Dalfampridine may activate latent trigeminal neuralgia in patients with multiple sclerosis.

OBJECTIVE: To determine the effect of dalfampridine (4-aminopyridine), a broad-spectrum, voltage-dependent potassium channel blocker, on patients with trigeminal nerve dysfunction due to multiple sclerosis (MS). METHODS: We reviewed histories of 71 patients in our clinic with clinically definite MS who were treated with dalfampridine for at least 2 to 3 months. Of the 71 patients, 5 had a history of either trigeminal neuralgia or altered facial sensation. RESULTS: Of these 5 patients, 3 with preexisting trigeminal neuralgia had a marked worsening of facial pain in close proximity to starting dalfampridine. One patient with altered facial sensation developed trigeminal pain after being on dalfampridine for 18 months. Pain in this individual rapidly subsided when dalfampridine was discontinued. Pain in the worsened 3 patients persisted, became more refractory to previously effective medications, and in one instance required trigeminal surgery for pain control. CONCLUSIONS: Dalfampridine should be used with caution in persons with trigeminal neuralgia due to MS. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that treatment with dalfampridine may precipitate or exacerbate preexisting trigeminal neuralgia.