnormalities of oropharyngeal swallowing.

The CP muscle is a major contributor to the functional area known as UES. Adequacy of UES opening depends on the degree of preservation of the pharyngeal swallowing response and on hyolaryngeal traction. [START_REF] Sivarao | Functional anatomy and physiology of the upper esophageal sphincter[END_REF][START_REF] Mu | The innervation of the human upper esophageal sphincter[END_REF][START_REF] Mu | Neuromuscular organization of the human upper esophageal sphincter[END_REF] An optimal assessment of failed CP muscle relaxation is obtained applying an electrophysiological method in which needle-EMG recording of this muscle is carried out during rest and swallowing. [START_REF] Merlo | Not paralysis, but dystonia causes stridor in multiple system atrophy[END_REF][START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF][START_REF] Ertekin | An electrophysiological investigation of deglutition in man[END_REF] All patients submitted to BTX treatment in our study showed absence of the EMG pause of the CP muscle during the hypopharyngeal phase of swallowing. However, our electrophysiological method revealed, in several patients, other abnormalities such as prolonged or reduced SHEMG-D, prolonged LPM-D, and increased I-SHEMG-LPM. Fifty percent of our patients were responders; in these patients CP-ID absence was observed alone or together with prolonged LPM-D. In our nonresponder patients (the remaining 50%), besides CP-ID absence, we observed SHEMG-D values exceeding, in most cases, both lower and upper limits of the responders, and I-SHEMG-LPM values exceeding, in most cases, the upper limits of the responders.

BTX treatment was able to completely restore swallowing function in responders with mild to moderate dysphagia, but not in those with severe dysphagia, who only improved to the mild/moderate degree on the DSS. A too low dose of BTX or the unilateral injection may explain our results. However, since the CP muscle spreads posteromedially to join the controlateral muscle, even a unilateral injection should give a good response.

Since our study included only a limited number of patients for each neurological disease, we cannot attempt to provide predictive data based on disease entity or duration. On the other hand, in a previous report of parkinsonian syndromes we observed that I-SHEMG-LPM prolongation is typical of PD dysphagia, and CP-ID absence characterizes most of MSA-P and PSP patients. [START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF] These observations have been confirmed in the present study; in fact, all MSA-P patients, 6 out of 9 PSP patients, but only 2 out of 7 PD patients responded to BTX (table 2). This suggests that CP hyperactivity is the main finding of dysphagia in both MSA-P and PSP, whereas it is often associated with other abnormalities in PD dysphagia.

When the only abnormality is the absence of CP muscle relaxation, BTX treatment is likely to be effective for dysphagia. This suggests that the success of this treatment has a high degree of probability when swallowing abnormalities are due exclusively to a dysfunction of the neural mechanisms influencing changes in neurogenic tone of the CP muscle during swallowing, as observed in lesions involving some specific inhibitory activities of the 'central swallowing pattern generator' of the brainstem. [START_REF] Sivarao | Functional anatomy and physiology of the upper esophageal sphincter[END_REF][START_REF] Cook | Opening mechanism of the human upper esophageal sphincter[END_REF][START_REF] Kahrilas | Upper esophageal sphincter function during deglutition[END_REF] In our study, LPM-D prolongation did not appear to have significant effect on the efficacy of BTX treatment. This measure includes both the infrahyoid-submental muscle activity which pulls up and holds up the larynx, and the passive forces which pull the larynx down; the latter are due to the viscous-elastic properties of the laryngopharyngeal structures and to gravitational forces. [START_REF] Cichero | Applied Anatomy and physiology of the normal swallow[END_REF][START_REF] Williams | Space-time pressure structure of pharyngoesophageal segment during swallowing[END_REF][START_REF] Bass | The Neurology of swallowing[END_REF] Therefore, LPM-D also depends on physical and anatomical characteristics of the subject examined.

The persisting contraction of the CP muscle during the hypopharyngeal phase of swallowing represents an obstacle to the smoothness of the laryngopharyngeal excursion, and it increases its duration (LPM-D). In the responders, BTX treatment led to a significant reduction of LPM-D.

The results of our study indicate that both abnormal reduction and increase of SHEMG-D are associated with inefficacy of BTX treatment. The EMG activity of the suprahyoid/ submental muscles indicates the propulsive action of the tongue and the pharyngeal phase of swallowing, including the elevation of the epiglottis. [START_REF] Logemann | Evaluation and treatment of swallowing disorders[END_REF][START_REF] Vaiman | Evaluation of normal deglutition with the help of rectified surface electromyography records[END_REF] In particular, the suprahyoid/ submental muscle group are considered to be the most important factor responsible for elevating the larynx. [START_REF] Cichero | Applied Anatomy and physiology of the normal swallow[END_REF][START_REF] Vaiman | Evaluation of normal deglutition with the help of rectified surface electromyography records[END_REF] The abnormal reduction of SHEMG-D reflects an insufficient activation of the suprahyoid/ submental muscles during the propulsive oral phase and the pharyngeal phase. This abnormality can be associated to hypokinesia of the oropharyngeal phase in parkinsonian syndromes, [START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF] or to a deficit of the oropharyngeal phase in other disorders of the Peripheral and Central Nervous Systems. A poor activation of suprahyoid/ submental muscles may fail to trigger the normal pharyngeal phase of deglutition. [START_REF] Cichero | Applied Anatomy and physiology of the normal swallow[END_REF][START_REF] Logemann | Evaluation and treatment of swallowing disorders[END_REF][START_REF] Vaiman | Evaluation of normal deglutition with the help of rectified surface electromyography records[END_REF] SHEMG-D prolongation can be due to either bradikinetic mechanisms, as observed in parkinsonian syndromes, [START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF] or to incoordination in the activity of pulling up the larynx, as observed in brainstem or cerebellar lesions. [START_REF] Abraham | Laryngopharyngeal dysmotility in multiple sclerosis[END_REF][START_REF] Crary | Surface Electromyographic characteristic of swallowing in dysphagia secondary to brainstem stroke[END_REF] SHEMG-D prolongation may represent a compensatory phenomenon which intervenes when the 'phasic activity' of these muscles, which is necessary to efficiently pull up the laryngopharyngeal structures, is missing. In other words, the deficit of force of the suprahyoid/ submental muscles for triggering the swallow reflex tends to be corrected by a prolonged activity of these muscles.

