Disrupted white matter integrity in depressed versus non-depressed Parkinson's disease patients: a tract-based spatial statistics study.

Depression is a common occurrence in patients with Parkinson's disease (PD), however, its pathophysiology still remains unclear. With increasing evidence suggesting that depression is a disconnection syndrome, we hypothesized that depression in PD is caused by degenerated fiber connections in the brain. We examined whole brain white matter integrity in 15 depressed PD patients and 15 non-depressed PD patients. All the patients were assessed with the Unified Parkinson's Disease Rating Scale, the Hamilton Rating Scale for Depression, and the Mini-Mental State Examination. White matter difference between the two groups and its correlation with disease severity was calculated. In depressed PD patients, decreased fractional anisotropy was found in the left uncinate fasciculus, superior longitudinal fasciculus, anterior thalamic radiation, forceps minor, and the inferior longitudinal fasciculus. Fractional anisotropy in the left deep temporal cortex was negatively correlated with severity of depression (r = -0.671, p = 0.034). Our results suggest that disrupted fiber connections in the anterior part of the left hemisphere may contribute to depression in PD patients.