Complete Text (Part 3)

the disease. This is because the faradic current can make a muscle contract only by exciting its motor nerve fibers and in this class of diseases the nerve fibers are degenerated. This degeneration also causes the muscles to waste by pre- venting them from receiving the normal influence of their trophic nerve centers. Moreover, they lose their tone and their tendon reflexes. When the faradic irritability of a muscle is merely diminished, the diminution may be de- tected by first applying the current to the affected muscle and then to another known to be healthy, preferably to the corresponding one on the opposite side. The tests of the galvanic irritability of a muscle are not so simple as the Faradic test because the positive and neg- ative electrodes have an unequal effect on the muscle and a reaction is sometimes caused by opening as well as by closing the circuit. Only the most elementary account of the galvanic reactions will be given here, but it will suffice for practical diagnosis. If the negative electrode, or kathode, be placed over the middle of a healthy muscle, the positive one being on any convenient part of the body, and a current of about five milliamperes gradually turned on, there will be no visible effect. But if the current be interrupted and then suddenly closed, the muscle will give a single quick contraction at the moment of closure. This is called the kathodal closure contraction and is often abbreviated to K. C. C. If the cur- rent now be reversed so that the positive pole, or anode, is EXAMINATION OF THE PATIENT. 39 on the muscle, and closure be made after an interruption, there will be no visible contraction or a weaker one than that obtained with the kathode : only by using a somewhat stronger current can the anode be made to cause a contrac- tion equal to the previously obtained kathodal closure con- traction. Hence it is said that kathodal closure contrac- tion is greater than anodal closure contraction, or, in abbreviated form, K. C. C > A. C. C. In functional paralysis and in paralysis due to organic disease of the upper motor segment the galvanic reactions of the muscles remain as in health. But in muscles whose -lower motor segment (For J/, Fig. 7) is diseased, espe- cially if the disease has advanced rapidly, there is a striking change. We have already seen that such muscles lose their faradic irritability. Galvanic irritability, on the contrary, is commonly increased, so that a contraction is caused by a weaker current than is necessary for the normal muscle. This contraction, however, instead of being quick, as in the normal muscle, is sluggish and suggests the contraction of a worm. Moreover, closing the current causes a greater con- traction with the positive pole on the muscle than it does with the negative pole, which is expressed by the formula A. C. C. > K. C. C, just the reverse of that for the healthy muscle. These two peculiarities, the sluggishness of the contraction and the excess of A. C. C. over K. C. C. con- stitute the reaction of degeneration, which is often abbre- viated to R. D. The reaction of degeneration appears within about two weeks of complete and rapid interruption of the lower motor segment and persists for some months, giving way to the normal reaction if the motor tract be re- stored and passing into complete loss of galvanic irritability if there be no restoration. In very gradual destruction of the lower motor segment, as in the slower cases of spinal muscular atrophy, it does not appear at all and there is a 40 NERVOUS AND MENTAL DISEASES. simple loss of galvanic irritability. Muscles showing the reaction of degeneration are flabby, have lost their tendon reflexes and are soon conspicuously wasted. THE REFLEXES. All reflex actions are alike in that their occurrence is proof of the organic integrity of the reflex arc, consisting of a sensory tract, nerve center and motor tract. They differ greatly, however, in diagnostic import and are gen- erally divided into three classes : (i) Tendon, or deep re- flexes ; (2) superficial, or skin reflexes, and (3) visceral reflexes. A tendon reflex is the process by which a sudden in- crease in the tension of a muscle, usually brought about by tapping its tendon, evokes a muscular contraction in response. Of all the tendon reflexes the knee-jerk is by far the most important and its utilization in diagnosis was one of the great achievements of modern neurology. It tells so much and tells it so quickly that every one who practices medicine should use it as habitually as he does percussion or auscultation. The knee-jerk is usually elicited by having the patient sit with one knee crossed over the other and then striking a recoiling blow upon the patellar tendon with the ends of the fingers. In ordinary cases the foot will promptly be jerked forward by a contraction of the quadriceps exten- sor muscle. If the patient is in bed the test may readily be made, without disturbing him, by raising the knee so that the leg and thigh form an angle a little greater than a right angle, the foot resting easily on the bed, and then striking the tendon. In this case the foot may not move, unless the reflex is exaggerated, but the contraction of the quadriceps is easily seen or felt. EXAMINATION OF THE PATIENT. 