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Vestibulocerebellar syndrome
Vestibulocerebellar syndrome, also known as vestibulocerebellar ataxia, is a progressive neurological disorder that causes a variety of medical problems. Initially symptoms present as periodic attacks of abnormal eye movements but may intensify to longer-lasting motor incapacity. The disorder has been localized to the vestibulocerebellum, specifically the flocculonodular lobe. Symptoms of vestibulocerebellar syndrome may appear in early childhood but the full onset of neurological symptoms including nystagmus (involuntary eye movement), ataxia (loss of voluntary muscle coordination), and tinnitus (perception of sound in the absence of external stimulation) does not occur until early adulthood. To date, vestibulocerebellar syndrome has only been identified in three families but has affected multiple generations within them. Based on the familial pedigrees it has been characterized as an autosomal dominant disorder, although the exact genetic locus has not been identified.〔〔 It has been found to be genetically distinct from other seemingly similar forms of neurological syndromes such as episodic ataxia types 1 and 2. Due to its rarity, however, little is known about specific details of the pathology or long-term treatment options.〔 There is currently no cure for vestibulocerebellar syndrome, although some drug therapies have been effective in alleviating particular symptoms of the disorder.
== Symptoms ==
The symptoms of vestibulocerebellar syndrome vary among patients but are typically a unique combination of ocular abnormalities including nystagmus, poor or absent smooth pursuit (ability of the eyes to follow a moving object), strabismus (misalignment of the eyes), diplopia (double vision), oscillopsia (the sensation that stationary objects in the visual field are oscillating) and abnormal vestibulo-ocular reflex (reflex eye adjustment to stabilize gaze during head movement). Gaze-paretic nystagmus, one of the most common symptoms among patients results in poor gaze-holding due to neuron integrator dysfunction. Rebound nystagmus is also frequently found in conjunction with gaze-paretic nystagmus and is characteristic of cerebellar malfunction. These abnormal eye movements are often the earliest indicators of the disorder and may appear during childhood. The time of full onset of symptoms, including motor abnormalities, ranges from age 30 to age 60. Initially, symptoms present as isolated episodic attacks but occur at increasing frequency over time and may eventually become a permanent condition.〔 In conjunction with eye abnormalities patients also present with periodic attacks of vertigo, tinnitus, and ataxia that are associated with sudden changes in head position.〔 Attacks were seen to vary in duration from a few minutes to months in different individuals and were often accompanied by nausea and vomiting.
During a typical attack, patients reported having ataxic gait with a tendency to fall to either side while lacking the ability to walk heel-to-toe.〔 With more severe attacks, patients had to sit down due to extreme unsteadiness. Fine motor abilities, such as writing and buttoning clothes, became impaired during an attack. However, speech remained unaffected. Attacks did not cause a loss of consciousness nor did they disturb mental activity.〔 Once the attack ended, oscillopsia faded and the intensity of nystagmus decreased.〔 Although these attacks are similar to episodic ataxia, patients with vestibulocerebellar syndrome do not completely lose motor control in arms and legs or experience dysarthria (poor speech articulation), as patients with episodic ataxia do. The disturbances to vestibular function during periodic attacks are the primary distinction between vestibulocerebellar syndrome and other similar neurological syndromes. These conditions do not consistently cause the symptoms of dizziness and ocular impairment that have been localized to the vestibulocerebellum, leading researchers to characterize veistibulocerebellar syndrome as a distinct disorder.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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