Postgrad Med J: first published as 10.1136/pgmj.22.251.255 on 1 September 1946. Downloaded from DIAGNOSIS OF THE COMMON FORMS OF NERVE INJURY OF THE EXTREMITIES By COLIN EDWARDS, M.B., B.S., M.R.C.P., D.P.M. History-taking is the first step in diagnosis and panying diminution or loss of reflexes. In the it is useful to know how varied the causes of peri- absence of an external wound or contusion near the pheral nerve injuries can be. Otherwise the true nerve concerned these muscle changes may be the nature of a traumatic lesion sometimes may not only guide. be suspected. Look first at the most peripheral muscles and The commoner ones are the result of:- particularly those which move the hands and feet. (I) Cutting and laceration. If these are normal (indicating an intact nerve (2) Stretching, which may be sudden (e.g. supply) it is uncommon, although not impossible, stretching of the sciatic by jumping upon the for muscles to be involved whose supply leaves extended foot) causing fibre rupture and those same nerves at a more proximal level. And haemorrhage, or prolonged (e.g. lying with the proximal involvement with normal peripheral arm extended for hours above the head) muscles only occurs close to the actual spot where ischaemia. causing the nerve is injured. The state of innervation of Contusion. the muscles moving the hands and feet gives no (3) to that of the limb (4) Concussion (including that produced by a guide, however, girdle muscles,Protected by copyright. "near miss" when a missile passes through as they are supplied by comparatively short nerves neighbouring tissues without touching the nerve). arising directly from the two great plexuses. (5) Pressure (e.g. crutch and "Saturday-night" Weakness or paralysis of a muscle having been palsies). found, one then follows the nerve proximally (6) Puncture (e.g. by an injection needle). muscle by muscle in the order in which their nerves (7) Local poisoning by injected substances; of supply leave the parent trunk. The most and proximally innervated of the muscles found affected is a useful pointer to the level of the lesion. Muscles (8) Freezing. should be tested by seeing and palpating the actual Loss or impairment of movement is usually the muscular contraction or the tensing of its tendon. presenting symptom of a peripheral nerve injury. Movement of a segment of a limb is not a safe test. But such loss may be caused by fractures, joint Very similar movements can sometimes be produced lesions (dislocation, inflammation, adhesions, by more than one muscle and they may not be ankylosis), muscle or tendon injuries, local in- supplied by the same nerve. There are also other flammatory or other swellings, and spasm, fibrosis varieties of "false movement." Furthermore, loss http://pmj.bmj.com/ or contracture of muscles. It may also be due to of the fixating action of certain paralysed muscles more remote causes such as Central Nervous may give a false impression that other healthy System diseases, non-traumatic peripheral nervous muscles are weakened (e.g. the apparent weakness lesions or hysteria. Care may sometimes be of the finger flexors when there is wrist drop.)* needed to exclude some of these conditions, but Impaired sensation can be useful in confirming usually the obvious paralysis of muscles following the fact of involvement of a particular nerve, upon trauma, with loss of sensation in the skin area particularly if motor signs are slight. It is of supplied by the corresponding nerve points directly little use, however, in locating the level at which on September 23, 2021 by guest. to peripheral nerve injury. Adequate diagnosis, the nerve is injured, particularly if the lesion is a however, involves first localising the lesion (ana- complete one, for then overlapping adjacent nerves tomical diagnosis) and then an estimate of its kind function to supply skin sensation in much of the and degree (pathological diagnosis). Localising area also supplied by the injured nerve. If the the lesion is the simpler of the two tasks, although lesion is old enough even the residual anaesthetic it requires a knowledge of a fairly large number of area unaffected by the phenomenon of "overlap" well-recognised facts. Many of the criteria of pathological diagnosis are also well established, * A very useful pamphlet containing numerous illustra- but some are still evolved. tions of good methods of testing various muscles is Medical being Research Council War Memorandum No. 7 entitled Aids The clearest guides to localisation are muscular to the Investigation of Peripheral Nerve Injuries, published weakness or paralysis, and wasting, with accom- by His Majesty's Stationery Office in I942. Postgrad Med J: first published as 