Extrapyramidal involvement in amyotrophic lateral sclerosis: backward falls and retropulsion

Three patients with sporadic amyotrophic lateral sclerosis (ALS) presented with a history of backward falls. Impaired postural reflexes and retropulsion accompanied clinical features of ALS. Hypokinesia, decreased arm swing, and a positive glabellar tap were noted in two of these three patients. Cognitive impairment, tremor, axial rigidity, sphincter dysfunction, nuchal dystonia, dysautonomia, and oculomotor dysfunction were absent. Brain MRI disclosed bilateral T2 weighted hyperintensities in the internal capsule and globus pallidus in one patient. Necropsy studies performed late in the course of ALS have shown degeneration in extrapyramidal sites-for example, the globus pallidus, thalamus, and substantia nigra. Clinically, backward falls and retropulsion may occur early in ALS. This may reflect extrapyramidal involvement.