Fixational eye movements in Tourette syndrome

• Type of Material: Article
• Authors: Aasef G. Shaikh, Case Western Reserve University; Shlomit Ritz Finkelstein, Emory University; Ronald Schuchard, Stanford University; Glen Ross, VA Medical Center; Jorge Juncos, Emory University
• Language: English
• Date: 2017-11-01
• Publisher: Springer Verlag (Germany)
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2017, © US Government (outside the USA).
• Final Published Version (URL): http://dx.doi.org/10.1007/s10072-017-3069-4
• Title of Journal or Parent Work: Neurological Sciences
• ISSN: 1590-1874
• Volume: 38
• Issue: 11
• Start Page: 1977
• End Page: 1984
• Grant/Funding Information: AS is supported by grant from Dystonia Medical Research Foundation and Dystonia Coalition.
• Keywords: Gaze holding; Clinical Neurology; Science & Technology; REFLEXIVE SACCADES; Microsaccades; NEURONS; SCALE; TASK; BASAL GANGLIA; MICROSACCADE GENERATION; Neurosciences; Vision; Neurosciences & Neurology; Life Sciences & Biomedicine; FOVEAL; Tics; Basal ganglia; ABNORMALITIES
• Research Categories: Biology, Neuroscience; Health Sciences, Opthamology

Abstract

Studies of saccadic eye movements in subjects with Tourette syndrome (TS) have provided additional evidence that there is a link between TS symptoms and deficits in fronto-striato-thalamic networks. These studies revealed impaired timing and inhibition of saccades. We compared fixational eye movements, such as microsaccades and ocular drifts, in subjects with TS and healthy controls.We measured horizontal and vertical eye positions with video-oculography in 14 subjects with Tourette syndrome. We found reduced microsaccade amplitude but increased time between adjacent microsaccades (intersaccadic interval). Hence, the rate of microsaccades was reduced in subjects with TS compared to controls. Measure of ocular stability during intersaccadic intervals revealed increased drift velocity and increased variance in eye position. We hypothesize that increased activity of the direct fronto-striatal pathway and the resulting reduction in basal ganglia outflow targeting the superior colliculus fixation zone affect the rate and amplitude of microsaccades in subjects with TS. The resulting impairment in frontal eye field fixation leads to increased drifts during intersaccadic interval in subjects with TS. Possible clinical implication for these results is that fixational eye movements can be objective biological markers of TS.