Brief Communication: Serum Serotonin Levels in Patients with Epileptic Seizures

Profound cardiovascular and/or respiratory dysfunction is part of the terminal cascade in sudden unexpected death in epilepsy (SUDEP). Central control of ventilation is mediated by brainstem rhythm generators, that are influenced by a variety of inputs, many of which use the modulatory neurotransmitter serotonin to mediate important inputs for breathing. The aim of this study was to investigate epileptic seizure induced changes in serum serotonin levels and if there are potential implications for SUDEP. Forty-one epileptic patients were pooled into 2 groups based on seizure type, as a) generalized tonic-clonic seizures (GTCS) of genetic generalized epilepsy and focal to bilateral tonic-clonic seizures (FBTCS) (n=19), and b) focal seizures (n=26) based on clinical signs using surface video electroencephalography (VEEG). Post-ictal serotonin levels were statistically significantly higher after GTCS and FBTCS, compared to interictal levels ( p =0.002) but not focal seizures ( p =0.941). The change in serotonin (post-ictal - interictal) was inversely associated with a shorter duration of tonic phase of generalized seizures. The interictal serotonin level was inversely associated with a shorter period of post-ictal generalized EEG suppression (PGES). This data suggests that peripheral serum serotonin levels may play a role in seizure features and earlier post-seizure recovery; these findings merit further study.