BACKGROUND: Periodic limb movements in sleep (PLMS) are repetitive movements usually of the legs strongly associated with Restless-legs syndrome (RLS), which appear more frequently in males, older age and other sleep disturbances, such as sleep-disordered breathing (SDB). Patients with Parkinson's disease (PD) suffer from various sleep disturbances including REM sleep behavior disorder, RLS and PLMS. Although a dopaminergic pathophysiology of PLMS is discussed, no systematic data on PLMS side-to-side distribution in PD and its correlation with asymmetry of motor symptoms are available.

OBJECTIVE: This study aimed at elucidating PLMS asymmetry in correlation to that of motor symptoms in PD compared to SDB and RLS.

METHODS: Cross-sectional, retrospective analysis of two polysomnography (PSG) recordings per patient scoring PLMS separately for both legs.

RESULTS: Of 105 patients (44 PD, 44 age- and sex-matched SDB and 17 RLS patients) PLMS measures (number of PLM, PLM-Index, PLM-arousal index) showed significant side-to-side differences in all disease entities in both PSGs (P < 0.001; Wilcoxon rank test). PLM-Index asymmetry (PLM-I difference of >5/h between both sides) was observed less frequently in PD (34% of patients) compared to RLS (77% , P < 0.05) and SDB (59% , P < 0.05; χ2 test). In asymmetric PD patients, predominant side of PLMS was more stable than in SDB and RLS comparing the two PSGs, but we did not detect an agreement between PLMS predominant side with that of motor symptoms in PD patients.

CONCLUSIONS: Only the minority of PD patients shows asymmetric PLMS distribution with relatively high night-to-night stability but no correlation with motor symptom asymmetry.