Abstract
Background and Objective: Parkinson's disease developed from essential tremor (ET-PD) is a distinct clinical syndrome that is different from essential tremor (ET) and Parkinson's disease (PD). There is currently a lack of research on ET-PD. Tremor characteristics (amplitude and frequency) are primary quantitative indexes for diagnosing and monitoring of tremors. In this study, we aimed to explore specific clinical and electrophysiological biomarkers for the identification of ET-PD.Methods: The study included patients with ET-PD (n = 22), ET (n = 42), and tremor-dominant PD (t-PD, n = 47). We collected demographic data, clinical characteristics (including motor and non-motor symptoms), and tremor analysis. The frequency, amplitude, contracting patterns of resting tremor and postural tremor were collected. The analysis of ET-PD and ET/t-PD was compared. The receiver operating characteristic (ROC) curve was used to analyze the electrophysiological features in distinguishing ET-PD from ET or t-PD.Results: Compared with ET, hyposmia, bradykinesia, rigidity, postural abnormality, and resting tremor were more common in the ET-PD group (P = 0.01, 0.003, 0.001, 0.001, 0.019, respectively). The postural tremor frequencies of the head, upper limbs, and lower limbs were significantly lower in the ET-PD than in the ET (P = 0.007, 0.003, 0.035, respectively), which were the most appropriate variables for distinguishing ET-PD from ET (AUC: 0.775, 0.727, and 0.701, respectively). Compared with t-PD, bradykinesia, rigidity, postural abnormality (both P < 0.001), and resting tremor (P = 0.024) were less common in the ET-PD. The postural tremor amplitudes of the head and upper limbs were significantly higher in the ET-PD than in the t-PD (P = 0.022, 0.001, respectively), which were the most appropriate variables for distinguishing ET-PD from t-PD (AUC: 0.793 and 0.716).Conclusions: Hyposmia and electrophysiological biomarkers (postural tremor frequencies and amplitudes) help early recognition of ET-PD.
Highlights
Essential tremor (ET) and idiopathic Parkinson’s disease (PD) are two of the most common movement disorders
Compared with ET, hyposmia, bradykinesia, rigidity, postural abnormality, and resting tremor were more common in the essential tremor–Parkinson’s disease (ET-PD) group (P = 0.01, 0.003, 0.001, 0.001, 0.019, respectively)
The postural tremor frequencies of the head, upper limbs, and lower limbs were significantly lower in the ET-PD than in the ET (P = 0.007, 0.003, 0.035, respectively), which were the most appropriate variables for distinguishing ET-PD from ET (AUC: 0.775, 0.727, and 0.701, respectively)
Summary
Essential tremor (ET) and idiopathic Parkinson’s disease (PD) are two of the most common movement disorders. PD’s motor and non-motor features may overlap with ET, making it difficult to distinguish them based on clinical characteristics [1]. Besides the typical resting tremor, patients with PD often exhibit postural tremor, which is more often observed in patients with ET [2]. In a population-based setting, resting tremor is a common clinical feature in patients with ET, and the prevalence can reach nearly 50% [3]. Depression, anxiety, cognitive disorders, and family history of tremors/PD were similar in both patient groups [5, 6]. Tremor characteristics (amplitude and frequency) are primary quantitative indexes for diagnosing and monitoring of tremors. We aimed to explore specific clinical and electrophysiological biomarkers for the identification of ET-PD
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