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Cortical and subcortical glucose metabolism in childhood epileptic encephalopathies
C D Ferrie1, P K Marsden, M N Maisey
1Department of Paediatric Neurology, The General Infirmary at Leeds, UK.
Insights
Nearly two-thirds of children with epileptic encephalopathies show diffuse cortical dysfunction. Subcortical involvement, particularly thalamic hypometabolism, is also common in these pediatric epilepsy cases.
Area of Science:
- Pediatric Neurology
- Neuroimaging
- Epileptology
Background:
- Cryptogenic epileptic encephalopathies affect children, with focal cortical defects noted in about one-third via 18-fluorodeoxyglucose (FDG) PET.
- Diffuse cortical dysfunction and subcortical involvement, especially the thalami, are hypothesized to contribute to seizures in these conditions.
Purpose of the Study:
- To investigate the frequency of bilateral and diffuse cortical metabolic defects in children with epileptic encephalopathies.
- To determine the prevalence of subcortical metabolic abnormalities, specifically in the thalami, in the same patient cohort.
Main Methods:
- 18-fluorodeoxyglucose (FDG) PET scans were performed on 32 children with epileptic encephalopathies during interictal periods.
- A semiquantitative analysis compared the ratio of FDG uptake in cortical and subcortical regions to cerebellar uptake against age-matched controls.
- Abnormal uptake was defined as more than 2 standard deviations above or below the control group.
Main Results:
- Almost two-thirds of patients exhibited diffusely abnormal cortical FDG uptake, predominantly hypometabolic.
- In nearly all remaining patients, at least one cortical region showed significantly decreased bilateral uptake.
- Ninety percent of patients displayed relative thalamic hypometabolism, with significantly reduced FDG uptake compared to controls across all age groups.
Conclusions:
- Diffuse cortical dysfunction is a frequent finding in epileptic encephalopathies, potentially indicating the cause or a consequence of uncontrolled seizures.
- Altered thalamic glucose metabolism provides further evidence for subcortical involvement in the pathophysiology of these pediatric neurological disorders.
Objectives:
Nearly one third of children with cryptogenic epileptic encephalopathies have been reported to have focal cortical defects on 18fluorodeoxyglucose (FDG) PET. As diffuse cortical dysfunction and involvement of subcortical structures, particularly the thalami, is postulated to underlie the propensity to seizures in these conditions, the aim was to determine the frequency of bilateral and diffuse cortical metabolic defects and of subcortical metabolic abnormalities in the same patients.
Methods:
The interictal uptake of FDG was studied in 32 children with epileptic encephalopathies. Using a semiquantitative technique, the ratio of uptake in cortical regions and subcortical structures to that in the cerebellum was compared with that of age matched historical controls. Uptake more than 2 SD above ("hypermetabolic") or below ("hypometabolic") that of age matched controls was considered abnormal.
Results:
Diffusely abnormal cortical up-take (nearly always hypometabolic) occurred in almost two thirds of patients; in all but two of the remaining patients at least one cortical region showed significantly 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 patients had evidence of relative thalamic hypometabolism and in each age group there was a significant reduction in relative thalamic FDG uptake compared with that of controls (P<0.005). In nine out of 11 patients with unilateral cortical hypometabolic defects thalamic FDG up-take was lower ipsilateral to the cortical abnormality.
Conclusions:
Diffuse cortical dysfunction is common in the epileptic encephalopathies and may reflect the underlying cause of the condition or arise as a consequence of uncontrolled seizures. Altered thalamic glucose metabolism is further evidence of subcortical involvement in these conditions.