Fluctuating neuromuscular transmission defects and inverse acetazolamide response in episodic ataxia type 2 associated with the novel CaV2.1 single amino acid substitution R2090Q.

We report on a 51-year-old woman with episodic ataxia type 2 (EA2) and a novel CaV2.1 C-terminal single amino acid substitution (R2090Q). She had a 4-year history of acute episodes with ataxia, hemihypesthesia and hemicrania. Furthermore, fluctuating neuromuscular transmission abnormalities rarely described in patients with EA2 were clinically and electrophysiologically documented in this patient. Upon initiation of acetazolamide treatment she experienced a dose-dependent severe increase of attack frequency and severity along with a shorter attack duration, while she responded well to subsequent therapy with 4-aminopyridine.