upper motor neuron disease

Upper motor neuron disease affects the nerve pathways from the brain to the spinal cord. This can lead to muscle weakness, often on one side of the body, with increased muscle tone. For example, in a stroke, the arm may become flexed and the leg extended. Unlike lower motor neuron diseases, muscle bulk is typically well-preserved. Conditions such as multiple sclerosis, brain tumors, and spinal cord injuries can cause upper motor neuron disease. The brain's upper motor neurons initiate muscle contraction by sending impulses to the spinal cord, where lower motor neurons then transmit these signals to the muscles.12