Diseases characterized by a selective degeneration of the motor neurons of the spinal cord, brainstem, or motor cortex. Clinical subtypes are distinguished by the major site of degeneration. In AMYOTROPHIC LATERAL SCLEROSIS there is involvement of upper, lower, and brainstem motor neurons. In progressive muscular atrophy and related syndromes (see MUSCULAR ATROPHY, SPINAL) the motor neurons in the spinal cord are primarily affected. With progressive bulbar palsy (BULBAR PALSY, PROGRESSIVE), the initial degeneration occurs in the brainstem. In primary lateral sclerosis, the cortical neurons are affected in isolation. (Adams et al., Principles of Neurology, 6th ed, p1089)

Synonyms: Lateral Scleroses, Primary, Motor Neuron Disease, Secondary, Motor Neuron Disease, Familial, Scleroses, Lateral, Sclerosis, Primary Lateral, Lateral Sclerosis, Motor Neuron Disease, Lateral Sclerosis, Primary, Sclerosis, Lateral, Anterior Horn Cell Disease, Familial Motor Neuron Disease, Neuron Diseases, Motor, Lateral Scleroses, Motor Neuron Disease, Lower, Motor System Diseases, Motor Neuron Diseases, Motor System Disease, Upper Motor Neuron Disease, Scleroses, Primary Lateral, Lower Motor Neuron Disease, Neuron Disease, Motor, Primary Lateral Sclerosis, Motor Neuron Disease, Upper, Primary Lateral Scleroses, Secondary Motor Neuron Disease