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

PurposeCyclic 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.MethodsThree 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.ResultsAll 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.ConclusionsOn 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.