The Association of Visually Guided Saccades and DAT-SPECT Findings in Parkinson’s Disease

Abstract

<b><i>Background:</i></b> In individuals with Parkinson’s disease (PD), visually guided saccades (VGSs) reportedly reflect general motor dysfunction and cognitive impairments. However, it has not been fully elucidated whether the VGS abnormalities result from nigrostriatal degeneration or other PD-related neural changes. <b><i>Methods:</i></b> We measured VGS latency and gain in 50 PD participants and 56 age-matched normal controls (NCs), and PD participants underwent dopamine transporter (DAT) single-photon emission computed tomography (SPECT) within 2 months of the measurement. VGSs were evoked by a white dot on a monitor, which was presented at the center and pseudo-randomly jumped off horizontally (10° or 20° eccentricity) or vertically (10° or 15°). First, we compared the parameters between PD participants and NCs for each target location. Second, in the participants who exhibited striatal DAT asymmetry on SPECT, VGSs contralaterally directed to the more severely affected striatum were compared with those ipsilaterally directed. Third, effects of the DAT-SPECT specific binding ratio (SBR) on VGSs were analyzed. <b><i>Results:</i></b> PD participants demonstrated prolonged latencies when the target was presented at the upward 15° eccentricity and decreased gains at all target locations. Contralateral VGSs relative to the side of the more severely affected striatum were more delayed and hypometric than ipsilateral. The SBR had a significant positive effect on VGS gain. <b><i>Conclusions:</i></b> In participants with PD, saccadic abnormalities were emphasized when VGSs were directed contralaterally to the more severely affected striatum. Moreover, the dopaminergic nigrostriatal degeneration on DAT-SPECT was mainly associated with VGS gain.

Cluster analysis reveals distinct patterns of saccade impairment and their relation to cognitive profiles in Parkinson's disease

“…This is in line with previous studies proposing that the amplitude of vertical saccades may be useful in differentiating PD from healthy individuals (Waldthaler et al, 2019; Zhang et al, 2020). Saccadic hypometria seems to be more directly linked to motor impairment than other saccade measures, as (horizontal) saccade gain has been associated with UPDRS subscores, Hoehn & Yahr stage and even striatal dopamine transporter density (Kobayashi & Kuwabara, 2021; Linder et al, 2012; Waldthaler et al, 2019). In our study, participants allocated to cluster 2, which was characterized by multidomain cognitive impairment, also executed saccades with lower horizontal gain than controls and in participants in cluster 3, however, without differences in motor disease severity between these clusters.…”

Electroencephalographic-Based Functional Connectivity Networks of Visual Hallucinations and Visuospatial Dysfunctions in Parkinson’s Disease

“…Parkinson's disease (PD) is the second most common neurodegenerative disease and is characterized by a loss of dopaminergic neurons in the substantia nigra, which causes several symptoms, such as visual dysfunctions [1][2][3]. Visual hallucinations (VHs) and visuospatial dysfunctions (VSDs) have been reported as common symptoms and have a major impact on patients with PD [4].…”