[MIM 108 500]

(episodic ataxia type 2, EA2)

Unknown prevalence. Autosomal dominant transmission of mutations of the gene CACNA1A (19p13) coding for the main subunit of the calcium channel P/Q, as for  spinocerebellar ataxia type 6 (see spinocerebellar ataxias). Other very rare forms of familial episodic ataxia close to type 2 are due to mutation of the gene CACNB4 EU (calcium channel Cav2.1: type 5) or another unidentified gene (type 7). Cerebellar ataxia characterised by acute episodes of ataxia, vertigo and nausea during from a few minutes to several days.

Crises are accompanied by diplopia, dysarthria, dystonia or hemiplegia. Half of patients also suffer of migraine headache. Crises can be triggered by stress, caffeine, alcohol or phenytoin. Between crises, individuals are usually asymptomatic even if nystagmus (90%) or discreet ataxia may persist.

The frequency and severity of crises can be reduced or even stopped in the majority of patients by administration of acetazolamide.

Treatment results in an increased risk for urinary lithiases.

Anesthetic implications:

avoid stress, check blood electrolytes (K+, HCO3-) in case of treatment with acetazolamide

References :

-        Riant F, Vahedi K, Tournier-Lasserre E.
Ataxies épisodiques.
EMC Neurologie 2011 17-066-A-10

Updated: November 2016