Popular Science Monthly/Volume 67/August 1905/A Suggestive Case of Nerve-Anastomosis
|A SUGGESTIVE CASE OF NERVE-ANASTOMOSIS.|
SUCCESSFUL cases of the anastomosis of motor nerves presiding over different groups of muscles have been several times reported since 1897. Some of these cases have resulted in the transference of function between the flexor and the extensor nerves of the same extremity; in other cases, nerves serving so different purposes as the sympathetic and the pneumo-gastric have been successfully crossed. The anastomosis of mixed nerves offers, of course, a more complicated problem.
In 1898 Dr. Faure attempted to cure a case of facial paralysis due to destruction of the Nervus facialis by uniting its peripheral end with that portion of the Nervus accessorius which supplies the trapezius muscle. But in this case a satisfactory restoration of the function of the facial nerve was not secured. Still later experiments upon animals in Munk's laboratory, with a view to effect a functionally satisfactory anastomosis of the same two nerves, resulted in a partial success. And one instance of this particular operation in the case of a man, which was attended by a somewhat marked recovery of function, was communicated to the Royal Society by Dr. Kennedy, of Glasgow, in November, 1900. The same authority reported several instances of the same class of cases in the London Lancet for March 1, 1902. In one of these cases, Dr. Kennedy, operating "for facial spasm, divided the facial nerve and united it to the spinal accessory with the result that the face recovered its power of movement to a great extent, but that whenever the patient lifted the right arm a spasm of the face was produced."
The case of anastomosis, to which I wish now to call your attention, was performed by Dr. Harvey Cushing of Baltimore, in the spring of 1902; and it consisted in transferring the proximal stem of the divided accessory nerve in toto into the distal end of the injured and paralyzed facial. The injury to the facial nerve was in this case caused by a bullet wound which completely severed the nerve on the right side of the face; and it involved a loss of the sensations of sweet, sour and bitter substances over the anterior two thirds of the tongue on that side, and a total motor paralysis of the same side. The patient could not close his right eye; lachrymation and other discomforts of facial paralysis were present; and none of the muscles responded either to the emotions or to the volitions which control them in their normal state.
The character of the anastomosis, surgically considered, will easily be seen from the charts (Fig. 1 and Fig. 2); and the unfortunate condition of the patient on making the effort to close his eyes is represented by the accompanying photograph (Fig. 3).
Dr. Cushing's surgery, so far as the completeness of the union effected between the two nerves was concerned, seems to have been unusually successful. This fact gives additional interest to the discussion of the results from the physiological and psychological points of view. At the time of the operation, owing to the healing of the injury done to the chorda tympani, the sense of taste had largely returned; but 'the patient's face had become, even during repose, much drawn to the left, and an effort to close the eyes would result in the peculiar grimace characteristic of facial paralysis, with tilting up of the eyeball,' as shown in the photograph (Fig. 3).
Almost immediately after the operation the patient insisted that his condition was improved; that he was no longer troubled with lachrymation, less troubled with saliva, and better able to dislodge food from his flaccid cheek. He also thought that some power of motion had returned to the eyelid. The doctor urges that this last symptom of improvement could only be due to the inhibitory action of the muscle concerned in raising the upper eyelid; the other 'subjective assurances of improvement' he confesses that he is at a loss to explain. About them it would seem we must say, either that the patient was altogether mistaken, or that at least some slight nervous impulse was already passing over the recently united nerve-tract?
On the tenth day after the operation the patient was sent home, provided with a small galvanic battery which he used for daily electrical treatment, and was later required to exercise the facial muscles persistently before a mirror. From this time on a fairly steady improvement was noticeable, beginning with the decrease in the asymmetrical appearance of the face while at rest, the lessening of the cleft between the eyelids; and ending with the more and more highly differentiated voluntary control of the facial muscles and even with the partial recovery of their response to the varied forms of emotional excitement. On the ninety-fifth day the patient reported that, while galvanizing the muscles and at the same time watching his face in a mirror, he noticed to his surprise, on moving his shoulder, that he could produce considerable contraction in the paralyzed muscles. As he expressed it: 'When I wish to laugh straight, I can help it out with my shoulder.'
