Lissencephaly : Fetal pattern of glucose metabolism on positron emission tomography?

In classical lissencephaly, the cerebral cortex is four-layered, containing neurons that have failed to complete their migration between 12 and 16 weeks of gestation. The authors studied the functional activity of lissencephalic cortex using 2-deoxy-2[(18)F]fluoro-D-glucose PET (FDG PET) in eight patients (six girls and two boys, mean age 7.5 years) with isolated lissencephaly sequence. The PET scans revealed a remarkably similar and bilaterally symmetric pattern of glucose metabolism in all eight patients. The cerebral cortex of lissencephaly showed two layers that could be differentiated based on metabolic activity. The inner layer, which probably corresponds to the inner cellular layer of lissencephalic cortex, showed 8 to 63% higher glucose utilization rate than the outer layer, which probably represents a composite of the molecular, outer cellular, and cell-sparse layers. Patients with a higher metabolic ratio between the cortical layers (inner/outer) showed greater delay in communication (p = 0.007) and socialization (p = 0.03). These findings are consistent with [(14)C]-2-deoxyglucose autoradiography studies in fetal sheep that have shown that before the development of significant numbers of axons, dendrites, and synapses, glucose metabolism appears to be highest in regions with the highest density of cell bodies, compared to the more mature state when glucose metabolism is highest in areas of greatest dendritic arborization. FDG PET studies of classical lissencephaly provide a different perspective in the analysis of brain gyral anomalies than those with traditional neuroanatomic imaging techniques.