Amyotrophic lateral sclerosis (ALS): what happens to eye movements?
Reviewed by Claire Howard

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of upper motor neurons of the corticospinal tract and lower motor neurons in brainstem nuclei and the anterior horn of the spinal cord. Limited literature is available on abnormal ocular movements in cases of ALS and their link with other disease features. This study aimed to describe and analyse eye movement abnormalities in ALS patients. Specifically, the authors aimed to investigate the correlation between non-motor signs and oculomotor impairment in order to understand the pathogenesis of the disease. All ALS patients seen from 2018 to 2020 in the department of neurology at Razi hospital underwent the recording of saccadic eye movements. Results were compared with healthy controls. Sixty-two patients were included. Altered saccadic eye movements (72.6%) correlated with tongue atrophy and bladder dysfunction. The most common finding was altered smooth pursuit (56.5%), which showed correlation with bladder dysfunction and altered frontal assessment battery (FAB) scores. Prolonged latencies of horizontal saccades (34%) correlated with sensory and extrapyramidal signs. This study is reported as the first to examine the characteristics of eye movements in a large African cohort of ALS patients and to show correlations with extra-motor clinical signs. Findings showed extra-motor cortex dysfunction in ALS with greater frequency of eye movement abnormalities in comparison with previous studies. Altered horizontal pursuit, the core abnormality, confirmed the extension of the neurodegenerative process to the frontal and prefrontal cortices. Prolonged horizontal saccade latencies reflect mainly the involvement of the parietal eye field. Anti-saccadic abnormalities were the least common finding and showed, paradoxically, no link with executive dysfunction. The authors conclude that the study of eye movement recordings is a valuable potential tool to evaluate the extension of the neurodegenerative process in ALS even in the sub-clinical stages of extra-motor involvement and should be included as an assessment method for ALS patients.

Eye movement abnormalities in amyotrophic lateral sclerosis in a Tunisian cohort.
Rekik A, Mrabet S, Kacem I, et al.
NEURO-OPHTHALMOLOGY
2022;46(4):227-35.