A 45-year-old man presents with weakness and wasting of the muscles of his right hand for 8 months. Physical examination shows fasciculations of the hand. The patient's speech is impaired, and 6 years later, he dies of respiratory insufficiency. Autopsy shows atrophy of ventral roots in the spinal cord. Which of the following is the most likely diagnosis?

ALS is a degenerative disease of motor neurons of the brain and spinal cord that results in progressive weakness and wasting of the extremities and eventually impairment of respiratory muscles. The disease affects motor neurons in three locations: (1) the anterior horn cells of the spinal cord; (2) the motor nuclei of the brainstem, particularly the hypoglossal nuclei; and (3) the upper motor neurons of the cerebral cortex. The injury to the motor neurons leads to the degeneration of their axons, visualized in striking alterations of the lateral pyramidal pathways in the spinal cord. The defining histologic change in ALS is a loss of large motor neurons accompanied by mild gliosis. ALS begins as weakness and wasting of the muscles of the hand, often accompanied by painful cramps of the muscles of the arm. The other choices do not affect the motor neurons of the spinal cord.Diagnosis: Amyotrophic lateral sclerosis