Mental Status Test Scores are Inversely Correlated with Tremor Severity: A Study of 161 Elderly Essential Tremor Cases

BACKGROUND There is an increasing awareness that patients with essential tremor (ET) may exhibit non-motor features, including cognitive dysfunction. Yet there are surprisingly few data in ET on the association, if any, between cognitive dysfunction and motor dysfunction (i.e., tremor severity). Establishing links between the cognitive and motor features of ET would imply that the two share a common underlying pathogenic process. Recent neuroimaging data support this notion. METHODS ET cases were enrolled in a clinical-pathological study at Columbia University Medical Center, New York. The Folstein Mini-Mental State Examination (FMMSE) and Modified Mini Mental Status Examination (mMMSE) were administered. Action tremor was rated with a total tremor score (TTS). RESULTS There were 161 ET cases (mean age 83.9±5.7 years, median FMMSE 28, median mMMSE 50). The FMMSE and mMMSE were inversely correlated with the TTS (r = -0.22, p = 0.005; and r = -0.17, p = 0.029). The association, while statistically significant, was modest in magnitude. In linear regression models that adjusted for age, gender, and education, the association between cognitive test scores and TTS remained robust (p<0.001). After excluding 68 (42.2%) cases taking ET medications with potential cognitive side effects, results remained unchanged. CONCLUSIONS Each of the two cognitive test scores was associated with tremor severity such that greater cognitive dysfunction occurred in cases with more marked tremor. These data support recent imaging data, which suggest that the cerebellar neurodegeneration underlying ET may be involved in the expression of cognitive symptoms in ET.