It is well recognized that some patients with Moyamoya disease frequently suffer from subarachnoideal and/or intracerebral hemorrhages. The morphogenesis of final massive encephalic hemorrhage is unsettled controversy. Moreover, little attention is paied for the histology of the perforating arteries which are probably responsible for intracerebral hemorrhage in patient with Moyamoya disease.
The present report dealed with an electron microscopic observation of the perforating arteries and circle of Willis in three cases of Moyamoya disease who dies of intracerebral hemorrhages. The perforating arteries in distal portion distributed in the basal ganglia revealed marked degeneration of the media; moth eaten-like atrophy of smooth muscle cells and intercellular deposition of increased basement membrane-like materials with electron dense cell debris. This medial alteration is provisionally termed “exhausted degeneration” and is similarly occurred in the same area of perforating arteries in patients with severe hypertension, frequently suffered from intracerebral hemorrhage. On the other hand, the perforating arteries in proximal portions showed well preserved media-smooth-muscle cells.
Ultrastructurally the circle of Willis in Moyamoya disease consisted of co-existence of a phase of remarkable intimal cell proliferation with vasospasm and a phase of consequent ischemic degeneration of the media and deeper thickened intima.
