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Head injury

A head injury is any injury that results in trauma to the skull or brain. The terms traumatic brain injury and head injury are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of injuries, there are many causes—including accidents, falls, physical assault, or traffic accidents—that can cause head injuries.

The number of new cases is 1.7 million in the United States each year, with about 3% of these incidents leading to death. Adults have head injuries more frequently than any age group resulting from falls, motor vehicle crashes, colliding or being struck by an object, or assaults. Children, however, may experience head injuries from accidental falls or intentional causes (such as being struck or shaken) leading to hospitalization. Acquired brain injury (ABI) is a term used to differentiate brain injuries occurring after birth from injury, from a genetic disorder, or from a congenital disorder.

Unlike a broken bone where trauma to the body is obvious, head trauma can sometimes be conspicuous or inconspicuous. In the case of an open head injury, the skull is cracked and broken by an object that makes contact with the brain. This leads to bleeding. Other obvious symptoms can be neurological in nature. The person may become sleepy, behave abnormally, lose consciousness, vomit, develop a severe headache, have mismatched pupil sizes, and/or be unable to move certain parts of the body. While these symptoms happen immediately after a head injury occurs, many problems can develop later in life. Alzheimer's disease, for example, is much more likely to develop in a person who has experienced a head injury.

Brain damage, which is the destruction or degeneration of brain cells, is a common occurrence in those who experience a head injury. Neurotoxicity is another cause of brain damage that typically refers to selective, chemically induced neuron/brain damage.

Classification
Head injuries include both injuries to the brain and those to other parts of the head, such as the scalp and skull. Head injuries can be closed or open. A closed (non-missile) head injury is where the dura mater remains intact. The skull can be fractured, but not necessarily. A penetrating head injury occurs when an object pierces the skull and breaches the dura mater. Brain injuries may be diffuse, occurring over a wide area, or focal, located in a small, specific area. A head injury may cause skull fracture, which may or may not be associated with injury to the brain. Some patients may have linear or depressed skull fractures. If intracranial hemorrhage occurs, a hematoma within the skull can put pressure on the brain. Types of intracranial hemorrhage include subdural, subarachnoid, extradural, and intraparenchymal hematoma. Craniotomy surgeries are used in these cases to lessen the pressure by draining off the blood.

Brain injury can occur at the site of impact, but can also be at the opposite side of the skull due to a contrecoup effect (the impact to the head can cause the brain to move within the skull, causing the brain to impact the interior of the skull opposite the head-impact). While impact on the brain at the same site of injury to the skull is the coup effect. If the impact causes the head to move, the injury may be worsened, because the brain may ricochet inside the skull causing additional impacts, or the brain may stay relatively still (due to inertia) but be hit by the moving skull (both are contrecoup injuries).

Specific problems after head injury can include • Skull fracture

• Lacerations to the scalp and resulting hemorrhage of the skin

• Traumatic subdural hematoma, a bleeding below the dura mater which may develop slowly

• Traumatic extradural, or epidural hematoma, bleeding between the dura mater and the skull

• Traumatic subarachnoid hemorrhage

• Cerebral contusion, a bruise of the brain

• Concussion, a loss of function due to trauma

• Dementia pugilistica, or "punch-drunk syndrome", caused by repetitive head injuries, for example in boxing or other contact sports

• A severe injury may lead to a coma or death

• Shaken baby syndrome – a form of child abuse

Concussion

A concussion is a form of a mild traumatic brain injury (TBI). This injury is a result due to a blow to the head that could make the person's physical, cognitive, and emotional behaviors irregular. Symptoms may include clumsiness, fatigue, confusion, nausea, blurry vision, headaches, and others. Mild concussions are associated with sequelae. Severity is measured using various concussion grading systems.

A slightly greater injury is associated with both anterograde and retrograde amnesia (inability to remember events before or after the injury). The amount of time that the amnesia is present correlates with the severity of the injury. In all cases, the patients develop post concussion syndrome, which includes memory problems, dizziness, tiredness, sickness and depression. Cerebral concussion is the most common head injury seen in children.

Intracranial bleeding
Types of intracranial hemorrhage are roughly grouped into intra-axial and extra-axial. The hemorrhage is considered a focal brain injury; that is, it occurs in a localized spot rather than causing diffuse damage over a wider area.

Intra-axial bleeding
Intra-axial hemorrhage is bleeding within the brain itself, or cerebral hemorrhage. This category includes intraparenchymal hemorrhage, or bleeding within the brain tissue, and intraventricular hemorrhage, bleeding within the brain's ventricles (particularly of premature infants). Intra-axial hemorrhages are more dangerous and harder to treat than extra-axial bleeds.

Extra-axial bleeding
Extra-axial hemorrhage, bleeding that occurs within the skull but outside of the brain tissue, falls into three subtypes:
 * Epidural hemorrhage (extradural hemorrhage) which occur between the dura mater (the outermost meninx) and the skull, is caused by trauma.  It may result from laceration of an artery, most commonly the middle meningeal artery. This is a very dangerous type of injury because the bleed is from a high-pressure system and deadly increases in intracranial pressure can result rapidly. However, it is the least common type of meningeal bleeding and is seen in 1% to 3% cases of head injury.
 * Patients have a loss of consciousness (LOC), then a lucid interval, then sudden deterioration (vomiting, restlessness, LOC)
 * Head CT shows lenticular (convex) deformity.
 * Subdural hemorrhage results from tearing of the bridging veins in the subdural space between the dura and arachnoid mater.
 * Head CT shows crescent-shaped deformity
 * Subarachnoid hemorrhage, which occur between the arachnoid and pia meningeal layers, like intraparenchymal hemorrhage, can result either from trauma or from ruptures of aneurysms or arteriovenous malformations. Blood is seen layering into the brain along sulci and fissures, or filling cisterns (most often the suprasellar cistern because of the presence of the vessels of the circle of Willis and their branch points within that space). The classic presentation of subarachnoid hemorrhage is the sudden onset of a severe headache (a thunderclap headache). This can be a very dangerous entity and requires emergent neurosurgical evaluation and sometimes urgent intervention.

Cerebral contusion
Cerebral contusion is bruising of the brain tissue. The piamater is not breached in contusion in contrary to lacerations. The majority of contusions occur in the frontal and temporal lobes. Complications may include cerebral edema and transtentorial herniation. The goal of treatment should be to treat the increased intracranial pressure. The prognosis is guarded.

Diffuse axonal injury
Diffuse axonal injury, or DAI, usually occurs as the result of an acceleration or deceleration motion, not necessarily an impact. Axons are stretched and damaged when parts of the brain of differing density slide over one another. Prognoses vary widely depending on the extent of the damage.

Compound head injury
Overlying scalp laceration and soft tissue disruption in continuity with a skull fracture constitutes "compound head injury", and has higher rates of infection, unfavorable neurologic outcome, delayed seizures, mortality, and duration of hospital stay.

Signs and symptoms
Three categories used for classifying the severity of brain injuries are mild, moderate or severe.

Mild brain injuries
Symptoms of a mild brain injury include headaches, confusion, ringing ears, fatigue, changes in sleep patterns, mood or behavior. Other symptoms include trouble with memory, concentration, attention or thinking. Mental fatigue is a common debilitating experience and may not be linked by the patient to the original (minor) incident. Narcolepsy and sleep disorders are common misdiagnoses.

Moderate/severe brain injuries
Cognitive symptoms include confusion, aggressive, abnormal behavior, slurred speech, and coma or other disorders of consciousness. Physical symptoms include headaches that do not go away or worsen, vomiting or nausea, convulsions or seizures, abnormal dilation of the eyes, inability to awaken from sleep, weakness in the extremities and loss of coordination. In cases of severe brain injuries, the likelihood of areas with permanent disability is great, including neurocognitive deficits, delusions (often, to be specific, monothematic delusions), speech or movement problems, and intellectual disability. There may also be personality changes. The most severe cases result in coma or even persistent vegetative state.

Symptoms in children
Symptoms observed in children include changes in eating habits, persistent irritability or sadness, changes in attention, disrupted sleeping habits, or loss of interest in toys.

Presentation varies according to the injury. Some patients with head trauma stabilize and other patients deteriorate. A patient may present with or without neurological deficit. Patients with concussion may have a history of seconds to minutes unconsciousness, then normal arousal. Disturbance of vision and equilibrium may also occur. Common symptoms of head injury include coma, confusion, drowsiness, personality change, seizures, nausea and vomiting, headache and a lucid interval, during which a patient appears conscious only to deteriorate later.

Symptoms of skull fracture can include:
 * leaking cerebrospinal fluid (a clear fluid drainage from nose, mouth or ear) is strongly indicative of basilar skull fracture and the tearing of sheaths surrounding the brain, which can lead to secondary brain infection.
 * visible deformity or depression in the head or face; for example a sunken eye can indicate a maxillar fracture
 * an eye that cannot move or is deviated to one side can indicate that a broken facial bone is pinching a nerve that innervates eye muscles
 * wounds or bruises on the scalp or face.
 * Basilar skull fractures, those that occur at the base of the skull, are associated with Battle's sign, a subcutaneous bleed over the mastoid, hemotympanum, and cerebrospinal fluid rhinorrhea and otorrhea.

