Paralysis is a temporary or permanent loss of muscle power or control. Paralysis may consist of inability to move a limb or part of a limb or individual muscles, paralysis of the muscles of breathing, swallowing and voice production being especially serious. Paralysis may be due to disease of the brain (e.g., stroke, tumor); spinal cord (poliomyelitis); nerve roots (slipped disk); peripheral nervous system (neuritis); neuromuscular junction (myasthenia gravis), or muscle (muscular dystrophy). Disturbance of blood potassium levels can also lead to paralysis.