Strabismus Surgery in Patients With Ocular Neuromyotonia: Potential Unmasking of the Condition and Effective Management Tool.

Abstract

Ocular neuromyotonia (ONM) is a rare motility disorder in which paroxysms of tonic extraocular muscle contraction from abnormal ocular motor nerve firing result in episodic diplopia and strabismus. Medical therapy with membrane-stabilizing agents has varied success. A surgical approach to treatment has not yet been described. We report the outcomes of strabismus surgery in patients with ONM. We describe 3 patients with sixth nerve paresis and ONM of the affected lateral rectus muscle who underwent strabismus surgery. All patients had a history of radiation therapy for intracranial tumors. Ophthalmologic and orthoptic examinations were performed with appropriate medical and neuroradiologic evaluation. Preoperative and postoperative data are presented and analyzed. Two patients were noted to have ONM after their first strabismus surgery for a sixth nerve palsy. Patients 1 and 2 had 3 surgeries, whereas Patient 3 had 1 operation. Extraocular muscles operated on included the medial rectus and lateral rectus. Preoperative primary gaze baseline esotropia ranged from 35 to 75 prism diopters (Δ). All patients achieved improvement in ocular alignment and motility. Postoperative primary gaze deviations ranged from orthotropia to 20Δ of esotropia. Abduction deficits were unchanged or improved. The follow-up period ranged from 15 months to 2 years. Patients with ONM of a paretic rectus muscle can achieve binocular fusion with strabismus surgery. ONM may manifest postoperatively in patients with a sixth nerve palsy and a contractured medial rectus who, preoperatively, were not noted to have ONM.