Because brain injuries can be life-threatening, even people with apparently slight injuries, with no noticeable signs or complaints, require close observation; They have a chance for severe symptoms later on. The caretakers of those patients with mild trauma who are released from the hospital are frequently advised to rouse the patient several times during the next 12 to 24 hours to assess for worsening symptoms.

The Glasgow Coma Scale (GCS) is a tool for measuring the degree of unconsciousness and is thus a useful tool for determining the severity of the injury. The Pediatric Glasgow Coma Scale is used in young children. The widely used PECARN Pediatric Head Injury/Trauma Algorithm helps physicians weigh risk-benefit of imaging in a clinical setting given multiple factors about the patient—including mechanism/location of the injury, age of the patient, and GCS score.

Location of brain damage predicts symptoms
Symptoms of brain injuries can also be influenced by the location of the injury and as a result, impairments are specific to the part of the brain affected. Lesion size is correlated with severity, recovery, and comprehension. Brain injuries often create impairment or disability that can vary greatly in severity.

Studies show there is a correlation between brain lesion and language, speech, and category-specific disorders. Wernicke's aphasia is associated with anomia, unknowingly making up words (neologisms), and problems with comprehension. The symptoms of Wernicke's aphasia are caused by damage to the posterior section of the superior temporal gyrus.

Damage to the Broca's area typically produces symptoms like omitting functional words (agrammatism), sound production changes, dyslexia, dysgraphia, and problems with comprehension and production. Broca's aphasia is indicative of damage to the posterior inferior frontal gyrus of the brain.

An impairment following damage to a region of the brain does not necessarily imply that the damaged area is wholly responsible for the cognitive process which is impaired, however. For example, in pure alexia, the ability to read is destroyed by a lesion damaging both the left visual field and the connection between the right visual field and the language areas (Broca's area and Wernicke's area). However, this does not mean someone with pure alexia is incapable of comprehending speech—merely that there is no connection between their working visual cortex and language areas—as is demonstrated by the fact that pure alexics can still write, speak, and even transcribe letters without understanding their meaning. Lesions to the fusiform gyrus often result in prosopagnosia, the inability to distinguish faces and other complex objects from each other. Lesions in the amygdala would eliminate the enhanced activation seen in occipital and fusiform visual areas in response to fear with the area intact. Amygdala lesions change the functional pattern of activation to emotional stimuli in regions that are distant from the amygdala.

Other lesions to the visual cortex have different effects depending on the location of the damage. Lesions to V1, for example, can cause blindsight in different areas of the brain depending on the size of the lesion and location relative to the calcarine fissure. Lesions to V4 can cause color-blindness, and bilateral lesions to MT/V5 can cause the loss of the ability to perceive motion. Lesions to the parietal lobes may result in agnosia, an inability to recognize complex objects, smells, or shapes, or amorphosynthesis, a loss of perception on the opposite side of the body.

Causes
Head injuries can be caused by a large variety of reasons. All of these causes can be put into two categories used to classify head injuries; those that occur from impact (blows) and those that occur from shaking. Common causes of head injury due to impact are motor vehicle traffic collisions, home and occupational accidents, falls, assault, and sports related accidents. Head injuries from shaking are most common amongst infants and children.

According to the United States CDC, 32% of traumatic brain injuries (another, more specific, term for head injuries) are caused by falls, 10% by assaults, 16.5% by being struck by or against something, 17% by motor vehicle accidents, and 21% by other/unknown ways. In addition, the highest rate of injury is among children ages 0–14 and adults age 65 and older. Brain injuries that include brain damage can also be brought on by exposure to toxic chemicals, lack of oxygen, tumors, infections, and stroke. Possible causes of widespread brain damage include birth hypoxia, prolonged hypoxia (shortage of oxygen), poisoning by teratogens (including alcohol), infection, and neurological illness. Brain tumors can increase intracranial pressure, causing brain damage.

Diagnosis
There are a few methods used to diagnose a head injury. A healthcare professional will ask the patient questions revolving around the injury as well as questions to help determine in what ways the injury is affecting function. In addition to this hearing, vision, balance, and reflexes may also be assessed as an indicator of the severity of the injury. A non-contrast CT of the head should be performed immediately in all those who have sustained a moderate or severe head injury. A CT is an imaging technique that allows physicians to see inside the head without surgery in order to determine if there is internal bleeding or swelling in the brain. Computed tomography (CT) has become the diagnostic modality of choice for head trauma due to its accuracy, reliability, safety, and wide availability. The changes in microcirculation, impaired auto-regulation, cerebral edema, and axonal injury start as soon as a head injury occurs and manifest as clinical, biochemical, and radiological changes. An MRI may also be conducted to determine if someone has abnormal growths or tumors in the brain or to determine if the patient has had a stroke.

Glasgow Coma Scale (GCS) is the most widely used scoring system used to assess the level of severity of a brain injury. This method is based on objective observations of specific traits to determine the severity of a brain injury. It is based on three traits eye-opening, verbal response, and motor response, gauged as described below. Based on the Glasgow Coma Scale severity is classified as follows, severe brain injuries score 3–8, moderate brain injuries score 9-12 and mild score 13–15.

There are several imaging techniques that can aid in diagnosing and assessing the extent of brain damage, such as computed tomography (CT) scan, magnetic resonance imaging (MRI), diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS), positron emission tomography (PET), single-photon emission tomography (SPECT). CT scans and MRI are the two techniques widely used and are the most effective. CT scans can show brain bleeds, fractures of the skull, fluid build up in the brain that will lead to increased cranial pressure. MRI is able to better detect smaller injuries, detect damage within the brain, diffuse axonal injury, injuries to the brainstem, posterior fossa, and subtemporal and sub frontal regions. However, patients with pacemakers, metallic implants, or other metal within their bodies are unable to have an MRI done. Typically the other imaging techniques are not used in a clinical setting because of the cost, lack of availability.

Management
Most head injuries are of a benign nature and require no treatment beyond analgesics such as acetaminophen. Non-steroidal painkillers such as ibuprofen are avoided since they could make any potential bleeding worse. Due to the high risk of even minor brain injuries, close monitoring for potential complications such as intracranial bleeding. If the brain has been severely damaged by trauma, a neurosurgical evaluation may be useful. Treatments may involve controlling elevated intracranial pressure. This can include sedation, paralytics, cerebrospinal fluid diversion. Second-line alternatives include decompressive craniectomy (Jagannathan et al. found a net 65% favorable outcomes rate in pediatric patients), barbiturate coma, hypertonic saline, and hypothermia. Although all of these methods have potential benefits, there has been no randomized study that has shown unequivocal benefit.

Clinicians will often consult clinical decision support rules such as the Canadian CT Head Rule or the New Orleans/Charity Head injury/Trauma Rule to decide if the patient needs further imaging studies or observation only. Rules like these are usually studied in depth by multiple research groups with large patient cohorts to ensure accuracy given the risk of adverse events in this area.

There is a subspecialty certification available for brain injury medicine that signifies expertise in the treatment of brain injury.

Prognosis
Prognosis, or the likely progress of a disorder, depends on the nature, location, and cause of the brain damage (see Traumatic brain injury, Focal and diffuse brain injury, Primary and secondary brain injury).

In children with uncomplicated minor head injuries the risk of intracranial bleeding over the next year is rare at 2 cases per 1 million. In some cases transient neurological disturbances may occur, lasting minutes to hours. Malignant post traumatic cerebral swelling can develop unexpectedly in stable patients after an injury, as can post-traumatic seizures. Recovery in children with neurologic deficits will vary. Children with neurologic deficits who improve daily are more likely to recover, while those who are vegetative for months are less likely to improve. Most patients without deficits have full recovery. However, persons who sustain head trauma resulting in unconsciousness for an hour or more have twice the risk of developing Alzheimer's disease later in life.

Head injury may be associated with a neck injury. Bruises on the back or neck, neck pain, or pain radiating to the arms are signs of cervical spine injury and merit spinal immobilization via application of a cervical collar and possibly a longboard. If the neurological exam is normal this is reassuring. Reassessment is needed if there is a worsening headache, seizure, one-sided weakness, or has persistent vomiting.

To combat overuse of head CT scans yielding negative intracranial hemorrhage results, which unnecessarily exposes patients to radiation and increase time in the hospital and cost of the visit, multiple clinical decision support rules have been developed to help clinicians weigh the option to scan a patient with a head injury. Among these are the Canadian Head CT rule, the PECARN Head Injury/Trauma Algorithm, and the New Orleans/Charity Head Injury/Trauma Rule all help clinicians make these decisions using easily obtained information and noninvasive practices.

Brain injuries are very hard to predict in the outcome. Many tests and specialists are needed to determine the likelihood of the prognosis. People with minor brain damage can have debilitating side effects; not just severe brain damage has debilitating effects. The side-effects of a brain injury depend on location and the body's response to injury. Even a mild concussion can have long term effects that may not resolve.

History
The foundation for understanding human behavior and brain injury can be attributed to the case of Phineas Gage and the famous case studies by Paul Broca. The first case study on Phineas Gage's head injury is one of the most astonishing brain injuries in history. In 1848, Phineas Gage was paving way for a new railroad line when he encountered an accidental explosion of a tamping iron straight through his frontal lobe. Gage observed to be intellectually unaffected but exemplified post-injury behavioral deficits. These deficits include: becoming sporadic, disrespectful, extremely profane, and gave no regard for other workers. Gage started having seizures in February 1860, dying only four months later on May 21, 1860.

