4-Aminopyridine in Episodic Ataxia Type 2

This study aims to determine whether 4-aminopyridine (4AP) can reduce attacks of ataxia in patients with episodic ataxia type 2 (EA2), a rare but often debilitating condition. Episodic ataxia (EA) is a group of inherited disorders characterized by recurrent, discrete episodes of vertigo and ataxia variably associated with progressive ataxia. EA2, the most common and the best characterized of all the EA syndromes, is caused by heterozygous mutations in CACNA1A, which encodes the main subunit of a neuronal voltage-gated calcium channel, Cav2.1. Although observational data suggest symptomatic resolution with acetazolamide in many EA2 patients, the investigators found in our patient databases that at least a third of the EA2 patients continue to suffer debilitating ataxia attacks, either because of incomplete control while on acetazolamide or because of intolerability or hypersensitivity to acetazolamide. For these patients there is no alternative intervention. 4-Aminopyridine (4AP) has been found to be helpful in a handful of patients with EA2. Recently, dalfampridine, an extended release formulation of 4AP (AMPYRA) by Acorda Therapeutics, received FDA approval to improve gait in multiple sclerosis. The investigators plan to recruit 20 subjects with genetically defined EA2 who suffer frequent ataxia episodes (at least 3 episodes a month) to conduct a randomized trial of 4AP to examine its efficacy and tolerability in EA2. Study subjects will be recruited at UCLA and the University of Rochester to participate in a randomized, double-blind, double-crossover trial of 4AP.Each treatment period is 2-months with a 1-week wash-out period in between each treatment period. Participating subjects will undergo standardized history and physical examination at the time of enrollment. Participants will log their ataxia attacks daily by interactive voice response (IVR) system and will be interviewed monthly for events and side effects/toxicity. Study visits will occur at the beginning and the end of the study.