EFFECTS OF CEREBRAL ANGIOMAS ON PERIFOCAL AND REMOTE TISSUE - A MULTIVARIATE POSITRON EMISSION TOMOGRAPHY STUDY

Background and Purpose: Using multitracer positron emission tomography, I investigated regional hemodynamic and metabolic changes in both perifocal and remote tissues of cerebral angiomas, with special reference to steal phenomena. Methods: In 22 patients (14 with arteriovenous malformations and eight with cavernomas) cerebral blood flow, cerebral blood volume, mean vascular transit time, cerebral metabolic rate for oxygen, oxygen extraction fraction, cerebral metabolic rate for glucose, and glucose extraction fraction were measured using standard positron emission tomographic methods. Twelve patients also had their cerebral glucose metabolism assessed during psychophysical activation. Regions of interest representing the angioma, perifocal and remote tissues, contralateral mirror regions, and standard brain regions were analyzed. Results: There were no significant changes in hemodynamic variables or oxygen metabolism in the ipsilateral cerebral hemisphere, but ipsilateral glucose metabolism was reduced both at rest (p<0.01) and during activation (p<0.05). Glucose (p<0.001) and oxygen (p<0.001) metabolism in regions of perifocal tissue with low blood flow were decreased, with substrate extraction fractions showing no increase to compensate for insufficient blood flow. Functional recruitment of the cortex overlying the angioma beyond its periphery and supplied by the same arterial branches was subnormal (p<0.05) despite relatively unchanged hemodynamics in this tissue compartment. Conclusions: These data suggest that dysfunction of the cortex supplied by arterial branches also feeding the vascular malformation is related to neuronal deafferentation, while the proportionate decrease in blood How and metabolism of perifocal tissue may be ascribed to neuronal loss in chronically hypoperfused areas, rather than to persistent hemodynamic steal effects.