Abstracts

Multiple structural and functional imaging modalities are currently available to help localize epileptogenic brain areas. In the present study we performed a preliminary look at data from a large project studying different imaging technologies in the presurgical evaluation of patients with intractable partial epilepsy and normal or non-localized MRI. Forty patients diagnosed with extratemporal lobe epilepsy at the UAB Epilepsy Center who were enrolled between August 2001 and October 2004, as part of a prospective presurgical multimodality imaging project, were included in this preliminary observational study. Imaging included the following:
High resolution MRI at either 1.5 or 3.0 T, using a standardized protocol optimized for extratemporal lobe epilepsy.
FDG-PET with analysis based on inspection by two independent reviewers with consensus on identification of relative focal deficits of FDG uptake. Not all patients had PET (not performed if patient had large abnormality on MRI).
MEG recorded with a 148-channel whole-head system and with simultaneous scalp EEG using the standard International System of electrode placement. Epileptiform spikes and sharp waves were analyzed with a single equivalent current dipole model.
Ictal SPECT scans performed with injections (within 30 s of seizure onset, and in the resting state) of 20-40 mCi of [99mTc]-hexylmethylene phenyloxaloacetae (HMPAO). Interpretation was based on coregistration and subtraction all but 9 patients who had unequivocal localizing ictal scans. The mean age of patients was 21.5 years (range, 1-60 years; 17 females). Eleven patients had normal MRI; 7 of 18 had normal PET; 9 of 40 had negative ictal SPECT (4 with unsuccessful ictal injection); 14 of 40 had negative MEG (no spikes). Seventeen patients had chronic implanted intracranial EEG. Of patients who underwent surgical treatment (23 resections, 1 MST, 2 hemispherotomies), outcome was successful in 14 (54%) patients (Engel Class I) and unsuccessful in 12 (46%) patients (Engel Class II:3, III:5 and IV:4). In this observational study multimodality imaging showed a more complementary than redundant effect on presurgical evaluation, selection of patients, and surgical decision-making. Combined multimodal imaging provides more information than does any single modality.