Evaluation of the autonomic nervous system in patients with essential tremor

BackgroundEssential tremor (ET) is a prevalent movement disorder that may be linked to neurodegenerative changes. It is marked by a mix of motor and non-motor symptoms, which include disturbances in the autonomic nervous system. Aim of the study: We aimed to assess autonomic dysfunction in individuals with essential tremor. Thirty patients with essential tremor (Group 1) and 30 age and sex-matched healthy subjects as the control group (Group 2) were recruited. Comprehensive medical and neurological examinations were conducted on all participants, followed by electrophysiological assessments of autonomic function, including heart rate variability (HRV) tests (E/I ratio, Valsalva ratio, 30:15 ratio), adrenergic tests (blood pressure responses to active standing and sustained hand grip), and sympathetic skin response (SSR) tests. Finally, the results of these tests were classified according to the Ewing classification of autonomic failure. Results: The study revealed significant differences between ET patients and the control group. Heart rate variability tests showed a marked difference between the groups. Adrenergic tests, measuring sympathetic innervation, also displayed a significant difference. The sudomotor function test exhibited noteworthy differences in onset latencies and amplitudes in the palm and sole, with ET patients showing prolonged onset latencies and decreased amplitudes. Moreover, the study found a significant correlation between disease severity and autonomic function test results and the Ewing score. Conclusion: The study highlights the presence of autonomic dysfunction in essential tremor patients, with disease severity being associated with the level of autonomic affection, as evidenced by various autonomic function tests and the Ewing score.