Reconsideration of the clinical classification of TIA, with special reference to the etiology of TIA

Abstract

TIA has mainly been explained by microembolism from a major cerebral artery. However, it is still unresolved as to whether this mechanism is applicable to Japanese cases or not, because of the low frequency and mild degree of cerebral arterial lesions in Japanese cases as compared to those in Whites. To examine the mechanisms of TIA in Japanese cases, we classified the patients, whose neurological deficits seemed to be caused by supratentorial lesions, into perforator TIA (the P group) with classical lacunar syndrome, and cortical TIA (the C group) with cortical signs such as monoparesis and aphasia. Cerebral angiographic findings in which major arteries were occluded or were stenosed by over 50% of the vessel diameter or had ulcerative plaque, were diagnosed as abnormal.
Thirty-eight patients were included in the present study. The respective numbers of patients in the P and C groups were 21 (55%) and 12 (34). The remaining 5 cases (13%) could not be classified into the P or C group because of nonspecific neurologic findings. Among the risk factors of TIA, hypertension was frequently observed in the P group, but arrythmia and heart disease were not. Cardiogenic embolism (CE) was suspected only in 4 cases of the C group. On angiography, half of all cases revealed normal findings; 62% of the cases in the P group and all the CE cases in the C group showed normal findings, but 87% of the cases in the C group (except for the CE cases) showed abnormal findings. The underlying mechanism of TIA in the P group was thus suspected to be mainly in-situ perforating arterial lesions, such as lipohyalinosis, and in part, microembolism. In the C group, on the other hand, the mechanism appeared to be mainly microembolism, and partially CE and cerebral blood flow insufficiency.
The present data suggest that there are many cases who exhibit lacunar syndrome and whose mechanism seems to be perforating arterial lesion. Also, to classify TIA caused by supratentorial lesions into perforator and cortical types is evidently useful for predicting cerebral vascular lesions and the mechanism of TIA.