Premanifest Huntington’s disease: Examination of oculomotor abnormalities in clinical practice

INTRODUCTION Different oculomotor abnormalities have been reported to occur in premanifest Huntington's disease. The aim of this study is to investigate which oculomotor items of the Unified Huntington's Disease Rating Scale (UHDRS) are affected in premanifest individuals compared to healthy controls, and if CAG repeat length and age are correlated with oculomotor abnormalities in premanifest Huntington's disease gene carriers. METHODS We compared baseline data of 70 premanifest individuals and 27 controls who participated in the Enroll-HD study at the Leiden University Medical Center, the Netherlands. Premanifest gene carriers were divided in individuals near to disease onset and individuals far from disease onset. RESULTS Using a logistic regression model, only horizontal ocular pursuit of the six oculomotor items of the UHDRS was significantly more frequently affected in premanifest individuals close to disease onset compared to controls (p = 0.044, OR 13.100). Age was significantly higher in premanifest individuals with affected horizontal ocular pursuit (p = 0.016, OR 1.115) and with affected vertical ocular pursuit (p = 0.030, OR 1.065) compared to premanifest individuals without ocular pursuit deficits. CONCLUSIONS Our results suggest that horizontal ocular pursuit is the only affected oculomotor item of the UHDRS in premanifest individuals and could be used to assess early clinical signs of Huntington's disease. Saccade initiation and saccade velocity do not seem useful for detecting differences between premanifest individuals and controls.