CORTICAL AND SUBCORTICAL GLUCOSE-METABOLISM IN CHILDHOOD EPILEPTIC ENCEPHALOPATHIES

Objectives-Nearly one third of children with cryptogenic epileptic enc ephalopathies have been reported to have focal cortical defects on (18 )fluorodeoxyglucose (FDG) PET. As diffuse cortical dysfunction and inv olvement of subcortical structures, particularly the thalami, is postu lated to underlie the propensity to seizures in these conditions, the aim was to determine the frequency of bilateral and diffuse cortical m etabolic defects and of subcortical metabolic abnormalities in the sam e patients. Methods The interictal uptake of FDG was studied in 32 chi ldren with epileptic encephalopathies. Using a semiquantitative techni que, the ratio of uptake in cortical regions and subcortical structure s to that in the cerebellum was compared with that of age matched hist orical controls. Uptake more than 2 SD above (''hypermetabolic'') or b elow (''hypometabolic'') that of age matched controls was considered a bnormal. Results-Diffusely abnormal cortical uptake (nearly always hyp ometabolic) occurred in almost two thirds of patients; in all but two of the remaining patients at least one cortical region showed signific antly decreased uptake bilaterally, When analysed as age cohorts, the mean cortical:cerebellar FDG uptake was significantly lower than that of controls in all cortical regions (P < 0.005). Ninety per cent of pa tients had evidence of relative thalamic hypometabolism and in each ag e group there was a significant reduction in relative thalamic FDG upt ake compared with that of controls (P < 0.005). In nine out of 11 pati ents with unilateral cortical hypometabolic defects thalamic FDG uptak e was lower ipsilateral to the cortical abnormality. Conclusions-Diffu se cortical dysfunction is common in the epileptic encephalopathies an d may reflect the underlying cause of the condition or arise as a cons equence of uncontrolled seizures. Altered thalamic glucose metabolism is further evidence of subcortical involvement in these conditions.