Episodic ataxia is a genetically heterogeneous neurologic condition characterized by spells of incoordination and imbalance, often associated with progressive ataxia. Episodic ataxia type 2 is the most common form of EA (Jen et al., 2007). For a discussion of genetic heterogeneity of episodic ataxia, see EA1 (160120).

Autosomal recessive spinocerebellar ataxia-10 is an autosomal recessive neurodegenerative disorder with onset in the teenage or young adult years of gait and limb ataxia, dysarthria, and nystagmus associated with marked cerebellar atrophy on brain imaging (summary by Vermeer et al., 2010). Some patients have low levels of coenzyme Q10 (CoQ10) in muscle and may show some clinical improvement with CoQ10 treatment (Balreira et al., 2014).

Cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS) is an autosomal recessive slowly progressive neurologic disorder characterized by imbalance due to cerebellar gait and limb ataxia with cerebellar atrophy on brain imaging, nystagmus, dysarthria, and peripheral sensory neuropathy with decreased or absent deep tendon reflexes. More variable features include vestibular dysfunction, chronic cough, autonomic dysfunction, saccadic pursuit, and pyramidal signs (extensor plantar responses). Most patients have onset in late adulthood, although earlier onset has been reported. Rare patients have features suggestive of lower motor neuron involvement (Szmulewicz et al., 2011, Miyatake et al., 2022).

A rare autosomal dominant cerebellar ataxia with characteristics of slowly progressive late-onset gait and limb ataxia, dysarthria and variable nystagmus. Brain imaging reveals cerebellar atrophy.

Late-onset spinocerebellar ataxia-27B (SCA27B) is an autosomal dominant neurodegenerative disorder characterized by the onset of gait and appendicular ataxia in adulthood, usually around age 55 (range 30 to late eighties). About half of patients present with episodic features. The disorder is slowly progressive, and some patients may lose independent ambulation. Additional features include downbeat and horizontal nystagmus, diplopia, vertigo, and dysarthria. Brain imaging tends to show cerebellar atrophy (Pellerin et al., 2023). For a general discussion of autosomal dominant spinocerebellar ataxia, see SCA1 (164400).