Abstracts

Seizures in the early post-operative period after temporal lobectomy are commonly discounted when assessing seizure outcome. However, several studies have indicated these events may predict ongoing seizures. In this study, we aimed to determine the risk of epilepsy recurrence among individuals who had early post-operative seizures. Early post-operative seizures were defined as seizures within 28 post-operative days. Epilepsy recurrence was nominated as seizures between day 29 and one post-operative year. Poisson regression analysed the recurrence risk associated with early seizures, as well as the effect of the presence of seizure precipitants (e.g. decreased medication, cerebral bleeding), and the timing, type and number of early seizures amongst those who experienced early seizures. Statistical adjustments were made for the pre-operative pathology. Of 321 cases who underwent temporal lobectomy at Austin Health in Australia, 69 (22%) experienced early post-operative seizures. Early seizures were associated with seizure recurrence (rate ratio [RR] 5.9; 95%CI 4.1 to 8.4). Amongst the patients who experienced early seizures, only the presence of precipitants to seizures was associated with (a decreased) risk of recurrence (RR 0.52, 95%CI;0.3-1.9). The timing of the initial seizure within the first 28 post-operative days did not have a significant effect (p=0.26). A further analysis was undertaken, comparing outcome for patients who did not experience early seizures against outcome for those who had early seizures with precipitants and outcome for patients who had early seizures without precipitants. Regardless of precipitant status, early seizures maintained an association with subsequent recurrence, although patients with precipitants to their seizures had a lower risk (RR 3.0; 95%CI 1.8-5.2) than those without precipitants (RR 7.6; 95%CI 5.0-11.5). Patients who experienced early post-operative seizures had a higher risk of subsequent seizure recurrence compared to those who did not have early seizures. The risk was decreased but still significant if early seizures were associated with precipitating factors. Given that most post-operative seizure outcome classifications discount early seizures, these findings have implications for the measurement of outcome after temporal lobectomy. (Supported by Australian NHMRC, Austin Hospital Medical Research Foundation, Epilepsy Association Australia)