Short vestibulo-ocular reflex time constants associated with oculomotor pathology in multiple sclerosis

Significantly short vestibulo-ocular reflex (VOR) time constants were found in significant high numbers in patients with multiple sclerosis who had oculomotor dysfunction, especially when this dysfunction comprised both the smooth pursuit/optokinetic and the saccadic systems. Some time constants were in the range of 2.5-6 s, i.e. shorter than the presumed time constant of the primary afferent canal neuron. Increase in oculomotor impairment was accompanied by a decrease in time constants in some patients, whereas others showed a combined renormalization of previously disturbed oculomotor function and short time constants. Significantly high numbers of combinations of asymmetry in oculomotor dysfunction and a directional preponderance in time constant were observed, with the shorter time constant on the side of the (more severe) defect.