Ocular neuromyotonia. A clinical description of six patients.

We report the cases of six patients with ocular neuromyotonia, a disorder believed to result from episodic involuntary discharge of ocular motor nerves producing sustained and inappropriate contraction of their respective ocular muscles. Transient disturbances of ocular motility and diplopia result. Four patients had involvement of ocular muscles supplied by the third cranial nerve: one had presumed involvement of the superior oblique muscle, and one the lateral rectus muscle, suggesting abnormal discharge in the fourth and sixth cranial nerves, respectively. Four of six patients received prior radiation therapy for pituitary tumors, implying a possible pathogenic link. Three patients improved after treatment with membrane-stabilizing medication, suggesting that unstable membranes of injured ocular motor axons may generate spontaneous impulses, which produce involuntary sustained and inappropriate ocular muscle contraction.