The Knee-Jerk in Diagnosis. BY WILLIAM M. LESZYNSKY, M.D., Lecturer on Mental and Nervous Diseases at the New York Post-Graduate Medical School; Neurologist to the Demilt Dispensary, etc. REPRINTED FROM THE Xcto Yorft JHeDical for June 29, 1895. Reprinted from the Rew York Medical Journal for June 29, 1895. THE KNEE-JERK IN DIAGNOSIS* By WILLIAM M. LESZYNSKY, M. D., LECTURER ON MENTAL AND NERVOUS DISEASES AT THE NEW YORK POST-GRADUATE MEDICAL SCHOOL ; NEUROLOGIST TO THE DEMILT DISPENSARY, ETC. It was at first my intention to read a short paper on some of the more prominent objective signs of structural disease of the nervous system, but as the time allotted to me is necessarily limited, I have concluded to confine my remarks to a consideration of the knee-jerk and its signifi- cance in diagnosis. As our knowledge upon this apparently circumscribed topic has materially increased within the last few years, and as numerous valuable and interesting- clinical observations have been added to our store of infor- mation, it would hardly be practicable, under existing con- ditions, to even attempt to enter into an elaborate study of this subject. I will therefore be as brief as is consistent with lucidity, and only dwell on some of the more common factors to be considered, and trust that the discussion may call forth some of the points that may have been omitted. The accompanying diagram represents a transverse sec- tion of a segment in the lumbar region of the spinal cord, and will serve to elucidate the text. * Read at the meeting of the Harlem Medical Association, Mav 1, 1895. Copyright, 1895, by D. Appleton and Company. , 2 THE KNEE-JERK IN DIAGNOSIS. Primarily, the knee-jerk depends on the integrity of the reflex arc situated in the third or fourth lumbar seg- ment. When the quadriceps tendon is struck, the sensory impression is carried backward through the sensory nerve fibres A to the posterior nerve roots B, thence traversing the posterior column C to the multipolar ganglion cell, D in the anterior horn of gray matter. This constitutes the sensory portion of the arc. The impulse is then projected forward through the anterior nerve roots E and. the ante- rior crural nerve F to the quadriceps, thus producing a con- traction in this muscle. This constitutes the motor por- tion of the arc. The reflex centre in the cord receives THE KNEE-JERK IN DIAGNOSIS. 3 fibers G from the cerebro-spinal portion of the motor tract, which serve to control its activity. It is assumed that these fibers originate in the cerebral cortex. While this description should not be accepted as ana- tomically accurate, yet for all practical clinical purposes this subdivision of the reflex arc and its inhibitory fibres will prove satisfactory as a working hypothesis. Method of Eliciting the Knee-jerk.-The ordinary and customary method of testing the knee-jerk while the per- son's legs are crossed may suffice when the knee-jerks are quite active. Under such conditions the position of the limbs is immaterial. The utmost care, however, is necessary when there is any doubt as to the character of the reaction. Under such circumstances it is advisable to place the patient sitting upon a high chair or upon the edge of a table, so that the feet are free from the floor. As a rule, both knee-jerks should be tested. Occasionally much patience is required in satisfactorily determining whether the knee-jerk is present or absent. In many in- stances the anticipation of the tap upon the patellar tendon occasions involuntary rigidity of the flexor group of mus- cles, thus bringing to bear sufficient opposing force to overcome the action of the quadriceps. Before and during the examination the patient should close his eyes, and his attention should be diverted from the purpose of the ex- aminer either by conversation or rapid interrogation. Or he may be directed to make some muscular effort with the hands, such as forcibly interlocking the fingers or elevating the arms, etc. With this object in view any other similar expedient may be resorted to that suggests itself to the examiner. It is never safe to say that the knee-jerk is ab- sent unless repeated and varied tests have been made with the clothing removed. The well-established principle that faulty methods in examination, like false premises in rea- 4 THE KNEE-JERK IN DIAGNOSIS. soning, result in erroneous conclusions, finds daily exem- plification in the investigation just mentioned. Not long ago, during a pleasant conversation with a well- known practitioner, the subject of the diagnostic importance (or, as he preferred to term