Trochlear nerve palsy associated with Moyamoya disease.

A 48-year-old woman with intracranial hemorrhage at the right hemisphere and the right midbrain was diagnosed as Moyamoya disease (MMD). While restoring consciousness, she complained of diplopia. The left hypertropia with a compensatory right head tilt was noted. The follow up brain image showed the evidence of past hemorrhage at the level of the right inferior colliculus. In this case, the hemorrhage directly damaged the right trochlear nucleus or intra-axial trochlear nerve before decussation and caused left (contralateral) hypertropia. To our knowledge, no report has been described of the trochlear nerve palsy in hemorrhagic Moyamoya disease. Here, we present a case of the patient with trochlear nerve palsy after hemorrhagic MMD and summarize the characteristics of trochlear nerve palsy according to its lesion sites.