Paralysis
Paralysis, loss of voluntary movement in a part of the human body, caused by disease or injury anywhere along the motor-nerve path from the brain to the muscle fiber. Paralysis may result from injury, poisoning, infection, hemorrhage, occluded blood vessels, or tumors. Occasionally paralysis is due to congenital deficiency in motor-nerve development. Permanent paralysis results from extensive damage to nerve cells or to a nerve trunk; severely damaged nerve cells cannot regenerate. Transient or incomplete paralysis, called paresis, is often caused by infections, trauma, or poisons that temporarily suppress motor activity but do not extensively damage nerve cells.
Because most of the motor nerves from either half of the brain supply the opposite side of the body, lesions in one part of the brain usually produce paralyses in the opposite half of the body. Paralysis of one limb is known as monoplegia; paralysis of two limbs on the same side of the body as hemiplegia; paralysis of both lower limbs as paraplegia or diplegia; and paralysis of all four limbs as quadriplegia or tetraplegia. Paralysis originating in the brain may sometimes be flaccid, that is, the affected muscles may be loose, weak, flabby, and without normal reflexes. More frequently it is spastic, that is, the affected muscles are rigid and the reflexes accentuated. Paralysis originating in a motor nerve of the spinal cord is always spastic; paralysis originating in peripheral nerves or thin ganglion cells is always flaccid.
Among well-known paralytic conditions are poliomyelitis (previously known as infantile paralysis), cerebral palsy, and multiple sclerosis. Bell's palsy is a common facial paralysis, generally temporary and produced by such conditions as neuritis or infection. Locomotor ataxia is a paralytic condition caused by infestation of the spinal cord and brain with microorganisms that cause syphilis. Alcoholic paralysis is caused by degeneration of nerve cells, in the spinal cord or, less often, in the brain, which have been deprived of essential nutrients.
Temporary paralyses are treated by removing the underlying cause. Permanent paralyses may be ameliorated by appropriate physical therapy and rehabilitation procedures.
Because most of the motor nerves from either half of the brain supply the opposite side of the body, lesions in one part of the brain usually produce paralyses in the opposite half of the body. Paralysis of one limb is known as monoplegia; paralysis of two limbs on the same side of the body as hemiplegia; paralysis of both lower limbs as paraplegia or diplegia; and paralysis of all four limbs as quadriplegia or tetraplegia. Paralysis originating in the brain may sometimes be flaccid, that is, the affected muscles may be loose, weak, flabby, and without normal reflexes. More frequently it is spastic, that is, the affected muscles are rigid and the reflexes accentuated. Paralysis originating in a motor nerve of the spinal cord is always spastic; paralysis originating in peripheral nerves or thin ganglion cells is always flaccid.
Among well-known paralytic conditions are poliomyelitis (previously known as infantile paralysis), cerebral palsy, and multiple sclerosis. Bell's palsy is a common facial paralysis, generally temporary and produced by such conditions as neuritis or infection. Locomotor ataxia is a paralytic condition caused by infestation of the spinal cord and brain with microorganisms that cause syphilis. Alcoholic paralysis is caused by degeneration of nerve cells, in the spinal cord or, less often, in the brain, which have been deprived of essential nutrients.
Temporary paralyses are treated by removing the underlying cause. Permanent paralyses may be ameliorated by appropriate physical therapy and rehabilitation procedures.