Ten years later, Paul Broca examined two patients exhibiting impaired speech due to frontal lobe injuries. Broca's first patient lacked productive speech. He saw this as an opportunity to address language localization. It wasn't until Leborgne, formally known as "tan", died when Broca confirmed the frontal lobe lesion from an autopsy. The second patient had similar speech impairments, supporting his findings on language localization. The results of both cases became a vital verification of the relationship between speech and the left cerebral hemisphere. The affected areas are known today as Broca's area and Broca's Aphasia.

A few years later, a German neuroscientist, Carl Wernicke, consulted on a stroke patient. The patient experienced neither speech nor hearing impairments but had a few brain deficits. These deficits included: lacking the ability to comprehend what was spoken to him and the words written down. After his death, Wernicke examined his autopsy that found a lesion located in the left temporal region. This area became known as Wernicke's area. Wernicke later hypothesized the relationship between Wernicke's area and Broca's area, which was proven fact.

Epidemiology
Head injury is the leading cause of death in many countries.

title: Head injury


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Tremor

A tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving oscillations or twitching movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the hands. In some people, a tremor is a symptom of another neurological disorder.

Types
Tremor is most commonly classified by clinical features and cause or origin. Some of the better-known forms of tremor, with their symptoms, include the following:
 * Cerebellar tremor (also known as intention tremor) is a slow, broad tremor of the extremities that occurs at the end of a purposeful movement, such as trying to press a button or touching a finger to the tip of one's nose. In classic cerebellar tremor, a lesion on one side of the brain produces a tremor in that same side of the body that worsens with directed movement. Cerebellar damage can also produce a "wing-beating" type of tremor called rubral or Holmes' tremor — a combination of rest, action, and postural tremors. The tremor is often most prominent when the affected person is active or is maintaining a particular posture. Cerebellar tremor may be accompanied by other manifestations of ataxia, including dysarthria (speech problems), nystagmus (rapid, involuntary rolling of the eyes), gait problems and postural tremor of the trunk and neck. Titubation is tremor of the head, hands, and torso and is of cerebellar origin.
 * Dystonic tremor occurs in individuals of all ages who are affected by dystonia, a movement disorder in which sustained involuntary muscle contractions cause twisting and repetitive motions or painful and abnormal postures or positions. Dystonic tremor may affect any muscle in the body and is seen most often when the patient is in a certain position or moves a certain way.  The pattern of dystonic tremor may differ from essential tremor. Dystonic tremors occur irregularly and can often be relieved by complete rest. Touching the affected body part or muscle may reduce tremor severity (a geste antagoniste).  The tremor may be the initial sign of dystonia localized to a particular part of the body. The dystonic tremor has usually a frequency of about 7 Hz.
 * Essential tremor (sometimes inaccurately called benign essential tremor) is the most common of the more than 20 types of tremor. Although the tremor may be mild and nonprogressive in some people, in others, the tremor is slowly progressive, starting on one side of the body but affecting both sides within 3 years. The hands are most often affected but the head, voice, tongue, legs, and trunk may also be involved.  Head tremor may be seen as a vertical or horizontal motion. Essential tremor may be accompanied by mild gait disturbance. Tremor frequency may decrease as the person ages, but the severity may increase, affecting the person's ability to perform certain tasks or activities of daily living.  Heightened emotion, stress, fever, physical exhaustion, or low blood sugar may trigger tremors or increase their severity.  Onset is most common after age 40, although symptoms can appear at any age.  It may occur in more than one family member. Children of a parent who has essential tremor have a 50 percent chance of inheriting the condition. Essential tremor is not associated with any known pathology. Its frequency is between 4 and 8 Hz.
 * Orthostatic tremor is characterized by fast (>12 Hz) rhythmic muscle contractions that occur in the legs and trunk immediately after standing up. Cramps are felt in the thighs and legs and the patient may shake uncontrollably when asked to stand in one spot. No other clinical signs or symptoms are present and the shaking ceases when the patient sits or is lifted off the ground. The high frequency of the tremor often makes the tremor look like rippling of leg muscles while standing. Orthostatic tremor may also occur in patients who have essential tremor, and there might be an overlap between these categories of tremor.
 * Parkinsonian tremor is caused by damage to structures within the brain that control movement. This resting tremor, which can occur as an isolated symptom or be seen in other disorders, is often a precursor to Parkinson's disease (more than 25 percent of patients with Parkinson's disease have an associated action tremor). A classic symptom is a characteristic fine tremor in the hands, which is traditionally described as a "pill-rolling" action of the hands, but Parkinsonian tremor may also affect the arms, chin, lips, legs, and trunk, and can be markedly increased by stress or emotion. Onset is generally after age 60. Movement starts in one limb or on one side of the body and usually progresses to include the other side. The tremor's frequency is between 4 and 6 Hz.
 * Physiological tremor occurs in every normal individual and has no clinical significance. It is rarely visible and may be heightened by strong emotion (such as anxiety or fear), physical exhaustion, hypoglycemia, hyperthyroidism, heavy metal poisoning, stimulants, alcohol withdrawal or fever. It can be seen in all voluntary muscle groups and can be detected by extending the arms and placing a piece of paper on top of the hands. Enhanced physiological tremor is a strengthening of physiological tremor to more visible levels. It is generally not caused by a neurological disease but by reaction to certain drugs, alcohol withdrawal, or medical conditions including an overactive thyroid and hypoglycemia. It is usually reversible once the cause is corrected. This tremor classically has a frequency of about 10 Hz.
 * Psychogenic tremor (also called hysterical tremor and functional tremor) can occur at rest or during postural or kinetic movement. The characteristics of this kind of tremor may vary but generally include sudden onset and remission, increased incidence with stress, change in tremor direction or body part affected, and greatly decreased or disappearing tremor activity when the patient is distracted. Many patients with psychogenic tremor have a conversion disorder (see Post traumatic stress disorder) or another psychiatric disease.
 * Rubral tremor is characterized by coarse slow tremor which is present at rest, at posture and with intention. This tremor is associated with conditions which affect the red nucleus in the midbrain, classically unusual strokes.
 * Neuropathic tremor may occur in patients with peripheral neuropathies, when the nerves that supply the body's muscles are traumatized by injury, disease, abnormality in the central nervous system, or as the result of systemic illnesses. It is most commonly observed in patients with an immunoglobulin M paraproteinaemic neuropathy (IgMNP), but also in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). The tremor is predominantely exhibited as an action or postural tremor with a frequency of 3 to 10 Hz. Peripheral neuropathy can affect the whole body or certain areas, such as the hands, and may be progressive. Resulting sensory loss may be seen as a tremor or ataxia (inability to coordinate voluntary muscle movement) of the affected limbs and problems with gait and balance. Clinical characteristics may be similar to those seen in patients with essential tremor.
 * Neurogenic tremor is a self-induced tremor that is activated in humans. The mechanism is activated passive supine position, bringing the knees up and splitting them apart. The tremor is akin to the natural shaking mechanism in mammals to discharge stress and trauma. The type of tremor is also known as "self-induced therapeutic tremor". It is considered a kind of "spontaneous movement".

Tremor can result from other conditions as well
 * Alcoholism, excessive alcohol consumption, or alcohol withdrawal can kill certain nerve cells, resulting in a tremor known as asterixis. Conversely, small amounts of alcohol may help to decrease familial and essential tremor, but the mechanism behind it is unknown. Alcohol potentiates GABAergic transmission and might act at the level of the inferior olive.
 * Tobacco withdrawal symptoms include tremor.
 * Most of the symptoms can also occur randomly when panicked.

Causes
Tremor can be a symptom associated with disorders in those parts of the brain that control muscles throughout the body or in particular areas, such as the hands. Neurological disorders or conditions that can produce tremor include multiple sclerosis, stroke, traumatic brain injury, chronic kidney disease and a number of neurodegenerative diseases that damage or destroy parts of the brainstem or the cerebellum,  Parkinson's disease being the one most often associated with tremor. Lesions of the Guillain-Mollaret triangle (also called myoclonic triangle or dentato-rubro-olivary pathway) impair the predictions performed by the cerebellum, causing repetitive muscle discharges by triggering oscillatory activity in the central nervous system. Other causes include the use of drugs (such as amphetamines, cocaine, caffeine, corticosteroids, SSRIs) or alcohol, mercury poisoning, or the withdrawal of drugs such as alcohol or benzodiazepine. Tremors can also be seen in infants with phenylketonuria (PKU), overactive thyroid or liver failure. Tremors can be an indication of hypoglycemia, along with palpitations, sweating and anxiety. Tremor can also be caused by lack of sleep, lack of vitamins, or increased stress. Deficiencies of magnesium and thiamine have also been known to cause tremor or shaking, which resolves when the deficiency is corrected. Tremors in animals can also be caused by some spider bites, e.g. the redback spider of Australia.