it, the unimportance) of the knee- jerk was touched upon. His conclusions were, that its absence indicated locomotor ataxy, and its exaggeration, sclerosis of the lateral columns of the cord. This is a fair illustration of the limited knowledge upon this subject possessed by a large majority of physicians throughout the ■country. While confining my remarks to this particular symp- tom, let me state at the outset that the presence, exagger- ation, or absence of the knee-jerk in itself is not sufficient for a diagnosis without corroborative signs. In other words, its exaggeration or absence per se is not pathogno- monic of any special type of disease. The absence of the knee-jerk is of more positive value than its exaggeration. Any interruption or interference with the integrity of the reflex arc will abolish it. The obstruction may be either in the sensory or motor portion. 1. Thus, a lesion which involves the posterior roots of the posterior columns in the region of the second, third, or fourth lumbar segments, such as tabes or transverse mye- litis, produces a break in the sensory path, and the knee- jerk is abolished. These are the only lesions in the sen- sory tract of the cord that are known to cause a loss of the knee-jerk. 2. A lesion involving the motor portion of the reflex arc, such as acute or chronic anterior poliomyelitis, or mul- tiple or isolated peripheral neuritis affecting the anterior crural nerves, will also abolish the knee-jerk. The perplexing question naturally arises, By what method are we to determine the cause of the loss of the THE KNEE-JERK IN DIAGNOSIS. 5 knee-jerk in an individual case ? Excluding the very re- mote possibility of its being a physiological anomaly, we interpret its significance only after a careful study of its association with other symptoms. I have tested for the knee-jerk nearly one thousand children over three years of age, and found it present in every case. In fifteen its presence was somewhat doubtful at first, but was ultimate- ly demonstrable. 1. Loss of the knee-jerk associated with severe, sharp, circumscribed, paroxysmal pains in the lower extremities ; incontinence or slowness in emptying the bladder, with preservation of muscular resistance, with or without inco- ordination, with or without objective sensory symptoms, is indicative of organic changes in the lumbar segments of the cord, such as tabetic degeneration or a lesion of their posterior nerve roots. 2. Loss of the knee-jerk associated with diminished mus- cular resistance or evident paresis or paralysis in the lower extremities, pain in the course of nerve trunks with ten- derness on pressure, some atrophy and quantitative de- crease in faradaic irritability, with or without objective sensory disturbances, and the absence of bladder symp- toms, is a clinical picture of multiple neuritis. 3. Loss of the knee-jerk with flaccid paralysis, atrophy, and loss of faradaic reaction in the quadriceps, and the ab- sence of all sensory symptoms, indicates a poliomyelitis in the lumbar portion of the cord upon the same side. Now, do not let us assume that the knee-jerk is com- pletely absent in all cases of tabes. In some, the degener- ation may begin in the cervico-dorsal portion of the cord, and, while symptoms such as ataxia, fulgurating pains, an- aesthesia, and paraesthesia are limited to the upper extremi- ties, the knee-jerks may remain well marked until later in the disease, when the pathological process attacks the lum- 6 THE KNEE-JERK IN DIAGNOSIS. bar cord. I have seen a number of cases of tabes where the absent knee-jerk was unilateral. Tn one instance the patient was a man fifty years of age, who suffered extreme- ly from the frequent and severe paroxysms of pain. Tie was under my observation nearly six years, but the knee- jerk persisted on one side. He died suddenly of cerebral haemorrhage. No autopsy was obtained. The knee-jerk has been known to reappear in tabetics during alcoholic in- toxication, and upon the same side after a hemiplegia from cerebral haemorrhage. This phenomenon can only be explained on the assumption that the sensory fibres which have remained intact regain their conductivity when released from the inhibitory cerebral influence. As a general rule, the knee-jerk does not disappear so long as there exist in the reflex paths a certain number of healthy muscle and nerve elements. Therefore, in certain forms of myelitis, neuritis, or myositis, and in the various muscle atrophies of spinal or peripheral origin, the knee-jerk may persist for a long time, although the efficiency of the mus- cle is