DISORDERS OF SPEECH.
BY EDWARD P. DAVIS, A.M., M.D.
Development of Speech.
The study of speech, a complex function, enlisting at once the activities of mind and body, invites the physician to enter alike the domains of the psychologist and physiologist.
Distinguishing man from beast, articulate expression has its foundation in purely mental phenomena; its successful accomplishment requires the reflex mechanism common to man and beast.
Let us consider as concisely as possible the physiology of speech.
DEVELOPMENT OF SPEECH IN THE INDIVIDUAL.—The earliest observation has noted in the common name of the new-born child its speechless condition; it is the infant, or not-speaking being. Born with a nervous system in a highly unstable condition, the babe is a most favorable recipient of the many impressions which stream upon it from all sides. With sight and hearing undeveloped, the field of early infantile impressions is limited to hunger, need of sleep, and cutaneous impressions. Speech under such conditions is inarticulate, an animal cry, unconscious and without intelligence. But with the growth of the cerebrum the child's environment suggests to the embryonic intelligence its primal impression. The parental relation is dimly apprehended, and designations of the father and mother are uttered in scarcely articulate sounds.
Sight and hearing open extensive fields of sensation, and with their development begin the primal, physical impressions from which proceed the emotions. The acoustic and optic centres of perception become established, and the mental formation of symbols and signs, an imitative process, marks the stage of childish cerebration, beyond which the savage often does not proceed. The symbolic function is the basis of language and of pictorial representation; as man requires the trade medium of the symbol for the interchange of his ideas, so his legal tender appears with the first emergence of mental enterprise. The hieroglyphic and the onomatopoetic word are as old as humanity.
The co-ordinating mechanism of speech is of equal development. With the growth of the child the varied impressions of education, of surroundings, of heredity, all are influencing speech. With mental growth, stimulated by these numerous impressions, comes the gradual mental habit of forming ideas after certain models—of trading, so to speak, in the coin of the country, of making and using a vocabulary. Intuition, induction, and deduction are established, the general nervous function of memory develops, observations are made, and mind and body, master and instrument, enter upon full activity.
PHYSIOLOGY OF NORMAL SPEECH IN THE ADULT.—Let us consider normal speech in the adult. From a purely mental aspect speech is not included in the nervous reflexes. The conception before the individual may arise without sight or sound, it may be the object of the mental processes only; but if it is to be communicated, or transferred from the subjective to the objective, it calls into play the denotative faculty or facultas signatrix.
As we are cognizant through the senses of phenomena only, so we communicate only phenomena, or more particularly symbols; the spoken or written word, the gesture, are necessary to make ideas tangible to another mind. The symbolic faculty, then, is the mental faculty most concerned in speech.
Cerebral localization has not included this faculty in its areas; it is assigned to the anterior cortex, which as yet is the indiscriminate site of the formation of ideas. The idea conceived, the symbol formed, the motor area whose integrity is essential, is found in the region commonly known as Broca's convolution, the posterior third of the left third frontal convolution. This region is especially connected with the corona radiata coming from the corpus striatum, with the corpus striatum and the anterior portion of the internal capsule: like the anterior, or motor, cornua of the spinal cord, it possesses giant, or branching, nerve-cells; its anatomy would assign to it a motor function. Its blood-supply is derived through the inferior frontal branch of the Sylvian vessel, whose occlusion in a case cited by Charcot was followed by complete aphasia.
Ferrier distinguishes just adjacent to this centre the motor centres for the tongue and mouth and upper extremities, showing an anatomical association of the processes of articulate and written speech.
But purely motor impulses comprise only a portion of the phenomena of speech. The external world must be brought into relation with the mind, and this is done through the perceptions. We may say that perceptions are apprehended sensations, and this apprehension demands a localized field of cerebral activity, as well as the motor energies. It seems natural enough that experiment should have located (Ferrier) perceptive, visual, and acoustic centres in the posterior cortical areas and temporo-sphenoidal lobes—that the motor and perceptive areas should be contiguous and sharing a common blood-supply.
The perceptive visual centre is found to occupy the occipital lobes, while the acoustic centre occupies the whole length of the first temporo-sphenoidal convolution.
As motor impulses found a path to the motor ganglia, and finally to the cord, so the course of sensory perceptive impressions can be traced back through the posterior internal capsule and through the optic thalami to the sensory columns of the medulla and cord.
