PARALYSIS (Gr., a loosing or relaxing), or PALSY, is a loss, more or less complete, of the power of motion; but by some writers the term is employed to express also loss of sensation. When the upper and lower extremities on both sides, and more or less of the trunk, are the affection is termed general paralysis. Very frequently only one half of the body laterally is affected, the other side remaining sound; to this condition the terib hemiplegia is given. When. the palsy is confined to all the parts below arrimag inary transverse line drawn through the body, or to the two lower extremities, the condi tion is termed paraplegia. When one part of the body, as a limb, one side of the face, etc., is exclusively attacked, the affection is known as local palsy. In some cases the loss of sensation and the power of motion in the paralyzed part is entire, while in others it is not so. Iu the former the paralysis is said to be complete, in the latter partial. In most cases, but not invariably, sensibility and motion are simultaneously lost or impaired. When motion is lost, but sensation remains unimpaired, the affection has received the name of akinesia (Gr. a, not, and kinesis, motion). More rarely, there is a loss of sensi bility while the power of motion is retained; and to such cases the term anaesthesia (Gr. a, not, and at:Ithesis, sensation) is applied. This affection occurs most frequently in the organs of sense; as in the tongue, for example, in which the sense of taste may be lost, without any defect of movement, Paralysis is in most eases in mere symptom of disease existing in some other part than that apparently affected; as, for example, in the brain or spinal cord, or in the conduct ing nerves between either of these organs and the palsied organ. Sometimes, however. it is a purely local affection, depending upon a morbid condition of the terminal extremi ties of the nerves. The varieties in the condition of the brain and spinal cord which occasion paralysis are somewhat numerous; as, for example, Congestion, hemorrhagic and serous effusion, softening, fatty degeneration, fibrinous exudation, suppuration, hydatids, various morbid growths, depressed bone from external violence, etc. It is highly probable, also, that palsy may sometimes result from mere functional disorder of the nervous centers—a view which is confirmed by the fact that a post-mortem examina tion of a patient who lies suffered from this affection sometimes fails to detect any apparent lesion. Paralysis may originate in a nervous trunk, if it is compressed by a
tumor, or otherwise mechanically affected, or if it is the seat of morbid action tending in any way to disorganize it; or it may be due to an abnormal condition of the termina tions of the nerves, which may be rendered unfit for receiving impressions either from the external world or from the brain by prolonged disuse, by continuous or severe pres sure, by exposure to cold, by disorganization of their own tissue, or by the depressing action of various metallic poisons, especially lend.
We shall briefly notice the symptoms and causes of the most important forms of paralysis, before oifering any remarks on the general principles of treatment. Hemi plegia (Gr. hemi, half, pTesso, I strike) affects one lateral half of the body, and is that form of palsy to which the term paralytic stroke is commonly applied. The parts gener ally affected 'are the upper and lower extremities, the muscles of mastication, and the muscles of the tongue on one side. In a well-marked case the patient when seized falls to the ground, all power of motion in the affected arm and leg being lost. The palsy of the face which accompanies hemiplegia is usually quite distinct from the affection known as facial pals-il, which is an affection of the facial nerve or portio Jura. See NERVOUS SYSTEM'. It is the motor branches of the fifth or trifacial nerve going to the muscles of mastication which are generally involved in hemiplegia, and consequently the cheek is flaccid and hangs down, and the angle of the month is depressed on the affected side. The tongue when protruded points towards the paralyzed side, and there is often imper fect articulation, in consequence of the lesion commonly affecting the hypoglossal nerve. llemiplegia may arise from lesions of various kinds, as, for example, (l) from hemor rhage. or sonic other morbid change in the brain, in which case the palsy is on the side of the body opposite to the lesion, in consequence of the deenssation or crossing over of nervous fibers from one side to the other that occurs at the upper part of the spinal cord (q.v.); (9) from spinal disease below the point of decussation Just noticed; in this case the palsy, and the lesion causing it, are on the same side of the body. It is also sometimes associated with epilepsy, and chorea, but in these cases it usually disappears in a few hours.