Diagnosis

During a physical exam, a doctor can determine whether the tremor occurs primarily during action or at rest. The doctor will also check for tremor symmetry, any sensory loss, weakness or muscle atrophy, or decreased reflexes. A detailed family history may indicate if the tremor is inherited. Blood or urine tests can detect thyroid malfunction, other metabolic causes, and abnormal levels of certain chemicals that can cause tremor. These tests may also help to identify contributing causes, such as drug interaction, chronic alcoholism, or another condition or disease. Diagnostic imaging using CT or MRI imaging may help determine if the tremor is the result of a structural defect or degeneration of the brain.

The doctor will perform a neurological examination to assess nerve function and motor and sensory skills. The tests are designed to determine any functional limitations, such as difficulty with handwriting or the ability to hold a utensil or cup. The patient may be asked to place a finger on the tip of her or his nose, draw a spiral, or perform other tasks or exercises.

The doctor may order an electromyogram to diagnose muscle or nerve problems. This test measures involuntary muscle activity and muscle response to nerve stimulation. The selection of the sensors used is important. In addition to studies of muscle activity, tremor can be assessed with accuracy using accelerometers.

Categories
Tremors are assessed according to amplitude, frequency, affected body parts, and the position or activity in which the tremor manifests. The combination of these four factors indicates likely diagnoses. For example, early Parkinson's first tends to manifest as a slow tremor in one hand while resting and disappears during intentional movements, but essential tremor appears symmetrically, during intentional movements and disappears while resting.

 * Amplitude: A fine tremor is very small or barely noticeable movement; a coarse tremor is a large movement.  Tremors in between these two may be described as medium amplitude.
 * Frequency: A slow tremor makes a motion at a few times per second.  A rapid or fast tremor is around 12 Hz or faster.  Tremors in between these two speeds may be described as intermediate speed.
 * Affected body parts: For example, the left hand, or both legs, or the voice.

The degree of tremor should be assessed in four positions. The tremor can then be classified by which position most accentuates the tremor:

Treatment
There is no cure for most tremors. The appropriate treatment depends on accurate diagnosis of the cause. Some tremors respond to treatment of the underlying condition. For example, in some cases of psychogenic tremor, treating the patient's underlying psychological problem may cause the tremor to disappear. A few medications can help relieve symptoms temporarily.

Medications
Medications remain the basis of therapy in many cases. Symptomatic drug therapy is available for several forms of tremor:
 * Parkinsonian tremor drug treatment involves L-DOPA or dopamine-like drugs such as pergolide, bromocriptine and ropinirole; They can be dangerous, however, as they may cause symptoms such as tardive dyskinesia, akathisia, clonus, and in rare instances tardive (late developing) psychosis. Other drugs used to lessen parkinsonian tremor include amantadine and anticholinergic drugs like benztropine
 * Essential tremor may be treated with beta blockers (such as propranolol and nadolol) or primidone, an anticonvulsant
 * Cerebellar tremor symptoms may decrease with the application of alcohol (ethanol) or benzodiazepine medications, both of which carry some risk of dependence or addiction
 * Rubral tremor patients may receive some relief using L-DOPA or anticholinergic drugs. Surgery may be helpful
 * Dystonic tremor may respond to diazepam, anticholinergic drugs, and intramuscular injections of botulinum toxin. Botulinum toxin is also prescribed to treat voice and head tremors and several movement disorders
 * Primary orthostatic tremor sometimes is treated with a combination of diazepam and primidone. Gabapentin provides relief in some cases
 * Enhanced physiological tremor is usually reversible once the cause is corrected. If symptomatic treatment is needed, beta blockers can be used

Lifestyle
Eliminating tremor "triggers," including stimulants such as caffeine, from the diet is often recommended. Essential tremor may benefit from slight doses of ethanol, but the potential negative consequences of regular ethanol intake need to be taken into account. Due to the risks, alternatives such as "GABAergic drugs like sodium oxybate and NASs, LVA Ca2+ channel blockers like zonisamide, glutamate receptor antagonists like perampanel, and long-chain alcohols like 1-octanol" are preferred. Beta blockers have been used as an alternative to alcohol in sports such as competitive dart playing and carry less potential for addiction.

Physical therapy and occupational therapy may help to reduce tremor and improve coordination and muscle control for some patients. A physical therapist or occupational therapist will evaluate the patient for tremor positioning, muscle control, muscle strength, and functional skills. Teaching the patient to brace the affected limb during the tremor or to hold an affected arm close to the body is sometimes useful in gaining motion control. Coordination and balancing exercises may help some patients. Some occupational therapists recommend the use of weights, splints, other adaptive equipment, and special plates and utensils for eating.

Surgery
Surgical intervention such as thalamotomy and deep brain stimulation may ease certain tremors. These surgeries are usually performed only when the tremor is severe and does not respond to drugs, and further evidence is required to determine the best course of treatment for any individual patient. Response to surgeries can be excellent, reducing some symptoms such as "tremors, stiffness, slowness, and dyskinesias" for patients with Parkinson's Disease.

Thalamotomy, involving the creation of lesions in the brain region called the thalamus, is quite effective in treating patients with essential, cerebellar, or Parkinsonian tremor. This in-hospital procedure is performed under local anesthesia, with the patient awake. After the patient's head is secured in a metal frame, the surgeon maps the patient's brain to locate the thalamus. A small hole is drilled through the skull and a temperature-controlled electrode is inserted into the thalamus. A low-frequency current is passed through the electrode to activate the tremor and to confirm proper placement. Once the site has been confirmed, the electrode is heated to create a temporary lesion. Testing is done to examine speech, language, coordination, and tremor activation, if any. If no problems occur, the probe is again heated to create a 3-mm permanent lesion. The probe, when cooled to body temperature, is withdrawn and the skull hole is covered. The lesion causes the tremor to permanently disappear without disrupting sensory or motor control.

Deep brain stimulation (DBS) uses implantable electrodes to send high-frequency electrical signals to the thalamus. The electrodes are implanted as described above. The patient uses a hand-held magnet to turn on and turn off a pulse generator that is surgically implanted under the skin. The electrical stimulation temporarily disables the tremor and can be "reversed", if necessary, by turning off the implanted electrode. Batteries in the generator last about 5 years and can be replaced surgically. DBS is currently used to treat parkinsonian tremor and essential tremor. It is also applied successfully for other rare causes of tremor.

The most common side effects of tremor surgery include dysarthria (problems with motor control of speech), temporary or permanent cognitive impairment (including visual and learning difficulties), and problems with balance.

Biomechanical loading
As well as medication, rehabilitation programmes and surgical interventions, the application of biomechanical loading on tremor movement has been shown to be a technique that is able to suppress the effects of tremor on the human body. It has been established in the literature that most of the different types of tremor respond to biomechanical loading. In particular, it has been clinically tested that the increase of damping or inertia in the upper limb leads to a reduction of the tremorous motion. Biomechanical loading relies on an external device that either passively or actively acts mechanically in parallel to the upper limb to counteract tremor movement. This phenomenon gives rise to the possibility of an orthotic management of tremor.

Starting from this principle, the development of upper-limb non-invasive ambulatory robotic exoskeletons is presented as a promising solution for patients who cannot benefit from medication to suppress the tremor. In this area robotic exoskeletons have emerged, in the form of orthoses, to provide motor assistance and functional compensation to disabled people. An orthosis is a wearable device that acts in parallel to the affected limb. In the case of tremor management, the orthosis must apply a damping or inertial load to a selected set of limb articulations.

Recently, some studies demonstrated that exoskeletons could achieve a consistent 40% of tremor power reduction for all users, being able to attain a reduction ratio in the order of 80% tremor power in specific joints of users with severe tremor. In addition, the users reported that the exoskeleton did not affect their voluntary motion. These results indicate the feasibility of tremor suppression through biomechanical loading.

The main drawbacks of this mechanical management of tremor are (1) the resulting bulky solutions, (2) the inefficiency in transmitting loads from the exoskeleton to the human musculo-skeletal system and (3) technological limitations in terms of actuator technologies. In this regard, current trends in this field are focused on the evaluation of the concept of biomechanical loading of tremor through selective Functional Electrical Stimulation (FES) based on a (Brain-to-Computer Interaction) BCI-driven detection of involuntary (tremor) motor activity.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Tremor


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Rationalism (disambiguation)

Rationalism is a philosophical position, theory, or view that reason is the source of knowledge.

Rationalism may also refer to:
 * Rationalism (architecture), a term applied to a number of architectural movements
 * Rationalism (international relations), a political perspective on the international system
 * Rationalism (theology), philosophical Rationalism applied in theology
 * Critical rationalism, an epistemological philosophy advanced by Karl Raimund Popper
 * Economic rationalism, an Australian term in discussion of microeconomic policy
 * Pancritical rationalism, a theory by William Warren Bartley developed from panrationalism and critical rationalism

title: Rationalism (disambiguation)


text:
Tiscali (disambiguation)

Tiscali may refer to:

 * Tiscali, an Italian telecommunications company
 * Tiscali Italia, an Italian telecommunications company
 * Tiscali UK, a British telecommunications company
 * Tiscali Short Film Award, sponsored by the company
 * Tiscali (village), an archaeological site in Sardinia, Italy

title: Tiscali (disambiguation)


text:
Amplitude

The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplitude (see below), which are all functions of the magnitude of the differences between the variable's extreme values. In older texts, the phase of a periodic function is sometimes called the amplitude.

Definitions
Sine voltage.svg curve 1.

