Christelle Kounchou

Marie-Pierre Pierre Bonnet

Anomalies d'insertion placentaire : prise en charge anesthésique

Keywords: placenta accreta, placenta percreta, accouchement, hémorragie de la délivrance placenta accreta, placenta percreta, obstetric haemorrhage

L'invasion anormale du placenta dans la paroi utérine caractérise le placenta acrreta qui expose à un risque d'hémorragie de la délivrance. La prise en charge des parturientes doit être planifiée avant l'accouchement en particulier en ce qui concerne la transfusion et la mise à disposition de produits dérivés du sang. Les patientes délivrées par césariennes ont le plus souvent une anesthésie générale. La transfusion peropératoire comporte du sang autologue et homologue et fait l'objet d'un monitorage biologique et hémodynamique. L'anticipation est la clé de la réduction du risque vital lié à cette situation.

Summary : Morbidly adherent implantation of the placenta in the uterine wall defines the placenta accreta which conveys a high risk of obstetrical haemorrhage. Planning of patient' care before delivery, is the cornerstone of the management of parturient due to the risk of massive haemorrhage. Pre operatively, the availability of transfusion products has to be checked. Peroperatively, C-section is usually performed under general anaesthesia. In case of massive haemorrhage, transfusion uses autologous and homologous blood, and needs biological and haemodynamic monitoring, and prevention of hypothermia and biological disorders. Anticipation is the key to success in preventing the risk of death in this setting.

Mots clés :

atteinte, et parfois les organes adjacents envahis, notamment la vessie [START_REF] Bonnet | Placenta Accreta Spectrum[END_REF] . Cet envahissement du myomètre par le placenta empêche la délivrance placentaire normale, et peut conduire à une hémorragie du postpartum massive aux conséquences potentiellement très sévères pour la mère. L'incidence du placenta accreta a augmenté ces 20 dernières années, directement en rapport avec l'augmentation de la réalisation de césariennes au cours du temps, pour atteindre 1,7 pour 10.000 grossesses [START_REF] Fitzpatrick | The management and outcomes of placenta accreta, increta, and percreta in the UK : a population-based descriptive study[END_REF] . En effet, un antécédent de césarienne constitue le principal facteur de risque de placenta accreta, et ce risque augmente avec le nombre de césariennes antérieures [START_REF] Bowman | Risk factors for placenta accreta : a large prospective cohort[END_REF] : L'association placenta praevia antérieur et utérus cicatriciel est la situation la plus à risque de placenta accreta [START_REF] Bowman | Risk factors for placenta accreta : a large prospective cohort[END_REF] . La présence d'un placenta accreta constitue une cause majeure de morbidité maternelle sévère, principalement par hémorragie et qui parfois met en jeu le pronostic vital de la mère. Le placenta accreta est l'indication la plus fréquente d'hystérectomie hémostase, notamment en France. Les autres complications décrites sont les coagulopathies, les infections, des défaillances multiviscérales et l'atteinte des organes adjacents en cas de placenta percreta.

La prise en charge des parturientes ayant une anomalie d'insertion du placenta est un problème pour tous les soignants en charge de ce type de patientes et notamment pour l'équipe d'anesthésie-réanimation, d'autant plus qu'il n'existe pas de consensus du fait de la rareté des données disponibles.

PROCÉDURE ORGANISATIONNELLE EN CAS DE SUSPICION DE PLACENTA ACCRETA : UNE PRISE EN CHARGE MULTIDISCIPLINAIRE, PLANIFIÉE ET SPÉCIALISÉE

La prise en charge des femmes ayant une suspicion de placenta accreta, et donc à haut risque d'hémorragie obstétricale massive, est avant tout multidisciplinaire, impliquant les gynécologues-obstétriciens, les anesthésistes-réanimateurs, les radiologues, les pédiatres néonatologistes et les intervenants au niveau du centre transfusionnel. La maternité de prise en charge doit être située à proximité d'unités de soins intensifs maternels et néonataux et d'un plateau technique permettant de réaliser de la radiologie interventionnelle ou de la chirurgie vasculaire, une transfusion massive et des bilans biologiques nombreux et répétés. Les équipes de chaque spécialité doivent être expérimentées dans la prise en charge de cette pathologie [START_REF] Silver | Center of excellence for placenta accreta[END_REF] . Idéalement, une réunion multidisciplinaire pré-partum avec tous les acteurs précédemment cités est recommandée, dont l'objectif est la mise en place d'une stratégie globale de prise en charge. Par ailleurs, en cas de changement de stratégie, tous les intervenants doivent en être informés le plus tôt possible.

La disponibilité des différents intervenants le jour de l'intervention programmée doit être vérifiée en amont. L'utilisation d'un protocole spécifique pour la prise en charge des suspicions de placenta accreta, écrit et validé par les équipes de manière multidisciplinaire et connu de tous, permet d'optimiser et de coordonner les différents intervenants. Il est reconnu que ces protocoles épargnent du temps précieux et accélèrent la prise en charge, évitent les omissions, le stress et les conflits, et apportent un support pour un travail en équipe multidisciplinaire, simultané, coordonné et efficace [START_REF] Hilton | Checklists and multidisciplinary team performance during simulated obstetric hemorrhage[END_REF] . Ainsi plusieurs études ont mis en évidence une amélioration du pronostic maternel en cas de prise en charge dans un centre spécialisé [START_REF] Silver | Center of excellence for placenta accreta[END_REF] , avec notamment une diminution de la fréquence de la transfusion massive, et de reprise chirurgicale dans les 7 jours suivant la naissance pour complications hémorragiques [START_REF] Eller | Maternal morbidity in cases of placenta accreta managed by a multidisciplinary care team compared with standard obstetric care[END_REF] . Par ailleurs, la prise en charge dans un centre spécialisé augmente également la proportion de placenta accreta diagnostiqués en ante natal [START_REF] Silver | Center of excellence for placenta accreta[END_REF] .

L'équipe d'anesthésie en obstétrique de Standford a ainsi rapporté récemment son expérience fondée sur la mise en place depuis 2009 d'un programme multidisciplinaire de prise en charge (Standford Program in placental disorders), dont l'objectif est de diminuer les complications maternelles et néonatales liées aux hémorragies obstétricales massives grâce à une approche coordonnée des soins. Ce programme comportait l'utilisation d'une check-list spécifique à la prise en charge des femmes avec une suspicion ante partum de placenta accreta. Un des volets de ce programme est spécifiquement dédié à la prise en charge anesthésique et de réanimation, avec une subdivision de cette prise en charge en 3 temps : pré, per, et postopératoire [START_REF] Panigrahi | A Standardized Approach for Transfusion Medicine Support in Patients With Morbidly Adherent Placenta[END_REF] .

SUSPICION DE PLACENTA ACCRETA : PRISE EN CHARGE D'ANESTHÉSIE-RÉANIMATION EN ANTEPARTUM

En cas de suspicion ante-partum de placenta accreta, la stratégie de prise en charge anesthésique doit être clairement planifiée en préopératoire.

