Familial paroxysmal ataxia

Familial paroxysmal ataxia, also known as episodic ataxia (EA), encompasses a group of rare inherited neurological disorders characterized by recurrent episodes of cerebellar ataxia — a lack of voluntary coordination of muscle movements — that occur in discrete attacks (paroxysms) rather than being constant. The condition primarily affects the nervous system, particularly the cerebellum, which controls balance and coordination. Between episodes, individuals may be neurologically normal or may develop progressive baseline cerebellar dysfunction over time. The most well-recognized subtypes are Episodic Ataxia Type 1 (EA1, caused by mutations in the KCNA1 gene encoding a potassium channel) and Episodic Ataxia Type 2 (EA2, caused by mutations in the CACNA1A gene encoding a calcium channel), though additional subtypes have been described. Key symptoms include recurrent episodes of imbalance, incoordination, slurred speech (dysarthria), vertigo, and nausea. In EA1, attacks are typically brief (seconds to minutes) and may be accompanied by myokymia (continuous fine muscle rippling), while in EA2, episodes tend to last longer (hours to days) and may be associated with interictal nystagmus (involuntary eye movements between attacks). Attacks can be triggered by physical exertion, emotional stress, startle, sudden postural changes, caffeine, or alcohol. Some patients develop progressive cerebellar atrophy and persistent ataxia over time. Treatment depends on the subtype. Acetazolamide, a carbonic anhydrase inhibitor, is the mainstay of preventive therapy, particularly effective in EA2, and can significantly reduce the frequency and severity of attacks. For EA1, carbamazepine or other antiepileptic medications may be beneficial. Avoidance of known triggers is also recommended. While there is no cure, many patients achieve good symptom control with appropriate medication. Genetic counseling is recommended for affected families.

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