Motor neuron disease (MND) is a type of slowly progressing degenerative disease with unknown etiology that selectively invades the motor system or a certain part. The range of lesions includes the anterior horn cells of the spinal cord, the motor nuclei of the cranial nerves in the brainstem, and the pyramidal tract. This type of disease includes amyotrophic lateral sclerosis, progressive spinal muscular atrophy, progressive bulbar palsy, primary lateral sclerosis, etc. Elderly people who suffer from this type of disease are called motor neuron diseases of the elderly. The pathological changes of this disease are mainly the loss of anterior horn cells of the spinal cord and motor nuclei in the lower brainstem. Many surviving nerve cells are shrunk and wrinkled, and the cytoplasm is full of lipofuscin. The lost cells are replaced by fiber-type astrocytes. Large neurons are affected earlier than smaller neurons, the ventral roots become thinner, and there is a disproportionate loss of large myelinated fibers in the motor nerves. Skeletal muscles show typical denervated muscular atrophy at different stages.