We investigated the relationship between the interictal metabolic patterns, the extent of resection of the 18FDG‐PET hypometabolism and seizure outcomes in patients with unilateral drug‐resistant mesial temporal lobe epilepsy (MTLE) following anterior temporal lobe resection (ATLR).
Eighty‐two patients with hippocampal sclerosis or normal MRI findings, concordant 18FDG‐PET hypometabolism and at least two years of postoperative follow‐up were included in this two‐centre study.
The hypometabolic regions in each patient were identified with reference to twenty healthy controls (p<0.005). The resected temporal lobe (TL) volume and the volume of resected TL PET hypometabolism (TLH) were calculated from the pre‐ and postoperative MRI scans co‐registered with interictal 18FDG‐PET.
Striking differences in metabolic patterns were observed depending on the lateralisation of the epileptogenic temporal lobe. The extent of the ipsilateral TLH was significantly greater in left MTLE patients (p<0.001), whereas right MTLE patients had significantly higher rates of contralateral (CTL) TLH (p=0.016). In right MTLE patients, CTL hypometabolism was the strongest predictor of an unfavourable seizure outcome, associated with a five‐fold increase in the likelihood of seizure recurrence (OR 4.90, CI:1.07‐22.39, p=0.04). In left MTLE patients, the greater the extent of the resection of ipsilateral TLH was associated with lower rates of seizure recurrence (p=0.004) in univariable analysis, however its predictive value did not reach statistical significance (OR 0.96, CI: 0.90‐1.02, p=0.19).
The difference in metabolic patterns depending on the lateralisation of MTLE may represent distinct epileptic networks in patients with right vs left MTLE, and can guide preoperative counselling and surgical planning.
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