La consultation d'anesthésie doit être réalisée précocement, dès que le diagnostic de placenta accreta est évoqué. Au cours de cette consultation, l'évaluation préopératoire comportera en particulier la recherche d'éléments au sein de l'interrogatoire faisant suspecter un risque hémorragique important et un risque de lésion d'organes adjacents. Si l'équipe d'anesthésie juge que les conditions locales de la structure de soins ne sont pas adaptées à la prise en charge de la patiente en toute sécurité, un transfert doit être envisagé. La facilité d'accès veineux périphériques multiples pour la pose de cathéter courts de gros calibre et la possibilité de pose d'un cathéter veineux central en jugulaire ou en sous clavier, doivent être évalués en consultation. En dehors des éléments habituels de la consultation d'anesthésie, le bilan préopératoire comprend une numération formule sanguine, pour identifier en particulier une anémie ou une thrombopénie préopératoire, des tests d'hémostase (TP, TCA, fibrinogénémie). La présence d'une carte de groupe sanguin valide et de RAI à jour en permanence est également vérifiée. L'information de la patiente en consultation d'anesthésie est primordiale : il s'agit de lui indiquer quelle technique d'anesthésie a été choisie et quels en sont les risques maternels et néonataux et de l'informer également du risque de conversion en anesthésie générale en cas d'anesthésie péri-médullaire si elle est préconisée en première intention. Enfin compte tenu du risque de saignement massif et de transfusion, ainsi que de la possibilité de complications sévères et d'admission en réanimation, ces éléments doivent être portés à la connaissance de la parturiente. A l'issue de la consultation d'anesthésie, la prise en charge de la patiente est discutée collégialement par l'ensemble des membres de l'équipe d'anesthésie.

La prise en charge au bloc doit être anticipée collectivement: la salle d'opération dédiée doit être suffisamment spacieuse et équipée, les produits sanguins labiles sont mis en réserve, l'équipement jugé nécessaire le jour de l'intervention est préparé et installé : cathéters central veineux et artériel, dispositif accélérateur et réchauffeur de perfusion pour l'administration de produits sanguins labiles, systèmes de récupération de sang (cell-saver). Les ressources humaines disponibles le jour de l'intervention sont également vérifiées : il est nécessaire que les praticiens en charge de ces femmes aient une bonne expérience du milieu obstétrical et soient assistés par des infirmiers anesthésistes en effectif suffisant. La stratégie d'anesthésie diffère selon que la césarienne est programmée ou en urgence.

SUSPICION DE PLACENTA ACCRETA : PRISE EN CHARGE EN ANESTHÉSIE-RÉANIMATION EN PEROPÉRATOIRE

Au-delà des considérations habituelles concernant les césariennes, plusieurs mesures sont nécessaires à fin d'optimiser la prise en charge de ces patientes. L'utilisation d'une check-list spécifique à la césarienne pour suspicion de placenta accreta est très utile dans ce contexte [START_REF] Panigrahi | A Standardized Approach for Transfusion Medicine Support in Patients With Morbidly Adherent Placenta[END_REF] .

La communication entre les équipes chirurgicale, anesthésique et transfusionnelle essentielle au long de la prise en charge peropératoire. La prise en charge anesthésique au bloc opératoire débute par la mise en place de voies veineuses de gros calibre et en nombre suffisant pour faciliter l'administration d'un remplissage vasculaire et d'une transfusion rapide. En cas d'abord veineux périphérique difficile, une voie veineuse centrale est mise en place. Un monitorage invasif de la pression artérielle est également instauré pour permettre à la fois une surveillance continue de la stabilité hémodynamique de la patiente et des prélèvements biologiques itératifs. Le jour de l'intervention, si l'organisation des soins le permet, on peut idéalement rapprocher les produits sanguins labiles comptabilisés de la patiente, notamment grâce à l'utilisation de thermo boutons.

CHOIX DE LA TECHNIQUE D'ANESTHÉSIE

La technique d'anesthésie à privilégier pour les césariennes, dans un contexte d'anomalies d'insertion placentaire, fait l'objet de controverses. Si la technique anesthésique de choix pour la césarienne classique est l'anesthésie péri-médullaire (APM), l'anesthésie générale (AG) a été initialement préférée en cas de suspicion de placenta accreta [START_REF] Weiniger | Anaesthetic management of placenta accreta : use of a pre-operative high and low suspicion classification[END_REF][START_REF] Wise | Strategies to manage major obstetric haemorrhage[END_REF] . Dans une série française rétrospective de 100 femmes accouchant par césarienne pour placenta accreta entre 2010 et 2016, 46 patientes avaient eu une AG d'emblée, 31 une APM secondairement convertie en AG, et 23 une APM seule (Kountchou-Tiofack Christelle, thèse de doctorat de médecine : Morbidité après placenta accreta : évaluation des différentes stratégies de prise en charge : une étude rétrospective multicentrique, Université de Reims Champagne-Ardenne, 2017). De même en 2015, une enquête sur les pratiques anesthésiques menées dans toutes les maternités d'Israël, avait montré qu'une AG était choisie par 96% des équipes en cas de forte suspicion de placenta accreta, et par 23,1% des équipes en cas de faible suspicion [START_REF] Ioscovich | Israeli survey of anesthesia practice related to placenta previa and accreta[END_REF] . L'étude rétrospective mono-centrique de Taylor et coll. publiée au Royaume-Uni en 2017 et portant sur 40 femmes opérées de césariennes pour placenta accreta/percreta, rapporte que, si 95% des interventions étaient débutées sous rachipéridurale combinée (RPC), une conversion en AG était pratiquée dans 45% des cas, dont la moitié avant la naissance [START_REF] Taylor | Anaesthesia for abnormally invasive placenta : a singleinstitution case series[END_REF] . Les motifs de conversion étaient divers : inconfort, instabilité hémodynamique, durée de l'intervention. Effectivement, l'AG a un retentissement hémodynamique moindre par rapport à l'APM, qui s'accompagne d'un bloc sympathique avec un risque d'hypotension artérielle prolongée. Par ailleurs, l'AG permet de contrôler les voies aériennes et facilite la réanimation dans le contexte du choc hémorragique. En cas d'AG une induction séquence rapide reste la référence chez la femme enceinte. L'entretien de l'anesthésie par AIVOC propofol/rémifentanil présente l'avantage d'éviter une atonie utérine associée à l'utilisation d'halogénés et l'imprégnation morphinique prolongée du nouveau-né à la naissance. Un monitorage de la profondeur d'anesthésie permet de diminuer le risque de mémorisation peropératoire et d'adapter l'anesthésie à ce qui est requis, notamment en cas de problème hémodynamique.

