AD = autosomal dominant: MOI = mode of inheritance; NA = not applicable

See Episodic Ataxia: OMIM Phenotypic Series to view genes associated with this phenotype in OMIM.

EA2 is allelic to SCA6 and familial hemiplegic migraine type 1.

EA3 has been described in a large Canadian kindred of Mennonite heritage [Steckley et al 2001].

EA4 (also referred to as periodic vestibulocerebellar ataxia) has been described in families from North Carolina of northern European origin by Farmer & Mustian [1963] and Vance et al [1984].

Steckley et al [2001]

EA4 does not link to loci identified with EA1, EA2, or spinocerebellar ataxia types 1, 2, 3, 4, and 5 [Damji et al 1996].

EA5 can result from pathogenic variants in CACNB4 as described in a French-Canadian family [Escayg et al 2000]. EA5 is allelic with susceptibility to juvenile myoclonic epilepsy 6 (EJM6, OMIM 607682); the semiology of seizures in EA5 is similar to EJM6.

EA6 can result from pathogenic variants in SLC1A3, which encodes the excitatory amino acid transporter 1. In cells expressing mutated proteins, glutamate uptake is reduced, suggesting that glutamate transporter dysfunction underlies the disease [Jen et al 2005, de Vries et al 2009].

EA7 has been described in a four-generation family whose affected individuals showed episodic ataxia [Kerber et al 2007]. A candidate region on chromosome 19q13, termed the EA7 locus, has been identified [Kerber et al 2007].

Genome-wide linkage analysis found linkage to an 18.5-Mb locus on chromosome 1p36.13-p34.3 [Conroy et al 2014].

The phenotype of paroxysmal kinesigenic dyskinesia can include benign familial infantile epilepsy (BFIE), infantile convulsions and choreoathetosis (ICCA), hemiplegic migraine, migraine with and without aura, and episodic ataxia.

The acquired form of Isaac's syndrome occasionally develops in association with peripheral neuropathies or after radiation treatment. Twenty percent of affected individuals have an associated thymoma. Antibodies that involve K+ channels have been detected in approximately 40% of affected individuals [Hart et al 2002]. Several of these auto-antibodies do not bind directly with Kv1.1, Kv1.2, or Kv1.6 channels, as previously believed, but rather to associated proteins such as leucine-rich glioma-inactivated protein 1, contactin-associated protein-like 2, contactin-2, or others as yet unidentified [Irani et al 2010, Lai et al 2010, Lancaster et al 2011].