Objective: To explore the correlation between the severity of axial tremor and balance disorder in Essential Tremor (ET).

Background: ET is a heterogeneous disorder and tremor typically manifests in the bilateral upper extremities, though axial structures can also be affected. Its heterogeneity may be one of the reasons why no genetic etiology has been identified so far³. The cerebellothalamocortical circuit is involved in the pathophysiology of ET but it is not known whether symptoms associated with cerebellar vermis pathology including central/truncal ataxia, head titubation and dysarthria⁸, co-localize with axial tremor in patients with ET. Identification of co-localizing symptoms can lead to better understanding of the pathophysiology of ET and recognition of sub-phenotypes which will facilitate phenotype-genotype correlations.

Method: This is a cross-sectional study using data obtained via chart review from a series of patients undergoing pre-operative testing for advanced surgical therapies for ET. Balance was assessed with the Berg Balance Scale. Tremor evaluations were adjudicated using the Fahn-Tolosa-Marin scale for each subtype, and then summed to create an aggregate axial tremor score. Spearman correlation analysis was performed to evaluate the association of each individual subtype of tremor and the aggregate axial tremor score with the Berg balance scale.

Results: Our analytic sample consisted of N individuals (x% female, mean age = x, etc). There was not a significant correlation (p<0.05) between tongue tremor and Berg balance scale (rho = -0.3, R² = 0.092), vocal tremor and Berg balance scale (rho = -0.027, R² = 0.001), head tremor and Berg balance scale (rho = -0.014, R² = 0.000), or the sum of axial tremors and Berg balance scale (rho= -0.105, R² = 0.011).  When adjusted for duration of disease, there was still no statistically significant correlation between Berg balance scale and any of the axial tremors or the aggregate tremor.

Conclusion: There was no statistically significant association between any axial tremors and Berg Balance Scale. This study is limited due to the small sample size and its exploratory nature. Larger studies are necessary to elucidate the relationship of axial tremor and balance in ET.

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