Scars form on the neurons in BOTH the upper motor neuron and lower motor neuron pathways. Degeneration of these motor neurons leads to progressive atrophy of muscles (LMN…usually beginning with the small muscles of the hands and feet. Degeneration of UMN pathways leads to spasticity & stiffness. Also degeneration of pathways leading to deficits in speech, swallow and respiration.
Amyotrophic lateral sclerosis