Exploring serum α‑synuclein and its autoantibodies in essential tremor: implications for diagnosis and symptom correlations.

There is no definite biomarker for confirming the diagnosis of essential tremor (ET) or differentiating it from other diseases, particularly Parkinson's disease. The present study aimed to investigate the serum levels of the α-synuclein protein (α-syn) and its autoantibodies in patients with ET compared with healthy controls and its relation to motor and non-motor symptoms in patients with ET. Serum α-syn and its autoantibodies were measured in 32 patients with ET and 32 age- and sex-matched controls. Both groups were assessed using the non-motor symptoms scale, MoCA, Beck Depression Inventory, Hamilton Anxiety Rating Scale, and the Short Form 36 Health Survey Questionnaire. Tremor was assessed using the Fahn-Tolosa-Marin Tremor Rating Scale. The serum α-syn concentration in patients with ET was significantly lower than that in healthy controls (P<0.001), with a positive predictive value of 0.81 and a negative predictive value of 0.75, while the serum anti-a-syn autoantibody concentration was not significantly different between the two groups. There were no correlations between serum α-syn or its autoantibodies and patients' clinical characteristics. Furthermore, patients with ET had worse cognitive impairment, depression, anxiety, non-motor symptoms and quality of life. The serum α-syn concentration was lower in patients with ET than in controls, with favorable predictive values, suggesting that it could serve as a biomarker for ET diagnosis.