抄録
Twenty five cases of watershed infarction were found on CT among 362 patients with cerebral infarction (7%). CT findings, contrast enhancement, angiography and clinical course of these patients were reviewed and results were as follows;
(1) In 23 cases, lesions were found at watershed area of anterior cerebral artery and middle cerebral artery, in which 3 showed bilateral low density zone. Lesions in middle cerebral-posterior cerebral borderzone were identified in 4 patients.
(2) On angiography, occlusion or stenosis of internal carotid artery were the most common findings (86%), including 2 cases of spontaneous occlusion of circle of Willis (so-called Moya Moya disease).
(3) Eleven had bilateral lesions, and hypoplastic proximal anterior cerebral artery (A1portion) were frequently observed in both unilateral and bilateral cases. These findings indicate that the circulatory disturbance of contralateral side will be the important factor for the appearance of watershed infarction in addition to the ipsilateral circulatory disturbance.
(4) Intrathalamic low density zone was found in 3 cases and was considered as an atypical type of watershed infarction.
(5) Contrast enhancement and follow up CT were useful for the detection of watershed infarction.
We conclude that watershed infarction on CT is the reliable sign of decreased cerebral blood flow and suggest the occlusion or stenosis of internal carotid artery with insufficient collateral circulation. Therefore, angiography should be followed and indication of bypass operation should be taken into consideration in such cases.
