Abstract:
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Purpose: Interictal [F-18]fluorodeoxyglucose (FDG) brain PET imaging has been used for localizing seizure foci. This study investigates the value of pre-operative FDG PET in predicting outcome with respect to seizure control in epilepsy patients who undergo temporal lobe surgery.
Methods and Materials: Nineteen epilepsy patients (age 20-59 years) with discordant semiology, MR, and EEG findings underwent standard FDG PET brain imaging preoperatively. Following anatomic standardization and extraction of gray matter activity using 3-dimensional stereotactic surface projections (3D-SSP), individual PET images were compared to those of 22 normal adult controls (age 37+/-9 years) using pixelwise Z-score mapping (abnormal pixels with p<0.05) for objective image interpretation. Separately, a metabolic pattern typical of temporal lobe epilepsy (TLE) was established from 18 patients who underwent temporal lobectomy, with Engel Class I outcome. Based on PET patterns of metabolic activity, individual cases were categorized as having a) findings typical of TLE (metabolic reductions in the medial and lateral temporal cortices, inferior frontal cortex, and thalamus) and b) atypical of TLE (diffuse or focal abnormalities not limited to the above structures). All patients had resection of temporal cortices that were suspected to have seizure foci. Post-operative outcomes were classified as seizure-free; worthwhile improvement (>75% seizure reduction); or no substantial improvement (<75% reduction).
Results: All five patients with PET patterns consistent with typical TLE improved postoperatively after corresponding temporal lobe resection. Of these, four were seizure-free. In contrast, of 14 patients having PET patterns atypical for TLE, only one became seizure-free, and 6 had no substantial improvement regardless of the side of resection (chi-square p<0.01). Of these, none of three patients who had diffuse cortical metabolic abnormalities (Z score>5) atypical for TLE were seizure-free postoperatively. MR findings showed no temporal abnormality in 3 of 5 patients with seizure-free outcome and 5 of 6 patients with no substantial improvement.
Conclusion: Refractory epilepsy patients who demonstrated atypical FDG PET findings for TLE had significantly less improvement in seizure control following temporal lobe surgery as compared to those having PET patterns typical for TLE. In addition to seizure focus localization, FDG PET may be useful in identifying patients who may not benefit from temporal lobe resection.
Mayer DO, C,
Predicting Outcome in Medically Refractory Epilepsy Patients: Prognostic Value of Presurgical FDG PET. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3107639.html
