IMPAIRED INTEGRITY OF COMMISSURAL AND ASSOCIATION FIBERS IN ESSENTIAL TREMOR PATIENTS: EVIDENCE FROM A DIFFUSION TENSOR IMAGING STUDY.

BACKGROUND/AIM Evolving definition of essential tremor (ET) introduced us a new concept of neurodegenerative disease pointing to diffuse brain network involvement with a wide spectrum of associated motor and non-motor symptoms. Considering the fact that the white matter should also be affected by the nature of the disease, our study aimed to evaluate integrity of white matter and its clinical correlations in ET patients. MATERIALS AND METHODS 40 patients diagnosed with ET and 40 age-and gender-matched control subjects (ranged between 18-80 years old) were included in the study. Sociodemographic characteristics and clinical features of the patients were recorded. Tremor was assessed using ?Fahn-Tolosa-Marin Tremor Rating Scale? (FTM-TRS). Diffusion Tensor Imaging (DTI) was performed to evaluate the integrity of white matter. The selected white matter regions used for DTI assessment were corpus callosum (CC) (i.e., largest commissural tract in human brain), superior longitudinal fasciculus (SLF), and inferior longitudinal fasciculus (ILF) (i.e., largest association fiber bundles). RESULTS The mean age of ET patients and control subjects were 44.23 ± 18.91 and 37.45 ± 10.95 years (p = 0.542). The fractional anisotropy (FA) values of the CC body (p = 0.003) and ILF (p = 0.016) and the average diffusion coefficient (ADC) values of the CC body (p = 0.001) and genu (p = 0.049), SLF (p < 0.001), and ILF (p < 0.001) were differed between groups. After controlling for age and gender, there was no correlation between tremor severity and DTI parameters, but impaired integrity in genu of CC FA (p = 0.035, r = 0.442) and splenium of CC ADC (p = 0.007, r = 0.543) were related with longer duration of tremor. Finally, positive family history was correlated with splenium of CC FA and ADC (p = 0.008, r = 0.536; p = 0.027, r = -0.461) and ILF ADC (p = 0.011, r = -0.519). CONCLUSIONS In our study, major white matter structures changes were found in ET patients. The result suggest that possible neurodegeneration also affects white matter structures in ET patients and duration of tremor and family history are related with impaired integrity of white matter.