4I After some practice the examiner can tell at once whether the knee-jerk is normal, exaggerated or diminished, espe- cially if the responses on the two sides are carefully com- pared. In exaggeration not only is the range of motion increased, but a response is evoked by a lighter blow on the tendon than is necessary in normal cases. When the response is slight it may be m ade more distinct by Jendras- sik's method of reinforcement, which consists in having the patient make some effort with the upper part of the body, such as pulling on his clasped hands or pressing the examiner's hand, at the moment the tendon is struck. The eyes should be closed at the same time. If the knee-jerk is not elicited by the tests so far described it is not to be regarded as absent until further trials show that it can not be elicited by any means whatever. Perfect relaxation of all the muscles of the knee is essential in all doubtful cases and the examiner should not only tell the patient to relax and let the leg hang limp, but he should feel of the flexor tendons and quadriceps to be sure that they are lax. Having the patient sit on the edge of a table with the legs hanging free may be necessary to secure full relaxation. A single distinct response is to be taken as outweighing all previous failures. But if relaxation has been secured and reinforcement employed and striking the tendon still evokes no response, especially if tests have been made on different days, the very signilicant note is to be made that the knee-jerk is absent. The reflex arc for the knee-jerk consists of sensory fibers of the anterior crural nerve passing from the quadriceps ex- tensor muscle to the second, third and fourth lumbar seg- ments of the spinal cord, of these segments themselves and of the motor fibers passing from them back to the muscle. Organic disease interrupting this arc at any point must ob- iously prevent the occurrence of the reflex and, for some J^ 42 NERVOUS AND MENTAL DISEASES. unexplained reason, traumatic destruction of a dorsal or cervical segment of the cord also abolishes it, although less severe injury or disease in the dorsal or cervical part of the cord exaggerates it. Accordingly we find the knee-jerk to be absent in all organic diseases of the anterior crural nerve, of the corresponding nerve roots or of the second, third and fourth lumbar segments of the cord (such as tabes, neuritis, poliomyelitis and myelitis) and also in the severer cases of fracture-dislocation of the spine. Con- versely, the persistent absence of knee-jerk is proof of some such organic disease. Exaggeration of the knee-jerk occurs in all organic dis- eases which impair the integrity of the upper (cortical) motor segment for the quadriceps extensor, provided the reflex arc is intact, or that only a moderate proportion of its motor or sensory neurons is degenerated, and that com- plete destruction of any cervical or dorsal segment of the cord has not occurred. Such diseases are vascular lesions, inflammations and degenerations in the brain, cervical or dorsal myelitis, lateral sclerosis, postero-lateral sclerosis and amyotrophic lateral sclerosis. They cause exaggera- tion of the knee-jerk and other tendon reflexes by inter- rupting the normal cerebral control over the spinal centers and, in proportion to the degree of interruption, the exag- geration may be slight or very great. In the latter case if the patella is grasped and quickly pulled downward a series of rapidly recurring contractions, constituting patellar clo- nus, may occur. In hysteria, neurasthenia and other func- tional diseases the knee-jerk is often exaggerated but not to the degree which is common in organic disease. Very great exaggeration, therefore, especially if accompanied by ankle clonus, is to be taken as presumptive proof of organic disease but moderate exaggeration may be due to either organic or functional disease. EXAMINATION OK TlIK PATIENT. 43 The presence of knee-jerks that are equal on the two sides and normal also has great significance ; their pres- ence and equality exclude any disease seriously affecting either of the reflex arcs and the absence of exaggeration excludes any disease of the brain or spine involving the upper motor segment. What the knee-jerk tells may be summed up thus : r. Its absence is evidence either of organic disease of some part of the reflex arc or of complete destruction of a' cross-section of the cord. 2. Its great exaggeration along with ankle clonus is proof of organic disease affecting the upper motor segment for the leg, but its moderate exaggeration may be due to either functional or organic disease. 3. Its presence in normal and equal degree on the two sides is proof of the absence of any organic disease of the reflex arc and of any organic disease of the brain or cord •iffecting the upper motor segment for extension of the knee. The Achilles tendon reflex, or heel-jerk is elicited by suppoiting the foot lightly, the knee being slightly flexed, and, after seeing that the limb is passive, striking the tendon a recoiling blov^- with the ends of the fingers. Ordinarily the blow is followed in about a tenth of a second by a con- traction of the calf muscles and a corresponding movement of the foot. This movement is normally much less con- spicuous than the knee-jerk but it may be much exagger- ated in disease. When thus exaggerated a form of the reflex called ankle clonus may be produced by supporting the leg with the knee slightly flexed and, after securing relaxation, making an abrupt but not too forcible attempt to passively flex the foot. The sudden tension of the calf muscles causes a reflex contraction and, if pressure is main- tained on the sole of the foot, the tension is instantly re- 44 NERVOUS AND MENTAL DISEASES. newed so that a series of contractions occurs, making the foot vibrate at the rate of five to nine times a second. In typical ankle clonus this vibration continues for a con- siderable time if the proper degree of pressure is main- tained. Ankle clonus may also be elicited by having the patient sit with the toe resting lightly on the floor, the heel being an inch or two above it, and then smartly pressing the knee downward so as to flex the foot. In some con- ditions clonus also appears when the patient