Cependant, plusieurs études de petite taille et monocentriques ont rapporté l'utilisation avec succès d'APM seule, notamment en cas de césarienne avec hystérectomie d'hémostase dans le même temps [START_REF] Lilker | Anesthetic considerations for placenta accreta[END_REF][START_REF] Nguyen-Lu | Mode of anesthesia and clinical outcomes of patients undergoing Cesarean delivery for invasive placentation : a retrospective cohort study of 50 consecutive cases[END_REF] . L'APM présente comme avantages par rapport à l'AG d'éviter le passage transplacentaire des agents anesthésiques et de procurer une analgésie postopératoire de meilleure qualité grâce à la mise en place d'un cathéter péridural. La technique préconisée dans ce contexte est la rachi-péridurale combinée. Dans une étude monocentrique rétrospective récente, Markley et coll. ont comparé le devenir des femmes dans le contexte de la césarienne programmée pour placenta praevia et suspicion d'AIP, en fonction du type d'anesthésie réalisé [START_REF] Markley | Neuraxial Anesthesia During Cesarean Delivery for Placenta Previa With Suspected Morbidly Adherent Placenta : A Retrospective Analysis[END_REF] . Les auteurs ont mis en évidence que la technique d'APM était réalisée d'emblée chez 95% des femmes incluses, et que parmi les femmes avec une APM d'emblée et qui ont eu une hystérectomie d'hémostase, une sur cinq avait une conversion en AG ; le taux de complications maternelles était similaire entre les femmes avec APM seule et celles ayant une conversion en AG (respectivement 7% et 11%). Les facteurs de risque de conversion en AG étaient une durée opératoire prolongée (Odd ratio ajusté : aOR=1,5 IC95% 1,0-2,4) et un antécédent de 3 césariennes ou plus (aOR=6,5, IC95% 1,1-45,0). Plusieurs études rétrospectives ont rapporté une diminution des pertes sanguines et des besoins transfusionnels chez les patientes ayant une césarienne sous APM par rapport à celles opérées sous AG ; cependant ces résultats s'expliquent très probablement par un biais de sélection important, les patientes les plus sévères appartenant au groupe AG d'emblée, et les résultats de ces études monocentriques sont difficilement généralisables. Enfin la technique chirurgicale préconisée en antepartum intervient dans le choix de la technique anesthésique, c'est-à-dire traitement radical d'emblée (césarienne hystérectomie) ou traitement conservateur, et en particulier la localisation de l'incision chirurgicale (médiane sous-ombilicale ou xypho-pubienne). Dans le contexte de la césarienne en urgence pour hémorragie antepartum, le choix de l'anesthésie générale s'impose le plus souvent et ne fait pas l'objet des mêmes controverses qu'en cas de césarienne programmée.

Ainsi la technique d'anesthésie est-elle décidée au cas par cas, en prenant en compte le risque hémorragique, le degré d'invasion placentaire suspecté, la technique chirurgicale et le type d'incision cutanée choisie, les comorbidités maternelles et foetales, les préférences de l'anesthésiste réanimateur en charge de la patiente, et le souhait maternel.

STRATÉGIE TRANSFUSIONNELLE ET DE PRISE EN CHARGE DE LA COAGULOPATHIE

Face au risque d'hémorragie massive, la stratégie transfusionnelle doit être anticipée. La présence d'une carte de groupe et de RAI valides, ainsi que la disponibilité et la possibilité d'une délivrance immédiate de produits sanguins labiles (PSL) comptabilisés doivent être vérifiées à l'entrée en salle d'opération. Dans certains centres, les PSL comptabilisés sont disponibles à proximité de la patiente et conservés de manière à pouvoir être renvoyés à la banque du sang en cas de non utilisation grâce à des thermoboutons qui monitorent la chaine du froid par un enregistrement continu de la température. En cas d'hémorragie obstétricale, l'administration de concentrés globulaires est guidée par l'importance des pertes sanguines, la tolérance hémodynamique et en dernier ressort par la mesure de l'hémoglobinémie par hémocue TM et NFS. En cas de saignement actif, l'administration précoce de facteurs de coagulation, guidée si possible par visco-élastométrie, peut être nécessaire pour prévenir et/ou traiter une coagulopathie précoce. La mise en place de protocoles de délivrance de « packs transfusionnels », composés d'une quantité fixe et importante de PSL, peut constituer un atout dans ces situations : le déclenchement de la procédure entraine par exemple la délivrance simultanée de 6 concentrés globulaires (CG), 4 plasmas frais congelés (PFC) et 1 concentré plaquettaire (CP). La mise en place de cette stratégie de pack transfusionnel raccourcit le délai d'obtention et optimise le ratio PFC/CG. Cependant l'anticipation des besoins transfusionnels est difficile du fait de l'absence d'identification de facteur de risque de saignement massif dans ce contexte. Le degré d'invasivité placentaire lui-même ne serait pas prédictif des pertes sanguines. Par ailleurs, l'utilisation de dispositifs accélérateurs-réchauffeurs de perfusion est recommandée pour la transfusion. L'hypothermie peropératoire doit être systématiquement prévenue pour éviter d'aggraver le saignement et la coagulopathie par l'utilisation de couverture chauffante et de réchauffeurs de perfusion. L'utilisation des techniques de récupération, de centrifugation, de lavage et filtration du sang type «cell-saver TM » avec filtre anti-leucocytaire, a été décrite sans complication rapportée ; la prise en charge d'anomalies de la placentation en constitue une des meilleures indications dans le contexte obstétrical [START_REF] Allam | Cell salvage in obstetrics[END_REF] . Pour prévenir le risque théorique d'embolie amniotique, le sang est récupéré après l'extraction foetale et l'aspiration du liquide amniotique.

Le monitorage biologique au cours de la prise en charge per et postopératoire est nécessaire notamment en cas de saignement actif. Dans ce contexte l'utilisation de mesure rapide de l'hémoglobine (hémocue TM ) et d'évaluation de l'hémostase par viscoélastométrie est particulièrement intéressante pour diminuer les délais d'obtention des résultats. La mesure des taux plasmatiques de fibrinogène doit être systématique et répétée car l'hypo fibrinogénémie est un excellent marqueur de la sévérité de l'hémorragie obstétricale. L'acide tranexamique est également recommandé en cas d'hémorragie, à la dose de 1g répétée une fois si le saignement n'est pas rapidement contrôlé. L'efficacité d'une administration préventive d'acide tranexamique n'a jamais été explorée dans ce contexte.

PRISE EN CHARGE POSTOPÉRATOIRE

En postopératoire immédiat, les enjeux qui concernent la réanimation sont la surveillance des pertes sanguines, la gestion de la douleur et l'initiation d'une anticoagulation préventive. Ces femmes doivent bénéficier d'une surveillance avec un monitorage hémodynamique prolongé en SSPI, USC ou réanimation selon la gravité de la situation clinique, en particulier en cas de traitement conservateur compte tenu du risque de saignement secondaire. L'analgésie postopératoire est assurée par voie péridurale associée à une analgésie systémique par des non-opiacés : paracétamol, néfopam et AINS. Chez les patientes qui ont présenté un saignement peropératoire important, l'utilisation de bas de compression intermittente pour les premières heures postopératoires est une option à considérer compte tenu du risque élevé de complications thromboemboliques.

