Eye movement in amyotrophic lateral sclerosis: a longitudinal study

Eye muscles and the sphincter muscles of the bowel and bladder were formerly thought to be spared in amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder. As frequent subclinical impairment of the anal sphincter muscles in ALS has recently been reported, We suspected an earlier and more frequent, if subclinical, involvement of the oculomotor system than hitherto described. Starting in 1993, we repeatedly studied oculomotor involvement in eight patients with (ALS) using routine orthoptic examination techniques as well as electro-oculographic recordings of ocular movements. Three patients had consistently normal clinical examinations but progressive changes in electro-oculography (EOG). Three patients showed intermittent impairment of eye movements with normal EOG (one patient) or with progressive changes on EOG examination. In two patients, both clinical examination and EOG were progressively pathologic. These findings provide further evidence of early oculomotor involvement, e.g., prior to respiratory failure, in ALS than previously suspected. Since EOG changes seemed to be detectable in all but one patient, EOG changes may allow earlier, subclinical detection of impaired eye movement and thus reveal even an increased frequency of oculomotor impairment in ALS. Due to the heterogeneity of ALS the number of patients examined to settle finally the question of oculomotor involvement in ALS needs to be increased. Newly developed software will allow further interpretation and comparison of more data and, thus, should offer further help in detecting early changes.