Paralysis is defined as complete loss of strength in an affected limb or muscle group.
The chain of nerve cells that runs from the brain through the spinal cord outto the muscle is called the motor pathway. Normal muscle function requires intact connections all along this motor pathway. Damage at any point reduces the brain's ability to control the muscle's movements. This reduced efficiencycauses weakness, also called paresis. Complete loss of communication prevents any willed movement at all. This lack of control is called paralysis. Certain inherited abnormalities in muscle cause periodic paralysis, in which the weakness comes and goes.
The line between weakness and paralysis is not absolute. A condition causingweakness may progress to paralysis. On the other hand, strength may be restored to a paralyzed limb. Nerve regeneration or regrowth is one way in which strength can return to a paralyzed muscle. Paralysis almost always causes a change in muscle tone. Paralyzed muscle may be flaccid, flabby, and without appreciable tone, or it may be spastic, tight, and with abnormally high tone thatincreases when the muscle is moved.
Paralysis may affect an individual muscle, but it usually affects an entire body region. The distribution of weakness is an important clue to the locationof the nerve damage that is causing the paralysis. Words describing the distribution of paralysis use the suffix "-plegia," from the Greek word for "stroke." The types of paralysis are classified by region:
- Monoplegia, affecting only one limb
- Diplegia, affecting the same body region on bothsides of the body (both arms, for example, or both sides of the face)
- Hemiplegia, affecting one side of the body
- Paraplegia, affecting both legs and the trunk
- Quadriplegia, affecting all four limbs and the trunk.
The nerve damage that causes paralysis may be in the brain or spinal cord (the central nervous system) or it may be in the nerves outside the spinal cord(the peripheral nervous system). The most common causes of damage to the brain are:
- Trauma (caused by a fall or a blow)
- Multiple sclerosis (a disease of that destroys the protective sheath that covers nerve cells)
- Cerebral palsy (a condition caused by a defect or injury to the brain that occurs at or shortly after birth)
- Metabolic disorder (a disorder that interferes with the body's ability to maintain itself).
Damage to the spinal cord or peripheral nerves is most often caused by trauma, such as a fall or a car crash.
The only treatment for paralysis is to treat its underlying cause. The loss of function caused by long-term paralysis can be treated through a comprehensive rehabilitation program. Rehabilitation includes:
- Physical therapy.The physical therapist focuses on mobility. Physical therapy helps develop strategies to compensate for paralysis by using those muscles that stillhave normal function, helps maintain and build any strength and control thatremain in the affected muscles, and helps maintain range of motion in the affected limbs to prevent muscles from shortening (contracture) and becoming deformed. If nerve regrowth is expected, physical therapy is used to retrain affected limbs during recovery. A physical therapist also suggests adaptive equipment such as braces, canes, or wheelchairs.
- Occupational therapy. The occupational therapist focuses on daily activities such as eatingand bathing. Occupational therapy develops special tools and techniques thatpermit self-care and suggests ways to modify the home and workplace so that apatient with an impairment may live a normal life.
- Other specialties. The nature of the impairment may mean that the patient needs the servicesof a respiratory therapist, vocational rehabilitation counselor, social worker, speech-language pathologist, nutritionist, special education teacher, recreation therapist, or clinical psychologist.