Optic nerve disintegration as a visuospatial cognitive predictor of Parkinson's disease

Abstract

Objective: To explore the microstructural integrity of the optic nerve and its role as a visuospatial cognitive predictor in patients with de novo Parkinson’s disease (PD) using diffusion tensor image-based magnetic resonance scans.

Methods: We enrolled 82 patients with de novo PD; 36 patients had drug-induced parkinsonism (DIP), and 36 were normal controls. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were measured on the mid-portion of the intraorbital optic nerve. A linear mixed-effects model was used to evaluate PD patients based on a longitudinal change in cognitive subscore of a comprehensive neuropsychological test and optic nerve integrity.

Results: The mean FA value in PD was significantly lower (0.552 ± 0.103, p < 0.001) than that in DIP (0.645 ± 0.099) or the normal controls (0.689 ± 0.089), whereas the mean ADC value was significantly higher in the PD group compared to the DIP or control group (p < 0.001). Optic nerve integrity was not significantly related to parkinsonian motor severity, striatal dopamine transporter activity, or olfactory performance in PD patents. In a longitudinal assessment of cognition in PD patients, the lower FA group had a more rapid decline in Rey complex figure test performance (-4.26; 95% CI, -8.31 to -0.40; p = 0.031) and Clock drawing tests (-1.35; 95% CI, -2.59 to -0.11; p = 0.034) than the higher FA group.

Conclusion: This study demonstrated that microstructural integrity in the optic nerve was distorted in PD patients, and that this nerve integrity might act as a cognitive predictor of visuospatial dysfunction.