2. Peak amplitude ($\scriptstyle\hat u$),

3. Peak-to-peak amplitude ($\scriptstyle2\hat u$),

4. Root mean square amplitude ($\scriptstyle\hat u/\sqrt{2}$),

5. Wave period (not an amplitude)]]

Peak amplitude and semi-amplitude
For symmetric periodic waves, like sine waves, square waves or triangle waves peak amplitude and semi amplitude are the same.

Peak amplitude
In audio system measurements, telecommunications and others where the measurand is a signal that swings above and below a reference value but is not sinusoidal, peak amplitude is often used. If the reference is zero, this is the maximum absolute value of the signal; if the reference is a mean value (DC component), the peak amplitude is the maximum absolute value of the difference from that reference.

Semi-amplitude
Semi-amplitude means half of the peak-to-peak amplitude. The majority of scientific literature employs the term amplitude or peak amplitude to mean semi-amplitude.

It is the most widely used measure of orbital wobble in astronomy and the measurement of small radial velocity semi-amplitudes of nearby stars is important in the search for exoplanets (see Doppler spectroscopy).

Ambiguity
In general, the use of peak amplitude is simple and unambiguous only for symmetric periodic waves, like a sine wave, a square wave, or a triangle wave. For an asymmetric wave (periodic pulses in one direction, for example), the peak amplitude becomes ambiguous. This is because the value is different depending on whether the maximum positive signal is measured relative to the mean, the maximum negative signal is measured relative to the mean, or the maximum positive signal is measured relative to the maximum negative signal (the peak-to-peak amplitude) and then divided by two (the semi-amplitude). In electrical engineering, the usual solution to this ambiguity is to measure the amplitude from a defined reference potential (such as ground or 0 V). Strictly speaking, this is no longer amplitude since there is the possibility that a constant (DC component) is included in the measurement.

Peak-to-peak amplitude
Peak-to-peak amplitude (abbreviated p–p or PtP or PtoP) is the change between peak (highest amplitude value) and trough (lowest amplitude value, which can be negative). With appropriate circuitry, peak-to-peak amplitudes of electric oscillations can be measured by meters or by viewing the waveform on an oscilloscope. Peak-to-peak is a straightforward measurement on an oscilloscope, the peaks of the waveform being easily identified and measured against the graticule. This remains a common way of specifying amplitude, but sometimes other measures of amplitude are more appropriate.

Root mean square amplitude
Root mean square (RMS) amplitude is used especially in electrical engineering: the RMS is defined as the square root of the mean over time of the square of the vertical distance of the graph from the rest state; i.e. the RMS of the AC waveform (with no DC component).

For complicated waveforms, especially non-repeating signals like noise, the RMS amplitude is usually used because it is both unambiguous and has physical significance. For example, the average power transmitted by an acoustic or electromagnetic wave or by an electrical signal is proportional to the square of the RMS amplitude (and not, in general, to the square of the peak amplitude).

For alternating current electric power, the universal practice is to specify RMS values of a sinusoidal waveform. One property of root mean square voltages and currents is that they produce the same heating effect as a direct current in a given resistance.

The peak-to-peak value is used, for example, when choosing rectifiers for power supplies, or when estimating the maximum voltage that insulation must withstand. Some common voltmeters are calibrated for RMS amplitude, but respond to the average value of a rectified waveform. Many digital voltmeters and all moving coil meters are in this category. The RMS calibration is only correct for a sine wave input since the ratio between peak, average and RMS values is dependent on waveform. If the wave shape being measured is greatly different from a sine wave, the relationship between RMS and average value changes. True RMS-responding meters were used in radio frequency measurements, where instruments measured the heating effect in a resistor to measure a current. The advent of microprocessor-controlled meters capable of calculating RMS by sampling the waveform has made true RMS measurement commonplace.

Pulse amplitude
In telecommunication, pulse amplitude is the magnitude of a pulse parameter, such as the voltage level, current level, field intensity, or power level.

Pulse amplitude is measured with respect to a specified reference and therefore should be modified by qualifiers, such as average, instantaneous, peak, or root-mean-square.

Pulse amplitude also applies to the amplitude of frequency- and phase-modulated waveform envelopes.

Formal representation
In this simple wave equation
 * $$x = A \sin(\omega [t - K]) + b \ ,$$

 * $$A$$ is the amplitude (or peak amplitude),
 * $$x$$ is the oscillating variable,
 * $$\omega$$ is angular frequency,
 * $$t$$ is time,
 * $$K$$ and $$b$$ are arbitrary constants representing time and displacement offsets respectively.

Units
The units of the amplitude depend on the type of wave, but are always in the same units as the oscillating variable. A more general representation of the wave equation is more complex, but the role of amplitude remains analogous to this simple case.

For waves on a string, or in a medium such as water, the amplitude is a displacement.

The amplitude of sound waves and audio signals (which relates to the volume) conventionally refers to the amplitude of the air pressure in the wave, but sometimes the amplitude of the displacement (movements of the air or the diaphragm of a speaker) is described. The logarithm of the amplitude squared is usually quoted in dB, so a null amplitude corresponds to −∞ dB. Loudness is related to amplitude and intensity and is one of the most salient qualities of a sound, although in general sounds it can be recognized independently of amplitude. The square of the amplitude is proportional to the intensity of the wave.

For electromagnetic radiation, the amplitude of a photon corresponds to the changes in the electric field of the wave. However, radio signals may be carried by electromagnetic radiation; the intensity of the radiation (amplitude modulation) or the frequency of the radiation (frequency modulation) is oscillated and then the individual oscillations are varied (modulated) to produce the signal.

Amplitude envelopes
Amplitude envelope refers to the changes in the amplitude of a sound over time, and is an influential property as it affects perception of timbre. A flat tone has a steady state amplitude that remains constant during time, which is represented by a scalar. Other sounds can have percussive amplitude envelopes featuring an abrupt onset followed by an immediate exponential decay.

Percussive amplitude envelopes are characteristic of various impact sounds: two wine glasses clinking together, hitting a drum, slamming a door, etc. where the amplitude is transient and must be represented as either a continuous function or a discrete vector. Percussive amplitude envelopes model many common sounds that have a transient loudness attack, decay, sustain, and release.

Amplitude normalization
With waveforms containing many overtones, complex transient timbres can be achieved by assigning each overtone to its own distinct transient amplitude envelope. Unfortunately, this has the effect of modulating the loudness of the sound as well. It makes more sense to separate loudness and harmonic quality to be parameters controlled independently of each other.

To do so, harmonic amplitude envelopes are frame-by-frame normalized to become amplitude proportion envelopes, where at each time frame all the harmonic amplitudes will add to 100% (or 1). This way, the main loudness-controlling envelope can be cleanly controlled.

In Sound Recognition, max amplitude normalization can be used to help align the key harmonic features of 2 alike sounds, allowing similar timbres to be recognized independent of loudness.

title: Amplitude


text:
Period

Period may refer to:

Common uses

 * Period (punctuation)
 * Era, a length or span of time
 * Menstruation, commonly referred to as a "period"

Arts, entertainment, and media

 * Period (music), a concept in musical composition
 * Periodic sentence (or rhetorical period), a concept in grammar and literary style.
 * Period, a descriptor for a historical or period drama
 * Period, a timeframe in which a particular style of antique furniture or some other work of art was produced, such as the "Edwardian period"
 * Period (Another American Lie), a 1987 album by B.A.L.L.
 * Period (mixtape), a 2018 mixtape by City Girls
 * Period, the final book in Dennis Cooper's George Miles cycle of novels
 * Periods., a comedy film series

Mathematics

 * In a repeating decimal, the length of the repetend
 * Period of a function, length or duration after which a function repeats itself
 * Period (algebraic geometry), numbers that can be expressed as integrals of algebraic differential forms over algebraically defined domains, forming a ring

Science

 * Period (gene), a gene in Drosophila involved in regulating circadian rhythm
 * Period (periodic table), a horizontal row of the periodic table
 * "Period-" or "per-iod-", in some chemical compounds, "per" refers to oxidation state, and "iod" refers to the compound containing iodine
 * Unit of time or timeframe
 * Period (geology), a subdivision of geologic time
 * Period (physics), the duration of time of one cycle in a repeating event
 * Orbital period, the time needed for one object to complete an orbit around another
 * Rotation period, the time needed for one object to complete a revolution
 * Wavelength, the spatial period of a periodic wave
 * Sentence (linguistics), especially when discussing complex sentences in Latin syntax

Other uses

 * Period (school), a class meeting time in schools
 * Period (ice hockey), a division of play in an ice hockey game
 * Accounting period, often shortened to "period" in business, an accounting timeframe analogous to a month
 * Periodt, slang of period used as an interjection

title: Period


text:
Kyoto

Kyoto (Japanese: 京都, Kyōto ), officially Kyoto City (京都市), is the capital city of Kyoto Prefecture in the Kansai region of Japan's largest and most populous island of Honshu. , the city had a population of 1.46 million, making it the ninth-most populous city in Japan. More than half (56.8%) of Kyoto Prefecture's population resides in the city. The city is the cultural anchor of the substantially larger Greater Kyoto, a metropolitan statistical area (MSA) home to a census-estimated 3.8 million people. It is also part of the even larger Keihanshin metropolitan area, along with Osaka and Kobe.