attempts to walk. The reflex arc for the heel-jerk consists of the fifth lum- bar and first sacral segments of the cord together with sensory and motor fibers of the spinal cord connecting them with the calf muscles. The presence of heel-jerks that are normal and equal on the two sides excludes organic disease (such as neuritis, tabes and myelitis) affecting the reflex arc at any point and also organic disease of the brain or upper part of the cord affecting the upper motor segment for the calf muscles. The absence of the reflex, on the other hand, is not to be taken as proof of disease unless corroborated by other signs. When exaggeration is so great that typical ankle clonus can be elicited organic dis- ease of the upper motor segment certainly exists ; the spurious clonus occasionally seen in severe hysteria has a slower rate, and generally ceases after a few vibrations. Moderate exaggeration, however, is often seen in func- tional as well as in organic disease. Although the knee-jerk and heel-jerk are by far the most important tendon reflexes, there are others which should al- ways be tested when disease of the corresponding sensory or motor tracts is in question. In the upper limb reflex muscu- lar contractions may often be evoked by tapping the tendons of the pectoralis major, triceps, biceps or any of the muscles moving the wrist or fingers. The limb should be passive I OF THI-: PATIENT. L in such a posture that the muscle to be tested is but sligh stretched. The centers for these reflexes are at various levels from the fifth to the eighth cervical segments. Undei any conditions the presence of a reflex is proof of the tegrity of its reflex arc. If a muscle is paralyzed absence of the tendon reflex, except in rare cases of hysteria, is proof of lesion of the lower motor segment, that is of the cord or nerves, while great exaggeration is proof of organic lesion in the upper motor segment. Moderate exaggeration may be a symptom of either organic or functional disease. Absence of the reflex in a muscle otherwise normal has no positive significance. A tendon reflex of the muscles of mastication, which has received the uueuphonious name of jaw-jerk, may sometimes be elicited by downward tapping on the half- dropped lower jaw. When exaggerated it indicates dis- ease of the upper motor segment for the muscles mastication. The superficial reflexes are muscular contractions caused by irritation of the skin or mucous membrane. The important of these are the plantar, gluteal, cremasteric, lower abdominal, epigastric, palmar and scapular, hav- ing their centers at various levels of the spinal cord, and the conjunctival, having its center at the base of the brain. The plantar reflex is elicited by scratching or tickling the sole of the foot, and consists iirst of a movement of the toes, if the irritation is slight, followed, if the irritation is stronger, by flexion of the hip, knee and ankle so as to withdraw the foot. Its center is in the first three sacral segments. It has recently been proved that except in in- fancy the normal response of the toes is flexion and that if their first movement, particularly that of the great toe, is extension, without dorsal flexion of the foot, a lesion of tly I JUS I 46 NERVOUS AND MENTAL DISEASES. the upper motor segment for the foot is almost always present. The gluteal reflex is a contraction of the gluteal muscles in response to an irritation of the skin of the buttock. Its center is in the fourth and fifth lumbar and first sacral segments. The cremasteric reflex is a contraction of the cremas- ter muscle, drawing the testicle upward, caused by irri- tating the skin on the inside of the thigh. Its center is in the first three lumbar segments. The lower abdominal reflex is a contraction of the ab- dominal muscles in response to an irritation of the skin in the iliac region. Its center is in the lower five dorsal and first lumbar segments. The epigastric, or upper abdominal reflex is a dimpling of the epigastrium in response to an irritation of the skin over the lower anterior margin of the chest and has its center in the fourth to seventh dorsal seg- ments. The palmar reflex is a flexion of the fingers caused by irritating the palm. It is generally absent except in young children and has its center in the lower two cervical and first dorsal segments. The scapular reflex is a contraction of the supraspinati and infraspinati muscles in response to an irritation of the skin over them. Its center is in the lower four cervical segments. The conjunctival reflex is the well-known closure of the eyelids caused by irritation of the conjunctiva. Its center is in the pons. In testing the superficial reflexes it is best to make the irritation of the skin rather sharp so as to get a response at the outset, as the reflex irritability is rapidly dulled by the repetition of gradually increasing irritations. The importance of the superficial reflexes consists in their presence being proof of the integrity of the respective reflex arcs ; the exaggeration or absence of most of them EXAMINATION OF THE PATIENT. 47 is of little significance because it may be caused by many trivial variations from health as well as by severe ones. The visceral reflexes to be kept in mind in a neurolog- ical examination are the palatal, pharyngeal and laryngeal and the anal and vesical. The three first named may be elicited in health by touching the respective parts with a feather or probe but are absent or diminished in bulbar paralysis, diphtheritic paralysis and some cases of hysteria. The anal and vesical reflexes are, of course, always nor- mal when micturition and defecation are normally per- formed ; they are abolished by disease of the third and fourth sacral segments or the corresponding nerves, in which case