A longitudinal study of surgical outcome and its determinants following posterior cortex epilepsy surgery

Abstract

To investigate the longitudinal seizure outcome and identify potential prognostic indicators following posterior cortex epilepsy (PCE) surgery. We reviewed patients who underwent a parietal, occipital, or parietooccipital resections between 1994 and 2006, using survival analysis and multivariate regression with Cox proportional hazard modeling. A favorable outcome was defined as Engel Class I at last follow-up. Fifty-seven patients were identified with a mean follow-up of 3.3 years (range 1-12 years). The estimated chance of seizure freedom (SF) was 73.1% at 6 postoperative months, 68.5% at 1 year, 65.8% at between 2 and 5 years, and 54.8% at 6 years and beyond. Most recurrences (75%) occurred within the first 6 postoperative months. Parietal resections had a worse outcome than occipital or parietooccipital resections (52% SF vs. 89% and 93%, respectively, at 5 years). Independent predictors of recurrence included an epilepsy etiology other than tumor or dysplasia [risk ratio (RR) 2.29], limiting resection to a lesionectomy (RR 2.10), having ipsilateral temporal spiking on preoperative scalp electroencephalography (EEG) (RR 2.06), or any ipsilateral spiking on postoperative EEG (RR 2.70) (Log likelihood-ratio test p < 0.0001). Only 40-50% of patients with a poor outcome predictor were SF at 5 postoperative years as opposed to about 80% otherwise. In surgical failures, recurrent seizure frequency was related directly to baseline seizure frequency and to the presence of ipsilateral spiking on postoperative EEG. These data highlight favorable long-term outcomes following PCE surgery. Limited surgical resection and diffuse baseline epileptogenicity may be important predictors of seizure recurrence.