Accurate prediction of postoperative outcome in mesial temporal lobe epilepsy: a study using positron emission tomography with 18fluorodeoxyglucose.

BACKGROUND

Recent studies suggest that positron emission tomography may be a reliable predictive indicator of clinical outcome following surgical treatment for epilepsy.

OBJECTIVE

We evaluated 30 patients with documented medial temporal lobe epilepsy to determine if prediction of postoperative outcome is improved with the use of positron emission tomography with (18)fluorodeoxyglucose.

PATIENTS AND METHODS

We performed a discriminant analysis to determine the combination of metabolic asymmetry indexes in temporal and extratemporal regions defined by magnetic resonance imaging that best predicted the postoperative outcome. Seizure outcome was assessed at least 2 years after surgery: patients were classified as seizure free (n = 14, group A), mostly improved (n = 10, group B), or as having persistent seizures (n = 6, group C).

RESULTS

Discriminant analysis was first performed in groups A and C. The temporal pole seemed to be the only temporal region for which metabolism was a significant predictor of the postoperative outcome (F(1,18) = 10.19; P =.005). The predictive value of positron emission tomography with (18)fluorodeoxyglucose was considerably improved by the multivariate analysis (F(4,15) = 7.21; P =.002), which correctly predicted the 2 -year prognosis in 100% of the patients using 4 regions: the temporal pole, the medial temporal region, the anterior part of the lateral temporal neocortex, and the basofrontal region. As a validation, we performed this 4-region analysis in the patients in group B. The difference among the 3 groups was highly significant (F = 15.5, P<.001).

CONCLUSION

These findings suggest that the interictal metabolic pattern reliably predicts the 2-year prognosis after surgery in patients with medial temporal lobe epilepsy.