Abstracts

Rationale: Ictal cardiac and respiratory dysfunction have been implicated as possible factors in sudden unexpected death in epilepsy (SUDEP). We (Bateman LM and Seyal M. Epilepsia 2007; 48(Suppl 7):62.) have previously shown that there is a high incidence of ictal hypoxemia associated with partial seizures. Methods: We studied 10 consecutive patients with intractable localization-related epilepsy admitted for inpatient video-EEG telemetry. Respiratory parameters including digital pulse oximetry, nasal airflow, abdominal excursions and end-tidal CO2 were recorded and synchronized with EEG, video and the electrocardiogram. One patient underwent monitoring with intracranial electrodes. Results: Thirty-six seizures were recorded in ten patients (3 female, 7 male) with a mean age of 38.3 years (range 22-51 years). Seven patients had left temporal onset seizures, one patient had right temporal onset seizures and one patient had bitemporal independent seizure onsets. Oxygen desaturations below 90% occurred with 23 of these 36 seizures, with a median saturation nadir of 79% (range <50% - 86%). Eight of these seizures were secondarily generalized while the remaining 15 were complex partial seizures without generalization. All seizures, including those that did not generalize, in which desaturations below 90% were recorded had concomitant increases in ETCO2, with a mean increase of 20.2 mmHg (range 2.8 - 77.8 mmHg) above preictal baseline. In some patients, this increase in ETCO2 persisted in excess of 30 minutes following termination of the seizure. Conclusions: The occurrence of ictal oxygen desaturations with associated hypercapnia provides evidence for alveolar hypoventilation in partial onset seizures. In some instances, this effect is pronounced and prolonged. Ictal alveolar hypoventilation may be a contributing factor for SUDEP in some patients with intractable localization-related epilepsy.