Eye movements in amyotrophic lateral sclerosis

Abstract

It has generally been assumed that the oculomotor system is not involved in amyotrophic lateral sclerosis (ALS). However, reports from the literature and recent experience with patients indicate that there are oculomotor abnormalities in some ALS patients. These appear to fall into two main categories. One group of patients has signs that reflect damage or degeneration in cortico-oculomotor pathways. These patients have problems in generating voluntary saccades, convergence and pursuit eye movements. It should be possible to corroborate deficits in ocular pursuit in these patients with deficits in visual suppression of the vestibulo-ocular reflex (VOR) and in optokinetic nystagmus (OKN). A second group of patients, much less common than the first, has a more global type of ophthalmoplegia, probably reflecting a loss of neurons in and around the ocular motor nuclei. There are probably also patients with mixed types of involvement. Testing the vestibulo-ocular reflex (VOR) in conjunction with other tests of visual-oculomotor function should help in identifying the deficits. The relative incidence of the various types of deficits is not known and is a subject for study. It would also be of interest to correlate the changes that are present in the oculomotor system of patients with ALS with deficits in other parts of the somatic motor system.