MR and positron emission tomography in the diagnosis of surgically correctable temporal lobe epilepsy.

PURPOSE

To determine the association of an MR abnormality and a positron emission tomography (PET) abnormality with a good outcome in patients with temporal lobe epilepsy after lobectomy, the association of combined PET and MR findings with good outcomes after lobectomy, and MR and PET pathologic correlation.

METHODS

MR and PET were performed on 27 patients in a blinded study. Histologic studies were correlated with foci of increased T2 signal.

RESULTS

Increased signal or decreased volume of the hippocampus was noted in 13 of 15 patients with mesial temporal sclerosis. Twelve of 15 had positive PET findings. MR identified 20 (83%) of the 24 patients with good outcomes. PET identified 71%. When MR and PET were combined, they detected 95% of the patients with good outcome. Region of interest measurements of the hippocampus in 11 study patients and 7 control subjects documented a significant increase in signal in the patients with seizures. Histologic correlative studies demonstrated that increased T2 signals related to astrocytosis in the hippocampus and adjacent white matter.

CONCLUSIONS

MR (increased signal and decreased volume of the hippocampus) significantly improved the capability to identify those persons who would be helped by lobectomy. MR sensitivity exceeded that of PET.