The motor neuron diseases (MNDs) are a group of progressive neurological disorders. The disease destroy motor neurons to affect the cells that control essential voluntary muscle activity such as speaking, walking, breathing, and swallowing.
When there are disruptions in these signals, the muscles do not work properly. This results in gradual weakening, wasting away and uncontrollable twitching (called fasciculations). When motor neurons are affected, the manifestations include spasticity or stiffness of limb muscles and over-activity of tendon reflexes such as knee and ankle jerks.
MNDs occur in adults and children. The diseases are more common in men than in women. In adults, symptoms may appear after age 40. In children, the symptoms can be present at birth or appear before the child learns to walk.
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