Cerebral circulation and oxygen metabolism in Moyamoya disease of ischemic type in children

Abstract

Cerebral rCBF, rOEF, rCMRO₂, and rCBV in moyamoya disease were studied by means of positron emmission tomography (PET), using ¹⁵O as a tracer. Steady-state methods with C¹⁵O₂ and ¹⁵O₂ were used to obtain the functional images of rCBF, rCMRO₂, and rOEF. The ¹⁵O single-inhalation method was used to obtain the rCBV image. Five children (two boys and three girls) with mean age of 11 years and eight normal volunteers with mean age of 31 years were included in the study. The symptoms of moyamoya disease were due to cerebral ischemia, such as transient ischemic attack (TIA), reversible ischemic neurological deficit (RIND), and minor stroke. The interval between the latest ictus and PET scan ranged from 3 days to 3 years 6 months. Physiological parameters (rCBF, rCMRO₂ etc.) in cerebral gray matter, cerebral white matter and basal ganglia were calculated from the single functional images. Any, low density areas appearing in X-ray-CT performed just prior to the PET study were carefully excluded from the analysis. The parameters of moyamoya disease were statistically compared with normal control parameters. Though the value of rCBF was slightly higher in moyamoya disease, this difference was not statistically significant. On the other hand, in moyamoya disease rCBV increased significantly in gray matter, white matter, and basal ganglia. The ratio of CBF to CBV is considered to be the index of perfusion pressure and reciprocal of cerebral mean transit time under the normal autoregulation of CBF. This ratio was calculated and compared with the normal value for each tissue. The ratio was significantly decreased in each tissue in moyamoya disease, indicating the presence of a low perfusion pressure in the moyamoya brain. In general, when the reduction of perfusion pressure becomes profound the decrease in the CBF-to-CBV ratio is followed by an increase in rOEF. In spite of the reduction in the CBF-to-CBV ratio there was no significant increase in rOEF in moyamoya disease. Thus, the cerebral circulation in childhood moyamoya disease of ischemic type was characterized by a mild decrease in perfusion pressure and a prolonged circulation time.