Objective: Assess the frequency of REM Sleep Behaviour Disorder (RBD) and dysautonomic symptoms in patients with Essential Tremor (ET), and evaluate the differences between ET-RBD and ET-NonRBD groups. 

Background: The presence of non-motor symptoms, well described in PD, is now being reported also in ET. Recent epidemiological evidence found that PD risk is 3 to 13 times higher in ET patients. This comes in line with neuropathological evidence showing higher prevalence and severity of Lewy Body pathology in ET patients than in controls. However, evidence is scarce on the prevalence, in ET patients, of RBD and autonomic symptoms, classically associated with synucleinopathies.

Methods: We selected all ET patients observed in our Movement Disorder Unit during the year of 2014. Patients were contacted by phone and demographic, clinical and familial data were collected. Autonomic symptoms were assessed using the SCOPA-AUT questionnaire and RBD symptoms with the RBD Screening Questionnaire (RBDSQ) using ≥5 as a cut-off for probable RBD (pRBD). A p value of <0.05 was considered to be statistically significant.

Results: Out of 93 ET patients, 53 (55% female) completed the interview. The mean age at assessment was 74.0 years with a disease duration of 20.0 ± 17.0 years. 14 patients (26.4%) had a diagnosis of pRBD and 52 (98.1%) reported at least one autonomic symptom (96% urinary symptoms, 70% gastrointestinal, 42% cardiovascular, 53% thermoregulatory  and 28% pupillomotor dysfunction). ET patients with probable RBD had higher SCOPA-total and thermoregulatory scores (13.9 ± 9.6 vs. 7.7 ± 5.1, p=0.017 and 2.5 ± 2.0 vs. 0.9 ± 1.6, p=0.001). There were no other differences between groups regarding age, age at onset, family history, duration of disease or tremor characteristics.

Conclusions: We found a prevalence of pRBD in our cohort of ET patients which was significantly higher than previously described in the global population. ET-pRBD patients had more severe dysautonomic symptoms, compared to ET-NonRBD. As RBD is known to be associated with dysautonomic symptoms, and both predate the development of synucleinopathies, we question if we could be facing ET patients harbouring a synuclein-related neurodegenerative phenotype, or patients at risk of progression to an alfa-synucleinopathy.  Long term follow-up of this group will be important to clarify these findings.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/relation-between-rem-sleep-behaviour-disorder-and-dysautonomic-symptoms-in-essential-tremor-patients/