APHASIA, AS A SYMPTOM. 73 highest part of the arch, and its mouth is so directed as to arrest rather than avoid any floating particles in the blood current. In case of such movable particles being arrested either by the innominate or left carotid arteries, the most direct course in both instances will be toward the middle cerebral arteries, and thus aphasia will generally be produced with hemiplegia upon the side opposite to that where the embolus may be found. The following deductions relative to disorders of speech may aid in recognizing the seat of the lesion during the life of the sufferer: 1. The cortex of the posterior part of the third frontal convolution, and possibly also the island of Reil, presides over the coördination of the muscular acts necessary to speech. It also stores the memories of such acts, so that any combination of articulate sounds can be voluntarily reproduced when the proper form of excitation is furnished (chiefly in response to sight or sound impressions). This center is connected by "associating fibers" with the centers of hearing (first temporal convolution) and those of sight (the occipital convolutions). It is also put in communication with the nuclei of the facial, hypoglossal, the pneumogastric, and glosso-pharyngeal nerves (within medulla) by means of two distinct tracts of fibers, viz., the "hypoglossal cerebral tract" and the so-called "speech tract," which pass through the internal capsule, the crus, and the pons, in order to reach the medulla. Thus, this cortical center of coördinated speech-movements is capable of receiving excitation from the centers of hearing, when replies to spoken language are demanded; and from the centers of sight, when written or printed language calls for a verbal response. It is also put in direct communication with the nerves which preside over the apparatus of speech (whose nuclei of origin are situated within the medulla). 2. The form of amnesic aphasia known as "word-deafness" (Kussmaul) indicates the existence of a lesion of the first temporal convolution' of the left side, which has impaired the memories of spoken language. Hearing may not be impaired, although the appreciation of words, music, etc., may be totally absent. 3. The condition known as "word-blindness" (Kussmaul) indicates the existence of a lesion of the left occipital lobe, which has impaired the memories of written or printed symbols of language, numerals, familiar objects, etc. 4. The condition termed "paraphasia" by Kussmaul (in which the amnesic and ataxic varieties of aphasia seem to be peculiarly combined) may be excited by a lesion which interferes with the action of the associating tracts of fibers, between the areas of hearing or sight and the motor speech center of Broca (Wernicke). 5. The condition of imperfect speech termed "anarthria" is produced by a lesion of the medulla, which interferes with the functions of the nuclei of the cranial nerves associated with speech. It is occasionally observed in connection with focal lesions of the floor of the fourth ventricle. These cases are to be differentiated from aphasia of cortical origin by the coexistence of other symptoms produced by the medullary lesion. 6. In order to properly pronounce any word, it is essential that both the cortical center of speech, and also the nuclei of the medulla, which are associated with it, must be called into action. 7. The peculiar course which the fibers of the "speech tract" take within the cerebral hemisphere sheds light upon these reported cases of aphasia where the lesion was situated posterior to the center of Broca. These fibers run from the third frontal gyrus close to the surface of the hemisphere, and in an antero-posterior direction (passing in the external capsule), to reach the posterior part of the lenticular nucleus. They dip at this point into the posterior part of the internal 1 In right-handed subjects the left hemisphere, and in left-handed subjects the right hemisphere, seems to monopolize the function of sound-interpretation to the speech center. APHASIA, AS A SYMPTOM. 75 capsule. They then pass through the middle part of the crus and pons to the medulla (Wernicke). Within the internal capsule, the fibers of the "speech tract" lie (according to this observer) between the optic fibers and those of the sensory tract. 8. Should aphasia be developed as a result of a lesion of the internal capsule, hemianopsia or hemianæsthesia would be liable to coexist, on account of the relationship of the optic and sensory fibers of the capsule to the speech tract. 9. It is possible to have aphasic symptoms develop as a result of a lesion within the crus or pons. This is because the speech tract passes through them to reach the medulla. 10. The cortical centers of hearing, smell, and taste are probably associated (wholly or in part) with the corresponding organ of the opposite side. Hence, we may clinically refer an abolition of the function of hearing (when due to a cortical lesion) to the hemisphere opposed to the deaf ear. "Word-deafness" may ensue, however, when the centers of hearing of only one cerebral hemisphere are involved. In right-handed subjects, the left superior temporal convolution appears to govern this function; while, in left-handed subjects, the right superior temporal convolution assumes it. This is probably due to the fact that the hemisphere which is the most exercised becomes more rapidly developed. 