Hemichorea associated with ipsilateral chronic subdural hematoma--case report.

Left-sided hemichorea developed suddenly in a 73-year-old male. Computed tomography revealed a left subdural hematoma (SDH) and infarction in the right corona radiata and temporo-occipital region. Hemichorea subsided completely after removal of the SDH. Postoperative single photon emission computed tomography with technetium-99m-hexamethyl-propyleneamine oxime revealed a global low-perfusion area in the right cerebral hemisphere. Right carotid angiography demonstrated severe stenosis of the trunk of the right middle cerebral artery. The cerebral blood flow in the right cerebral hemisphere had probably already decreased to nearly the critical level and was reduced further by the left SDH, inducing the left-sided hemichorea due to dysfunction of the right cerebral hemisphere. This case shows that when hemichorea ipsilateral to a SDH is present, it is important to ascertain whether there is a pre-existing ischemic lesion in the contralateral cerebral hemisphere, particularly in the basal ganglia, thalamus, or corona radiata.