Does the Severity of Arm Tremor in Essential Tremor Correlate with Impaired Balance?

Background: Motor features aside from tremor are increasingly recognized in essential tremor (ET) patients. The relationship between these features and tremor has received sparse attention. We examined whether the severity of action tremor in the arms was correlated with the severity of tandem gait difficulty and balance confidence. Methods: 212 ET cases enrolled in a prospective clinical study, from which baseline data on the following variables were analyzed: severity of action tremor (total tremor score [TTS] from the Washington Heights-Inwood Genetic Study of Essential Tremor rating scale, range = 0-36 [severe tremor]), tandem gait mis-steps (range = 0-10), and Activities of Balance Confidence (ABC-6) Scale (range = 0 [least confident] - 100). Results: Higher TTS was associated with a greater number of tandem gait mis-steps (Spearman's rho = 0.216, p = 0.002) and higher tertile of number of tandem gait mis-steps (Spearman's rho = 0.237, p < 0.001). Higher TTS was associated with reduced balance confidence (i.e., lower ABC-6 score) (Spearman's rho = -0.196, p = 0.004) and lower tertile of balance confidence (Spearman's rho = -0.175, p = 0.01). Discussion: We report an association between the severity of upper limb action tremor in ET and both a self-reported measure of balance confidence and a performance-based measure of balance. These data support the model that upper limb action tremor and tandem gait difficulty are associated in some way, with one possible interpretation being that they are both related to a common underlying element, cerebellar dysfunction.