Abstracts

Rationale: Sudden unexpected death in epilepsy (SUDEP) incidence ranges in general epilepsy populations from 0.9-2.3 per 1000 person-years in the wider epilepsy population to 1.1-5.9 per 1000 person-years in those with chronic refractory epilepsy. It is 7.5 to 9.3 per 1000 person-years in patients who fail epilepsy surgery. Cardiac, respiratory and primary electrocerebral shutdown have been postulated as possible mechanisms of SUDEP. The insula is a cortical structure implicated in the autonomic control and insular damage in patients with cerebral infarction is associated with increased sympathetic activity, cardiac arrhythmias and conduction blocks and mortality, including due to sudden death. We report two failed epilepsy surgery cases with insular damage who later suffered SUDEP.Methods: We studied two prospectively surveilled SUDEP cases from the NINDS Prevention and Risk Identification of SUDEP Mortality (PRISM) Project with EEG and EKG monitoring before and after iatrogenic insular damage with subsequent progressive cardiac conduction and rhythm disturbances without apnea/hypopnea (Figure 1 and 2).Results: We analyzed heart rhythm and HRV during ictal and interictal periods in two cases of SUDEP, during several admissions in our Epilepsy Monitoring Unit. Both patients progressively developed changes in Heart Rate Variability (HRV) and abnormal post-ictal cardiac conduction/rhythm patterns. Case 1 who underwent a left temporal lobectomy developed increase of vagal tone as manifested by increased HRV and HF, and a consequent high grade AV block (Figure 1). Case 2, who had a left insular resection developed increased sympathetic tone (decrease HRV and HF) and prolonged, abnormal recovery from post-ictal tachycardia (Figure 2).Conclusions: The observation that HRV changes were progressive even in comparison between consecutive post-operative studies is intriguing and raises the possibility that neuronal responses to injury and the cardiovascular alterations produced took place over years rather than days or weeks. Both cases suggest that surgical failures who show evidence of insular damage on post-operative MRI should be studied carefully for evidence of cardiac instability. Treatable abnormalities such as high grade AV block should be offered pacemaker implantation.