AUTHOR=Jabarkheel Zakia , Wagle Shukla Aparna 

TITLE=Clinical and physiological characteristics of tremor in a large cohort of focal and segmental dystonia

JOURNAL=Dystonia

VOLUME=Volume 3 - 2024

YEAR=2024

URL=https://www.frontierspartnerships.org/journals/dystonia/articles/10.3389/dyst.2024.12551

DOI=10.3389/dyst.2024.12551

ISSN=2813-2106

ABSTRACT=Clinical studies have shown that tremors are frequent, especially in patients with focal and segmental dystonia. However, there is insufficient characterization of tremor physiology. We aimed to ascertain the characteristics of tremors, specifically in focal and segmental forms of dystonia. We enrolled dystonia patients with head and arm tremors presenting to our center (n = 72). These patients mainly had focal cervical dystonia and focal cervical + arm or focal cervical + cranial dystonia (segmental). We recorded the frequency, amplitude, rhythmicity, burst duration, and discharge pattern on accelerometer and electromyography recordings. We compared the physiology of tremors in focal vs. segmental dystonia. We determined whether the physiology was affected by clinical features such as demographics, age at onset, dystonia duration, alcohol responsiveness, family history, and botulinum toxin responsiveness. In the analysis of the head tremor recordings (n = 66; frequency range 3 -6.5 Hz), we found that focal vs. segmental dystonia comparisons revealed a significantly lower frequency (mean ± standard deviation; 4.0 ±0.9 Hz vs. 4.7 ±1.0 Hz; p=0.02), lower amplitude (0.004 ±0.008 g2/Hz vs. 0.006 ±0.008 g2/Hz; p=0.03) and longer muscle burst durations (111.1 ±0.4 ms vs. 91.5 ±24 ms; p=0.04). In the arm tremor recordings (n = 31; frequency range 3.5 -7 Hz), focal vs. segmental comparisons revealed a lower amplitude (0.04 ±0.07 g2/Hz vs. 0.06 ±0.06 g2/Hz; p=0.045). In the stepwise regression analysis, the age at evaluation (β -0.44; p = 0.006) and age at onset (β -0.61; p = 0.005) significantly predicted the head tremor frequency whereas the alcohol responsiveness tended to predict the amplitude of the head tremor (β -0.5; p = 0.04) and the arm tremor (β -0.6; p = 0.02). Our study found that some aspects of physiological characteristics of tremor in focal and segmental dystonia are somewhat distinct, suggesting that the spread of dystonia symptoms from one body region to another may have a bearing on the physiology of co-occurring tremor. The frequency of head tremor in younger participants was higher than in older participants. The head and arm tremors tended to be less severe in patients reporting alcohol responsiveness.