Evaluation of cognitive functions in patients with essential tremor, Parkinson's disease, and combination of essential tremor-Parkinson's disease

Abstract

Objective: Essential Tremor (ET) has become a clinical spectrum with motor and non-motor elements rather than a mono-symtomatic condition with motor features. In many studies more than expected mild cognitive deficits have been observed in ET patients and increased incidence and prevelance of dementia is pointed to attention. In postmortem studies as well as cerebellar degeneration, Lewy bodies were identified in locus ceruleus in brain stem and increased risk and coexistence of Parkinson's Disease (PD) has been observed in ET patients. In this study, we planned to investigate the possible presence of cognitive dysfunction in patients with ET, ET-PD and PD patients compared with the control group.Material and Method: Patients with ET, ET-PD and PD and age-matched healthy control group were included to our study. Twenty patients from each patient group and 13 people from control group with the age range of 40-80 were included. Detailed neurocognitive battery and for scanning Geriatric Depression Scale was applied to patients and control group who were examined by two different neurologists.Results: Significant differences were observed in the visual and verbal memory, attention, executive functions and verbal fluency tests in which the control and patient groups compared. As a result of comparison of the patient groups with no differences in terms of age, gender and education, especially complex attention was found to be statistically impaired in PD compared to ET. Personal and actual information, visual memory, simple and complex attention, abstract thinking, executive functions were increasingly getting worse by order of ET, ET-PD and PD.Conclusion: It suggests that ET is also associated with a deficit of multiple catecholaminergic pathways, including fronto-subcortical pathways like PD. However, in order to understand the ET-PH relationship and the mechanism of cognitive abnormalities more clearly, detailed clinical follow-up and long-term studies involving more patients and control groups and histopathological examinations are required.