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[A pathological study of basilar artery sclerosis resulting from vertebral artery asymmetry].

We conducted a pathological study of the arteries of Willis ring in 130 autopsied specimens to evaluate the influence of vertebral artery (VA) asymmetry on basilar artery (BA) sclerosis. The cases studied comprised 109 of non-brainstem infarction (control) and 21 of thrombotic basilar artery occlusion (BAO). The frequency of VA asymmetry was significantly higher (p < 0.01) in BAO cases (13 out of 21 cases; 61.9%) than in the controls (35 out of 109; 32.1%). In the controls, the mean scores for stenosis of the caudal (p < 0.01) BA were significantly higher in VA asymmetry pattern than in VA normal pattern, but the mean score of the rostral BA was nearly equal in both patterns. In BAO cases with VA asymmetry, the score for stenosis was higher in the caudal portion than in the rostral portion, and occlusion was frequently found in the lower BA and continuing from the thicker VA to the BA. These findings suggest that atherosclerotic changes may occur more preferentially in the lower BA in cases of VA asymmetry, and that VA asymmetry is considered to be one of the risk factors for BA occlusion.