[MIM 160120]

(EA1)

Autosomal dominant transmission of mutations of the gene KCNA1 (12p13) coding for the subunit α of the voltage-dependent potassium channel Kv1.1 that is highly expressed in the  central and peripheral nervous system.

Clinical picture:

-        onset in the first two decades of life

-        ataxic episodes of the trunk and the limbs that last from a few seconds to a few minutes

-        accompanied by visual phenomena: visual blurring, oscillopsia

-        frequently: headache, nausea

-        triggered by stress or a sudden change in position

-        the hyperexcitability of the peripheral nervous system is expressed by myokymia (twitching or  involuntary and localized tremor of muscle fibers, often at the level of the face or a limb) or a neuromyotonia (involuntary and often painful tonic muscle contractions ) that often are only  visible at the EMG

-        clinical examination is normal between crises, but epilepsy is present in 10% of cases

There are some variants:

-        with partial epilepsy

-        without myokymia

-        with paroxysmal dyspnea

-        with isolated neuromyotonia

Treatment: acetazolamide or carbamazepine

The Canadian Kwakiutl native population uses Fucus gardneri, Physocarpus caîtatus and Urtica dioica to treat locomotor ataxia. These plants contain gallic acid and tannic acid, which increase the activity of non-mutated Kv1.1.1 channels.

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: January 2024