Postictal serotonin levels are associated with peri-ictal apnea.

Abstract

To determine the relationship between serum serotonin (5-HT) levels, ictal central apnea (ICA), and postconvulsive central apnea (PCCA) in epileptic seizures. We prospectively evaluated video EEG, plethysmography, capillary oxygen saturation (SpO₂), and ECG for 49 patients (49 seizures) enrolled in a multicenter study of sudden unexpected death in epilepsy (SUDEP). Postictal and interictal venous blood samples were collected after a clinical seizure for measurement of serum 5-HT levels. Seizures were classified according to the International League Against Epilepsy 2017 seizure classification. We analyzed seizures with and without ICA (n = 49) and generalized convulsive seizures (GCS) with and without PCCA (n = 27). Postictal serum 5-HT levels were increased over interictal levels for seizures without ICA (<i>p</i> = 0.01), compared to seizures with ICA (<i>p</i> = 0.21). In patients with GCS without PCCA, serum 5-HT levels were increased postictally compared to interictal levels (<i>p</i> < 0.001), but not in patients with seizures with PCCA (<i>p</i> = 0.22). Postictal minus interictal 5-HT levels also differed between the 2 groups with and without PCCA (<i>p</i> = 0.03). Increased heart rate was accompanied by increased serum 5-HT levels (postictal minus interictal) after seizures without PCCA (<i>p</i> = 0.03) compared to those with PCCA (<i>p</i> = 0.42). The data suggest that significant seizure-related increases in serum 5-HT levels are associated with a lower incidence of seizure-related breathing dysfunction, and may reflect physiologic changes that confer a protective effect against deleterious phenomena leading to SUDEP. These results need to be confirmed with a larger sample size study.