Saccade, pupil, and blink abnormalities in prodromal and manifest alpha-synucleinopathies
- PMID: 39973506
- DOI: 10.1177/1877718X241308193
Saccade, pupil, and blink abnormalities in prodromal and manifest alpha-synucleinopathies
Abstract
BackgroundSaccade, pupil, and blink control are impaired in patients with α-synucleinopathies (αSYN): Parkinson's disease (PD) and multiple system atrophy (MSA). Isolated REM (rapid eye movement) Sleep Behavior Disorder (iRBD) is a prodromal stage of PD and MSA and a prime candidate for investigating early oculo-pupillo-motor abnormalities that may precede or predict conversion to clinically manifest αSYN.ObjectiveDetermine whether saccade, pupil, and blink responses in iRBD are normal or similar to those identified in PD and MSA.MethodsVideo-based eye-tracking was conducted with 68 patients with iRBD, 49 with PD, 17 with MSA, and 95 healthy controls (CTRL) performing an interleaved pro-/anti-saccade task that probed sensory, motor, and cognitive processes involved in eye movement control.ResultsHorizontal saccade and blink behavior was intact in iRBD, but abnormal in PD and MSA. iRBD patients, however, demonstrated reduced pupil dilation size, which closely resembled the changes found in PD and MSA. In the iRBD group, the extent of these pupillary changes appeared to correlate with the degree of hyposmia and reduction in dopamine transporter imaging signal.ConclusionsPupil abnormalities were present in iRBD, but blink and horizontal saccade responses were intact. Future longitudinal studies are required to determine which prodromal pupil abnormalities predict conversion from iRBD to PD or MSA and to identify the time window, in relation to conversion, when horizontal saccade responses become abnormal.
Keywords: Parkinson's disease; eye movements; isolated rapid eye movement sleep behavior disorder; multiple system atrophy.
Plain language summary
Neurodegenerative diseases like Parkinson's disease (PD) are on the rise. In the clinic, the phenotypic similarities between early stage PD and conditions such as early-stage multiple system atrophy (MSA) complicate treatment strategies. Accurately distinguishing these disorders is essential for developing treatments that can delay the progression from even prodromal through early symptomatic stages to full-blown disease. Eye tracking, an affordable and non-invasive diagnostic tool, measures eye movements, pupil size, and eye blinks to help locate problems in the brain. These measurements are important to help identify PD from other related brain disorders and assessing the severity of impairments. Our study compared eye movement behaviors between groups, including individuals diagnosed with PD, MSA, and people at risk of developing PD, such as those with isolated rapid eye movement sleep behavior disorder (iRBD), and healthy controls. Our results show that PD and MSA patients had irregular eye movements and pupil responses. iRBD patients, who carry a high risk of developing PD or MSA, had changes in pupil size similar to PD, suggesting that pupil changes could serve as early indicators for patients at risk for developing PD. Improved diagnostic accuracy enhances the testing of new treatment approaches and the quality of life for those affected by or at risk of developing PD.
Conflict of interest statement
Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
MeSH terms
LinkOut - more resources
Full Text Sources
Medical
