Comparison of dynamic and xenon computed tomography in the evaluation of cerebrovascular ischemia

Cerebral blood flow in mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes

BACKGROUND AND PURPOSE

The precise mechanism of neurological symptoms with mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS) is still controversial. We investigated the correlation between strokelike episodes and cerebral blood flow in two patients with MELAS and discuss the pathogenesis of strokelike episodes with MELAS.

SUMMARY OF REPORT

Cerebral dynamic computed tomography and cerebral angiography were used to measure cerebral circulation in the first case, that of a 20-year-old woman with MELAS. The second subject was a 13-year-old female who was studied with xenon-enhanced computed tomography. The cerebral blood flow studies were performed 3-72 hours after the onset of strokelike episodes. Serial cerebral angiography, dynamic computed tomography, and xenon-enhanced computed tomography showed vasodilation localized in the affected cerebral cortexes during strokelike episodes, without any reduction in regional cerebral blood flow.

CONCLUSIONS

Our study suggests that the strokelike episodes associated with MELAS are different in origin from ischemic stroke.

Assessment of risk of carotid occlusion with balloon Matas testing and dynamic computed tomography

Temporary occlusion of the internal carotid artery with a balloon catheter (balloon Matas test) and simultaneous dynamic computerized tomography scanning (DCT) were performed to determine the tolerance of permanent carotid occlusion in eight cerebral aneurysm and two carotid-cavernous fistula (CCF) cases, in whom internal carotid occlusion might be necessary during operation or as a choice of treatment. All patients were evaluated by mean transit time (MTT), especially % transit time (MTT of the occluded side x 100/MTT of the control side). In six patients, % transit time (%TT) was less than 155 and no neurological signs appeared after permanent internal carotid occlusion. Neurological deficit appeared when mean arterial blood pressure was 80, and disappeared when mean arterial blood pressure was 100 during the balloon Matas test in a case whose %TT was 200. Neurological deficit appeared several seconds after the balloon Matas test in a case whose %TT was 250. The critical %TT value to cause symptomatic ischaemia was 200 from our results. Therefore, it is necessary to undertake treatment such as bypass surgery for the patients whose %TT is near 200, even if the balloon Matas test was negative.