Abnormal Oculomotor Functions in Amyotrophic Lateral Sclerosis

Abstract

Background and purpose: Although traditionally regarded as spared, a range of oculomotor dysfunction has been recognized in amyotrophic lateral sclerosis (ALS) patients. ALS is nowadays considered as a neurodegenerative disorder of a third compartment comprising widespread areas of extra-motor brain including cerebellum. Our objective was to perform an observational study to examine for ocular motor dysfunction in patients with ALS and for any differences between bulbar-onset and spinal-onset patients.

Methods: Thirty two ALS patients (bulbar onset: 10, spinal onset: 22) underwent the standardized systemic evaluations using video-oculography.

Results: Oculomotor dysfunctions such as square wave jerks, saccadic dysmetria, abnormal cogwheeling smooth pursuits and head shaking and positional nystagmus of central origin have been observed in the ALS patients at a relatively early stage. Abnormal smooth pursuits and saccadic dysmetria were increased in the bulbar-onset compared to the spinal-onset (p<0.05).

Conclusions: These oculomotor abnormalities may be a marker of neuro-degeneration beyond motor neurons in ALS, especially in bulbar-onset disease. Future longitudinal studies of eye movement abnormalities have provided insights into the distribution and nature of the disease process.

Keywords: amyotrophic lateral sclerosis; central nystagmus; central positional nystagmus; direction-changing head-shaking nystagmus; oculomotor dysfunction; perverted head-shaking nystagmus.

Conflict of interest statement

The authors have no financial conflicts of interest.

Copyright © 2018 Korean Neurological Association.

Figures

Fig. 1. Examples of abnormal oculomotor functions in our patients with amyotrophic lateral sclerosis. A: Square-wave jerks, B: Abnormal smooth pursuits, and C: Saccadic hypometria and hypermetria.