Cyclic (alternate day) vertical deviation--possible forme fruste of ocular neuromyotonia

Cyclic ocular deviations are relatively uncommon and are seldom seen in adults. We report 3 adult patients with cyclic hypotropia that has clinical characteristics similar to neuromyotonia, suggesting a possible common etiology.

Three consecutive patients with 48-hour cyclic hypotropia underwent full neuro-ophthalmologic, oculoplastics, and orthoptic evaluations as well as appropriate medical and neurologic studies. Examinations were arranged on consecutive days on multiple visits to document the cyclic pattern.

All 3 patients had sustained contraction of a vertically acting extraocular muscle lasting 24 hours and demonstrated characteristics of ocular neuromyotonia. The contraction was absent for the next 24 hours. Two of the patients had thyroid eye disease; the third patient had unilateral ophthalmoparesis and had subsequent frameless robotic radiosurgery for a cavernous sinus schwannoma. Regular cycles lasting 6, 9, or 14 months were documented by all 3 patients. In 2 patients, treatment with carbamazepine and gabapentin effectively reduced or eliminated the cycle. The cyclic deviation in the third patient resolved spontaneously.

On the basis of the response of these patients to membrane-stabilizing medications and the behavior noted as the cycle broke each day, we propose that cyclic vertical strabismus and ocular neuromyotonia may be related conditions with similar underlying physiology.