Ocular neuromyotonia: differential diagnosis and treatment.

Ocular neuromyotonia (ONM) is a rare but distinctive clinical entity characterized by involuntary episodic contraction of one or more muscles supplied by the ocular motor nerves. A retrospective review was conducted on all patients with ONM seen by the neuroophthalmology service in the past 20 years. Ten patients were identified with ONM; six affecting vertical muscles (superior oblique; inferior rectus; superior rectus) and four affecting lateral rectus muscles. Case 1 has been reported previously. Most episodes occurred every 10-40 min, lasted a few seconds to several minutes, and were repeated throughout the day. Only two patients had previously undergone cranial radiation. Two had thyroid eye disease. One patient presented with superior oblique myokymia and subsequently developed ONM. Membrane stabilizing medications were prescribed in 7 of the 10 patients with varied success. ONM episodes ceased after extraocular muscle surgery in one patient with thyroid eye disease.