L'anesthésiste-réanimateur est impliqué dans la prise en charge des complications maternelles postopératoires en particulier dans le contexte de traitement conservateur. L'équipe doit toujours être informée de la présence dans le service d'une femme qui a été opérée de césarienne pour placenta accreta car une hémorragie secondaire sévère peut survenir à tout moment, souvent associée à une coagulopathie, ainsi qu'une complication infectieuse sévère de type endométrite. La vigilance doit donc être maintenue de manière prolongée.

Pour conclure, quel que soit le traitement, la stratégie anesthésique de prise en charge des femmes présentant un grossesse compliquée de placenta accreta doit être clairement anticipée et organisée, en particulier la prise en charge transfusionnelle. Elle s'intègre au sein d'une prise en charge multidisciplinaire organisée dans des centres


Dr Quentin Lisan
email: quentin.lisan@gmail.com

François Rubin

Alfred Werner

Sophie Guiquerro

Pierre Bonfils

Ollivier Laccourreye

Management of stylohyoid syndrome: a systematic review following PRISMA guidelines

Keywords: Stylohyoid syndrome, styloidectomy, systematic review

Objectives: A systematic review of the literature on stylohyoid syndrome treatment was performed according to PRISMA guidelines.

Material and methods: 349 articles were retrieved in the PubMed and Cochrane databases using the search-terms "stylohyoid syndrome" and synonyms. Articles documenting treatment and outcome with more than 1 month's follow-up were selected. Treatment-related complications and rate of cure, defined as disappearance of symptoms and/or of revelatory complication, were analyzed. Overall analysis was performed for series and a mixed logistic regression model for case reports.

Results: 102 articles (12 series, 90 case reports) were selected. The 12 series included 482 patients with pain syndrome managed by styloidectomy, with 84.2% and 73.7% cure rates for cervical and transoral approaches, respectively. There were no complications with the transoral approach, versus 1.2% transient facial paresis with the cervical approach. In the 90 case reports, 112 patients had pain syndrome (Group I) and 16 neurological deficit (Group II). Cure rate in Group I varied significantly (p = 0.005; OR 8.33, 95% CI [2.12 -32.81]) from 64.3% following medical treatment (antiepileptics, muscle relaxants, analgesics, per os and/or locally injected anti-inflammatory drugs) to 91.8 % following styloidectomy, without any significant impact of surgical approach (p = 0.1; OR 0.17, 95% CI [0.02 -1.60]). In Group I, no complications occurred after medical treatment, versus 4.3% and 16.3% after transoral and cervical styloidectomy, respectively. In Group II, cure and complication rates were 87.5% and 6.2%, respectively. Due to the small sample size and heterogeneity of Group II, no statistical assessment of the contribution of styloidectomy to medical treatment (antiplatelet drugs, with or without stenting) was performed.

Conclusion:

Styloidectomy appears to be the treatment of choice for stylohyoid syndrome. The surgical approach does not significantly influence the cure or complications rate.

Introduction.

In 1937, the American ENT specialist Watt Eagle of Duke University, North Carolina, published the first series of pain syndrome induced by elongation and ossification of the stylohyoid process [START_REF] Eagle | Elongated styloid processes: reports of two cases[END_REF][START_REF] Eagle | Elongated styloid process: further observation and a new syndrome[END_REF][START_REF] Eagle | Symptomatic elongated styloid process; report of two cases of styloid process-carotid artery syndrome with operation[END_REF][START_REF] Eagle | Elongated styloid process ; symptoms and treatment[END_REF][START_REF] Eagle | The symptoms, diagnosis and treatment of the elongated styloid process[END_REF]. However, it was Marchetti [6] in 1652, Lucke [START_REF] Lucke | Practische bedeutung des abnormlangen und verbogenen processus styloides des schlafenbeins[END_REF] in 1870 and Kulvin [START_REF] Kulvin | Elongated styloid processes, their formation and clinical significance[END_REF] in 1930, who first, respectively, described the styloid process, implicated ossification in the pain syndrome, and introduced the term "elongated styloid process" to explain its onset (Figure 1).

There have since been very many reports dealing with this pathology. In 2012, Morrison et al. [START_REF] Morrison | Familial ossification of the styloid ligament in a three generation family -a new clinical entity displaying autosomal dominant inherence[END_REF] found more than 9,000 articles on stylohyoid syndrome in PubMed, although they did not explain how they arrived at this figure. To our knowledge, however, there have been no studies of treatment based on systematic review using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) criteria [10]. We therefore sought to assess cure and complications rates for the various treatments advocated, and the presenting symptoms and pathophysiology of the syndrome which, in Finland, was reported to have an incidence of 1/250 consultations for cervicopharyngeal pain [START_REF] Härmä | Stylalgia: clinical experiences of 52 cases[END_REF].

Methodology.

Search strategy:

The key words syndrome stylo hyoïdien, syndrome styloïdien, syndrome stylo carotidien, syndrome de la longue apophyse styloïde, syndrome de l'apophyse styloïde calcifiée, syndrome de l'os hyoïde, stylalgies, carotidynies, syndrome d'Eagle and their English translations (stylohyoid syndrome, styloid syndrome, stylocarotid syndrome, long styloid process syndrome, calcified styloid process syndrome, hyoid bone syndrome, carotidynia, Eagle syndrome) were used as search-terms in the Medline (PubMed) and Cochrane data-bases up to the date April 1,

2018.

Data selection and extraction: 349 articles were retrieved and analyzed on the PRISMA criteria [10]. Those not reporting series and/or case reports, not reporting the type and/or results of treatment and/or with follow-up not specified or less than 1 month were excluded (Figure 2). Data extracted from the selected articles comprised: gender, age, type of treatment, success (resolution of symptomatology and/or of revelatory complication), follow-up duration (months), and onset and type of treatment-related complications.

Statistical analysis:

In series reports (with more than 6 patients), cure rates were analyzed globally. In case reports providing individual data, mixed logistic regression models were used to estimate adjusted odds ratios (OR) with 95% confidence intervals (95%CI); adjustment was on age and gender (fixed effects), with additional adjustment for publication to take accountof non-independence of data from the same publication (random effect). Analyses used R software, version 3.3.3 (www.r-project.org). The significance threshold was set at p < 0.005 [START_REF] Laccourreye | Towards a new threshold for the p value ?[END_REF][START_REF] Ioannidis | The proposal to lower p value thresholds to .005[END_REF].

Results

After applying the exclusion criteria (Figure 2), 102 articles were analyzed: 12 series [14-24] and 90 case reports (Appendix 1).

Global data analysis (series)

The 12 series [START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF] included 460 patients, aged 20 to 79 years. All had pain syndrome without neurologic deficit, and were treated by styloidectomy (Table 1). Cure rates ranged from 45.4% to 100%, for a mean 78.7% (362/460) overall: 73.7% (180/244) for the transoral approach and 84.2% (182/216) for the cervical approach. There were no complications with the transoral approach, but a 1.2% rate (3/244) of ipsilateral inferior cervicofacial paresis with the cervical approach.

