PARALYSIS (Lat., from Gk. rapdXvats, palsy. paralysis, from rapaVav, pa ralyein, to disable the side, from rapd, pare, beside, beyond + View, lyein, to loose), sometimes called PAL SY. A loss, more or less complete, of the power of motion. By some writers the term is made to include loss of sensation. When the upper and lower extremities on both sides and more or less of the trunk is involved, the affection is termed general paralysis. Frequently only one-half of the body laterally is affected. the other side remaining sound. To this condition the term hemiplegia is applied. When the par alysis is confined to all the parts below an imaginary transverse line drawn through the body, or to the two lower extremities, the con dition is known as paraplegia. When one part of the body. e.g. a limb or one side of the face, is exclusively affected, the condition is known as a local palsy or local paralysis. In some cases the loss of sensation and of motion in the paralyzed part is complete, while in others there is only some loss of power. In the former case the paralysis is said to be complete, in the latter partial. In most eases, but not invariably. sensation and motion are simultaneously lost or impaired. When motion is lost but sensation remains unaffected, the condition is known as akinesia. :Nlore rarely there is a loss of sensibil ity while the power of motion is retained. To such a condition the term anaesthesia is applied. This latter affection occurs most frequently in the organs of special sense, as. for example, in the tongue, where the sense of taste may be lost without any impairment of motion.
Paralysis is not a disease in itself, but merely a symptom of disease usually located in sonic part of the body other than that affected by the paralysis. Rarely are disturbances of sensation or of motion due to changes which are primarily in the skin area or muscles affected by the par alysis. This does, however, sometimes occur, as in the paralysis of progressive muscular dystro phy, where the primary lesion is in the muscles affected. The proper appreciation of external stimulation, i.e. sensation, and the proper carry ing out of voluntary movements of the muscles, are dependent upon the integrity of the parts of the nervous system which govern such sensations and movements. The nerve terminations in nms de, skin, etc., serve as means for the reception and distribution of nervous impulses. The nerves themselves carry impulses between the nerve centres in the brain, spinal cord, and ganglia, and the peripheral nerve terminations. The brain, spinal cord, and ganglia serve as centres in which nervous impulses originate, are transformed, and associated. It thus follows that paralysis is a symptom which is usually indicative of patho logical changes in (1) the peripheral nerves, or (2) the nerve trunks, or (3) the nerve centres in the brain, cord, or ganglia. and it is in these organs that the lesions of paralysis must usually be sought, and not in the paralyzed parts them selves. Thus disease of the peripheral nerves
may cause paralysis, e.g. the paralyses occurring in peripheral neuritis. More frequently disease of or injury to nerve trunks. or tumors, or dis placed bone pressing upon nerve trunks, causes paralysis in the parts supplied by the nerve or nerves affected. The completeness of the paraly sis is determined by the extent of the injury to the nerve fibres and by the completeness of the interruption of nerve impulses. The spinal cord (see NERVOUS SYSTEM AND BRAIN) acts by means of Its gray matter as a centre for automatic, reflex, and trophic impulses, also through its fibre tracts (white matter) as a pathway by means of which impulses are transmitted t(:) and from the higher centres in the brain. After in jury to the cord, such as results from dislocation or fracture of the with the consequent pressure upon or tearing of the tissues of the cord itself, a paralysis supervenes in the parts of the body below the seat of injury. If the par alysis results from pressure alone without an actual injury to the cord, it may be only tem porary, recovery taking place when the pressure is removed. More often there is some crushing of the curd, in which case the paralysis is perma nent. its extent depending upon the extent of the injury. When the cord is crushed completely across there is a complete paralysis. both motor and sensory, of all parts below the seat of injury, with the excejotion of such internal organs as are supplied by nerves which arise above the injury. Tumors, benign or diseased conditions extending from neighboring tissues and organs, hemorrhages into the spinal canal or into the substance of the cord. etc., determine. by the pressure upon the cord which they cause, paraly ses similar to those resulting from injury. The main difference between the two is a clinical one, the paralysis from injury coming on suddenly and immediately after the injury. while the par alysis from disease has a gradual onset. Again, certain diseases of the spinal cord itself cause paralysis. Thus acute anterior often called (because of its most prominent symp tom and because of its most frequent occurrence in children) acute infantile spinal paralysis, is a disease of the gray matter of the anterior horns and causes paralysis of those museles governed by the affected cells. In the early stages of this disease the number of cells affected is large, and the paralysis is extensive. Some of the cells are so severely injured that they die, and the paralysis in the muscles which these cells govern is permanent. The majority of the cells first affected usually recover, and this recovery in the cells is marked by a of the paralysis in the muscles which these cells gov ern. Among the other diseases of the spinal mill in which paralysis occurs or may occur may be mentioned Landry's paralysis. spastic para plegia, or spastic spinal paralysis, amyotrophie lateral sclerosis. tabes dorsalis, ataxic para plegia, and myelitis.