A more particular description of this patient's condition at only two points of time subsequently will be quite sufficient for my purpose. Fig. 1. At the end of 168 days the asymmetry of his face when at rest was barely appreciable. He could to a slight extent dissociate movements of eve, nose and mouth. He could almost close his eye by voluntary effort. He could pronounce labials perfectly. He could pucker his lips, although not enough to whistle. He had considerable freedom of facial movement without lifting the arm or shrugging the shoulder. But "Elevation of arm and shrugging of shoulder still called forth general contraction of facial muscles which could not be controlled and which was sustained." The condition of the patient's facial muscles at rest is seen by the photograph taken at this time (Fig. 4). Another photograph (Fig. 5) shows the result of a volitional effort to contract Fig. 2. the facial muscles, when aided by the' arm elevated but completely at rest. At the end of 287 days the volitional control of individual groups of muscles had quite completely returned and could 'be effected without associated shoulder movements of contraction in the other. facial muscles' And although emotional expression had not improved to the same extent, it had returned in considerable measure. How involuntary contraction of the face was still produced by a sudden and vigorous elevation of the arm and shoulder is apparent from a photograph taken at this time (Fig. 6). But how, at the same date, symmetrical closure of the eyes was possible, without associated shoulder movements or the contraction of other facial muscles is seen illustrated in another photograph (Fig. 7).
A recent letter from Dr. Cushing summarizes the results obtained at this date, November 1904, by several similar operations in the
|Fig. 3.||Fig. 4.|
|Fig. 5.||Fig. 6.|
supplied properly by the spinal accessory. Following this in a few weeks there is some power of volitional movement in the paralyzed muscles of the face, without association of shoulder movements. Last of all comes—if it comes at all—the emotional movements over which the patient has no conscious volitional control."
This case which I have now presented in barest outline (and all similar cases of recovery of voluntary and emotional control of paralyzed muscles after anastomosis) raises a number of questions of interest to students both of cerebral physiology and of psychology from the physiological and experimental points of view. Among these the chief is, perhaps, the problem as to what takes place in the cortical centers that is brought about by the changes in the peripheral tracts through which the centers control the different groups of muscles. No completely satisfactory answer to this problem seems at present to be anywhere in sight. But there are three or four tenable hypotheses which may—probably with at least some factors taken from each—contribute toward the better understanding of the problem.
Of such hypotheses the first which I will mention suggests that a more or less nearly complete substitution of function took place between the center of the N. facialis and that of the N. accessorius. Their proximity would be favorable to this—the two centers being not more than about one inch apart. That the cortical center of the accessory nerve did exercise some control over the facial muscles through the united accessory and facial nerves is apparent from the effect produced upon those muscles by raising the arm or shrugging the shoulder. With the general fact of a certain power of substitution of new cerebral areas for disused or injured ones, cerebral physiology is familiar. But how centers so unlike in the character and variety of the muscular functions which they control as are the center for the facial muscles and the center for the trapezius muscle could substitute for each other, is difficult to imagine. Inasmuch, however, as the cortical area, which was formerly 'accessory' in the control of the arm movements, evidently was accessory still in the control of the facial movements, as soon as the juncture of the new nerve-tract was complete; it is possible that the continued exercise of its functions by electrical and volitional stimulus developed the required variety and differentiation of function necessary for facial control. How the cortical center for the N". accessorius knew (sic) that it was called upon to come to the rescue and improve its discerning qualities, as a part of a more complex and intelligent motor system, may remain for us an unanswerable question.
In connection with this hypothesis we may perhaps help ourselves out with another. The fitting of hitherto unused nerve elements with the medullary sheaths necessary for their employment in voluntary motor functions would seem not to be an improbable assumption in the present case. The researches of Ballana, Stewart and others have shown that the regeneration of fibers in cut nerves is not, as was formerly supposed, effected by the growth of the proximal extremities of the axis-cylinders, but by axis-cylinders shot out from logitudinal cells which appear in the distal segment itself. Thus chains of cells are formed which fuse together and become invested with medullary sheaths. Flechsig has also shown that in the human infant at birth, while all the fibers of the spinal cord except those of the pyramidal tracts, which are used especially as conductors of voluntarily initiated impulses, have become myelinated, the vast multitude of fibers in the brain have not become so. According to Professor Sherrington, all this suggests a conclusion which has other evidence in its favor, namely, that a nerve-fiber is not a single nerve-cell process, but a series or chain of nerve-cells forming a functional continuum. The reason, then, why regenerated nerve-fibers do not attain maturity, and so perform their appropriate functions, unless they become united with the central end of some nerve, is that only by this union can they get an opportunity of actually performing these functions. That seems to amount to saying that the call upon them to perform unaccustomed work causes them to fit themselves for this work.
