Regional cerebral blood flow (rCBF) was measured in 13 cases of Moyamoya disease by means of the 133Xe intracarotid injection method. Patients' age ranged from 5 to 55 (average 32), 6 were male and 7 were female.
Mean hemispheric CBF (mCBF) in the symptomatic hemisphere ranged from 19.0 to 41.0 (average 31.3±7.5) ml/100g/min. and from 33.0 to 57.6 (average 48.2±7.0)ml/100g/min. in the asymptomatic side. In the asymptomatic hemisphere, 6 cases had normal mCBF and only one case with cerebral infarction, confirmed by CT had abnormally low flow (33.0 ml/100g/min.). Decrease of mCBF correlated well with the severity of clinical signs. But, at the same level of decreased mCBF, clinical signs were more milder in Moyamoya disease than in the other cases of cerebral infarction such as occlusion of middle cerebral artery. This phenomenon may be explained by the slow progress of steno-occlusive process with concomitant development of netlike collateral circulation (Moyamoya-vessels).
Relative hyperemic regions were found mainly on the base of the frontal lobe, but absolute hyperemic area was not observed in the regions of angiographically verified Moyamoya-vessels.
CO2 response appeared to be disturbed during CO2 inhalation and preserved during hyperventilation tests. This dissociation of CO2 response is known as one of the characteristic features of Moyamoya disease. The authers' explanation is, that the vessels are already maximally dilated under normocapnic circumstance in order to maintain adequate CBF and cerebral function. Therefore, further dilatation due to hypercapnia is impossible, however, hypercapnia by hyperventilation is still able to cause vasoconstriction.
Autoregulation observed during blood pressure changes was disturbed frequently, but further analysis will be necessary. The 133Xe intracarotid injection method bears many problems in evaluating rCBF in Moyamoya disease. Three dimensional rCBF and metabolism measurements by Emission CT will be of great help to know more precise pathophysiological condition of Moyamoya disease.
