Objective: To examine the relationship between blink rate and DaTScan in Parkinson’s disease.

Background: Spontaneous eye-blink rate (BR) is blinking without external triggers. Parkinson’s disease (PD) patients showed a decrease in BR [1–4], which is expected given the link between dopamine activity and BR [1,5,6]. The studies investigating the relationship between BR and PD characteristics have inconsistent conclusions, due to variability of blink measure and small cohort sizes [1,4]. Although BR is included in the MDS-UPDRS assessment as part of facial expression [7], it is not a quantified assessment. Since blinking is related to cognitive and motor processing, it is critical to do a quantitative assessment using standardized methods of EOG [3] or eye tracking [8]. To initiate progress towards this, we analyzed eye-tracking data from PD patients and investigated the relationship of BR to dopamine deficiency from a DaTScan.

Method: Eye tracking data from 54 PD patients were analyzed in the best-ON condition while they performed reflexive horizontal saccades collected in 2 blocks (video-eye tracker-SMI (500 Hz) and ey(e)brain software). Blink detection was done on each block using a custom algorithm (Matlab). The BR was calculated as the number of blinks per minute. Each patient also performed a DaTScan. The regions of interest over putamen, accumbens, and caudate nucleus were segmented and the normalized mean bilateral signal intensity was used for correlation analysis (Spearman’s ρ coefficient; results considered significant for p≤0.05).

Results: The BR was found to be correlated with DaTScan signal intensity in putamen (Spearman correlation-SC: ρ=0.27; p=0.04) but no significant correlation was observed in accumbens nucleus (SC, ρ=0.14; p=0.30) or caudate nucleus (SC, ρ=0.13; p=0.34) (Figure 1). We found no correlation between BR and UPDRS-III scores in ON and OFF-levodopa medication conditions (respectively ρ=-0.10, p=0.49, n=50 and ρ=-0.19, p=0.16, n=54). The age of patients and PD duration did not correlate with BR (respectively ρ=0.19, p=0.16, n=54 and ρ=-0.09, p= 0.49, n=54).

Conclusion: Blink assessment is a simple, sensitive, and non-invasive test to study the anatomic-functional alterations in PD. Our results suggest that BR may be considered a potential marker for the motor network alterations (reduced DaTScan signal intensity in the putamen) independent of the associative and limbic networks (accumbens and caudate nucleus).

Figure 1

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MDS Abstracts - https://www.mdsabstracts.org/abstract/eye-blink-rate-and-putamen-datscan-covariation-in-parkinsons-disease/