Articles
Reduced Frequency of Ipsilateral Express Saccades in Cervical Dystonia: Probing the Nigro-Tectal Pathway
Authors:
- Rebecca B. Beck
- Simone L. Kneafsey
- Shruti Narasimham
- Sean O’Riordan
- Tadashi Isa
- Michael Hutchinson
- Richard B. ReillyEmail Richard B. Reilly
Abstract
Background: Cervical dystonia is a hyperkinetic movement disorder of unknown cause. Symptoms of cervical dystonia have been induced in animals in which the integrity of the nigro-tectal pathway is disrupted, resulting in reduced inhibition of the deep layers of the superior colliculus. This same pathway is believed to play a critical role in saccade generation, particularly visually guided, express saccades. It was hypothesized that individuals with cervical dystonia would present with a higher frequency of express saccades and more directional errors.
Methods: Eight individuals with cervical dystonia and 11 age- and sex-matched control participants performed three saccadic paradigms: pro-saccade, gap, and anti-saccade (120 trials per task). Eye movements were recorded using electro-oculography.
Results: Mean saccadic reaction times were slower in the cervical dystonia group (only statistically significant in the anti-saccade task, F(1, 35) = 4.76, p = 0.036); participants with cervical dystonia produced fewer directional errors (mean 14% vs. 22%) in the anti-saccade task; and had similar frequencies of express saccades in the gap task relative to our control population (chi-square = 1.13, p = 0.287). All cervical dystonia participants had lower frequencies of express saccades ipsilateral to their dystonic side (the side to which their head turns), (chi-square = 3.57, p = 0.059).
Discussion: The finding of slower saccadic reaction times in cervical dystonia does not support the concept of reduced inhibition in the nigro-tectal pathway. Further research is required to confirm the observed relationship between the lateralization of lower frequencies of express saccades and direction of head rotation in cervical dystonia.
- Year: 2018
- Volume: 8
- Page/Article: 592
- DOI: 10.5334/tohm.404
- Submitted on 20 Jul 2018
- Accepted on 2 Oct 2018
- Published on 16 Nov 2018
- Peer Reviewed