considerably diminished. On the other hand, in all lesions which affect the nerves in their totality, such as atrophy of the greater part of the nerve or muscle fibres, the knee-jerk is abolished. A very remarkable case of tabes was reported by Eich- horst, where the knee-jerk was lost late in the disease. The patient died of apoplexy. The autopsy revealed that the upper portion of the cord was typical of tabes. The lower dorsal and lumbar portions were normal. The loss was explained by demonstrable extensive degenerative neu- ritis of both anterior crural nerves, which is often a late complication of tabes. In all of the cases reported by Bastian, Hughlings Jack- son, and others, where the cord was completely destroyed in its transverse diameter by a fracture-dislocation, or THE KNEE-JERK IN DIAGNOSIS. 7 •otherwise, the knee-jerk has never returned. Jackson thinks this is due to a loss of " cerebellar influx." These •cases all support the rule that in a complete transverse lesion of the cord the knee-jerk will be lost at once. In all cases of transverse myelitis, spinal-cord haemorrhages, and traumatisms of the cord, if we observe an abolition of the knee-jerks an unfavorable prognosis should be given. The same loss may be produced, however, by extreme pressure upon the cord without destruction. In irritative lesions of the cerebellum (especially tumor) the knee-jerk is either absent or diminished at some period of the dis ease. In some patients it may disappear for a few weeks and then return. In cases of chronic organic intracranial disease, in which indications of the position of the lesion are absent, the occurrence of this symptom suggests a cerebellar process. The changes in the unilateral reflexes permit of the ■diagnosis of a one-sided lesion with the greatest certainty, while an involvement of the reflexes on both sides (exclud- ing polyneuritis) always indicates an affection of the central nervous system in its totality and an unfavorable prognosis. It has been contended that in diphtheria the knee-jerk is frequently absent in the early period of the disease. Its loss was supposed to be due to a multiple neuritis, but this view can not be accepted as conclusive. From a report of a hundred cases in children over four years of age it was absent in sixty one. In these there was evidence of neu- ritis in thirty-four. The writer has, however, personally studied the condition of the knee-jerk in seventy-five cases on the second and third day of the disease, and its pres- ence was clearly demonstrable in every case. Of course, it is well known that in a certain proportion of these patients a complication or sequel may occur in the form of a multiple neuritis involving both anterior crural nerves. Then the 8 THE KNEE-JERK IN DIAGNOSIS. knee-jerk will be lost, and there will be weakness or paraly- sis of both lower extremities. As the clinical manifesta- tions and a confirmatory bactfti iological examination arc sufficient evidence of the disease, we should be unwilling to lay much stress on the importance of the absence of the knee-jerk as a factor in diagnosis. I have seen three cases of meningitis in which the knee- jerk was absent in the early stage of the disease. A boy eight years of age was admitted to the hospital complain- ing of occipital headache of four days' duration. He had vomited once on the day of admission. A quarter of a grain of calomel was administered every half hour until the bowels acted thoroughly. I saw him two days later. Headache continued. There was slight tenderness over the occiput. Rectal temperature, 102° F. Pulse, 100, and regular; respirations 24. No vomiting. Pupils and ocular fundi normal. No hyperaesthesia. There were neither physical signs nor evidence of infectious fever to account for the symptoms. Both knee-jerks were absent. This was a valuable sign, as it was known that they had been pres- ent. Provisional diagnosis of meningitis. Within thirty- six hours, hebetude increasing to stupor, rigidity of neck muscles, headache. Temperature, 103°. Nystagmus and hippus pupillae. It was then learned that he had fallen and struck the occipital region about a week before admis- sion, but was not rendered unconscious at the time. Diag- nosis, convexity meningitis of traumatic origin. Prognosis doubtful. The disease assumed a favorable course under appropriate treatment. Complete recovery occurred at the end of about five weeks. When the symptoms of cerebral irritation subsided, on the fifteenth day, the knee jerks re- turned and were well marked. Their loss was probably due to the cerebral irritation exciting excessive inhibition. In the fatal case of a child with lobar pneumonia, com- THE KNEE-JERK IN DIAGNOSIS. 