Pattern of paresis in ALS is consistent with the physiology of the corticomotoneuronal projections to different muscle groups.

Objective: A recent neuroanatomical staging scheme of amyotrophic lateral sclerosis (ALS) indicates that a cortical lesion may spread, as a network disorder, both at the cortical level and via corticofugal tracts, including corticospinal projections providing direct monosynaptic input to α-motoneurons. These projections are involved preferentially and early in ALS. If these findings are clinically relevant, the pattern of paresis in ALS should primarily involve those muscle groups that receive the strongest direct corticomotoneuronal (CM) innervation.