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Circadian rhythm of interictal epileptiform discharges and changes of spindles in patients with temporal lobe epilepsy

Yun-Li Yu, Yong-Li Yan, Su-Fen Tian, Zhan-Hui Feng, Meng-Ting Shi

Background: This study aims to explore the circadian rhythm of interictal epileptiform discharges (IEDs) and changes of spindles in patients with temporal lobe epilepsy (TLE).

Methods: Subjects were divided into two groups: research group (patients diagnosed with TLE, n=50) and control group (n=30). The whole-night natural sleep of all subjects was monitored, analysis and statistics were performed on IED, and the number, amplitude and the average duration of spindles were compared between these two groups.

Results: (1) In TLE patients, the number of IED was larger in non-rapid eye movement (NREM) stages 1+2 and NREM stages 3+4 than in the waking stage and rapid eye movement (REM) stage, and the differences were statistically significant (P<0.05). (2) TLE patients had bilateral asymmetric sleep spindles, and their amplitude was lower in the affected side than in the unaffected side. Furthermore, the number, amplitude and mean duration of sleep spindles in the affected side in NREM stage 2 was significantly reduced compared with that in the control group (P<0.05).

Conclusions: (1) TLE patients have the highest frequency of IED in slow wave sleep, followed by NREM stages 1+2, waking and REM stages. Slow wave sleep easily induces IED. (2) The number, amplitude and mean duration of sleep spindles in the affected side in NREM stage 2 were significantly reduced, compared with that in the control group. This suggests that changes in spindles have a lateralization value.