Individual data analysis (case reports)

The 91 case reports included 128 patients: 79 female, 49 male, aged 32 to 58 years (mean, 45 years). Two populations were distinguished, according to symptomatology: 112 patients with pain syndrome (Group I) and 16 with neurologic deficit (8 cases of ischemic stroke and 8 of transient ischemic attack, associated with pain syndrome in 5 cases (Group II). In Group II, CT found 7 cases of carotid dissection and 9 of carotid compression.

In Group I, treatment was medical (non-steroidal anti-inflammatory drugs, analgesics, muscle relaxants, anesthetic and/or anti-inflammatory injection to the styloid process or tonsils) in 14 cases, and surgical (styloidectomy: 48 by transoral and 50 by cervical approach) in 98, following failure of medical treatment in 23.5% of cases (23/98). In Group II, medical treatment (antiplatelets, with or without stenting) was systematic, with associated styloidectomy in 9 cases.

Cure rate in Group I, at a mean 15 months' follow-up (range, 1 month to 13 years), was 91.8% (90/98) after styloidectomy and 64.3% (9/14) after medical treatment (p = 0.005), whether without adjustment (OR 8.33, 95%CI [2.12 -32.81]; Table 2) or after adjustment on age and gender (OR 8.90, 95%CI [2.18 -36.5]; Table 2). In the styloidectomy subgroup, cure rate was 89.1% (41/46) with the transoral approach and 95.8% (48/49) with the cervical approach (non-significant: p = 0.1; adjusted OR, 0.17, 95%CI [0.02 -1.60]; Table 2). The complications rate was 4.3% with the transoral approach (1 brachiocephalic pain syndrome, 1 transient trismus), and 16.3 % (8/49) with the cervical approach (2 cervical hematomas, 1 transient deficit in the marginal branch of the ipsilateral facial nerve, 1 transient cranial nerve (CN) XII deficit, 1 combined IX-X-XI-XI deficit of non-specified duration, 1 subcutaneous emphysema, 1 first-bite syndrome, and 1 depressive syndrome).

In Group II, at a mean 8 months' follow-up (range, 1-32 months), the cure rate was 87.5% (14/16) and the complications rate 6.2% (1/16). One patient with carotid compression, non-operable due to fragile general health status, received oral anti-inflammatory drugs but was lost to follow-up at 32 months. One patient with carotid dissection treated medically suffered recurrence of ischemic stroke with stent fracture, successfully managed by styloidectomy. The small size and clinical heterogeneity of Group II, with transient ischemic attack and ischemic stroke and internal carotid wall lesions, prevented analysis of the impact of styloidectomy, approach or indication (primary or secondary) on cure rate.

Discussion

The styloid process is attached to the temporal bone and runs through two angles, downward then medially toward the pharynx. The cartilage extremity is prolonged by a fibrous band, the stylohyoid ligament, inserting on the lesser horn of the hyoid bone. Stylohyoid syndrome implicates trauma (contact sports, road accidents, etc.) or ossification in adulthood of the styloid process and stylohyoid ligament (Figure 3) or styloglossus muscle, for which various etiopathogenic factors have been identified: tonsillectomy, adult activation of ossification centers within embryonic residues stimulated by factors such as carrying heavy loads on the head, styloid process tension inducing bone hyperplasia and/or metaplasia, osteoporosis or menopause, or osteoarthritis and genetic predisposition [START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF][START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF][START_REF] Kamil | Transoral resection of stylopharyngeus calcification: a unique manifestation of a stylohyoid complex syndrome[END_REF].

Diagnosis is often not quickly established. In 1948, Eagle [START_REF] Eagle | Elongated styloid process: further observation and a new syndrome[END_REF] reported that he had been monitoring his first case for 5 years before reaching diagnosis, and that symptoms resolved on transoral resection of the styloid process (styloidectomy). The infrequency of the syndrome [START_REF] Härmä | Stylalgia: clinical experiences of 52 cases[END_REF] and wide variation in symptoms, and especially in pain location [START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF][START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF][START_REF] Kamil | Transoral resection of stylopharyngeus calcification: a unique manifestation of a stylohyoid complex syndrome[END_REF], account for the frequent delay in diagnosis.

The associated pain is very intense, sharp or shooting, localized mainly in the pharynx and/or neck, or sometimes ear, temporomandibular joint, face, eye, oral floor, mandible and/or skull. It is often triggered by swallowing, turning the neck or yawning [START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF][START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF]. These variations in pain location depend on the contacts made by the calcified and prolonged stylohyoid complex (Figure 1): sensory branches of CN V, VII, IX and/or X, or sympathetic plexi of the parietal adventitia of the external (facial or peri-and retro-orbital pain) or internal carotid artery (cranial pain in the form of parietal headache at the vertex or frontal supraorbital headache) [START_REF] Eagle | Elongated styloid process: further observation and a new syndrome[END_REF][START_REF] Eagle | Symptomatic elongated styloid process; report of two cases of styloid process-carotid artery syndrome with operation[END_REF][START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF][START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF].

Pain is often accompanied by a sensation of pharyngeal foreign body, globus, dysphagia or sometimes tinnitus and balance disorder. Various authors have also reported palsy of CN X and XII or of the lingual or cervical sympathetic nerve, trismus, taste and speech disorder and dysphonia [START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF][START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF]. A more infrequent presentation, found in 16 out of the 128 patients (12.5 %) in our review of 90 case reports, follows direct trauma (compression, pseudoaneurysm) caused by the calcified and elongated stylohyoid complex (Figures 1 and4) in the wall of the ipsilateral internal carotid artery [START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF][START_REF] Kamil | Transoral resection of stylopharyngeus calcification: a unique manifestation of a stylohyoid complex syndrome[END_REF][START_REF] Messer | The stylohyoid syndrome[END_REF][START_REF] Ogura | Carotid artery dissection caused by an elongated styloid process: three case reports and review of the literature[END_REF]; presenting symptomatology is then dominated by vertigo, dizziness, drop attacks, epileptic attacks or stroke with motor deficit, language disorder and/or visual disorder, due to the anatomic effects of contact (stenosis, thrombosis and/or dissection) or to compression by the stylopharyngeus muscle triggering symptoms on ipsilateral neck rotation [START_REF] Tubbs | Compression of the cervical internal carotid artery by the stylopharyngeus muscle: an anatomical study with potential clinical significance. Laboratory investigation[END_REF].

In the literature, it is often claimed that a styloid process longer than 3 cm increases the incidence of stylohyoid syndrome, due to increased displacement of the tip with increasing length (all the more in case of stylohyoid ligament calcification), leading to contact with neighboring neurovascular structures [START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF]. However, many studies based on anatomic dissection or radiologic analysis failed to confirm any such 3 cm threshold: in 2017, analysis of CT data for 2,000 styloid processes in adults free of stylohyoid syndrome found styloid processes exceeding 3.5 cm in length in 34.2% of cases [START_REF] Buyuk | Morphological assessment of the stylohyoid complex variations with cone beam computed tomography in a Turkish population[END_REF]; conversely, in CT assessment of 133 stylohyoid syndromes, Chen et al. [START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF] found lengths of less than 3 cm in 15.4% of cases.

