An eye movement disorder in amyotrophic lateral sclerosis.

Defective pursuit eye movements were recorded by electrooculography (EOG) in 11 of 18 patients (61%) with amyotrophic lateral sclerosis. Pursuit defects consisted of a breakdown of smooth tracking into saccadic motions that were grossly in excess (frequencies and amplitudes) of saccadic interruptions of pursuit in normal subjects. In nine patients, defective pursuits cogwheeling) were obvious by visual inspection as well as by EOG; in two, this abnormality was seen only by EOG. In eight patients, the pursuit defect was the only abnormality of oculomotor function; in three, there were also saccadic defects (optokinetic nystagmus or conjugate gaze) discerned by EOG. Autopsy revealed neuronal degeneration in substantia nigra and demyelination in integral capsule in one patient with the pursuit defect but not in another patient without the defect. The pursuit defect may be a sign of extrapyramidal or supratentorial pyramidal involvement in ALS.