Oculomotor Paresis with Cyclic Spasms: Description of Four Cases and Hypothesis of the Mechanism

Oculomotor paresis with cyclic spasms (OPCS) is a rare and usually congenital disorder. It typically presents at birth or within the first 2 years of life. Acquired OPCS resulting from aneurysm compression on the nerve and after irradiation therapy has been reported. OPCS is characterized by unilateral third nerve paresis with periodic spasms causing eyelid elevation, miosis and contraction of 1 or more of the extraocular muscles innervated by the third nerve. Here we report four patients with this rare ocular condition, and propose possible mechanisms and differential diagnoses for their presentation. In case of patient #4 the symptoms secondary to gamma knife radiosurgery is confusingly similar to that of Ocular neuromyotonia (ONM). The association of COPS and gamma knife radiosurgery is hitherto unreported in the literature. It seems likely that COPS may share some similarity on peripheral mechanisms of ONM.