Evaluation of mild cognitive impairment in older patients with essential tremor.

Introduction: Recent studies have reported that essential tremor (ET) presents with not only motor symptoms but also cognitive dysfunction. However, detailed pathological mechanisms remain unclear. Here, we evaluate the characteristics of cognitive changes in older patients.

Methods: Eighty-five patients aged 65 years or older with ET but without dementia were evaluated for cognitive function using the Addenbrooke Cognitive Examination Revised (ACE-R). The patients were compared with healthy controls (HCs), and the characteristics of cognitive dysfunction were examined. Age at onset and correlations with tremor severity were also investigated. Moreover, we performed resting-state network (RSNs) analysis in a subset of these patients, and the functional connectivity (FC) within the networks was compared with age-matched controls.

Results: Compared to HCs, older patients with ET showed a clear reduction in the total (p = 0.001), attention (p = 0.005), verbal fluency (p = 0.001), and memory (p = 0.001) ACE-R scores. Older-onset patients showed significant cognitive dysfunction compared with younger-onset patients. Verbal fluency correlated with tremor severity in the multiple regression analysis (p < 0.001). RSNs showed an increase in FC in the frontal lobes within the language network in patients with ET compared to HCs (p < 0.05, FWE-corrected).

Conclusion: Older patients with ET showed obvious cognitive dysfunction compared to HCs, indicating that cognitive dysfunction varies by age of onset and correlates with tremor severity. The results of the RSNs analysis suggest that the pathological mechanism of cognitive dysfunction in ET patients involves network changes similar to those in the early stages of Alzheimer's disease.