Objective: To study the probability of conversion of essential tremor (ET) and ET-plus patients to Parkinson’s disease (PD).

Background: ET-plus syndrome represents a wide spectrum encompassing various soft neurological including parkinsonian features. Its complexity in terms of motor and non-motor presentation can raise challenges regarding its categorization into ET-plus or early-Parkinson’s disease (PD). With the lack of access to functional dopaminergic imaging in low-middle income countries, a web-based probability score can be of great use to identify patients at risk of pheno-conversion to PD.

Method: We conducted a cross-sectional study in our department of Neurology of Sahloul Hospital including ET patients classified into two groups: ET and ET-plus syndromes based on the most recent classification of tremors by movement disorder society (MDS). We used the online Prodromal PD calculator from the MDS website (https://www.movementdisorders.org/MDS/Members-Only/Prodromal-PD-Calculator.htm) to evaluate the estimated probability of PD. Using this calculator, we included the assessment of global cognitive function based on the MMSE score, depression screening using the geriatric depression scale (GDS), rapid eye movement disorders (RBD) based on the RBD-SQ.

Results: We included 54 patients. ET-plus phenotype was identified in 32 patients with rest tremor being present in 16 cases, bradykinesia in 12 and rigidity in 5. ET-plus group had significantly higher mean probability risk of conversion to PD(0.52%±0.16 versus 0.78%±=0.23, p=0.042). Among the ET-plus group, 54% were classified as prodromal PD and correlated with the presence of hyposmia(p=0.036), cognitive dysfunction (p=0.012) and presence of RBD(p=0.048). The presence of dysautonomic features noted in 48% of ET-plus cases (constipation and/or orthostatic hypotension) correlated with the probability score of conversion to PD(p=0.024).

Conclusion: Our study pinpointed that ET-plus is at higher risk of developing PD in comparison with ET group. Hyposmia, RBD and autonomic dysfunction correlated with ET-plus patients classified as prodromal PD which is plausible since the such features do present markers of synucleinopathy. Finally, our study highlighted the pertinence of using the prodromal PD calculator among ET and ET-plus patient to identify patients in need of close monitoring on both motor and non-motor level.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/is-essential-tremor-plus-phenotype-a-prodromal-phase-of-parkinsons-disease/