Factors affecting spiking related to sleep and wake states in temporal lobe epilepsy (TLE)

The aim of the study was to investigate the influence of different clinical factors on spiking during sleep and wakefulness in temporal lobe epilepsy. The study included 38 temporal lobe epilepsy (TLE) patients who underwent long-term electroencephalography (EEG) monitoring. In addition to traditional sleep scoring, waking was subdivided into eyes opened (WEO) and eyes closed (WEC) states. The following spike measures were investigated: spiking rates for each state, mean spike rate, spiking stability across wake and sleep states and relative spike density for each state. These measures were investigated according to clinical variables, such as age, age at epilepsy onset, duration of epilepsy, seizure frequency, the presence of secondarily generalised tonic-clonic (SGTC) seizures and the data on epileptogenic lesions based on MRI. Spiking rates during most states and spiking stability showed a significant positive correlation with epilepsy duration. Relative spike density during sleep stage NREM3,4 significantly increased with age at epilepsy onset. Relative spike density during WEC was significantly higher in the presence of hippocampal sclerosis (HS). Spiking rate during REM was significantly higher if a patient had SGTC seizures. Our data provide evidence that different aspects of spiking are associated with different aspects of TLE. We suggest that spike behaviour analysis offer new aspects both for diagnosis and research.