Positive neurologic phenomena with initiation of dalfampridine for multiple sclerosis.

OBJECTIVE: Review cases of positive neurologic phenomena initiated or worsened with dalfampridine in patients with multiple sclerosis. BACKGROUND: Oral, extended release dalfampridine (4-aminopyridine or 4-AP) is a potassium-channel blocker approved for the treatment of gait impairment in multiple sclerosis (MS). The enhanced conduction along demyelinated axons promoted by dalfampridine could potentially lead to development of positive neurologic phenomena. METHODS: We reviewed the medical records of patients who were started on dalfampridine for activation of positive sensory or motor symptoms. RESULTS: Four of 76 patients (5.3%) developed positive sensory symptoms within one month of starting dalfampridine; one additional patient had new-onset seizure. Cessation of dalfampridine was insufficient to resolve symptoms in two patients with recurrent trigeminal neuralgia. CONCLUSIONS: Initiation of dalfampridine may be associated with initiation or recurrence of positive sensory symptoms in patients with multiple sclerosis. The increased axonal conduction from potassium channel blockade may contribute to this exacerbation of positive sensory phenomena.