According to Eagle [START_REF] Eagle | Elongated styloid process: further observation and a new syndrome[END_REF], the styloid process is pathological if palpable and painful in the ipsilateral tonsil. Various authors [START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF][START_REF] Oueslati | Le syndrome de Eagle[END_REF][START_REF] Costantidines | Eagle's syndrome: signs and symptoms[END_REF][START_REF] Palesy | The involvement of the styloid process in head and neck pain -a preliminary study[END_REF][START_REF] Mishra | Stylalgia: a missed diagnosis[END_REF][START_REF] Kunachak | Anterior cervical pain syndromes: hyoid, thyroide and cricoid cartilage syndromes and their treatment with trimacinolone acetonide[END_REF] highlight the diagnostic contribution of pain resolution on tonsillar injection of anesthetic and/or steroidal anti-inflammatory drugs: otherwise, stylohyoid syndrome, along with other pathologies with similar pain symptomatology, should be considered. Clinical examination should rule out dental problems, such as wisdom tooth, tumor or infection, and screen for signs of various differential pathologies. Pain on cervical spine palpation suggests occipital neuralgia (e.g., Arnold's neuralgia); pain on glossotonsillar sulcus palpation suggests glossopharyngeal neuralgia; pain on thyrohyoid membrane palpation suggests superior laryngeal neuralgia; and tears with facial erythema and ocular signs suggest trigeminal neuralgia (e.g., Sluder syndrome) or nasal neuralgia (e.g., Charlin syndrome). Pain on palpation of the carotid bulb suggests carotidynia; pain on palpation of the temporomandibular joint or temporal muscle tendon suggests joint dysfunction; pain on percussion of the mastoid suggests mastoiditis; pain on palpation behind the horizontal branch of the mandible or of the extremity of greater horn of the hyoid bone respectively suggest stylomandibular ligament insertion tendinitis (e.g., Albert syndrome) or hyoid bone syndrome (bursitis); pain on palpation of the thyroid or cricoid cartilage plate suggests corresponding tendinitis. When clinical data are atypic and/or diagnosis is uncertain, several authors [6,[START_REF] Hampf | A holistic approach to stylalgia[END_REF][START_REF] Ettinger | The styloid or "Eagle" syndrome: an unexpected consequence[END_REF][START_REF] Prasad | Elongated styloid process (Eagle's syndrome): a clinical study[END_REF] stress the contribution of a psychiatric opinion.

While clinical examination is important in guiding diagnosis toward stylohyoid syndrome, definitive diagnosis relies on CT, which has replaced plain X-ray in this role. Modern imaging (3D CT reconstruction with contrast enhancement and dynamic views in rotation) provides optimal visualization of the morphology and angulation of the elongated calcified styloid process (Figures 3 and4), and relations to or involvement of the carotid artery (Figure 4). CT also simultaneously analyzes deep spaces, to rule out infection (mastoiditis, osteitis), tumor (skull base, deep parotid lobe, parapharyngeal space, pharynx) or malformation (ponticulus posticus), which presents very similar pain symptoms [START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF][START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF]. CT may be supplemented by MRI, determining the etiology of glossopharyngeal or geniculate ganglion neuralgia, and visualizing inflammatory thickening of the carotid bulb wall typical of carotidynia, or calcification in retropharyngeal tendinitis. Normal findings serve to reorient diagnosis toward more "general" conditions, such as temporal arteritis, migraine, tension neuralgia, angina pectoris or psychosomatic disorder [START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF][START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF]. It is also the key to diagnosis when stylohyoid syndrome presents as a syndrome of transient or lasting neurologic deficit [START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF][START_REF] Fusco | Eagle's syndrome: embryology, anatomy, and clinical management[END_REF].

Several articles suggest that stylohyoid syndrome can be successfully treated non-operatively [START_REF] Mishra | Stylalgia: a missed diagnosis[END_REF][START_REF] Kunachak | Anterior cervical pain syndromes: hyoid, thyroide and cricoid cartilage syndromes and their treatment with trimacinolone acetonide[END_REF][START_REF] Hampf | A holistic approach to stylalgia[END_REF][START_REF] Ettinger | The styloid or "Eagle" syndrome: an unexpected consequence[END_REF][START_REF] Prasad | Elongated styloid process (Eagle's syndrome): a clinical study[END_REF][START_REF] Kawasaki | Non-surgical therapy for bilateral glossopharyngeal neuralgia caused by Eagle's syndrome, diagnosed by three-dimensional computed tomography: a case report[END_REF][START_REF] Green | Elongated styloid processes and calcified stylohyoid ligaments in a patient with neck pain: implications for manual therapy practice[END_REF][START_REF] De Santana Santos | Clinical-radiographic analysis of Eagle syndrome[END_REF][START_REF] Taheri | Nonsurgical treatment of stylohyoid (Eagle) syndrome: a case report[END_REF][START_REF] Maher | Ultrasound-guided peristyloid steroid injection for eagle syndrome[END_REF][45][START_REF] Camarda | Stylohyoid chain ossification: a discussion of etiology[END_REF][START_REF] Yoshimira | Does Eagle syndrome always require operative intervention for treatment[END_REF][START_REF] Gervickas | Clinic, diagnostics, and treatment peculiarities of Eagle's syndrome[END_REF][START_REF] Han | Non surgical treatment of Eagle's syndrome -a case report[END_REF][START_REF] Malik | Seizures with an atypical aetiology in an elderly patient: Eagle's syndrome -how does one treat it ?[END_REF]. This option was taken in 12.5% (14/112) of clinical cases without neurologic deficit in our literature review, and is based on various oral treatments (non-steroidal anti-inflammatory drugs, analgesics, antiepileptics or muscle relaxants) and/or injection of anesthetics or steroidal anti-inflammatory drugs to the styloid process or tonsil. The advocates of this option point out its safety and efficacy, especially when pain is not intense or surgery is contraindicated [START_REF] Mishra | Stylalgia: a missed diagnosis[END_REF][START_REF] Kunachak | Anterior cervical pain syndromes: hyoid, thyroide and cricoid cartilage syndromes and their treatment with trimacinolone acetonide[END_REF][START_REF] Hampf | A holistic approach to stylalgia[END_REF][START_REF] Ettinger | The styloid or "Eagle" syndrome: an unexpected consequence[END_REF][START_REF] Prasad | Elongated styloid process (Eagle's syndrome): a clinical study[END_REF][START_REF] Kawasaki | Non-surgical therapy for bilateral glossopharyngeal neuralgia caused by Eagle's syndrome, diagnosed by three-dimensional computed tomography: a case report[END_REF][START_REF] Green | Elongated styloid processes and calcified stylohyoid ligaments in a patient with neck pain: implications for manual therapy practice[END_REF][START_REF] De Santana Santos | Clinical-radiographic analysis of Eagle syndrome[END_REF][START_REF] Taheri | Nonsurgical treatment of stylohyoid (Eagle) syndrome: a case report[END_REF][START_REF] Maher | Ultrasound-guided peristyloid steroid injection for eagle syndrome[END_REF][45][START_REF] Camarda | Stylohyoid chain ossification: a discussion of etiology[END_REF][START_REF] Yoshimira | Does Eagle syndrome always require operative intervention for treatment[END_REF][START_REF] Gervickas | Clinic, diagnostics, and treatment peculiarities of Eagle's syndrome[END_REF][START_REF] Han | Non surgical treatment of Eagle's syndrome -a case report[END_REF][START_REF] Malik | Seizures with an atypical aetiology in an elderly patient: Eagle's syndrome -how does one treat it ?[END_REF]. In our review of case reports, however, the cure rate was only 64.3%, significantly (p = 0.005) lower than the 91.8% found with styloidectomy, with or without adjustment on age and gender (Table 2).

