Colour vision abnormalities do not correlate with dopaminergic nigrostriatal degeneration in Parkinson's disease

Sensory disturbances such as olfactory or visual dysfunctions are common in Parkinson's disease (PD). A possible relationship between distorted colour discrimination and the nigrostriatal dopamine deficit is still a matter of debate. We examined 31 de novo Parkinsonian patients with [123I]beta-CIT single photon emission tomography (SPECT). We used a single-head gamma-camera and calculated the binding ratio striatum/cerebellum (specific/nonspecific binding) of [123I]beta-CIT uptake. On the same day, we performed the Farnsworth-Munsell 100 Hue Test (FMT) in these patients and estimated the total error score, in order to investigate abnormalities of colour vision. Parkinsonian patients' total error score was higher compared with an age- and sex-matched control group (P = < 0.0001), whereas disability scores of the Hoehn and Yahr scale (P = 0.019, Spearman r = 0.419) and the Unified Parkinson's Disease Rating Scale (P = 0.039, Spearman r = 0.373) correlated with total error score. No significant association appeared between total error score (Spearman r = -0.119, P = 0.525) and [123I]P-CIT-SPECT ratio. Thus both total error scores of the FMT and [1231]beta-CIT-SPECT binding ratios have been found to reflect the severity of PD. However, only [123I]beta-CIT SPECT reflects degeneration of dopaminergic neurons of the basal ganglia, but does not reflect alterations of the visual system and/or extranigral lesions in PD. From our results, we speculate that FMT may be a valuable clinical method to measure extranigral lesions of the visual system in PD.