Hemifacial spasm caused by a pilocytic astrocytoma of the fourth ventricle.

An 11-year-old male in whom hemifacial spasm was the presenting sign of a pilocytic astrocytoma within the fourth ventricle is reported. The child's hemifacial spasm decreased substantially after resection of the tumor. Hemifacial spasm is largely a disease of adults and only rarely is attributed to brain tumors. In contrast, this marks the fifth case of hemifacial spasm reported in a child, three of which have been attributed to tumors of the fourth ventricle.