Clinical findings of a patient with hemiballism after superficial temporal artery-middle cerebral artery anastomosis for idiopathic middle cerebral artery stenosis

A 32-year-old woman experienced several episodes of transient numbness on the left side of her face and body. MR angiography revealed severe stenosis in the right middle cerebral artery (MCA). Abnormal collateral vessel networks were not observed, and idiopathic MCA stenosis was diagnosed. She underwent superficial temporal artery (STA)-MCA anastomosis of the right hemisphere. The surgery eliminated the transient ischemic attacks; however, she developed hemiballism in the left side of her face and left upper limb 2 weeks after the surgery. The ballism disappeared 1.5 years after onset without any treatments. A few patients with development of chorea after STA-MCA anastomosis has been reported in moyamoya disease, but not in those with MCA stenoses. It has been previsouly reported that the development of an involuntary movement might be associated with hypermetabolism in the contra lateral striatum after STA-MCA anastomosis. We considered that a similar mechanism may have caused hemiallism in our patient. We need to recognize that STA-MCA anastomosis could cause hemichorea or hemiballism.