Abstracts

Rationale: The occurrence of hypoxemia in adults with focal seizures with dyscognitive features (CP), primarily (1GTC) and secondarily (2GTC) generalized tonic-clonic seizures, and psychogenic nonepileptic (PNES) seizures have been well-characterized.1,2 Our aim was to study the timing of oxygen desaturation in epileptic seizures. PNES were used as a control. Methods: Long-term video/EEG monitoring patients underwent monitoring of oxygen saturation using a digital SpO2 (pulse oximeter) transducer. We evaluated 119 consecutive seizures (50 CP, 7 1GTC, 12 2GTC, 50 PNES) in 37 patients (17 male, 20 female). Results: Oxygen saturation data was available from 101 seizures (pulse oximeter malfunction in 18 seizures) equally distributed amongst seizure types. Epileptic seizures were associated with 11.21.1% reduction in SpO2 versus 3.60.7% for PNES (p < 0.01). There was no significant difference in ictal hypoxemia between seizure types (10.11.1% CP; 11.67.1% 1GTC; 15.32.7% 2GTC). There was a nonsignificant trend toward 1GTC (114.446.7 sec) and 2GTC (126.219.3 sec) being of longer duration than CP (112.517.8 sec). Maximal oxygen desaturation occurred during the ictal rather than post-ictal period in the majority of seizures (69 of 101 analyzable seizures). The time to maximal desaturation was significantly longer for GTC (combine 1GTC and 2GTC, 148.619.5) than CP (104.417.5) (p=0.05). Conclusions: Epileptic seizures were significantly more likely than PNES to be associated with oxygen desaturations. Oxygen desaturation was a function of duration of seizure rather than ictal versus post-ictal state. There was a trend toward GTC seizures, particularly 2GTC being more prolonged, and there was significant prolongation of time to desaturation in GTC versus CP seizures suggesting different mechanisms for ictal hypoventilatory dysfunction. 1Epilepsia, 41(5):536-541, 2000. 2Brain, 131: 3239-3245, 2008. Funding: none