10.1136/pgmj.22.251.255 on 1 September 1946. Downloaded from 256 POST-GRADUATE MEDICAL JOURNAL Sefitember, I946 may show returning sensation due to the ingrowth nosed, the muscles it supplies should be tested in of fibres from adjacent uninjured nerves. the following order-distalo-proximally:--the two So much for general principles in localisation. lateral lumbricals, the opponens and short flexor Individual nerves can now be considered. of the thumb, the short abductor of the thumb, the Isolated lesions of the Ulnar Nerve are common, lateral two heads of the flexor digitorum pro- due to its fairly superficial course, particularly "iear fundus, the long flexor of the thumb, the flexor the elbow. PLATE I shows a hand where there digitorum sublimis, the flexor carpi radialis and is a severe ulnar lesion. Atrophy of the first dorsal the pronator teres. interosseous muscle and of the adductor pollicis is Sensory loss is to be sought over the two terminal obvious from the hollowing of the first interspace phalanges of the index and middle fingers. If the and there is some indication of clawing of the hand lesion is at all severe loss of tactile sensibility is with hyperextension at the metacarpo-phalangeal more extensive than this and can be found over joints and flexion at the interphalangeal joints. the radial half of the palm as well. Such a finding would lead one to test in order the No picture of the appearance of the hand in remaining interossei and the medial two lumbricals, lesions of the Radial Nerve has been included. the opponens and the abductor digiti minimi, the This nerve, of course, supplies no muscles in the slips of the flexor digitorum profundus to the ring hand itself, and the reader can produce the charac- and little fingers and finally the flexor carpi ulnaris. teristic wrist-drop simply by relaxing the extensors This search would give one the most peripheral of the hand. With this as a usual initial sign, one possible site of the injury.* can confirm the fact of a radial lesion by noting Confirmatory sensory loss should be sought over that the thumb cannot be extended in the plane of the ulnar edge of the hand and the little finger. As the palm (e.g. with the palm held flat on a table), in all nerve injuries, sensation of light touch will be nor can the proximal phalanges of the fingers be found lost over a wider area than is pin-prick. extended. Ascending the arm one then tests the Isolated injury of the Median Nerve is not seen supinator, extensor carpi radialis longus, brachio-Protected by copyright. except as a result of penetrating wounds. Its radialis and triceps, Sensory changes in radial position makes it less prone to injuries in general lesions are limited to a small area on the back of than either ulnar or radial. Trophic and vasomotor the hand overlying the first and second metacarpals disturbances and causalgia are commoner in and perhaps the base of the thumb. median nerve lesions than in any other. PLATE 2 The radial nerve is apt to show extensive paraly- shows a right hand where there is a severe lesion sis of good prognosis after relatively trivial injuries of the median nerve and the normal left hand of and. it is from the radial that one gets the most the same subject. Note the atrophy of the thenar striking examples of neurapraxia following pressure muscles and of the pulp of the first finger. Note and stretching. also the thumb lying back in the plane of the palm. Musculo-Cutaneous palsy is very obvious with It is this falling backwards of the t.humb with hyper- biceps paralysed and brachialis largely inactive and extended index and middle fingers which give rise to sensory impairment over the proximal part of the the term "ape-hand" in median nerve palsy. The radial border of the forearm. (It should be re- middle finger in this case happens to be flexed due membered that the brachialis is also supplied by the to the development of a contracture. Before this radial). Damage to the musculo-cutaneous nerve http://pmj.bmj.com/ occurred there was the usual great difficulty in usually occurs as part of a brachial plexus injury. flexing its two distal phalanges. Characteristic Deltoid paralysis is the outstanding sign of and easily elicited signs in median paralysis are Axillary Nerve lesions. PLATE 3 shows the flatten- inability to oppose the tips of the thumb and little ing of the outline of the shoulder produced when finger so as to make a circle (opponens, and short wasting of the deltoid supervenes. Palpation of and long flexors pollicis), to abduct the thumb at the muscle is particularly important when testing to of the the deltoid because action the right angles the plane palm (abductor compensatory by on September 23, 2021 by guest.