ALS is the most common type of motor neuron disease and is called amyotrophic lateral sclerosis in Chinese. In the early stages of the disease, patients often feel muscle twitching, which is caused by tremor of muscle bundles. This is a disease in which both upper and lower motor neurons are involved, and lower motor neuron injury refers to brainstem motor nuclei and spinal cord anterior horn cell injury. Patients with early onset of the disease show weakness and atrophy of the small muscles of the hands, so muscle twitching is most pronounced in the hands and can involve the upper arms. Spastic paralysis is often present in the lower extremities and is associated with upper motor neuron damage, and muscle fasciculations are milder compared to the upper extremities.