Steno-Occlusive Changes in External Carotid System and Moyamoya Disease Steno-occlusive changes of the cerebral arteries in moyamoya disease occur first in the anterior half of the circle of the Willis. This location is the terminal portion of the internal carotid artery. It is known that the similar changes occur in the extracranial arteries, i.e., superficial temporal artery in some patients with moyamoya disease. One neuroradiological paper reported that such steno-occlusive changes were observed in some moyamoya patients in cerebral angiograms. We studied the angiograms of moyamoya patients in the similar fashion, but we could not find any steno-occlusive changes in cerebral angiograms. It is of interest whether angiograms of the extracranial arteries or pathological (surgical) specimen of the superficial temporal artery may or may not suggest the steno-occlusive changes of the intracranial arteries. Investigating the etiology of moyamoya disease, this information provides some clues to the etiologies of moyamoya disease. We think that there is no or little relationship in the steno-occlusive changes between the intracranial and extracranial vessels. There has been no report on the occlusion of the extracranial arteries, and if such steno-occlusive changes might occur, surgical anastomosis would become non-effective. In fact, stenosis of the surgical anastomosis may occur, but this is usually technical error of bypass surgery. In the extracranial arterial system, stenosis does not occur except for the site of surgical anastomosis. Reference 1. Komiyama M, Nishikawa M, Yasui T, Kitano S, Sakamoto H, Fu Y: Steno-occlusive changes in the external carotid system in moyamoya disease. Acta Neurochir (Wien) 142: 421-424, 2000 [abstract]