Abstracts

Rationale: Previous research has demonstrated a high prevalence of sleep disorders in patients with drug-resistant epilepsy, but few studies consider the impact of laterality. Cortical stimulation and functional imaging studies have indicated separation of the modulation of physiological functions in the temporal lobes, and periodic limb movements of sleep (PLMS) have previously been associated with right temporal lobe epilepsy (TLE). Furthermore, sleep architecture has previously been investigated in relationship to memory consolidation in patients with epilepsy but has not been examined in terms of laterality. We aimed to examine the structure of sleep and prevalence of obstructive sleep aponea (OSA) and PLMS in relationship to laterality in patients with TLE. Methods: This was a cross-sectional study evaluating sleep architecture and prevalence of OSA and PLMS in patients with bilateral, left and right TLE. Consecutive patients admitted for inpatient video-EEG monitoring at The Royal Melbourne Hospital between January 2014 and December 2018 were included. The diagnosis of TLE was established by clinical, electrophysiological and radiological features, and was reviewed by two independent neurologists. Patients underwent routine diagnostic polysomnography on the final night of the admission. Patients with an existing diagnosis of OSA were excluded. The Fisher’s Exact test was used for comparisons of categorical data across groups. Kruskal-Willis test and paired Mann-Whitney U test was used for comparisons of continuous data. Results: 111 patients were included: 23 patients had bilateral TLE, 54 left TLE, and 34 right TLE. Sex, age, body-mass index, and neck circumference did not differ among sub-groups. Patients with bilateral TLE were more likely to have drug-resistant epilepsy compared to those with right or left TLE (91.3% vs 63% and 63.6%; p=0.027), and had less rapid eye movement sleep (%REM Sleep/Total sleep time - 14% vs 19% and 18.2%; p=0.031). Patients with right TLE had more slow-wave sleep compared to those with bilateral or left TLE (%N3 Sleep/Total sleep time - 30.8% vs 24.8% and 23.9%; p=0.035). The prevalence of moderate-to-severe OSA (AHI 15) differed significantly across the three groups, being common among patients with left (n=11/54, 20.4%) or bilateral TLE (n=5/23, 21.8%) and rare among those with right TLE (1/34, 2.9%; p=0.04). The prevalence of PLMS tended to be higher in right TLE, but was non-significant (right 8/34, 23.5%; left 7/54, 12.9%; bilateral 8/34, 23.5%). Conclusions: OSA is more common in TLE patients in whom the seizure onset involves the left temporal lobe. It could be hypothesised that the left temporal lobe and the neighbouring structures such as the insula, may play a critical role in the control of nocturnal respiration. This study also provided evidence that sleep architecture is altered by the laterality of seizure focus, which has implications for further research in sleep and cognition. Funding: This study was supported by funding from the RMH Neuroscience Foundation.