Periictal cerebral tissue hypoxemia: a potential marker of SUDEP risk

Cerebral oximetry has not been explored in patients experiencing seizures in the epilepsy monitoring unit (EMU). The purpose of our study was to evaluate the feasibility of periictal measurement of cerebral oxygenation using noninvasive cerebral tissue oximetry and to determine whether there was evidence of cerebral hypoxemia during generalized seizures. Cerebral oxygen saturation findings were subsequently correlated with sudden unexpected death in epilepsy (SUDEP) risk factors. We prospectively evaluated six patients admitted to our EMU with histories of generalized tonic-clonic seizures (GTCS) with prolonged scalp electroencephalography (EEG) and two regional cerebral oxygen saturation (rSO(2)) sensors. Minimum rSO(2) values were recorded in the 5 min preceding seizure onset, during the seizure, and in the 5 min following seizure offset. SUDEP risk was assessed using the SUDEP-7 Inventory. Cerebral oximetry was well tolerated, with a mean duration of rSO(2) monitoring of 81.1 h. Cerebral oxygen saturation data were available from at least one sensor in 9 (90%) of 10 seizures; only 6 (60%) of 10 seizures had useable periictal digital pulse oximetry data. GTCS were associated with significantly lower minimum ictal (p = 0.003) and postictal (p = 0.004) %rSO(2) values than the minimum preictal value. Patients with at least one seizure with a %rSO(2) decrease of ≥20% tended to have higher SUDEP-7 Inventory scores (mean SUDEP-7 Inventory score 7 ± 2.8) versus patients without recorded desaturations (4.3 ± 0.5, p = 0.08). Larger studies are needed to determine the value of cerebral oximetry in the identification of patients at risk of SUDEP.