Evaluating Mild Cognitive Impairment in Essential Tremor: How Many and Which Neuropsychological Tests?

Objectives: Essential tremor (ET) confers an increased risk for developing both amnestic and non-amnestic mild cognitive impairment (MCI). Yet, the optimal measures for detecting mild cognitive changes in individuals with this movement disorder have not been established. We sought to identify the cognitive domains and specific motor-free neuropsychological tests that are most sensitive to mild deficits in cognition as defined by a Clinical Dementia Rating (CDR) of 0.5, which is generally associated with a clinical diagnosis of MCI. Methods: A total of 196 ET subjects enrolled in a prospective, longitudinal, clinical-pathological study underwent an extensive motor-free neuropsychological test battery and were assigned a CDR score. Logistic regression analyses were performed to identify the neuropsychological tests which best identified individuals with CDR of 0.5 (mild deficits in cognition) versus 0 (normal cognition). Results: In regression models, we identified five tests in the domains of Memory and Executive Function which best discriminated subjects with CDR of 0.5 versus 0 (86.9% model classification accuracy). These tests were the California Verbal Learning Test II Total Recall, Logical Memory II, Verbal-Paired Associates I, Category Switching Fluency, and Color-Word Inhibition. Conclusions: Mild cognitive difficulty among ET subjects is best predicted by combined performance on five measures of memory and executive function. These results inform the nature of cognitive dysfunction in ET and the creation of a brief cognitive battery to assess patients with ET for cognitively driven dysfunction in life that could indicate the presence of MCI. (JINS, 2018, 24, 1084-1098)