11. When the third frontal convolution is alone diseased, the patient will be able to understand spoken or written questions perfectly, but will not be able to coördinate the movements of the speech apparatus requisite to a reply. 12. When the superior temporal convolution is alone diseased, the patient can not recognize or properly interpret spoken language. He may, however, be able to repeat single words when propounded, but not sentences. Exclamations of various kinds may be uttered by these subjects when irritated or distressed; but they are more or less involuntary, and often irrelevant. 13. When the associating fibers between the different centers functionally connected with speech are alone diseased, the patient can comprehend written or spoken language perfectly; but, in talking, such a subject is apt to interpolate, from time to time, some irrelevant and unexpected word in a sentence in place of the one desired. THE PRE-FRONTAL LOBES.-There are innumerable cases on record where the frontal lobes anterior to the motor centers have suffered frightful lacerations and loss of substance, and yet recovery has taken place; and where disease of an extensive character has also produced negative results, both as regards motion and sensation. This region is often called the "pre-frontal lobe." 5 A crowbar has been shot through the head, and recovery followed. Again, Bouillaud' reports the passage of a bullet through the frontal lobes with a like result, and with no effect upon sensation or motion. Cases somewhat similar are recorded by Trousseau,' Congreve Selwyn,' Pitres, Morgagni, Marot, Tavignot, and others, all of which go to prove the possibility of the most serious injury to this portion of the cerebrum without symptoms indicative of its presence. On the other hand, numerous cases of hæmorrhage and of abscess within the frontal lobes, as reported by Andral,' Hertz, Reed, Begbie, and others (quoted by Charcot and Ferrier), show the same absence of positive diagnostic symptoms either in sensory or motor paralysis. From such sources of clinical reasoning, as well as from the physiological deductions which experiments upon animals have taught, the following conclusion of Ferrier is of value to the reader: "With such evidence before us, we can not regard cases in which, with lesions of the præfrontal lobes, sensation or motion has been affected as other than cases of coexistence or of multiple lesions, whether organic or functional." 1 Bigelow, "Am. Jour. of Med. Sciences," July, 1850; Harlow, "Recovery from the Passage of an Iron Bar through the Head"; "Reports of Mass. Med. Soc.," Boston, 1869. 2 Op cit. 4 "London Lancet," February 28, 1838. 3 Quoted by Peter and Ferrier. 6 "Prog. Méd.," February 26 and June 3, 1876. MOTOR AREA OF CEREBRUM. 77 THE MOTOR REGIONS OF THE CEREBRUM.-It may now be positively stated that the bases of the three frontal convolutions, the convolutions which bound the fissure of Rolando, and the para-central lobule upon the internal surface of each hemisphere of the cerebrum, are distinctly motor in their function. The distribution of the middle cerebral artery to this region gives to that vessel an importance not before appreciated; since it is now known that the four or five branches which are given off from the main artery each nourish a separate area of brain substance, and that emboli may obstruct either the trunk or some of its individual branches. It is thus possible to explain how the basal ganglia may still perform their functions while other parts supplied by some of the cortical branches may be impaired. The preponderance of clinical testimony goes to show that most of the destructive lesions which are associated during life with paralysis of voluntary motion are confined to this motor area, although a rare case is on record' where the motor area was the seat of cystic disease, and still voluntary motion remained unaffected. It is a matter of great doubt whether the gray matter of the convolutions was impaired, even in this case, in spite of the existing lesion. The effect of very extensive lesions affecting the motor area of the monkey (which is commonly used for experiments, as the nearest approach to the type of mankind) may be summarized as follows: 1. A hemiplegia, which is at first absolute; 2. An improvement in associate, alternating, or bilateral movements, but no improvement in voluntary motion. Respecting this point, I quote from Ferrier's work as fol lows: "As examples of the improvement which follows the onset of the hemiplegia, the hand becomes more paralyzed than the arm, the arm more than the leg, and the lower facial movements more than the upper; while the muscles of the trunk are scarcely, if at all, affected."" 1 Samt, "Archiv für Psychiatrie," 1874. 9 Ferrier, "Localization of Cerebral Disease." |