Intuitive and sense perception, even when reinforced with motor power, cannot result in articulation. The mechanism of speech requires a co-ordinating centre, and this basal phonic centre of Kussmaul is located in the medulla near the origin of the hypoglossal and facial nerves. From the medulla proceed the nerves supplying the machinery of phonation, the superior laryngeal nerve to the mucous membrane of the larynx and to the crico-thyroid muscle, the most important muscle of phonation. The remaining laryngeal muscles are supplied by the recurrent laryngeal; the motor processes of articulation are guided by the hypoglossal, facial, and fibres of the glosso-pharyngeal.
The larynx is a reed, with the addition of numerous resonance-cavities producing abundant overtones. It may be considered as a box composed of two segments, the lower of which has vertical motion upon the joint at the posterior junction of the superior and inferior segments. By this motion the tongue of the reed (vocal cords, stretching antero-posteriorly from lower segment to junction with upper segment) is tightened or relaxed, the vibratory blast of air coming through the trachea from the lungs. The superior aperture of the tube is guarded by the epiglottis and false vocal cords. As auxiliaries are the pharyngeal, oral, and nasal cavities, with the associated bony cavities of the skull, the soft palate acting as a movable partition or switch, the hard palate as a sounding-board or resonance-surface. The reed is applicable to the production of musical sounds; the tongue, lips, and teeth are required for the checks in those sounds, constituting the consonants or division utterances.
The curious phenomenon of the falsetto voice is thought by Helmholtz to be produced by the attenuation of the true cords and the vibration of their thinned edges.
DEVELOPMENT OF LANGUAGE.—The study of language demonstrates its origin to have been largely in exclamations and imitative sounds, from which our vowels can easily have arisen. The growth of all synthetic language illustrates the aggregation of accessory sounds about the primitive root-sound, while the common tendency to the insertion of consonants shows their addition to the primitive vowels. That the long vowels should have undergone countless modifications from the physical peculiarities and environment of those speaking them is but natural, for the number of vowels remaining in actual use in any language is not large. Consonants serve to make more clear by their separation of vowel-sounds the meaning to be conveyed; their development resulted from vowel changes, and their number is small.
The written characters of language represent only the usage of the majority. Individual speech and pronunciation vary as greatly as do languages themselves, and it is evident that the speech of any individual is as truly peculiar as his physical conformation.
To recapitulate, we find ideas, the material of speech, formed in the cerebral cortex. Speech-volition becomes motor impulse at Broca's convolution; such impulse passes along the internal capsule to the corpus striatum, where it is co-ordinated probably in the formation of syllables, thence to the medulla, whence the mechanism of the larynx receives its co-ordinated stimulation.
Disorders of Speech.
The classification of the disorders of speech should depend on the anatomical site of the lesions by which they are occasioned. Broadly speaking, speech disorders resolve themselves into those of the formative apparatus for ideas and symbols and those of the purely co-ordinating and conducting mechanism. Abbreviating the schedule of Potter, we may say that the disorders of speech may be included in three classes—alalia, or lack of speech; paralalia, defective speech, the stammering of most observers; and dyslalia, difficult speech or stuttering.
The anatomy of the blood-supply of the speech-centres affords some explanation of alalia. The Sylvian artery will be remembered as the feeder of the speech-centres—an artery often the source of hemorrhage, as Charcot suggests, from the angle at which it leaves the carotid. Ducrot explains the frequency of left-sided softening and hemorrhage from the manner of origin of the left carotid, its axis being more nearly that of the ascending aorta and furnishing a ready channel for cardiac clots. In regard to the relative frequency of peripheral and central hemorrhage, Andral and Durand-Fardel cite 119 cases, of which but 17 were in the anterior or posterior lobes. It is admitted that cerebral lesions are largely those of the circulatory system, and the fact that such lesions result in the suspension of the activity of restricted areas is due to the circumstance that the cerebral arteries are terminal vessels giving off no anastomosing branches and supplying restricted areas only. With blood-supply so arranged it is not difficult to understand how the different portions of the motor centres may be separately involved, and thus the motor functions of speech may become singly at fault.
Inability to remember words and inability to form the motor impulses necessary for speech or writing are the common forms of alalia or aphasia, the former being known as amnesic, the latter as ataxic, alalia. In addition, we may cite the failure of cerebral power occurring in general softening, in microcephalic brains, and the curious instances of voluntary silence from some strong belief or prejudice. Instances of the gradual resumption of cerebral function after its loss are not wanting; and, occurring where subsequent post-mortem examinations reveal a limited area of destruction of brain-tissue, they afford examples of the vicarious performance of cerebral functions by contiguous areas.
