Abstracts

Rationale: Glucose transporter type1 deficiency syndrome (Glut1-DS) presents with early infantile seizures and motor retardation due to the deficient transport of glucose across the blood brain barrier. Myoclonic/absence seizures are frequently seen with generalized discharges (2-3Hz) during the course. FDG-PET findings of GLUT1-DS were described earlier which suggested hypometabolism in bilateral thalamus, cerebellum, frontal and temporal corticies. Here, we examined the regional differences in brain glucose hypometabolism in GLUT1-DS and compared the findings to patients with unilateral temporal lobe epilepsy (TLE). Methods: Patients with GLUT1-DS and focal epilepsy who had FDG-PET imaging were enrolled. The patients were grouped as Glut1-DS (n=16, mean age +SD of 12±2.5yrs), adults (a) with right TLE( n=19, 37.5±2.4yrs) and children (c) with right TLE (n=10, 12.5±1.4 yrs) and healthy participants (n=7, 44± X yrs). FDG-PET images were preprocessed and regions of interest (ROI) for frontal, temporal, occipital and parietal cortex were manually defined bilaterally in all planes (PMOD software, version 2.5, Zurich, Switzerland) for each subject. In Glut1-DS, frontal lobe metabolic activity was not different compared to control. Therefore, sub-frontal regions were examined and metabolic activity was found relatively preserved compared to orbitofrontal anddorsolateral regions. Prefrontal cortex was accepted to calculate ROI-based parameter values in several anatomical regions in temporal cortex (the hippocampus, amygdale, lateral temporal cortex, subcortical structures (thalamus, lentiform and caudate nucleus) and cerebellum bilaterally. Then the activity of selected regions was divided by the activity of prefrontal cortex. Student t-test was applied for independent samples to compare group differences. No correction was made for group comparisons. Significance was defined as p<0.05. Results: 1) In GLUT1-DS; hypometabolism was significant in bilateral cerebellum, thalamus, hippocampus and amygdala. It was also seen to a lesser degree in lateral temporal cortex and basal ganglia. 2) In focal epilepsy; hypometabolism was evident in contra-lateral cerebellum in both TLE groups; and in both hippocampi and ipsi-lateral globus pallidus in aTLE (p<0.05). 3) Comparison between GLUT1-DS and TLE demonstrated that hypometabolism was present in cerebellum, thalamus, amygdala bilaterally in Glut1-DS and ipsi-lateral globus pallidus in aRTLE only (p<0.05). Hypometabolism was also present in ipsi-lateral thalamus, bilateral hipocampi in cTLE which did not reach statistical significance. Conclusions: This study demonstrates the regional differences in brain glucose metabolism of patients with Glut1 DS and patients with unilateral TLE. The distribution of hypometabolism demonstrates similarities between GLUT1-DS and TLE patients involving temporal structures in spite of the unique EEG and clinical findings in these epilepsy syndromes.