Gervickas et al. [START_REF] Gervickas | Clinic, diagnostics, and treatment peculiarities of Eagle's syndrome[END_REF], in the largest series of medical treatment for stylohyoid syndrome, reported that in most cases pain was not relieved or else recurred within 6-12 months. Moreover, safety is debatable: as well as side-effects of the various drug classes, injection to the styloid process incurs a risk of facial palsy [START_REF] Kunachak | Anterior cervical pain syndromes: hyoid, thyroide and cricoid cartilage syndromes and their treatment with trimacinolone acetonide[END_REF]. Medical treatment also does not act upon the causal process, leaving open a risk of neurologic deficit caused by internal carotid artery impingement [START_REF] Ogura | Carotid artery dissection caused by an elongated styloid process: three case reports and review of the literature[END_REF][START_REF] Malik | Seizures with an atypical aetiology in an elderly patient: Eagle's syndrome -how does one treat it ?[END_REF] or even of death from asphyxia or cardiovascular arrest [START_REF] Han | Non surgical treatment of Eagle's syndrome -a case report[END_REF][START_REF] Malik | Seizures with an atypical aetiology in an elderly patient: Eagle's syndrome -how does one treat it ?[END_REF][START_REF] Subedi | Carotid artery dissection: a rare complication of Eagle syndrome[END_REF][START_REF] Winkler | Styloid syndrome[END_REF][START_REF] Kumar | Sudden death due to Eagle syndrome[END_REF][START_REF] Gupta | A rare fatality due to calcified stylohyoid ligament (Eagle syndrome)[END_REF].

The alternative to medical treatment is styloidectomy. In his princeps article, Eagle [START_REF] Eagle | Elongated styloid processes: reports of two cases[END_REF] mentioned that a European physician, Weinlecher, first reported its efficacy in the late 19 th century [START_REF] Eagle | Elongated styloid processes: reports of two cases[END_REF]. Initial reports were of transoral surgery [START_REF] Eagle | Elongated styloid processes: reports of two cases[END_REF], usually under general or sometimes local anesthesia, with 6 classical stages: transoral exposure and palpation of the styloid process, tonsillectomy, incision of the pharyngeal constrictors against the styloid process, sectioning against the styloid process of the inserted ligaments and muscles, fragmentation of the styloid process, which is resected, and closure in several planes [START_REF] Eagle | Elongated styloid processes: reports of two cases[END_REF][START_REF] Eagle | Elongated styloid process: further observation and a new syndrome[END_REF][START_REF] Eagle | Symptomatic elongated styloid process; report of two cases of styloid process-carotid artery syndrome with operation[END_REF][START_REF] Eagle | Elongated styloid process ; symptoms and treatment[END_REF][START_REF] Eagle | The symptoms, diagnosis and treatment of the elongated styloid process[END_REF][START_REF] Murthy | Elongated styloid process an overview[END_REF][START_REF] Fini | The long styloid process syndrome or Eagle's syndrome[END_REF][START_REF] Yadav | Stylalagia: an indian perspective[END_REF][START_REF] Beder | Current diagnosis and transoral surgical treatment of Eagle's syndrome[END_REF][START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF][START_REF] Yavuz | Modified intraoral approach for removal of an elongated styloid process[END_REF][START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF][START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF]. In the decade following 2000, systematic primary tonsillectomy was abandoned [START_REF] Torres | A modified transoral approach for carotid artery type Eagle syndrome: technique and outcomes[END_REF][START_REF] Kadakia | Tonsilelctomy sparing transoral robot assisted styloidectomy[END_REF], endoscopes were introduced and a piezoelectric technique was used to fracture the styloid process, with coblation for hemostasis, and use of robotic surgery [START_REF] Cheng | The experience of coblation assisted surgical approach to Eagle's syndrome[END_REF][START_REF] Kamil | Transoral resection of stylopharyngeus calcification: a unique manifestation of a stylohyoid complex syndrome[END_REF][START_REF] Kadakia | Tonsilelctomy sparing transoral robot assisted styloidectomy[END_REF][START_REF] Strauss | Elongated styloid process syndrome: intraoral versus external approach for styloid surgery[END_REF][START_REF] Leclerc | Eagle syndrome: teaching the intraoral surgical approach with a 30° endoscope[END_REF][START_REF] Matsumoto | Endoscopy-assisted transoral resection of the styloid process in Eagle's syndrome; case report[END_REF][START_REF] Weteid | Transoral endoscopic-assisted styloidectomy: how should Eagle syndrome be managed surgically ?[END_REF][START_REF] Sukegawa | Use of an intraoperative navigation system and piezoelectric surgery for styloidectomy in a patient with Eagle's syndrome: a case report[END_REF], although there was no published evidence of benefit. However, resolution of pain on lidocaine injection in the tonsil demonstrated strong predictive value for the efficacy of styloidectomy [START_REF] Singhania | Lidocine infiltration test : a useful test in the prediction of results of styloidectomy for Eagle's syndrome[END_REF]. Postoperative antibiotic therapy was also replaced by intraoperative antibiotic prophylaxis [START_REF] Martins | Eagle's syndrome: treatment by intraoral bilateral resection of the ossified stylohyoid ligament. A review and report of two cases[END_REF]. A very large number of authors reported risk of infection and of neurovascular lesions with a transoral approach for styloidectomy; Mohanty et al. [START_REF] Mohanty | Significance of styloidectomy in Eagle's syndrome analysis[END_REF], in a cohort of transoral styloidectomies, reported difficulty in controlling intraoperative tonsillar bleeding and in dissecting the styloid process, especially when the medial angle was absent. In contrast, however, the present review of case reports and series (Table 1) found no cases of infection, hemorrhage, neurovascular complications or postoperative death in published reports of transoral styloidectomy.