The phenomena of amnesic alalia are commonly seen in cases of recovery from cerebral hemorrhage, cerebral injury, and severe febrile affections. Numerous cases are recorded where the memory of things themselves remained, but the faculty of denoting them had been destroyed.
Kussmaul distinguishes here two conditions: 1st, where the word is entirely effaced from memory, 2d, where it still remains, but its association with that which it represents is suppressed. Cases of the second class are the most frequent, the fundamental part which the association of ideas plays in mental activity and the extent to which memory is dependent on association explaining this fact. A marked example of the failure of the denotative faculty lies in the cases of forgetfulness of one's own name, as described by Crichton in the case of an ambassador at the Russian court, who was obliged to say to his companion, when visitors asked his name, “For Heaven's sake, tell me what I call myself!” Piorry mentions the case of an aged priest who after right-sided paralysis lost entirely the use of substantives; wishing to ask for his hat, the word hat failed him utterly, and he was obliged to express himself in the remaining parts of speech: “Give me that which I place upon the ——;” but the word head, denoting the object most commonly in relation with the hat, was wanting also. When either hat or head was mentioned he spoke the word without difficulty.
Instances of failure in linguistic faculty are not uncommon. Witness a case, reported by Proust, of an Italian who after long residence in France, though understanding his native tongue, could speak only in French. Cases in which after acute disease one language is gone entirely while several others are retained are not wanting. A striking case of amnesic alalia was that of Lordat, a French physician, who thus described his malady: “I find myself deprived of the value of all words. If any words remain to me, they become useless, because I can no longer remember the manner in which I must co-ordinate them to express my thoughts. I am conscious that I recognize all ideas, but my memory does not suggest a word. In losing the memory of the meaning of spoken words I have lost that of their visible signs.”
Fortunately, these cases are among the more tractable of cerebral disorders. Bristowe has reported a case wherein elementary instruction in speech-formation was tried with marked success. The patient, aged thirty-six, after a violent cerebral disturbance without traumatism became paraplegic, speechless, and deaf. Gradual recovery ensued until, seven months after his first illness, he was admitted into St. Thomas's Hospital in the following condition: Numbness and paresis in left leg, less in left arm; special senses healthy; no incontinence; some pain about head and neck; complete loss of speech. It was found that the patient was very intelligent, wrote legibly, could make all kinds of voluntary movements with lips, tongue, and teeth, and was capable of vocal intonation; articulation alone was lacking.
The law of the evolution of language designates as primitive forms of word-signs those words affirming qualities, while those denoting relative positions are of secondary formation (Whitney.) Remembering, also, the fact that amnesia in general “is a regression from the new to the old, from the complex to the simple, from the voluntary to the automatic, from the least organized to the best organized,”1 we are able to understand the cause of amnesic alalia, and also the steps of the process of recovery, in which the inverse order is observed.
1 Ribot, Diseases of Memory.
Amnesic alalia can hardly be regarded as susceptible of treatment other than as a general neurasthenia. Though we may develop memory by cultivating the association of ideas and by repetition, yet, regarding it as a general function of the nervous system, it is evident that recovery from its disorders is conditioned by the general vigor of the nervous centres. A partial recovery usually occurs in such cases; complete recovery is more infrequent.
Ataxic alalia, the failure of the motor powers of speech, occurs in all forms of general paralysis, most typically in bulbar paralysis. This disease is fully described in the standard works on neurology. Ataxic alalia will also occur in disseminated sclerosis, posterior spinal sclerosis, dementia paralytica, and cretinism. It forms in general disorders an instructive symptom, and is to be distinguished by a tremulous utterance and by facial spasm from the hesitation of the stammerer and from the convulsive utterance of the stutterer.
Paralalia embraces all abnormalities of speech, from trivial mannerisms to difficulties in the utterance of certain letters, including those painful defects which depend upon physical malformations.
The free discussion of paralalia would cover the domain of elocution; the physician is called upon to advise in those cases only where either a physical malformation is evident or the difficulty experienced by the patient in enunciating certain letters has led to a suspicion of the existence of malformation. The former cases lie in the province of the surgeon; the latter come within the scope of those elocutionists, speech-trainers, and instructors who hope to cure stammering and stuttering.
