Objective: Using objective instrumental methods, we aimed to verify the clinical utility of sitting/supine test and other clinical features to differentiate between ET and DT.

Background: Head tremor is a common clinical manifestation in both essential tremor (ET) and cervical dystonia. Various clinical tests have been suggested to facilitate their differentiation, such as dissipation of head tremor due to ET in supine position while dystonic tremor (DT) is persisting.

Methods: We collected the group of 28 patients with head tremor consisting of 16 patients with ET (8 F, 8 M, mean age 62, SD 10) and 12 with DT (8 F, 4 M, mean age 57, SD 9 yrs). Beside clinical scales of tremor and dystonia, head tremor was measured by an Xsens wireless accelerometer placed on the patient’s forehead. Hand tremor was recorded by the Optitrack camera system measuring 3D positions of reflexive markers. Power spectral densities were computed from accelerations and the highest power value representing tremor intensity was transformed to decibels (dB).

Results: Family history of tremor was present in 11 out of 16 ET patients and in 1/12 DT (p = 0.006). Voice tremor was present in 7/16 ET and 2/12 DT (p = 0.04). The intensity of hand tremor in wing position was higher in ET than DT group (p < 0.001). Finger tapping was the strongest factor to increase head tremor in both ET and DT (p < 0.001 and p = 0.005, resp.), while sustained phonation was not effective in enhancing head tremor in either group.

To directly differentiate between ET and DT of the head, we selected 10 ET and 10 DT patients with visible tremor over 5 dB. In the supine compared to sitting position, head tremor visually disappeared in 6/10 ET, but also in 9/10 DT patients (p = 0.02). In ET, there was a strong correlation between head tremor power in sitting and supine position (rho = 0.93, p < 0.001), while no correlation was found in DT.

Conclusions: We cannot confirm the value of head tremor disappearance in supine position in clinical differential diagnosis of ET and DT. Only a positive family history and intensity of hand tremor appeared to distinguish patients with ET from cervical dystonia.

Support: Czech Ministry of Health, AZV 16-28119A

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MDS Abstracts - https://www.mdsabstracts.org/abstract/head-tremor-in-supine-position-does-not-differentiate-essential-tremor-and-cervical-dystonia/