Alternating skew deviation due to hemorrhage in the cerebellar vermis.

A 76-year-old Japanese woman with essential hypertension and diabetes mellitus abruptly presented with nausea, dizziness, an occipital headache, truncal ataxia, gaze-evoked nystagmus and alternating skew deviation (ASD) with abducting eye hypertropia. Cranial computed tomography demonstrated hemorrhage in the cerebellar vermis and its vicinity. These symptoms gradually resolved within three weeks. This is the first reported case of ASD secondary to cerebellar hemorrhage without hydrocephalus. The vertical misalignment of the eyes during the right-sided gaze was consistently larger than during the left-sided gaze. We speculated that bilateral and asymmetrical damage to the utricular pathway due to the bilateral involvement of the nodulus and uvula might have caused the ASD.