Post-irradiation neuromyotonia affecting trigeminal nerve distribution: an unusual presentation.

We describe two patients who developed neuromyotonia of the floor of the mouth after irradiation of a motor branch (V3) of the trigeminal nerve. The neuromyotonia manifested as sustained muscle contraction due to peripheral nerve dysfunction. The neuromyotonia in both patients was controlled with carbamazepine. Radiation-exposed nerves can become symptomatic months or years after completion of radiation therapy.