Definition.—Aphasia is that condition due to cerebral lesions, whereby there is an inability to comprehend words properly and use them correctly, or a total suppression of the power of speech. It must not be confused with—
(1) Anarthria, a defect of articulation due to lesions of the medulla oblongata (bulbar paralysis).
(2) Mental aberrations independent of demonstrable lesions of the cerebral centers.
The language or speech centers are found in the third or inferior left frontal convolution (Broca's convolution), and when associated with hemiplegia—and it is in most cases—it is with a right hemiplegia.
There are various phases and degrees of aphasia, according to the extent of the lesion and the center involved; thus a patient may be able to, say only one or two words, as yes or no, and repeats these to every question, or he may not be able to speak a single word. Others have a larger vocabulary, but are unconscious of the fitness of words to express their ideas, while others recognize their unfitness after speaking.
"One may be unable (a) to hear words spoken; (b) to understand words spoken; (c) to see words written and printed; (d) to understand words written and printed; (e) to speak from memory; (f) to repeat words; (g) to read aloud, i. e., to speak from sight; (h) to write from memory; (i) to write from dictation, i. e., from words heard; (k) to write from a copy, i. e., from words seen."
"Speech not only depends upon perfect coordinating and motor processes, but also upon the senses of hearing- and sight. In aphasia therefore certain centers are involved, and are as follows: (i) The auditory speech center, in the upper-extremity of the left temporo-sphenoidal convolutions; (2) The visual-speech center, in the left angular gyrus and supramarginal gyrus; (3) The motor-speech center, in the posterior part of the third left frontal convolution, or Broca's convolution; (4) The motor-writing center, probably in the posterior part of the second left frontal convolution, related to the muscles of the hand; (5) Commissural fibers between these."
Lesions of the first four centers of the commissural fibers between them will cause some form of aphasia or agraphia.
Where the motor-speech center is destroyed there is motor aphasia, and where the visual-speech center is involved there is sensory aphasia, and an involvement of two or more centers gives rise to the various combinations of aphasia.
Etiology.—Since almost the entire cerebral centers for language are in the cortex or immediately beneath it, any organic or functional disease that interferes with this portion of the brain is a cause of aphasia.
The most common causes are embolism and thrombosis, with their consequent softening. Hemorrhage is also a not infrequent cause. Severe congestion, without hemorrhage or softening, may give rise to a more transient aphasia. Trauma, as fractures of the skull; meningitis by impairing the cortex; degenerative diseases, and toxemias form cerebral abscesses; or the severe infectious diseases, may also be responsible for aphasia.
Symptoms.—Motor Aphasia.—The inability to articulate, or even gesture, usually comes on suddenly, and at first may be complete, though a limited power is usually retained or early regained. The patient may be able to say only one or two syllables or words, and repeats them on all occasions regardless of their propriety. Sometimes it will be an exclamatory oath, used automatically. Sometimes the words will consist of some part of a sentence that he was about to utter just before the attack rendered him speechless.
His sensory centers being unimpaired, he can understand what is said to him and appreciate his own errors, but is unable to correct them.
His ability to write is also affected (agraphia), and he finds it impossible to write even the few words that he can articulate, though he may be able to sign his name. Along with this inability to articulate and write there is frequently lost the power of understanding printed or written words.
Sensory Aphasia.—In this form there is a disturbance of the auditory and visual speech centers; word-deafness in lesion of the auditory speech-center, and word-blindness in lesion of the visual speech-center.
In word-deafness, while the patient can hear ordinary sounds. he is unable to recognize and understand spoken words, and can not repeat words or write from dictation.
In word-blindness the patient can not see or understand words printed or written, can not read aloud, and can not write spontaneously from dictation or copy, as writing is simulated directly from the visual center, but he may be able to talk well.
Two other conditions may be associated with sensory aphasia: mind-deafness, or inability to recognize the meaning of any kind of sound; and mind-blindness, or inability to recognize the meaning or use of any kind of object.
Prognosis.—This depends largely upon the cause and extent of the lesion. Where it is functional, and due to congestion, inflammation, or toxemia, the aphasia is transient and disappears with a correction of the exciting cause.
If in children, although the speech centers be destroyed, patient and persistent instruction may result in the education of the speech centers in the opposite hemispheres. If due to tumors, bone-pressure, or abscess, relief may follow operative measures.
Treatment.—Save in functional aphasia, but little may be expected from medication.
When due to pressure from any source, the only promise of relief is at the hands of the surgeon. For special instruction in developing speech centers, one should consult those who make it their life-work.