We found that also I-SHEMG-LPM prolongation was associated with inefficacy of BTX treatment. I-SHEMG-LPM indicates the transition between the oral and the pharyngeal stages of swallowing; it is also called the 'pharyngeal delay time'. [START_REF] Kim | Temporal measurements of pharyngeal swallowing in normal populations[END_REF] I-SHEMG-LPM prolongation can be observed in different neurological disorders, such as parkinsonian syndromes, [START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF] multiple sclerosis, [START_REF] Abraham | Laryngopharyngeal dysmotility in multiple sclerosis[END_REF] and stroke. [START_REF] Bass | The Neurology of swallowing[END_REF][START_REF] Crary | Surface Electromyographic characteristic of swallowing in dysphagia secondary to brainstem stroke[END_REF] Several mechanisms can increase I-SHEMG-LPM. An inappropriate planning of the voluntary swallowing activity related to a dysfunction of the cortical-subcortical loops connecting the basal ganglia to the premotor and supplementary motor areas of the frontal cortex, as found in parkinsonian syndromes; [START_REF] Alfonsi | Electrophysiologic patterns of oral-pharyngeal swallowing in parkinsonian syndromes[END_REF] a dysfunction of the brainstem interneurons involved in the programming and coordination of the swallowing sequence, as observed in disorders like stroke, and multiple sclerosis; [START_REF] Bass | The Neurology of swallowing[END_REF][START_REF] Abraham | Laryngopharyngeal dysmotility in multiple sclerosis[END_REF][START_REF] Crary | Surface Electromyographic characteristic of swallowing in dysphagia secondary to brainstem stroke[END_REF] or a cerebellar dysfunction, with disruption of accuracy of movement and harmonious actions, both leading to a dysfunction of time-related neural control. [START_REF] Schmahmann | Disorders of the cerebellum: ataxia, dysmetria of thought, and the cerebellar cognitive affective syndrome[END_REF] I-SHEMG-LPM prolongation, can in itself be responsible for dysphagia. In particular, it has been linked to aspiration, which is the entry of food or liquid into the airways below the level of the true vocal cords. [START_REF] Bass | The Neurology of swallowing[END_REF][START_REF] Kim | Temporal measurements of pharyngeal swallowing in normal populations[END_REF][START_REF] Abraham | Laryngopharyngeal dysmotility in multiple sclerosis[END_REF] In conclusion, our study indicates that the electrophysiological evaluation of oropharyngeal swallowing can recognize swallowing abnormalities which may interfere with the outcome of the therapeutic approach to dysphagia with BTX treatment. Electrophysiological evidence of isolated CP hyperactivity predicts good response to BTX. In this case the treatment can be appropriately used, when expected to be successful, saving on cost and patients' expectations.

A preliminary evaluation of oropharyngeal swallowing, applying this electrophysiological method, can be a useful screening tool for choosing strategies for treatment of dysphagia.

In the future we will need to verify if higher doses of BTX or bilateral injection can make patients with severe dysphagia due to CP hyperactivity symptom-free.

1 )

 1 duration of EMG activity of suprahyoid/submental muscles (SHEMG-D); 2) duration of the laryngopharyngeal mechanogram (LPM-D); 3) duration of the inhibition of the cricopharyngeal muscle EMG activity (CPEMG-ID); and 4) interval between onset of EMG activity of suprahyoid/submental muscles and onset of laryngopharyngeal mechanogram (I-SHEMG-LPM).

Figure legend : Figure 1 -

 :1 Figure legend:

Figure 2 -

 2 Figure 2-Box-plots of baseline measures I-SHEMG-LMP (a) and SHEMG-D (b). The "warning

Table 3

 3 Quantitative evaluations of electrophysiological measures at baseline and 2 months after Botulinum Toxin (BTX) injection *P value was obtained by Mann-Whitney U-test †(IQR) = interquartile range ‡ ↑ = median increase §↓ = variation after treatment, median ↑380 ↑195

The authors have no financial or others relationships that might lead to a conflict of interest.

ACKNOWLEDGMENTS

We would like to thank our Clinical Neurophysiology technicians Alessandra Montini and Daniele Marchese for their professional assistance and enthusiastic commitment.

ABSTRACT

Objectives: Botulinum toxin (BTX) injection into the cricopharyngeal (CP) muscle has been proposed for the treatment of neurogenic dysphagia due to CP hyperactivity. We aimed to find out whether an electrophysiological method exploring oropharyngeal swallowing could guide treatment and discriminate responders from non-responders, based on the association of CP dysfunction with other electrophysiological abnormalities of swallowing. Conclusions: Our electrophysiological method can recognize swallowing abnormalities which may affect the outcome of the therapeutic approach to dysphagia with BTX treatment.

Methods