or disease of nervous and muscular structures, and is then termed
organic paralysis; or (2) from purely dynamic disturbances
in the nervous structures of the brain which preside over
voluntary movement. The latter is functional motor paralysis,
a symptom common in certain neuroses, especially hysteria.
For general paralysis of the insane, see Insanity.
Whether the loss of motor power be functional or organic in origin, it may be generalized in all the muscles of the body, or localized to one or many. The different forms of paralysis of the voluntary muscles which may arise from organic disease can be understood by a consideration of the motor path of voluntary impulses from brain to muscle. There are two neural segments in this path, an upper cerebral and a lower spinal; the former has its departure platform in the brain and its terminus in the whole of the anterior grey matter of the spinal cord, whence issues the lower spinal segment of the motor path to the muscles. The nerve fibres of the upper cerebral segment are prolongations of the large psycho-motor cells; the nerve fibres of the lower segment are prolongations by the anterior roots and motor nerves of the large cells in the grey matter of the cord. Disease or destruction of any part of the upper cerebral segment will give rise to loss of voluntary power, for the influence of the mind on the muscles is removed in proportion to the destruction of this efferent path (see diagram in Neuropathology). Disease or destruction of the lower spinal segment causes not only loss of voluntary power but an atrophy of the muscles themselves. Paralysis may therefore be divided into three great groups: (i) loss of voluntary power without muscular wasting except from disuse, and without electrical changes in the muscles due to injury or disease of the upper cerebral segment of the motor path of volition; (2) loss of muscular power with wasting and electrical changes in the muscles due to disease or injury of the lower spinal segment formed by the cells of the grey matter of the spinal cord, the anterior roots and the peripheral motor nerves; (3) primary wasting of the muscles.
The more common forms of paralysis will now be described.
1. Hemiplegia, or paralysis affecting one side of the body, is a frequent result of apoplexy (q.v.); there is loss of motion of the tongue, face, trunk and extremities on the side of the body opposite the lesion in the brain. In a case of severe complete hemiplegia both arm and leg are powerless; the face is paralysed chiefly in the lower part, while the upper part moves almost as well as on the unparalysed side, and the eye can be shut at will, unlike peripheral facial paralysis (Bell's palsy). The tongue when protruded deviates towards the paralysed side, and the muscles of mastication contract equally in ordinary action, although difficulty arises in eating, from food accumulating between the cheek and gums on the paralysed side. Speech is thick and indistinct, and when there is right-sided hemiplegia in a right-handed person, there may be associated various forms of aphasia (q.v.), because the speech centres are in the left hemisphere of the brain. Some muscles are completely paralysed, others are merely weakened, while others, e.g. the trunk muscles, are apparently unaffected. In many cases of even complete hemiplegia, improvement, especially in children, takes place after a few weeks or months, and is generally first indicated by return of movement in the muscles which are habitually associated in their action with those of the opposite unparalysed side; thus, movement of the leg returns first at the hip and knee joints, and of the arm at the shoulder and elbow, although the hand may remain motionless. The recovery however in the majority of cases is only partial, and the sufferer of hemiplegia is left with a permanent weakness of one side of the body, often associated with contracture and rigidity, giving rise to a characteristic gait and attitude. The patient in walking leans to the sound side and swings round the affected leg from the hip, the inner side of the toe of the boot scraping the ground as it is raised and advanced. The arm is adducted at the shoulder, flexed at the elbow, wrist and fingers, and resists all attempts at extension. According to the part of the brain damaged variations of paralytic symptoms may arise; thus occasionally the paralysis may be limited more or less to the face, the arm or the leg. In such case it is termed a monoplegia, a condition sometimes arising from cerebral tumour. Occasionally the face is paralysed on one side and the arm and leg on the other side; this condition is termed alternate hemiplegia, which is due to the fact that the disease has damaged the motor path from the brain to the leg and arm before it has crossed over to the opposite side, whereas the path to the face muscles is damaged after it has crossed. In rare cases both leg, arm and face on one side may be paralysed—triplegia; or all four limbs—bilateral hemiplegia. Infantile spastic paralysis, infantile diplegia, or as it is sometimes called Little's disease, is a birth palsy caused by injury from protracted labour, the use of forceps or other causes. The symptoms are generally not observed until long after birth. Convulsions are common, and the child is unable to sit up or walk long after the age at which it should do so.
Paraplegia is a term applied to paralysis of the lower extremities; there are many causes, but in the great majority of instances it arises from a local or general disease or injury of the spinal cord. A localized transverse myelitis will interrupt the motor and sensory paths which connect the brain with the spinal grey matter below the lesion, and when the destruction is complete, motor and sensory paralysis in all the structures below the injury results; thus fracture, dislocation and disease of the spinal column (e.g. tubercular caries, syphilitic disease of the membranes, localized tumours and hemorrhages) may cause compression and inflammatory softening, and the result is paralysis of the voluntary muscles, loss of sensation, loss of control over the bowel and bladder, and a great tendency to the development cf bed-sores. The muscles do not waste except from disuse, nor undergo electrical changes unless the disease affects extensively the spinal grey matter or roots as well as the cerebral path. When it does so, as in the case of acute spreading myelitis, the symptoms are usually more severe and the outlook is more grave.
In cases of focal myelitis from injury or disease, recovery may take place and the return of power and sensation may occur to such an extent that the patient is able to walk long distances; this happy termination in cases of localized disease or injury of the spinal cord often takes place by keeping the patient on his back in bed, daily practising massage and passive movements, and so managing the case as to avoid bedsores and septic inflammation of the bladder—the two dangerous complications which are liable to arise.
2. Paralysis may result from acute inflammatory affections of the spinal cord involving the grey and white matter—myelitis (see Neuropathology).
Infantile or Essential Paralysis.—This is a form of spinal paralysis occurring with frequency in young children; in Scandinavian countries the disease is prevalent and sometimes assumes an epidemic form, whereby one is led to believe that it is due to an infective organism. The names infantile and essential paralysis were given before the true nature of the disease in the spinal cord was known; precisely the same affection may occasionally occur, however, in adults, and then it is termed adult spinal paralysis. The medical name for this disease is acute anterior poliomyelitis (Gr. πολιός, grey, and μυελός, marrow), because the anterior grey matter of the spinal cord is the seat of acute inflammation, and destruction of the spinal motor nerve path to the muscles. The extent of the spinal grey matter affected and the degree of destruction of the motor nerve elements which ensues determine the extent and permanency of the paralysis. The term atrophic spinal paralysis is sometimes employed as indicating the permanent wasting of muscles that results.
Infantile paralysis often commences suddenly, and the paralysis may not be observed until a few days have elapsed; the earliest symptoms noticeable are fever, convulsions and sometimes vomiting; and, if the child is old enough, it may complain of pains or numbness or tingling in the limb or limbs which are subsequently found to be paralysed. It is characteristic, however, of the disease that there is no loss of sensation