Kyoto is one of the oldest municipalities in Japan, having been chosen in 794 as the new seat of Japan's imperial court by Emperor Kanmu. The original city, named Heian-kyō, was arranged in accordance with traditional Chinese feng shui following the model of the ancient Chinese capitals of Chang'an and Luoyang. The emperors of Japan ruled from Kyoto in the following eleven centuries until 1869. It was the scene of several key events of the Muromachi period, Sengoku period, and the Boshin War, such as the Ōnin War, the Honnō-ji Incident, the Kinmon incident, and the Battle of Toba–Fushimi. The capital was relocated from Kyoto to Tokyo after the Meiji Restoration. The modern municipality of Kyoto was established in 1889. The city was spared from large-scale destruction during World War II and, as a result, its prewar cultural heritage has mostly been preserved.

Kyoto is considered the cultural capital of Japan and is a major tourist destination. The agency for cultural affairs of the national government is headquartered in the city. It is home to numerous Buddhist temples, Shinto shrines, palaces and gardens, some of which have been designated collectively as a World Heritage Site by UNESCO. Prominent landmarks include the Kyoto Imperial Palace, Kiyomizu-dera, Kinkaku-ji, Ginkaku-ji, and Kyoto Tower. The internationally renowned video game company Nintendo is based in Kyoto. Kyoto is also a center of higher learning in the country, and its institutions include Kyoto University, the second-oldest university in Japan.

Name
In Japanese, Kyoto was previously called Kyō (京), Miyako (都), Kyō no Miyako (京の都), and Keishi. After becoming the capital of Japan at the start of the Heian period (794–1185), the city was often referred to as Heian-kyō (平安京, "Heian capital"), and late in the Heian period the city came to be widely referred to simply as "Kyōto" (京都, "capital city"). After the seat of the emperor was moved to the city of Edo and that city was renamed "Tōkyō" (東京, meaning "eastern capital"), Kyoto was briefly known as "Saikyō" (西京, meaning "western capital"). As the capital of Japan from 794 to 1868, Kyoto is sometimes called the thousand-year capital (千年の都).

Historically, foreign spellings for the city's name have included Kioto and Miaco or Meaco.

Origins
Ample archeological evidence suggests human settlement in the area of Kyoto began as early as the Paleolithic period, although not much published material is retained about human activity in the region before the 6th century, around which time the Shimogamo Shrine is believed to have been established.

During the 8th century, when powerful Buddhist clergy became involved in the affairs of the imperial government, Emperor Kanmu chose to relocate the capital in order to distance it from the clerical establishment in Nara. His last choice for the site was the village of Uda, in the Kadono district of Yamashiro Province.

The new city, Heian-kyō (平安京), modeled after Chinese Tang dynasty capital Chang'an, became the seat of Japan's imperial court in 794, beginning the Heian period of Japanese history. Although military rulers established their governments either in Kyoto (Muromachi shogunate) or in other cities such as Kamakura (Kamakura shogunate) and Edo (Tokugawa shogunate), Kyoto remained Japan's capital until the transfer of the imperial court to Tokyo in 1869 at the time of the Imperial Restoration.

Middle Ages
In the Sengoku period, the city suffered extensive destruction in the Ōnin War of 1467–1477, and did not really recover until the mid-16th century. During the war, battles between samurai factions spilled into the streets, and came to involve court nobility (kuge) and religious factions as well. Nobles' mansions were transformed into fortresses, deep trenches dug throughout the city for defense and as firebreaks, and numerous buildings burned. The city has not seen such widespread destruction since.

In the late 16th century, Toyotomi Hideyoshi reconstructed the city by building new streets to double the number of north–south streets in central Kyoto, creating rectangle blocks superseding ancient square blocks. Toyotomi also built earthwork walls called odoi (御土居) encircling the city. Teramachi Street in central Kyoto is a Buddhist temple quarter where Toyotomi gathered temples in the city.

Early modern period
Throughout the Edo period, the economy of the city flourished as one of three major cities in Japan, the others being Osaka and Edo. At the end of the period, the Hamaguri rebellion of 1864 burned down 28,000 houses in the city, which showed the rebels' dissatisfaction towards the Tokugawa Shogunate.

Modern period
At the start of the Meiji period, the emperor's move from Kyoto to Tokyo in 1869 weakened the economy of Kyoto. The modern city of Kyoto was formed on April 1, 1889. The construction of Lake Biwa Canal in 1890 was one measure taken to revive the city. The population of the city exceeded one million in 1932.

Contemporary history
There was some consideration by the United States of targeting Kyoto with an atomic bomb at the end of World War II because of the possibility that the city's importance was great enough that its loss might persuade Japan to surrender. In the end, at the insistence of Henry L. Stimson, Secretary of War in the Roosevelt and Truman administrations, the city was removed from the list of targets and replaced by Nagasaki. The city was largely spared from conventional bombing as well, although small-scale air raids did result in casualties. During the occupation, the U.S. Sixth Army and I Corps were headquartered in Kyoto.

As a result, Kyoto is one of the few Japanese cities that still have an abundance of prewar buildings, such as the traditional townhouses known as machiya. However, modernization is continually breaking down traditional Kyoto in favor of newer architecture, such as the Kyōto Station complex.

Kyoto became a city designated by government ordinance on September 1, 1956. In 1994, 17 historic monuments in Kyoto were inscribed on the list as UNESCO World Heritage Sites. In 1997, Kyoto hosted the conference that resulted in the protocol on greenhouse gas emissions (United Nations Framework Convention on Climate Change).

Terrain
Kyoto is located in a valley, part of the Yamashiro (or Kyoto) Basin, in the eastern part of the mountainous region known as the Tamba highlands. The Yamashiro Basin is surrounded on three sides by mountains known as Higashiyama, Kitayama and Nishiyama, with a maximum height of approximately 1000 m above sea level. This interior positioning results in hot summers and cold winters. There are three rivers in the basin, the Uji River to the south, the Katsura River to the west, and the Kamo River to the east. Kyoto City takes up 17.9% of the land in Kyoto Prefecture and has a total area of 827.9 km².

Kyoto sits atop a large natural water table that provides the city with ample freshwater wells. Due to large-scale urbanization, the amount of rain draining into the table is dwindling and wells across the area are drying at an increasing rate.

Climate
Kyoto has a humid subtropical climate (Köppen Cfa), featuring a marked seasonal variation in temperature and precipitation. Summers are hot and humid, but winters are relatively cold with occasional snowfall. Kyoto's rainy season begins around the middle of June and lasts until the end of July, yielding to a hot and sunny latter half of the summer. Kyoto, like most of the Pacific coast and central areas of Japan, is prone to typhoons during the summer and autumn.

Cityscape
Kyoto contains roughly 2,000 temples and shrines. The main business district is located to the south of the Kyoto Imperial Palace. In the center of the city, there are several covered shopping arcades only open to pedestrian traffic, such as Teramachi Street and Shinkyōgoku Street.

The original city was arranged in accordance with traditional Chinese feng shui following the model of the ancient Chinese capital of Chang'an/Luoyang. The Imperial Palace faced south, resulting in Ukyō (the right sector of the capital) being on the west, while Sakyō (the left sector) is on the east. The streets in the modern-day wards of Kamigyō-ku, Nakagyō-ku, and Shimogyō-ku still follow a grid pattern. Areas outside of the city center do not follow the same grid pattern, though streets throughout Kyoto are referred to by name, a practice that is rare in most regions of Japan.

Administrative divisions
In the 1870s, the city was divided into a northern ward (Kamigyō-ku) and a southern ward (Shimogyō-ku), each working as individual administrative divisions of Kyoto Prefecture. The modern municipality was created by the unification of these wards into the city of Kyoto in 1889.

Due to the creation of new administrative districts and a number of municipal mergers that took place between the 1920s and the 1970s, the contemporary city of Kyoto is divided into eleven wards (区). The central wards, located to the west of the Kamo River, are small and densely populated. The city hall is located in Nakagyō-ku, and the Kyoto prefectural offices are located in present-day Kamigyō-ku.

Demographics
Kyoto was the largest city in Japan until the late 16th century, when its population was surpassed by those of Osaka and Edo. Before World War II, Kyoto vied with Kobe and Nagoya to rank as the fourth or fifth largest city in Japan. Having avoided most wartime destruction, it was again the third largest city in 1947. By 1960 it had fallen to fifth again, and by 1990 it had fallen to seventh. , it was the ninth largest city in Japan by population and had led the country in population decrease for two consecutive years. However, the population of the city rises during standard working hours, and Kyoto ranks seventh in Japan in terms of daytime population.

Approximately 55% of the total population of Kyoto Prefecture is concentrated in the city of Kyoto, which is the highest ratio among the prefectures of Japan.

Government
The city of Kyoto is governed by the mayor of Kyoto and the Kyoto City Assembly, a municipal council.

Kyoto City Assembly
The legislative city assembly has 67 elected members, and terms are four years in length. As of 2024, the assembly is controlled by a coalition of members affiliated with the Liberal Democratic Party, Komeito, and the Democratic Civic Forum.

List of mayors
Between the founding of the modern city and 1898, the governor of Kyoto Prefecture also acted as the mayor of the city of Kyoto. From 1898 through the Second World War, mayors were nominated by the Kyoto City Assembly and appointed by the Minister of Home Affairs.

