Prevalence of rem behavioral disorder and rem sleep without atonia in patients suffering from parkinson’s disease

Zoltán Szakács¹, *Terèzia Seres², Éva Kellős², Márta Simon¹, Attila Terray Horváth¹, Veronika Fáy³, Jelena Karaszova³, Andrea Kontra³, Olívia Lalátka³, Mária Csóka⁴, Gyula Domján⁵

Summary
Introduction. The atypical, non-motor symptoms of Parkinson’s disease have been drawing more and more attention recently. These symptoms include: neuropsychiatric dysfunctions, dysautonomy, sleep disorders and sensory symptoms, such as pain. Neurodegeneration resulting from Parkinson’s disease may affect the REM-on and REM-off neurons that are responsible for the structure of sleep. This may result in sleep fragmentation, decreased sleep efficiency, decreased amount of deep sleep and REM sleep and behavioral disorders during REM sleep (REM sleep behavior disorder – RBD). RBD is a primary sleep disorder that is characterized by the appearance of the activity of skeletal muscles during REM sleep. REM sleep without atonia (RWA), on the other hand, is characterized by abnormal muscle activation without complex behavioral expression.
Aim. To determine the prevalence of REM sleep without atonia and RBD in patients with Parkinson's disease.
Material and methods. We assessed the frequency of RWA and RDB in 50 non-selected patients with Parkinson’s disease by a polisomnographic observation (PSG). A demographic analysis was conducted. 50 patients, aged on average 71.9 ± 11.8 years and suffering from Parkinson’s disease, average Hoehn-Yahr stadium 1.9 ± 0.8, participated in the study. The results were compared to the data of 16 healthy control persons without sleep disorders with age and gender matching the study group (average age 62.31 ± 6.87 years).
When RWA is suspected in a patient, additional monitoring during polysomnography must be ensured. Apart from the obligatory video monitoring, EMG channels recording the tone on all the four limbs (musculi tibialis anterior, soleus and biceps brachii bilaterally) and in the chin muscle are recommended.
Results. RBD was present in the anamnesis of 4 (8%) patients with Parkinson’s disease. During polysomnography, RWA was detected in 17 patients (34%). In the vast majority of cases, no behavioral manifestation of RBD could be detected. RBD patients were characterized by a much higher limb movement index in the REM phase (18.6 ± 4.39 events/hour) than the control group (4.4 ± 2.3 events/hour; p = 0.0001). During their sleep, RBD patients spent more time in the deep slow-wave sleep (2.64 ± 1.31%) than the control group (0.76 ± 0.27%; p = 0.004). Furthermore, the RBD patients had a higher percentage of REM sleep (12.8 ± 3.19% vs. 8.6 ± 1.67%; p = 0.01) than the controls. REM density was lower in RBD patients than in the control group (20.8 ± 2.77% vs. 31.2 ± 4.16%; p = 0.01). During their REM sleep, patients with Parkinson’s disease spent lower amount of time in muscle atonia than the persons from the control group (61.5 vs. 95.6%; p = 0.004).
Conclusions. RWA was significantly more prevalent among patients with Parkinson’s disease than in the healthy persons. Furthermore, nearly two-thirds of the patients suffering from Parkinson’s disease had submental tonic muscle activity detected in EMG in at least 20% of their total REM sleep duration. REM sleep without atonia was detected in many patients with Parkinson’s disease without anamnestic data suggesting sleep disorder or behavioral disorder during REM sleep. The connection between RBD and RWA is still unclear, however, two mutually non-exclusive hypotheses can provide an explanation for the phenomenon of RBD without RWA. Longitudinal studies with PSG examinations are needed to clarify whether, with the passage of time, the clinical features of RBD indeed evolve to RWA in patients without behavior disorder.

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