Background and purpose: Modern neuroimaging has demonstrated progression of disease in multiple sclerosis (MS) that may not be detected by standard clinical protocols, prompting a search for new, sensitive tests.
Methods: In fifty patients with MS, we examined eye movements, with particular attention to the speed and accuracy of saccades, and the vestibulo-ocular reflex during small, high-speed head rotations. We also measured the subjective visual vertical (SVV), using a modified laser-pointer. Visual function was measured, and patients were graded using the Kurtzke Functional Neurological Status (FSS), and Expanded Disability Status Scale (EDSS).
Results: Our main finding was that patients showing abnormalities of eye movements (20/50) were more disabled than those with a normal examination (EDSS scores significantly different, p < 0.01), although the ages and duration of disease were similar in both groups. Saccadic dysmetria and internuclear ophthalmoparesis were common. SVV was abnormally large in 36 % of patients; these showed abnormal eye movements and poorer visual acuity more commonly than those with normal SVV. In patients with the largest deviations of SVV, Kurtzke FSS cerebellar functions were significantly worse (p = 0.021).
Conclusions: Clinical examination of eye movements, with attention to dynamic properties of saccades and the vestibulo-ocular reflex, takes only a few minutes to perform, but may provide better information concerning the presence of brainstem and cerebellar involvement than Kurtzke protocols. Measurement of SVV is possible in the clinic and is a sensitive sign of brainstem dysfunction; our present study suggests that SVV is also affected when cerebellar circuits are involved in MS. Prospective studies are required to determine whether the development of abnormalities with ocular motor and SVV testing are predictive of disease activity and progressive disability in MS.