NERVES, WOUNDS AND INJURIES OF.
Wounds of Nerves.
In civil life division of nerves is fre quently met with among mechanics, as the result of machinery accidents, cuts with sharp tools, chisels, knives, etc. Brawls are common causes of such acci dents, breaking of glass bottles and tum blers or suddenly thrusting the arm through a window offering ample oppor tunities for deep cuts involving the di vision of one or more nerves. In mili tary life the nerves are frequently sev ered in the course of gunshot wounds, saber-cuts, bayonet-thrusts, etc.
Symptoms.—Whether the division of a nerve oc:cur as the result of contusion, compression, or of any of the factors just enumerated, the symptoms are prac tically the same. There is functional dis turbance, sensory and motor, in the area to which the severed nerve is distributed. The symptoms attending other injuries, —pain, shock, haamorrhage, etc.,—how ever, vary g,reatly in intensity, and in no way correspond to the severity of the le sion present. Thus, a slight wound in which a small nerve has been divided may give rise to intense pain, great shock, loss of consciousness, etc., while a much more serious lesion, involving several nerves, may hardly give rise to any immediate symptoms, local or constitutional. The immediate signs, therefore, do not con vey reliable information regarding the severity of the injury or afford a clue to the extent of the lesion. The sensory or motor disturbances, the changes observed in the area of distribution, and the re mote symptoms afford far more valuable data.
— Small nerves, when cut, often give rise to paresis of remote regions. Thus, a slight wound of the thigh may be attended by paralysis of the other thigh, of the arm on the opposite side, etc. All the muscular system may, in fact, be paralyzed, the result, according to Mitchell, Morehouse, and Keen, of exhaustion of nerve-centres of motion and sensation. Injuries of the ear may give rise to spasmodic cough, or traumatism on one side of the neck may cause palsy of some of the muscles of the arm and leg of the opposite side, etc. Shock and fainting in slight wounds— vaccination, for instance—may thus be produced.
MuscuLAR PowER.—Loss of muscular power is easily determined by the use of the dynamometer or, better still, the dynamograph.
The former shows the amount of power exerted by the hand upon the spring; the latter simultaneously gives a tracing of the regularity with which the muscle acts.
The strength of the muscles of the lower extremities can be tested by re questing the patient to jump on "tip toe," as suggested by Cowers. Again, the strength of the various muscles may be ascertained by causing the patient to perform some special movement bring ing the snspected muscle into use.
Loss of muscular power is, obviously, a valuable diagnostic symptom if it is not merely ephemeral (a blow, pressure, etc., causing temporary paralysis of motion) and is sustained by the other signs indi eating loss of nervous function, deficient nutrition, and impaired electrical reac tion. (See PATHOLOGY.) LOCAL TEMPERATURE.—The area to which the branches of the severed nerves are distributed is often unduly cold. In deed, this hypothermia has reached to 31° F., a difference of seventeen degrees from the normal (Kraussold and Roh den). As a rule, the local temperature varies from 96° to 93° F. Occasionally, however, the temperature is higher than normally, the excess ranging from 1° to 9. F.
—The skin over the area to which the cut nerves are distributed may be anmsthetic or hypermsthetic. In the latter case the patient complains of a sensation of formication, pricking, or pain. The suffering is sometimes in tense, a violent burning pain causing the patient to resort to various means of re lief: allowing cold water to run upon the part, filling his shoes with cold water if the lesion be one involving the foot, etc.
Although complete division of a sen sory nerve is likely to cause definite loss of sensation, the latter may continue nevertheless, owing probably to nerve anastomosis. A long section of the Inns culo-spiral may, for instance, be removed without causing loss of sensation corre sponding to the radial (Moullin). The fact that after some time the area of anxsthesia sometimes becomes smaller also suggests that collateral branches are developed or that the neighboring nerves, Niearytisly for the trunks which ore di, idt.11, are able to extend their spl ere of influence. Again, one region mar be absolutely an:esthetic, while an itan inumdiately adjoining, may be much itss or irregularly so.
To determine the exact degree of sen sitil(ness present, the patient should be bli nd folded and the gentlest means should be employed. A feather may Ix used, or, when there are hairs on the surface. delicate stroking of these will often be sufficient. A pair of compasses and a foot-rule offer ready means when hyperzesthesia is not present. Compari son between corresponding areas on both legs. or both arms, or both sides of the trunk, taking care that the same condi tions are observed, will then indicate to what deg,ree the areas of the affected part differ front the corresponding ones. The condition of the temperature sense may be determined by applying to the skin mops thoroughly' soaked in water of a known temperature or dipping the ex tremities in the latter, or alternately in hot or cold water.