Objective: To explore the hypothesis that color discrimination impairment seen in Lewy body disorders is a specific biomarker of visual hallucinations rather than just overall global cognitive decline.

Background: There is emerging evidence indicating that color discrimination impairments can predict the development of Lewy body dementia in idiopathic REM sleep behavior disorder and Parkinson’s disease[1]. Despite its assumed role as a marker of dementia, color vision deficits are not seen uniformly in patients with Dementia with Lewy Bodies(DLB), suggesting a more nuanced association[2]. Visual hallucinations(VH) represent a discriminating feature of DLB, and recent evidence implicates visual pathway dysfunction as a significant contributor to this phenomenon[3]. We therefore hypothesized that color impairment will correlate with VH in DLB rather than overall measures of cognition.

Method: In this study, we examined the relationship between color vision impairment and VH, along with other clinical and neuropsychological features in 24 patients with DLB alongside 25 age-matched controls. Color discrimination was assessed using the Farnsworth-Munsell-100 Hue(FM-100) test.

Results: Color discrimination impairment was seen in 16/24 DLB participants(67%) with a higher error score relative to controls(p=0.001). We demonstrate for the first time a strong association between color discrimination errors and both the presence and severity of VH in DLB based on clinician-derived(p=0.008) and questionnaire-derived(p=0.03) measures. Correlation with clinical and neuropsychological variables revealed that color discrimination is significantly related to visuospatial impairment(p=0.02) but not to global measures of cognition (MMSE), motor severity (UPDRS-III), age or disease duration. Factor analysis confirmed a unique relationship between color discrimination, visual hallucinations and visuospatial function.

Conclusion: Our results suggest that color discrimination in Lewy body disorders is not simply a marker of dementia but specifically associates with hallucinations and associated visuoperceptual deficits which together may share a common pathophysiological substrate.

References: [1] Postuma RB, Gagnon JF, Bertrand JA, Genier Marchand D, Montplaisir JY. Parkinson risk in idiopathic REM sleep behavior disorder: preparing for neuroprotective trials. Neurology. 2015;84(11):1104-1113. [2] Flanigan PM, Khosravi MA, Leverenz JB, Tousi B. Color Vision Impairment Differentiates Alzheimer Dementia From Dementia With Lewy Bodies. J Geriatr Psychiatry Neurol. 2018;31(2):97-102. [3] Onofrj M, Taylor JP, Monaco D, et al. Visual hallucinations in PD and Lewy body dementias: old and new hypotheses. Behavioural neurology. 2013;27(4):479-493.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/impaired-colour-discrimination-is-associated-with-hallucinations-in-dementia-with-lewy-bodies/