Here we present the case of a 53-year old man with progressive double vision due to isolated left trochlear nerve palsy. Cranial magnetic resonance imaging (MRI) showed a small tumor within the left quadrigeminal cistern that did not increase in size after several months. Explorative neurosurgical intervention revealed a left trochlear nerve cavernoma. The lesion was microsurgically excised followed by end-to-end anastomosis of the trochlear nerve. After a one-year follow up, double vision totally disappeared and cranial MRI showed no recurrence. Cerebral cavernous malformations usually become symptomatic in seizures or focal neurological deficits after intracerebral hemorrhage. Rarely, cavernomas arise from cranial nerves. To the authors' knowledge, this is the first report on a symptomatic cavernous malformation arising from the trochlear nerve and on its successful surgical management.