Neural compensation preserves white matter integrity in early Parkinson's disease but not atypical Parkinsonism: a diffusion tensor imaging study.

Parkinsonism is a common clinical manifestation of Parkinson's disease (PD) and other atypical parkinsonism (AP). Diffusion tensor imaging (DTI) may help characterize pathological alterations in cerebral white matter (WM). This study aimed to analyze the differences in early white matter microstructural alterations between PD and AP using DTI and to explore the potential value of DTI in the early differential diagnosis of PD and AP. DTI data were acquired from 12 patients with early PD, 11 with late PD, 12 with AP, and 11 healthy controls (HCs). Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were measured in the pons, corona radiata, cingulum, corpus callosum, caudate nucleus, thalamus and substantia nigra. Significant group differences in FA were observed in the bilateral pons, right caudate nucleus and left thalamus (P < 0.05). Significant group differences in ADC were found in the left pons, bilateral cingulum, bilateral caudate nucleus, bilateral thalamus, and left substantia nigra (P < 0.05). These findings indicate DTI-detectable microstructural differences in the pons, caudate nucleus, and thalamus among early PD, late PD, and AP. Motor system pathway alterations in Parkinsonian syndromes appear to involve the cortico-striato-thalamo-cortical (CSTC) and cerebellar basal ganglia bidirectional circuits. Compared with AP, PD showed later and less severe microstructural alterations, potentially reflecting early neural compensation within these circuits.