Teaching NeuroImages: Ocular neuromyotonia: An underrecognized cause of transient diplopia

A 63-year-old man presented with several months of intermittent vertical diplopia mainly while reading. He consistently developed a transient right hypertropia (with left supraduction deficit) after looking down for approximately 10 seconds and then back to primary (figure 1). Neurovascular contact between the left third nerve and posterior cerebral artery was demonstrated with magnetic resonance constructive interference in steady state imaging (figure e-1 on the Neurology(R) Web site at Neurology.org), and episodes were resolved with carbamazepine. Aside from presumed transient tonic contraction of the left inferior rectus, there was no evidence that other third-innervated muscles were involved.