It is not, therefore, too violent an assumption to suppose that, in such a case of recovery of voluntary and emotional control of paralyzed muscles by anastomosis as I have narrated, a new cerebral apparatus of control may be called into use by the process of myelinating the necessary nerve-elements. Such a process might be relied upon either to equip the cortical center of the accessory nerve for its new and more varied functions of control, or to prepare new paths of connection between this center and that which had formerly exercised exclusive control of the muscles of the face through the facial nerve. In a word, tin-building process in the brain, finding much of the old mechanism thrown out of its accustomed use, may have made ready another center and new tracts for the same use.
This hypothesis leads pretty directly to another which seems to be demanded by some of the facts of the case under examination. A more and more highly differentiated volitional control was obtained over the facial muscles; the stimulus of the various emotions, without the accompaniment of volition, met with a better response; and the sight of the condition of the facial muscles as afforded by a mirror was of help in gaining this increased control. All this experience would seem to prove beyond doubt that the higher cortical centers concerned in conscious volition, in emotion and in the perceptions of sight had somehow established the necessary new connections with the center, lower down, in control of the N. accessorius. In a word, whereas formerly, when the accessory nerve was only concerned in helping to lift the arm and shrug the shoulder, these volitional emotional, and visual centers, had paid little or no attention to their influence over the cortical center of this nerve, now that this center and this nerve were being called upon for unaccustomed and more elaborate functions, they found out a way to get into connection, and to bring the new apparatus under their control. But these volitional, emotional and visual centers are widely spread over the cortical area. About their special connections with one another, and especially with the center of the accessory nerve, under normal conditions, we are much in the dark. And how they could go to work to solve, in any length of time and even partially, the problem of readjusting their functional relations to the new and abnormal conditions, offers a problem as yet quite unanswerable by cerebral physiology.
There is one other assumption which would seem to be at once more simple, more sure, and more effective in explanation, than either of those hitherto made. What was the old cortical center for the control of the muscles of the face through the N. facialis doing all this time? We can scarcely suppose it to have been entirely idle or resting in indifference to the functions of which it had been so suddenly and rudely dispossessed. Indeed, it is as certain as anything about such matters can be that the cortical center of the facial nerve would not be allowed to rest. The fifth pair of nerves, whose function is to transmit the sensory impulses from the facial areas, was unimpaired; and since the discomfort from increased lachrymation, saliva and gathering food in the flaccid cheek was very great, this cortical center must have been perpetually sharply reminded of its neglect of duty. Moreover, every time the faradaic current was applied to the cheek, and the patient tried to get control over the facial muscles, helping himself meanwhile by looking in the mirror, there was undoubtedly a very excessive demand for activity made upon this now powerless area from the other cortical areas, which were under excitement.
Now we know with certainty that increased intensity of the stimulation is followed by increased area of neural excitement. A spreading of the nervous processes on which the initiation of motor impulses depends—whatever the chemico-physical character of those processes may be—would, then, necessarily take place in the center of the N. facialis, in answer to the increased demands made upon it by the more intense stimulation from various higher areas. This spreading would, it is likely, have the double effect of enabling the center to use hitherto unused paths between itself and the center of the accessory nerve; and it might also compel the immature nerve-elements to myelinate themselves in preparation for the discharge of their new functions. When this enlarging area occupied, during its excitement, by the center of the facial nerve, had broken over, so to say, into the center of the accessory nerve, and had made good and useful the newly established connection between the two, then it could virtually resume its old functions of control, although now by a new and more roundabout path.
The assumptions previous to the last would all seem to be helpful, if not needful, to explain some of the features of this case of nerve-anastomosis and sequent recovery from facial paralysis. The last assumption is absolutely essential in order to make any satisfactory progress toward explaining it at all. The other assumptions very speedily bring us to the hitherto impenetrable veil of mystery which is met when any attempt is made to explain the facts of experience by our theories of cerebral physiology or of experimental and physiological psychology. But the last assumption seems somewhat to lengthen the distance to the veil. The picture of the unity in variety of the histological elements, and collections of elements, and of the physiological functions, which belong to the nervous system, offered by such experiences as that of this patient, assists in confirming the views arrived at experimentally by Professor Sherrington and other explorers in this field. But the unity and the variety of this infinitely complex system are not so much matters of wholly predetermined and, so to say, 'made-up' sort, dependent upon unchangeable histological peculiarities externally combined into a whole; they are, the rather, a growth, changeful, adaptable to varying conditions, dependent upon need and use, and conditioned' chiefly, if not wholly, upon the possibility of establishing the necessary connections amongst the differently located elements.
