The impact of epilepsy surgery on mortality

Patients with refractory epilepsy suffer from an increased risk of death, primarily due to seizure-related fatalities including sudden unexpected death (SUDEP), which could be conceivably avoided by surgical cure of the epilepsy. Several series have addressed this issue by comparing the mortality rate between medically and surgically treated drug resistant populations, as well as between patients, seizure free and non seizure free post-operatively. Results from some studies suggest that successful temporal lobe surgery reduced the risk of death to that observed in the normal population, whereas patients who continue to suffer recurrent seizures still present an increased standardized mortality ratio (SMR). However, other series have failed to replicate this finding, or found no difference in the overall mortality and SUDEP rates between operated and medically treated patients. All the above studies suffer various types of methodological limitations, hampering any definite conclusion regarding the impact of epilepsy surgery on mortality. However, part of the apparently discordant reported findings might be reconciled through the following framework. Patients who will eventually respond favourably or unfavourably to an anterior temporal lobectomy might already differ in the risk of seizure-related death, pre-operatively. Specifically, patients whose temporal lobe epileptogenic network extends to the perisylvian region (temporal plus epilepsy) appear to be at higher risk of failed TLE surgery, secondary generalised tonic-clonic seizures, ictal apnoea or insula-driven severe cardiac arrhytmias. This population might carry most of the SUDEP burden, both pre- and post-operatively, accounting for the lack of an obvious net reduction of seizure related deaths after temporal lobe surgery. A multicentric study has recently been launched in order to test this hypothesis, and will hopefully help to conclude on the impact of epilepsy surgery on mortality outcome.