Obstructive sleep apnea affects interictal epileptiform discharges in patients with focal epilepsy.

OBJECTIVE

Although bidirectional interactions between obstructive sleep apnea (OSA) and epilepsy have long been recognized, the effects of OSA on interictal epileptiform discharges (IEDs) remain unclear. This study examined how respiratory events (RE) modulate IED activity across sleep stages, sleep cycles, and epilepsy localizations in patients with focal epilepsy using combined video-electroencephalography (VEEG) and polysomnography (PSG).

METHODS

Combined VEEG-PSG was performed in 300 consecutive patients, of whom 52 with coexisting focal epilepsy and OSA were included in the analysis. IEDs were visually identified and quantified during apneic, hypopneic, and nonrespiratory periods across wakefulness, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. Perievent analyses were performed to evaluate IED rate before, during, and after RE.

RESULTS

The IED rate during sleep with RE was higher than during wakefulness (p < .05) but lower than during sleep without RE (p < .05). Across all sleep stages, the IED rate was significantly higher during NREM sleep than REM sleep, regardless of RE presence (p < .001). Among respiratory events, hypopneas were associated with higher IED rate than apneas (p < .001), particularly during NREM sleep (p < .001). Perievent analysis demonstrated dynamic modulation of IED activity, with the lowest IED rate observed in the postevent period compared with during the event period. IED rate declined from the first to the last sleep cycle, with the most prominent reduction observed during hypopnea events. These effects were more pronounced among patients with temporal lobe epilepsy (TLE). No statistically significant difference was observed in the IED rate between RE with and without arousals.

SIGNIFICANCE: RE are associated with dynamic perievent modulation of IED activity in patients with focal epilepsy, especially those with TLE, providing novel insight into the relationship between OSA and epilepsy.