It is a loss of muscle function in part of your body. It can be temporary or permanent. The most common causes are stroke, spinal cord injury, and multiple sclerosis. It happens when something goes wrong with the way messages pass between your brain and muscles. Paralysis can be complete or partial. It can occur on one or both sides of your body. It can also occur in just one area, or it can be widespread. Paralysis of the lower half of your body, including both legs, is called Paraplegia. Paralysis of the arms and legs is Quadriplegia. Paralysis of half of the body is Hemiplegia, and only one limb of body is called Monoplegia.