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

Background: A retinal dysfunction is a well-known problem in PD. Previous pathological and in vivo studies have described PD patients to exhibit retinal dopaminergic cell loss and thinning in retinal nerve fiber layer. With regard to cognition, higher-order dysfunctions in visual processing are considered to be an indicator of dementia in PD, whereas the role of primary visual dysfunction in the cognitive prognosis is unknown.

Methods: We enrolled 82 patients with de novo PD, 36 patients with drug-induced parkinsonism (DIP), and 36 controls. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were measured on the mid-portion of the intraorbital optic nerve. Using a linear mixed-effects model, a longitudinal change in cognitive subscore of a comprehensive neuropsychological test was evaluated in PD patients according to 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 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 associated with Parkinsonian motor severity, striatal dopamine transporter activity, olfaction, or baseline cognitive 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.

Conclusions: This study demonstrated optic nerve integrity to be a useful marker for distinguishing PD from normal controls, and a parameter of DTI of the optic nerve could be used as a valuable predictor of declining visuospatial function in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/optic-nerve-integration-as-a-visuospatial-cognitive-predictor-in-parkinsons-disease/