9 plicated by meningitis, the knee-jerks disappeared before the symptoms of meningitis were manifested. They were absent over a week and became well marked, even exagger- ated, when pressure symptoms were evident a day or two before death. It is of interest to note that Hughlings Jackson has re- cently shown that the knee-jerk is lost when there is a supervenosity of the blood, in asphyxia from coal gas, in the acute stage of some cases of apoplexy, etc. In distinguishing a genuine epileptic convulsion from simulation, we must consider the absence of the knee-jerks and the absence of the light-retiex with dilated pupils as crucial tests in excluding simulation. Of course, it is within the range of possibility that an epileptic fit may be simulated by a person whose knee-jerks are absent as the result of an organic lesion, and in whom dilated and immo- bile pupils have been artificially produced by atropine. Such an individual would indeed be a rara avis. The knee-jerk is absent in cases of diabetes only where there is peripheral nerve degeneration. This is manifested by symptoms such as muscular weakness in the extremi- ties, circumscribed anaesthesia, and possibly persistent neu- ralgia, isolated paralyses, and disturbances in the nutrition of the skin, especially perforating ulcers and other gangre- nous processes. We now come to the significance of an exaggerated knee-jerk. It may be considered as exaggerated when slight percussion on the tendon above the patella elicits an active response. In brief, it may be said that any obstruc- tive or destructive process involving the upper or cerebro- spinal segment of the motor tract is likely to and generally does occasion an exaggeration of the knee-jerk. Should the lesion be situated above the crossing of the motor tract, the exaggeration occurs upon the opposite side of the body, 10 THE KNEE-JERK IN DIAGNOSIS. while a lesion below this point would manifest its symp- toms on the same side. The prevailing and accepted view to-day is that the re- flex centres in the cord receive fibres from the brain which serve to inhibit or control their activity. In patients who have received large doses of bromide in sufficient quantity to produce some of its physiological effects, as in epileptics, the knee-jerk can always be found either well marked or exaggerated. During the last ten years I have been in the habit of demonstrating this pe- culiarity in all cases of epilepsy appearing at the clinic. This phenomenon is due to the sedative action of the bro- mide on the motor cortex, thus diminishing the cerebral control over the lower reflex centres. Primary or secondary degeneration affecting the lateral columns of the cord (spinal portion of the upper segment of the motor tract) is usually attended by exaggeration of the knee-jerk upon the same side as the lesion. In some cases of hemiplegia resulting from haemorrhage in the in- ternal capsule I have found the knee-jerk exaggerated (and ankle-clonus) on the third or fourth day. This is too soon for the development of a secondary descending degen- eration, but is more likely due to a cutting off of the in- hibitory fibres. In the early stage of paretic dementia, owing to the pathological changes in the cortex, the knee- jerk is often found markedly exaggerated, save in those cases where the posterior columns of the cord have been primarily involved. Then the knee-jerk may be lost. As the knee-jerks are often found pronounced or excessive in neurasthenia, hysteria, and alcoholism, or from mental fatigue, we must admit that in many instances the interpre- tation of such a symptom is more difficult than when the knee-jerks are absent. This is particularly the case when the overactivity is bilateral and uniform in character. A THE KNEE-JERK IN DIAGNOSIS. 11 unilateral exaggeration of the knee-jerk is often of consid- erable pathological significance, and is usually associated with other objective symptoms, such as diminished muscu- lar resistance, paresis, or rigidity. From these cursory remarks it will be seen that in the study of the knee-jerk, as in other conditions, " correct ob- servation is a matter of the greatest necessity, for on what we observe we have to make an interpretation and frame a line of action ; consequently, if the observations are faulty, the interpretations we place upon them are valueless." The New York Medical Journal. A WEEKLY REVIEW OF MEDICINE. EDITED BY FRANK P. 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