Relationship of the level of orexin in serum and cerebrospinal fluid with sleep stages and seizures in epilepsy patients

One of the unknown mechanisms in epilepsy pathogenesis is protein called orexin. Although the relation of orexin to sleep has been revealed, its place in epilepsy has not been fully clarified yet. In this study, we aimed to show the relationship of orexin with the seizures that occur during sleep and wakefulness. The study included 40 drug-resistant focal epilepsy patients and 37 healthy controls. Basal night and basal morning orexin levels were measured in the patient and control groups, before the night's sleep and after waking up in the morning. In the patient group, blood samples were taken again after epileptic seizures, and if the seizure was asleep, the stage of sleep seizure was recorded. In addition, neurophysiological and neuroimaging findings of patients such as EEG and MRI were also examined. In the patient and control groups, basal morning orexin levels were measured higher than basal night orexin levels. Basal orexin levels of the patient group are lower than the control group. The level of post-seizure orexin increased compared to the basal values, especially in seizures during sleep. However, no relation was found between sleep phases and levels of orexin. There was a relationship between seizure duration and the level of orexin. As the duration of seizures shortened in awake seizures, the level of orexin was measured higher. The levels of post-seizure orexin after sleep seizure were measured higher in patients who had a left hemisphere onset in the EEG, a lesion in the left temporal lobe in MRI, and patients with MR-EEG compliance than those in the left hemisphere lateralization. The increase in the levels of the orexin, especially after seizures, suggests that the orexin may be associated with the epileptogenic effect. In further studies, determination of orexin from CSF and correlation of CSF and serum orexin level may provide more useful information in terms of relationship between orexin and epilepsy.