| Paralysis is a loss or impairment of motor function in one or more muscle groups as a result of a lesion of the neuromuscular mechanism. When applied to motor function, paralysis is the loss of voluntary movement, precluding the use of muscles, tendons, or joints that normally control body movements. Paralysis is a sign of an underlying condition such as paraplegia or quadriplegia. Paraplegia refers to weakness or paralysis of both legs and the lower part of the body. Quadriplegia or tetraplegia refers to weakness or paralysis of all four extremities.
Paralysis is the result of an interruption of one or more motor pathways at any point from the cerebrum to the muscle fiber. This interruption can be caused by spinal cord injuries (fractures, dislocations) incurred from blunt trauma, automobile and boating accidents, falls, or sports injuries. Spinal cord disease or other diseases and conditions may also interrupt neuromuscular functioning. Paralysis may be manifested by partial or complete loss of function of the involved muscles and may be temporary or permanent. Complete paralysis indicates a total loss of function below the level of the injury. Incomplete paralysis indicates that the individual has some motor function below the injury level. If all the peripheral motor nerve fibers supplying a muscle are interrupted, all voluntary, postural, and reflex movements are lost. In loss of motor nerve fibers outside the central nervous system (brain and spinal cord), the muscle becomes loose and soft and does not resist passive stretching, a condition known as flaccidity. Muscle tone appears to be reduced (hypotonia or atonia), and atrophy of the muscles occurs. If this effect occurs in only a portion of motor fibers supplying the muscle, the result is partial paralysis. In partial paralysis, there is less atrophy, and the tendon reflex will be reduced but not completely lost. In conditions involving the brain or spinal cord, the paralysis may be spastic, in which case the affected muscles are stiff and movements are awkward as a result of damage to the upper motor neuron system.
In paraplegia, paralysis of the legs may develop as a result of diseases of the spinal cord, nerve roots, or peripheral nerves; it may also result from hereditary causes, spinal tumors, and injury. Paraplegia may be either acute or chronic. In acute spinal cord diseases, paralysis or weakness affects all muscles below a given level, often with a loss of sensation, including pain and temperature. In bilateral disease or injury of the spinal cord, there may be loss of bladder and bowel function. The most common cause of acute paraplegia is spinal cord trauma, usually associated with fracture/dislocation of the spine. Other causes are obstruction (thrombosis) of the spinal artery, occlusion of aortic branches due to an aneurysm, or hemorrhage into the spinal cord (hematomyelia) due to a blood vessel (vascular) malformation, the use of anti-coagulant medications, or bleeding diseases.
In adults, multiple sclerosis is the most common cause of chronic spinal paraplegia. Other conditions that may cause chronic paraplegia include vitamin B12 deficiency, protruded cervical disc and cervical spondylosis, syphilitic meningomyelitis, brain abscess and other infections, classic motor neuron disease (amyotrophic lateral sclerosis or ALS), syringomyelia, and degenerative disease of the spinal cord of unknown cause. An infectious or inflammatory process such as transverse myelitis may be responsible, but an etiology is often not determined.
Hereditary spastic paraplegia (HSP), also called familial spastic paraparesis, is characterized by progressive spasticity in the lower extremities that can become severe and incapacitating. It develops as a result of degeneration of corticospinal tracts inside the spinal cord; the longer fibers that supply the legs are more affected than fibers that supply the arms. HSP is considered to be a group of heterogeneous syndromes described as “uncomplicated” or “pure” when only the spine is involved, and as “complicated” if neurologic abnormalities such as ataxia, epilepsy, mental retardation, dementia, visual or hearing dysfunction, or adrenal insufficiency are also involved.
Quadriplegia is the result of injury to the brain or cervical spine or may result from diseases of the peripheral nerves, muscles, myoneural junctions, gray matter of the spinal cord, brainstem, or cerebrum. The lesion typically occurs in the cervical area of the spinal cord. Depending on the lesion’s location in the cervical area, paralysis of the arms may be flaccid and areflexic in type, and that of the legs may be spastic. Compression of the cervical spinal cord segments may occur with osteo- or rheumatoid arthritis. The incidence of quadriplegia is difficult to determine due to the various possible underlying causes of the paralysis.
Both paraplegia and quadriplegia occur less often than paralysis of one side of the body (hemiplegia).Risk: Motor vehicle and boating accidents are the main causes of spinal cord injury leading to paralysis, followed by sports-related injuries, acts of violence, falls, and other causes. Sports and recreation are the second most common cause of acute spinal cord injury worldwide, representing 20% or more cases in various countries (Tator).
Whites and males are at increased risk for spinal cord injury, with a male-to-female ratio of 4:1; about half of all cases of spinal cord injury occur in those between 16 and 30 years of age (Dawodu). Approximately 80% of all sports-related spinal cord injuries occur in males (Tator). Incidence and Prevalence: Spinal cord injury affects 30 to 60 people in 1 million each year: 27.9% have total paraplegia, and 18.5% have total tetraplegia or quadriplegia (Dawodu). Increased incidence of spinal cord injury is found among individuals who participate in sports such as diving, football, hockey, gymnastics, and motor sports (Tator). Two million individuals in the US live with some form of paralysis of the extremities (Tator). Hereditary paraplegia is rare, with only 3 individuals in 100,000 estimated to be affected in most populations, including fewer than 10,000 cases in the US (Paik). |