Eye-tracking-aided Characterization of Saccades and Antisaccades in SYNE1 Ataxia Patients – A Pilot Study

Abstract

BackgroundSYNE1 ataxia is an autosomal recessive hereditary condition, the main characteristic features of which are gait and limb ataxia and cerebellar dysarthria. Previous reports revealed that the clinical phenotype of SYNE1 ataxia is more complex than the first published cases with pure cerebellar signs. The aim of this study was to characterize the eye movement alterations of the first diagnosed Hungarian SYNE1 ataxia patients.ResultsSaccades and antisaccades were examined with eye tracker device in 3 SYNE1 (one patient has two frameshift mutations [c.8515_8516insA, p.Met2839Asnfs*53 and c.11594_11595insG, p.Glu3866*] in compound heterozygous state, whereas two subjects have a splicing variant [c.23146-2A>G] in homozygous state), 6 Friedreich ataxia (FA) patients and 12 healthy controls. Besides that, detailed clinical phenotyping and comprehensive neuropsychological assessment were implemented as well in all patients with ataxia.In addition to the characteristic cerebellar alterations, pyramidal signs and polyneuropathy were observed at least in 2 SYNE1 ataxia patients without any other underlying reason. The eye tracking assessment revealed hypometric saccades in the longer amplitude (18.4°) saccadic paradigm in all SYNE1 patients, whereas 2 out of 3 SYNE1 subjects performed slow saccades as well. In the antisaccade task, higher incorrect ratio of antisaccades were demonstrated in SYNE1 patients compared to healthy controls, showing inverse correlation with working memory test results. The corresponding data of FA patients dispersed in a wide range partially overlapping with control data.ConclusionsThe current study draws attention to the presence of eye movement disorders in patients with SYNE1 ataxia and demonstrates that alterations in the antisaccade paradigm may be related to working memory deficits.