Firdapse for Post-BOTOX Vocal Weakness

Spasmodic dysphonia (SD) is a dystonia which results in vocal breaks. The mainstay of treatment involves injections using Botox (onabotulinumtoxinA), a neuromuscular blocker which inhibits pre-synaptic release of acetylcholine into the neuromuscular junction. Botox injections into the thyroarytenoid muscle are a predictable and effective treatment for SD, but typically result in transient symptoms of voice weakness and breathiness during the first 2-3 weeks after injection. These symptoms can be present for even longer if Botox is over- dosed. Investigators hypothesize that these initial, transient symptoms of voice weakness and breathiness after Botox treatment can be alleviated using amifampridine which acts at the neuromuscular junction to increase synaptic presence of the neurotransmitter acetylcholine. In these initial studies, investigators will look at patients who have significant breathiness following an injection.