Abducens ocular neuromyotonia in a patient with nasopharyngeal carcinoma following concurrent chemoradiotherapy.

We describe a case of ocular neuromyotonia (ONM) following concurrent chemoradiotherapy for nasopharyngeal carcinoma (NPC). During an episode of neuromyotonia, the patient developed involuntary contraction of the left lateral rectus muscle and globe retraction with down-shoot movement in the left eye. In the quiescent period, ocular motor examination revealed a partial left sixth nerve palsy. While diplopic complaints in patients with NPC raise suspicion of tumor recurrence or radiation-related cranial neuropathy, ONM must also be kept in the differential diagnosis.