Discrimination between stammering and stuttering will give the physician a basis for judgment from which he can reasonably offer encouragement in many cases and avoid the creation of false hopes in others. As a cardinal point of difference, it will be remarked that in the case of the stutterer the muscles of phonation are thrown into a state of spasm when speech is attempted, while in the stammerer their movements are merely lacking in proper co-ordination. It may also be observed that the respiration of the stammerer is marked by irregular contractions of the diaphragm, which render the expiratory blast of air irregular in its delivery. In the stutterer the spasm is pronouncedly laryngeal and facial. The nervous embarrassment of the stutterer is proverbial, and is increased by excitement, while a moderate degree of excitement, stimulating respiration, greatly improves the speech of the stammerer.
Whispering, a difficult respiratory act, exaggerates the stammerer's fault, but the spasm of the stutterer is often relaxed by the diminished pressure of whispered breath.
As articulation is effected by the larynx and the oral organs, the stutterer makes his spasmodic articulation particularly noticeable, while the stammerer finds little difficulty in the utterance of words. R, L, S, and other letters whose enunciation demands the continued expiratory blast, are imperfectly uttered by the stammerer, while these letters when joined to a long vowel-sound occasion little or no difficulty for the stutterer.
TREATMENT.—It follows that if stammering is recognized as inco-ordinate enunciation, owing largely to irregular action of the diaphragm, any training of the respiratory muscles which will ensure a regular delivery of the expiratory air will improve this defect. It follows, then, that the treatment of stammering resolves itself into careful attention to general hygiene, associated with such persistent respiratory and vocal gymnastics as shall effectually develop regularity, depth, and co-ordination of action on the part of all the muscles concerned in the act of respiration. Drugs will be of service only as aids to the correction of errors in the essential physiological functions. In the child the powers of imitation may be enlisted to effect a cure, and the familiar fact that the habits of childhood are easily formed would indicate this as the best time for treatment.
Childhood once passed, however, the steadiness of purpose of the adult is requisite to break up a confirmed habit, and active treatment should be deferred until after adolescence. Most important in all cases are judicious moral influences exerted by those about the patient, the ridicule so often visited upon the unfortunate stammerer being most harmful in its consequences. The many tricks and devices so often employed in these cases are of use simply by varying the monotony of vocal drill; they may be employed or abandoned as the judgment of the physician may dictate.
Regarding the prognosis in these cases, it follows that with a fairly developed and healthful nervous system, reinforced by proper mental and physical hygiene, the stammerer's case is far from hopeless in the hands of a patient and intelligent physician.
An unfavorable prognosis would be demanded by hereditary defects and vices of the nervous system, by the lack of general nervous vitality, by enfeeblement of the will and the mental tone of the individual, by advanced age, and by irremediable hygienic conditions. Under favorable conditions recovery should be the rule.
DYSLALIA OR STUTTERING.—Recalling to mind the points of difference between stuttering and stammering, it becomes evident that while the prospect of success in the treatment of the stammerer is often favorable, the case of the stutterer presents such difficulties as render it too frequently hopeless.
We may liken the confirmed stutterer to those rare cases of chorea which defy treatment, and to those cases of hereditary deterioration of the nervous system where the most patient and painstaking care fails to overcome the defect. The laryngeal and facial spasms depend upon no malformation for their exciting cause; hence surgery fails to remedy the defect. Drugs which are given with hope of invigorating the nervous system have only a general tonic influence, while the motor depressants and antispasmodics find but partial success. We must again rely upon hygiene, and also upon those aids to enunciation which come from rhythmical associated movements, such as stamping with the foot, beating time with the hand, the employment of a sing-song tone, or other modes of specially rhythmic enunciation. The sing-song mode of utterance is a familiar resource with parents in attempting to aid a stuttering child, and the measured forms of articulation offer the only vocal drill that possesses any permanent value. It is especially essential in the stutterer's case that the patient be protected from ridicule and from all disturbing emotions: the burden of difficult speech is sufficient to greatly depress the nervous system without the added suffering of emotional distress. It is evident that childhood, characterized as it is by especial instability of the nervous system, is the period when we can hope for the best results from care and training; the long-formed habits of the adult are rarely broken.
We have thus traced the disorders of speech to their origin as symptoms of grave central lesions of the nervous system, as results of heredity or of a general neurasthenic condition; very rarely are they dependent upon malformations of the organs of speech.
The treatment of such malformations, when they occur, is largely unsatisfactory and is seldom curative.
The thorough treatment of those speech disorders that are not susceptible of surgical aid would embrace such mental and physical hygiene and training as should ensure the formation of a thoroughly conceived vocabulary and its co-ordinated expression by words either spoken or written. The study of expression in its highest forms would necessarily conduct the investigator far into the realm of the plastic, harmonic, and literary arts.