Since 1947, mayors of Kyoto have been chosen by direct election to four-year terms. As of 2024, there have been ten mayors elected using this system. While some mayors have resigned or died in office, no mayor has lost a reelection bid in the postwar period. In the 2024 Kyoto mayoral election, independent candidate Koji Matsui was elected for the first time, supported by the Liberal Democratic Party, Komeito, the Constitutional Democratic Party, and the Democratic Party for the People.

Economy
Information technology and electronics are key industries in Kyoto. The city is home to the headquarters of Nintendo, Intelligent Systems, SCREEN Holdings, Tose, Hatena, Omron, Kyocera, Shimadzu, Rohm, Horiba, Nidec Corporation, Nichicon, Nissin Electric, and GS Yuasa.

Domestic and international tourism contributes significantly to Kyoto's economy. In 2014, the city government announced that a record number of tourists had visited Kyoto. As a result of a sharp decline in tourism during the COVID-19 pandemic, the mayor acknowledged in 2021 "the possibility of bankruptcy in the next decade" and announced job cuts in the administration and cuts in social assistance, including reductions in funding for home care.

Traditional Japanese crafts are also a major industry of Kyoto; Kyoto's kimono weavers are particularly renowned, and the city remains the premier center of kimono manufacturing. Sake brewing is another prominent traditional industry in Kyoto, and the headquarters of major sake brewers Gekkeikan and Takara Holdings are found in Kyoto.

Other notable businesses headquartered in Kyoto include Aiful, Ishida, Nissen Holdings, Gyoza no Ohsho, Sagawa Express, Volks, and Wacoal.

Primary and secondary education
As of 1 May 2023, there were 154 municipal public elementary schools in Kyoto, with a total of 55,736 pupils. At the secondary level, there were 66 municipal public junior high schools with 27,046 students and 11 municipal public senior high schools with 5,117 students.

Tertiary education
Home to 40 institutions of higher education, Kyoto is one of the academic centers in Japan. Kyoto University is ranked highly among all universities nationwide, with eight Nobel laureates and two Prime Ministers of Japan among its alumni. The Research Institute for Mathematical Sciences and the Yukawa Institute for Theoretical Physics, both part of the university, have been affiliated with influential mathematicians and physicists. Private universities such as Doshisha University and Ritsumeikan University are also located in the city.

The Consortium of Universities in Kyoto is a Kyoto-based higher education network consisting of three national universities, three public (prefectural and municipal) universities, 45 private universities, five other organizations, and representatives from the city government. The Consortium does not offer degrees, but allows students of member universities to take courses at other member universities.

In addition to Japanese universities and colleges, educational institutions from other countries operate programs in the city. The Kyoto Consortium for Japanese Studies (KCJS) is a group of 14 American universities that runs overseas academic programs in Japanese language and cultural studies for university students. Similarly, the Associated Kyoto Program runs a study-abroad academic program with a focus on cultural, language, and historical learning in and around the Kansai metropolitan area.

Railways
Kyoto is served by rail transportation systems operated by several different companies and organizations. The city's main gateway terminal, Kyōto Station, connects the Tokaido Shinkansen bullet train line with five JR West lines, a Kintetsu line, and a municipal subway line.

The Keihan Electric Railway, the Hankyu Railway, and other rail networks also offer frequent services within the city and to other cities and suburbs in the Kinki region. Although Kyoto does not have its own commercial airport, the limited express Haruka operated by JR West carries passengers from Kansai International Airport to Kyōto Station in 73 minutes.

The Kyoto Railway Museum in Shimogyō-ku, operated by JR West, displays many steam, diesel, and electric locomotives used in Japan between the 1880s and the present.

High-speed rail
The Tokaidō Shinkansen, operated by JR Central, provides high-speed rail service linking Kyoto with Nagoya, Yokohama, and Tokyo to the east and with nearby Osaka to the west. Beyond Osaka, many trains boarding at Kyoto continue on the San'yō Shinkansen route managed by JR West, providing access to cities including Kobe, Okayama, Hiroshima, Kitakyushu, and Fukuoka. The trip from Tokyo to Kyoto takes around 2.5 hours, and the trip from Hakata Station in Fukuoka to Kyoto takes just over three hours by the fastest train service Nozomi. All Shinkansen trains stop at Kyōto Station, including Hikari and Kodama trains.

Conventional lines

 * West Japan Railway Company (JR West)
 * Tōkaidō Main Line (JR Kyoto Line/Biwako Line)
 * San'in Main Line (Sagano Line)
 * Kosei Line
 * Nara Line

 * Hankyu Railway
 * Hankyu Kyoto Main Line
 * Hankyu Arashiyama Line

 * Keihan Electric Railway
 * Keihan Main Line
 * Keihan Ōtō Line
 * Keihan Uji Line
 * Keihan Keishin Line

 * Kintetsu Railway
 * Kintetsu Kyoto Line

 * Sagano Scenic Railway
 * Sagano Scenic Line

Subways
The Kyoto Municipal Transportation Bureau operates the Kyoto Municipal Subway consisting of two lines: the Karasuma Line and the Tōzai Line. The two lines are linked at Karasuma Oike Station near Kyoto's central business district.

The Karasuma Line runs primarily north to south between the terminal of Kokusaikaikan Station and Takeda Station, and takes its name from the fact that trains run beneath Karasuma Street between Kitaōji Station in Kita-ku and Jūjō Station in Minami-ku. The Karasuma Line connects to the Hankyu Kyoto Main Line at the intersection of Shijō Karasuma in Kyoto's central business district and to JR lines and the Kyoto Kintetsu Line at Kyōto Station. In addition, the Transportation Bureau and Kintetsu jointly operate through services which continue to Kintetsu Nara Station in Nara, the capital city of Nara Prefecture.

The Tōzai Line runs from the southeastern area of the city towards the center, then east to west (tōzai in Japanese) through the Kyoto downtown area where trains run beneath the east–west streets of Sanjō Street, Oike Street, and Oshikōji Street. The Keihan Keishin Line has been integrated into this line, and thus Keihan provides through services to Hamaōtsu in the neighboring city of Ōtsu, the capital of Shiga Prefecture. Within the city of Kyoto, the Tōzai Line also connects to the Keihan lines at Yamashina Station, Misasagi Station, and Sanjō Keihan Station, and to the Keifuku Electric Railroad at the terminal of Uzumasa Tenjingawa Station.

Tramways

 * Keifuku Electric Railroad (Randen)
 * Keifuku Arashiyama Main Line
 * Keifuku Kitano Line

 * Eizan Electric Railway (Eiden)
 * Eizan Main Line
 * Eizan Kurama Line

Buses
Kyoto's municipal bus network is extensive. Private carriers also operate within the city. Many tourists join commuters on the public buses, or take tour buses. Kyoto's buses have announcements in English and electronic signs with stops written in the Latin alphabet. Buses operating on routes within the city, the region, and the nation stop at Kyōto Station. In addition to Kyōto Station, bus transfer is available at the intersection of Shijō Kawaramachi, Sanjō Keihan Station, and the intersection of Karasuma Kitaōji near Kitaōji Station.

Roads and waterways
Because many older streets in Kyoto are narrow, there are a significant number of one-way roads without sidewalks. Cycling is a common form of personal transportation in the city, although there are few areas set aside for bicycle parking and bicycles parked in restricted areas are impounded.

Kyoto has fewer toll-highways than other Japanese cities of comparable size. There are nine national highways in the city of Kyoto: Route 1, Route 8, Route 9, Route 24, Route 162, Route 171, Route 367, Route 477, and Route 478.

The city is connected with other parts of Japan by the Meishin Expressway, which has two interchanges in the city: Kyoto-higashi Interchange (Kyoto East) in Yamashina-ku and Kyoto-minami Interchange (Kyoto South) in Fushimi-ku. The Kyoto Jūkan Expressway connects the city to the northern regions of Kyoto Prefecture. The Second Keihan Highway is another bypass to Osaka.

Traditionally, trade and haulage took place by waterway, and there continue to be a number of navigable rivers and canals in Kyoto. In contemporary Kyoto, however, waterways are no longer commonly used for transportation of passengers or goods, other than for limited sightseeing purposes such as excursion boats on the Hozu River and cormorant fishing boats on the Ōi River.

Culture
Although ravaged by wars, fires, and earthquakes during its eleven centuries as the imperial capital, Kyoto suffered only minor damage in World War II. It was removed from the atomic bomb target list (which it had headed) by the personal intervention of Secretary of War Henry L. Stimson, as Stimson wanted to save this cultural center, which he knew from his honeymoon and later diplomatic visits. Kyoto remains Japan's cultural center. About 20% of Japan's National Treasures and 14% of Important Cultural Properties exist in the city proper. The government of Japan relocated the Agency for Cultural Affairs to Kyoto in 2023.

