P4‐135: Mild cognitive impairment in Parkinson's disease is associated with white matter damage

Parkinson's disease (PD) patients with quantifiable cognitive deficits, but who do not meet criteria for dementia, can be considered to have mild cognitive impairment (MCI). In this study, we assessed the white matter (WM) damage in patients with PD and MCI compared to healthy controls (HC) and cognitively unimpaired PD patients. Diffusion tensor (DT) MRI were obtained from 45 PD patients and 42 age- and gender-matched HC. Cognition was assessed using the Revised Addenbrooke's Cognitive Examination (ACE-R) battery. According to standardized criteria, those patients who scored 1.5 standard deviations below the normative mean value in at least one cognitive domain were diagnosed as having MCI. Tract-based spatial statistics was applied to compare voxel-by-voxel mean diffusivity and fractional anisotropy between groups. Nineteen PD patients had a MCI (amnestic in 11 patients, non-amnestic in 8 patients). The cognitive domains most frequently affected were orientation and attention (13 patients), memory (11 patients), verbal fluency (8 patients), visuospatial abilities (6 patients), and language (2 patients). PD patients with and without MCI were similar for age, gender, and disease duration, Hoehn and Yahr stage, and motor impairment. No region of altered WM was found when comparing PD patients without MCI with HC. Compared with HC, PD-MCI showed a diffuse pattern of WM abnormalities in the corpus callosum, cingulum, anterior thalamic radiation, superior longitudinal fasciculus (SLF), corticospinal tract (CST), inferior fronto-occipital fasciculus (IFOF), uncinate fasciculus (UF), parahippocampal WM, bilaterally. The direct comparison between patient groups showed that, compared with PD without MCI, those with MCI had DT MRI alterations in the corpus callosum, cingulum, CST and SLF, bilaterally, and right anterior thalamic radiation, IFOF and UF. No region of WM damage was found in PD patients without MCI when contrasted to those with MCI. This study shows that MCI in PD patients is associated with an intrinsic structural damage to the major WM interhemispheric and cortico-cortical pathways. DT MRI may contribute to our understanding of the development of cognitive dysfunction in patients with PD.