In 1948, Eagle [START_REF] Eagle | Elongated styloid process ; symptoms and treatment[END_REF] noted that Loeser and Caldwell [63] were the first to report styloidectomy via a transcutaneous cervical approach. It offers an alternative to the transoral approach and its reputed risks, and can deal with the possible absence of a medial angle in the elongated and calcified stylohyoid complex, sometimes revealed by painful cervical swelling at the junction with the lesser horn of the hyoid bone. The procedure consists in 4 successive stages: cervicotomy in the superior cervical fold, location of the anterior edge of the sternocleidomastoid muscle and posterior belly of the digastric muscle, palpation of the calcified styloid process, sectioning the styloid curtain muscles and ligaments strictly in contact with the styloid process, then fracturing and resecting the styloid process [START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF][START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF][START_REF] Chen | Surgical approach to Eagle syndrome[END_REF][START_REF] Gupta | A rare fatality due to calcified stylohyoid ligament (Eagle syndrome)[END_REF][63][START_REF] Müderris | Surgical management of elongated styloid process: intraoral or transcervical ?[END_REF][START_REF] Buono | Surgical approach to the stylohyoid process in Eagle's syndrome[END_REF]. In the decade following 2000, it was sought to optimize cervical incision esthetics [START_REF] Buono | Surgical approach to the stylohyoid process in Eagle's syndrome[END_REF], reducing its length by use of endoscopy [START_REF] Chen | Surgical approach to Eagle syndrome[END_REF]; cervical approaches were used in case of recurrent or persistent pain after transoral styloidectomy [START_REF] Papadiochos | Treatment of eagle syndrome with trans cervical approach secondary to a failed intraoral attempt. Surgical technique and litterature review[END_REF]; and short-course fluoxetine (an antidepressant) was introduced postoperatively [START_REF] Peng | Eagle' syndrome treated with dissection of the styloid process via an extraoral approach combined with antidepressant[END_REF].

Whatever the means of assessment, whether global rates for series or regression models for case reports, cure rates were higher on a cervical than a transoral approach: respectively, 84.2% vs. 73.7 % for series and 95.8% vs. 89.1% for case reports in our review of the literature. The fact that the mean global cure rate of 73.7% in the 12 published series (Table 2) was lower than the 91.8% rate for case reports without neurologic deficit in our opinion highlights the problem of case reports, which rarely focus on complications or failure and tend to overstate real efficacy.

Statistically, the difference between the two approaches in case reports was not significant, and one approach cannot be said to be superior to the other. On the other hand, the cervical approach was associated with a higher rate of complications (16.3% vs. 4.3%), notably involving CN VII, IX, X, XI and/or XII, but again without significant difference.

Complete resolution of pain showed no association with styloid process length, morphology, angulation or degree of resection; if, however, resolution is incomplete, it should be checked whether resection was sufficient [START_REF] Ceylan | Surgical treatment of elongated styloid process: experience of 61 cases[END_REF], given that Steinmann [START_REF] Steinmmann | A new light on the pathogenesis of the styloid syndrome[END_REF] demonstrated that the styloid process may regrow years after styloidectomy, which is attributed to embryonic cartilage residue. In such cases, another etiology, such as first-bite syndrome [START_REF] Cernea | First-bite syndrome after resection of the styloid process[END_REF], should also be sought for the pain, and various causes of subjective impact, such as stress, anxiety or psychiatric disorder, should be assessed [START_REF] Hampf | A holistic approach to stylalgia[END_REF][START_REF] Ettinger | The styloid or "Eagle" syndrome: an unexpected consequence[END_REF][START_REF] Prasad | Elongated styloid process (Eagle's syndrome): a clinical study[END_REF].

Treatment of stylohyoid syndrome revealed by transient or lasting neurologic deficit is a special case. It constitutes a neurovascular emergency, involving internal carotid compression, dissection or aneurysm detected on CT (Figure 4) [START_REF] Ogura | Carotid artery dissection caused by an elongated styloid process: three case reports and review of the literature[END_REF]. In the 16 case reports in our review, antiplatelet treatment was systematic, sometimes associated to stenting (in case of dissection or aneurysm) and, in 9 cases, to styloidectomy; the cure rate was 87.5% and the complications rate 6.2%. The small sample size and heterogeneity of clinical presentation, between transient ischemic attacks and stroke, of the internal carotid wall lesions and of follow-up precluded analysis of the impact of styloidectomy or approach on cure rate, or of indications for styloidectomy: primary, or secondary following recurrence of neurologic deficit or onset of complications such as stent fracture.

Conclusion.

Several points emerged from the present systematic review of the literature on treatment of stylohyoid syndrome following the PRISMA methodology [10]. Pain triggered by cervical rotation and intraoral palpation of the tonsils is highly indicative, but CT is essential for definitive diagnosis. Medical treatment is reserved to formal contraindications to or refusal of surgery, and the patient should be informed of the neurological risk incurred. Surgery is recommended, due to its high success rate, and low rate of non-hemorrhagic and non-infectious postoperative complications, and to avoid neurologic complications. Any associated neurologic deficit should be treated as a neurovascular emergency, in which primary or secondary styloidectomy again shows real efficacy.

Table and

Table 1 :

 1 Treatment and cure and complications rates in the 12 series (CS: cervical styloidectomy; OS: oral styloidectomy; *: video-assisted; + with coblation; ¤: with tonsillectomy; °: with oral fluoxetine).

Table 2 :

 2 Associations between treatments and success in the group of 112 patients with pain syndrome without neurologic deficit (Group I). (n: number; ref: reference category; * odds ratio adjusted on age and gender).

Figure 1 :

 1 Figure 1: Illustration of calcification and elongation of styloid process and stylohyoid ligament

Figure 2 :

 2 Figure 2: Flowchart (PRISMA methodology [10]).

Figure 3 :Figure 4 :

 34 Figure 3: Stylohyoid syndrome: 3D CT reconstruction (from Raina D, Gothi R, Rajan S. Eagle

Table 1 :

 1 Treatment and cure and complications rates in the 12 series (CS: cervical styloidectomy; OS: oral styloidectomy; *: video-assisted; + with coblation; ¤: with tonsillectomy; °: with oral fluoxetine).

	Authors	Treatment	Cure rate	Follow-u	Complications
				p
				(months
				)
	Murthy et al. 14	OS	20/20 (100%)	3-60	None
	Fini et al. 15	OS¤	5/11 (45.4%)	5-48	None
	Yadav et al. 16	OS¤	31/40 (77.5%)	6-24	None
	Beder et al. 17	OS	11/19 (57.8%)	3-12	None
	Ceylan et al. 18	CS	57/61 (93.4%)	12-60	2 facial pareses
	Mohanty et al. 19	OS¤	27/28 (96.4%)	6	None
	Peng et al. 20	CS°	18/22 (81.8%)	7-26	None
	Yavuz et al. 21	OS¤	22/27 (81.4%)	3-63	None
	Singhania et al. 22	OS	18/26 (69.2%)	3	ND
	Torres et al. 23	OS	10/11 (90.9%)	9-84	None
	Chen et al. 24	CS*	107/133 (80.5%)	12-50	1 facial paresis
	Cheng et al. 25	OS +	36/62 (58.1%)	3-60	None

Acknowledgments:

We thank the Progrès 2000 association for technical support

Articles identified on search N=349

Articles included in treatment analysis (individual data) N=90

Full-text articles analyzed N=174

Articles excluded N=72 -misdiagnosis (n=6) -< 1 month's follow-up (n=41) -no details of treatment (n=25)

Articles not reporting series or cases N=175

Articles reporting series (global data) N=12