With its 2,000 religious places – 1,600 Buddhist temples and 400 Shinto shrines, as well as palaces, gardens and architecture intact – it is one of the best preserved cities in Japan. Among the most famous temples in Japan are Kiyomizu-dera, a magnificent wooden temple supported by pillars off the slope of a mountain; Kinkaku-ji, the Temple of the Golden Pavilion; Ginkaku-ji, the Temple of the Silver Pavilion; and Ryōan-ji, famous for its rock garden. The Heian Jingū is a Shinto shrine, built in 1895, celebrating the imperial family and commemorating the first and last emperors to reside in Kyoto. Three special sites have connections to the imperial family: the Kyoto Gyoen area including the Kyoto Imperial Palace and Sentō Imperial Palace, homes of the emperors of Japan for many centuries; Katsura Imperial Villa, one of the nation's finest architectural treasures; and Shugakuin Imperial Villa, one of its best Japanese gardens. In addition, the temple of Sennyu-ji houses the tombs of the emperors from Shijō to Kōmei.

Other sites in Kyoto include Arashiyama, the Gion and Ponto-chō geisha quarters, the Philosopher's Walk, and the canals that line some of the older streets.

The "Historic Monuments of Ancient Kyoto" are listed by the UNESCO as a World Heritage Site. These include the Kamo Shrines (Kami and Shimo), Kyō-ō-Gokokuji (Tō-ji), Kiyomizu-dera, Daigo-ji, Ninna-ji, Saihō-ji (Kokedera), Tenryū-ji, Rokuon-ji (Kinkaku-ji), Jishō-ji (Ginkaku-ji), Ryōan-ji, Hongan-ji, Kōzan-ji, and the Nijō Castle, primarily built by the Tokugawa shōguns. Other sites outside the city are also on the list.

Kyoto is renowned for its abundance of delicious Japanese foods and cuisine. The special circumstances of Kyoto as a city away from the sea and home to many Buddhist temples resulted in the development of a variety of vegetables peculiar to the Kyoto area (京野菜). The oldest restaurant in Kyoto is Honke Owariya which was founded in 1465.

Japan's television and film industry has its center in Kyoto. Many jidaigeki, action films featuring samurai, were shot at Toei Uzumasa Eigamura. A film set and theme park in one, Eigamura features replicas of traditional Japanese buildings, which are used for jidaigeki. Among the sets are a replica of the old Nihonbashi (the bridge at the entry to Edo), a traditional courthouse, a Meiji Period police box and part of the former Yoshiwara red-light district. Actual film shooting takes place occasionally, and visitors are welcome to observe the action.

The dialect spoken in Kyoto is known as Kyō-kotoba or Kyōto-ben, a constituent dialect of the Kansai dialect. Until the late Edo period, the Kyoto dialect was the de facto standard Japanese, although it has since been replaced by modern standard Japanese. Traditional Kyoto expressions include the polite copula dosu, the honorific verb ending -haru, and the greeting phrase okoshi-yasu.

Festivals
Kyoto is well known for its traditional festivals which have been held for over 1,000 years and are a major tourist attraction. The first is the Aoi Matsuri on May 15. Two months later (July) is the Gion Matsuri known as one of the 3 great festivals of Japan, culminating in a massive parade on July 17. Kyoto marks the Bon Festival with the Gozan no Okuribi, lighting fires on mountains to guide the spirits home (August 16). The October 22 Jidai Matsuri, Festival of the Ages, celebrates Kyoto's illustrious past.

UNESCO World Heritage Site
The UNESCO World Heritage Site Historic Monuments of Ancient Kyoto (Kyoto, Uji and Otsu Cities) includes fourteen temples, shrines, and castles in Kyoto dating from between the sixth century (Shimogamo Shrine, though extant structures are more recent) and the seventeenth century (Nijō Castle). The sites were designated as World Heritage in 1994.

Museums

 * Hakusasonso Hashimoto Kansetsu Garden and Museum (白沙村荘 橋本関雪記念館)
 * Hosomi Museum (細見美術館)
 * Joutenkaku Museum (承天閣美術館)
 * Kitamura Museum (北村美術館)
 * Koryo Museum of Art (高麗美術館)
 * Kyoto Arashiyama Orgel Museum (京都嵐山オルゴール美術館)
 * Kyoto Art Center (京都芸術センター)
 * Kyoto Botanical Garden (京都府立植物園)
 * Kyoto City Archaeological Museum (京都市考古資料館)
 * Kyoto City Heiankyo Sosei-Kan Museum (京都市平安京創生館)
 * Kyoto International Manga Museum (京都国際マンガミュージアム)
 * Kyoto Kaleidoscope Museum (京都万華鏡ミュージアム)
 * Kyoto Municipal Museum of Art (京都市美術館)
 * Kyoto Museum for World Peace (国際平和ミュージアム)
 * Kyoto Museum of Traditional Crafts (京都伝統産業ふれあい館)
 * Kyoto National Museum (京都国立博物館)
 * Kyoto Prefectural Garden of Fine Arts (京都府立陶板名画の庭)
 * Kyoto Prefectural Insho-Domoto Museum of Fine Arts (京都府立堂本印象美術館)
 * Kyoto Railway Museum (京都鉄道博物館)
 * Kyoto University Museum (京都大学総合博物館)
 * Museum of Kyoto (京都府京都文化博物館)
 * Namikawa Cloisonne Museum of Kyoto (並河靖之七宝記念館)
 * National Museum of Modern Art, Kyoto (京都国立近代美術館)
 * Nomura Art Museum (野村美術館)
 * Onishi Seiwemon Museum (大西清右衛門美術館)
 * Raku Museum (楽美術館)
 * Ryozen Museum of History (幕末維新ミュージアム 霊山歴史館)
 * Sen-oku Hakuko Kan (泉屋博古館)
 * Shigureden (時雨殿)
 * Tin Toy Museum (ブリキのおもちゃ博物館)
 * Toei Kyoto Studio Park (東映太秦映画村)
 * Yurinkan Museum (藤井斉成会有鄰館)

Sports

Kyoto has been the site of many annual sporting events, ranging from the 400-year-old Tōshiya archery exhibition held at the Sanjūsangen-dō Temple to the Kyoto Marathon and the Shimadzu All Japan Indoor Tennis Championships.

Several sports teams are based in Kyoto, including professional football and basketball teams. In football, Kyoto has been represented by Kyoto Sanga FC, a club which won the Emperor's Cup in 2002 and rose to J. League's Division 1 in 2005. Kyoto Sanga began as an amateur non-company club in the 1920s, making it the J. League team with the longest history, although it was only after professionalization in the 1990s that it was able to compete in the Japanese top division. Until 2019, Kyoto Sanga used Takebishi Stadium Kyoto in Ukyō-ku as its home stadium, but home matches were moved to the city of Kameoka, Kyoto in 2020. There are also several amateur football clubs based in Kyoto. The amateur clubs AS Laranja Kyoto, Ococias Kyoto AC, and Kyoto Shiko Soccer Club compete in the regional Kansai Soccer League.

Another professional team based in Kyoto is the Kyoto Hannaryz, a men's basketball team in the First Division of the B.League that plays its home games at the Kyoto City Gymnasium in Ukyō-ku. Kyoto has also been the home of other professional teams that have subsequently moved or been disbanded. Between 1949 and 1952, the Central League professional baseball team Shochiku Robins played home games at Kinugasa Ballpark in Kita-ku and Nishi-Kyōgoku Baseball Park (now known as Wakasa Stadium) in Ukyō-ku. This team eventually became the Yokohama DeNA BayStars. Kyoto also hosted two teams in the Japan Women's Baseball League before the league folded in 2021.

Company teams in Kyoto include two rugby squads, the Mitsubishi Motors Kyoto Red Evolutions and the Shimadzu Breakers, which compete in the Kansai regional rugby league Top West. In baseball, company teams have competed in the regional JABA Kyoto Tournament annually since 1947.

Kyoto Racecourse in Fushimi-ku is one of ten racecourses operated by the Japan Racing Association. It hosts notable horse races including the Kikuka-shō, Spring Tenno Sho, and Queen Elizabeth II Cup.

Twin towns – Sister cities
The city of Kyoto has sister-city relationships with the following cities:

 * 🇺🇸 Boston, United States (since June 1959)
 * 🇩🇪 Cologne, Germany (since May 1963)
 * 🇮🇹 Florence, Italy (since September 1965)
 * 🇲🇽 Guadalajara, Mexico (since October 1980)
 * 🇺🇦 Kyiv, Ukraine (since September 1971)
 * 🇨🇿 Prague, Czech Republic (since April 1996)
 * 🇨🇳 Xi'an, China (since May 1974, friendship city)
 * Zagreb, Croatia (since October 1981)

Partner cities
In addition to its sister city arrangements which involve multi-faceted cooperation, Kyoto has created a system of "partner cities" which focus on cooperation based on a particular topic. At present, Kyoto has partner-city arrangements with the following cities:

 * 🇧🇪 Brussels, Belgium (since April 2006)
 * Huế, Vietnam (since February 2013)
 * 🇹🇷 Istanbul, Turkey (since June 2013)
 * 🇰🇷 Jinju, South Korea (since March 1999)
 * 🇹🇷 Konya, Turkey (since December 2009)
 * 🇫🇷 Paris, France (since June 1958)
 * 🇨🇳 Qingdao, China (since August 2012)
 * 🇨🇦 Quebec City, Canada (since May 2016)
 * 🇹🇼 Tainan, Taiwan (since June 2021)
 * 🇮🇳 Varanasi, India (since August 2014)
 * Vientiane, Laos (since November 2015)
 * 🇹🇼 Yilan City, Taiwan (since August 2018)

title: Kyoto