Many of the more important and interesting problems of psychology are suggested by this case of anastomosis. No other group of muscles is so expressive, so responsive to ideas and emotions, as those which are controlled normally by the facial nerve. To read the face is to read the soul, so far as the latter can express itself, or repress its expression, in any physical way. The whole history of this case reverses the normal history of the original development. Instead of the power of control being more and more acquired by experience of muscular and tactual sensations, and of the results produced by the external or emotional stimulation of these sensations, we have the increasing effect of the deliberate and persistent voluntary attempt to regain control, with its advancing degrees of success and increased differentiation; and last of all, and most imperfectly, the resumption of non-volitional motor functions under the stimulation of sensation and emotion. All this certainly looks like the picture of a mind learning how to use a tool, the construction of which has been suddenly so changed as to render it, for the time being, substantially a different tool. This, so far as the cerebral functions are concerned. The transmission of the motor impulses, when once started from the cortical centers, by new and unaccustomed tracts, is an affair of comparatively little significance either to physiology or to psychology.
In this psycho-physical progress, which I will call the evolution of a more highly differentiated self-control, all the various familiar forms of functioning, and laws of functioning, when seen from the psychological point of view, are apparent. The ease and ability increase with practise; the motor results are in a measure cumulative; the different forms of sensation-experiences inhibit or supplement and assist each other; and the effects of fatigue make themselves manifest. Such an evolution does not, however, seem explicable as nothing more than an increasing complexity, ease and precision of sensory-motor reflexes; although it has all the marks of dependence upon such a mechanical basis. To speak figuratively, what takes place in such cases of nerve anastomosis can not be completely and satisfactorily explained in terms that are applicable to a nervous mechanism, however complex, or complexly and mysteriously subject to improvements of a mechanical sort. An agency, that must be described in terms of ideation, apperception of an end to be attained, and purposeful volition consciously directed toward that end, seems also necessary to account for the whole result. If involuntary emotion and externally originated sensory-stimuli were ihe means of evoking and educating the motor organism, in the first instance; it is, on the other hand, conscious and purposeful voluntary effort which is the most important factor in the recovery of function and new education of the motor organism. And how astonishingly complex and even antecedently improbable, we might almost say, are the resulting histological and functional changes in the organism brought about by repeated volitions, our conjectural analysis of this case has suggested, if it has not made clear.
I am well aware that I shall be charged by some, both physiologists and psychologists, of harping again upon the same old string. But I confess that I am more and more indifferent to this charge. For I am more and more convinced that neither the idealistic nor the psychoparallelistic theories of the relations of the nervous mechanism to the life of consciousness explain such a case of recovery from paralysis as this to which your attention has just been called. Indeed, both forms of theory seem to me to introduce a confusion, which increases rather than clears up, the fundamental mystery of the facts. To my thinking, nothing which can possibly be said as to why the mind has a body goes any way at all toward explaining how this patient got control of his paralyzed facial muscles, for purposes expressive of his emotions and his volitions, through the N. accessorius and its cortical center, after the direct connection by the N. facialis with its center had been totally destroyed. Nor does any explanation which could conceivably express itself in terms of psycho-physical parallelism seem much more satisfactory.
In a word, this suggestive case of anastomosis, and all similar cases, together with hundreds of other species of phenomena—some of them belonging to our ordinary experience and some of them due to extraordinary situations and developments—all seem to me to point unmistakably to the existence of dynamical relations between the nervous mechanism and the conscious mental life. And is not our science, whether we start from the physiological or from the psychological point of view, nothing but a description of this net-work of dynamical interrelations? But in being this, how is it any less scientific or any more essentially mysterious than is any other science? To all science, indeed, of every species, it is just these dynamical interrelations which are the ultimate facts. Behind them it is impossible for science to go. Every science consists in the discovery, classification and formulating under so-called 'laws' of these interrelations. To say a priori that that can not be, or is not, which most obviously is—this is to be essentially unscientific.