OCULAR NEUROMYOTONIA - CLINICAL-FEATURES, PHYSIOLOGICAL-MECHANISMS, AND RESPONSE TO THERAPY

Ocular neuromyotonia (ONM) is a rare disorder characterized by episodi c diplopia, occurring either spontaneously or following sustained ecce ntric gaze. Most patients have had prior radiation therapy to the sell ar and parasellar region. ONM is thought to reflect impaired muscle re laxation due to inappropriate discharges from oculomotor, trochlear, o r abducens neurons or axons with unstable cell membranes. Patients wit h ONM often benefit from membrane stabilizing agents such as carbamaze pine. Here we describe a 71-year-old man, with no history of radiation therapy, who for 18 months had had transient episodic diplopia that o ccurred after down gaze. Clinical examination indicated ONM in muscles supplied by the right oculomotor nerve. Binocular scleral search coil eye movement recordings revealed a defect not only of muscle relaxati on but also of maximal muscle contraction. The patient was treated wit h carbamazepine 200 mg per day with complete resolution of his symptom s. ONM may be more common than previously recognized, and patients wit h unexplained transient episodic diplopia should be specifically teste d for diplopia and ocular misalignment following sustained eccentric g aze.