What Does Flumazenil PET Add to an Evaluation for Temporal Lobectomy?

Abstract

Periventricular White Matter Flumazenil Binding and Postoperative Outcome in Hippocampal Sclerosis Hammers A, Koepp MJ, Brooks DJ, Duncan JS Epilepsia 2005;46(6):944–948 Purpose In patients with hippocampal sclerosis (HS), anterior temporal lobe resection offers the possibility of a long-lasting suppression of seizures in two-thirds of patients. White matter (WM) [11C]flumazenil volume of distribution (FMZ-Vd) reflects the number of neuronal cell bodies in WM. Our objective was to correlate WM FMZ-Vd in patients with unilateral HS and postsurgical outcome. Methods We performed [11C]flumazenil positron emission tomography ([11C]FMZ-PET) in 15 patients with refractory mesial temporal lobe epilepsy (mTLE) and a quantitative MRI diagnosis of unilateral HS subsequently histologically verified in all cases. Median follow-up was 7 years (range, 6–9 years). Metabolite-corrected arterial plasma input functions and spectral analysis were used to generate parametric images of [11C]FMZ-Vd. Statistical parametric mapping (SPM99) with explicit masking was used to investigate the entire brain volume including WM. Results Eight patients had Engel class IA outcome (completely seizure-free since surgery), and seven were not seizure-free. Comparison of seizure-free patients with those who continued to have seizures after surgery revealed areas of increased FMZ binding around the posterior horns of the ipsilateral (z = 3.7) and contralateral (z = 2.7) ventricles in those with suboptimal outcomes. Conclusions Preoperative [11C]FMZ-PET can detect periventricular increases of WMFMZ binding, implying heterotopic neurons in WM, in patients with mTLE. The presence of such increases correlates with a poorer outcome.