aphasia

a speech disturbance consisting in the loss of the ability to use words and phrases as the means of expressing thought; it is caused by lesions in certain zones of the cerebral cortex. Expressive speech (that is, the utterance of words and phrases) may also be impaired as a result of an affection of the executive speech apparatus (tongue, lips, vocal cords). However, such impairments are not included in the concept of aphasia, since in aphasia the patient is able to utter all sounds, but is incapable of speaking. The impairment of impressive speech (that is, understanding speech that is heard) in aphasia differs from that in deafness, since all sounds are perceived, but words sound like unknown signals. Aphasia occurs when there is an affection of the cortex of the left cerebral hemisphere in right-handed persons; and of the right hemisphere in left-handed ones. Motor, sensory, amnesic, conduction, and total aphasias are differentiated.

Motor aphasia is principally caused by an affection of the posterior portions of the inferior frontal gyrus and is manifested by the impairment of expressive speech (speech is either completely impossible or difficult); the grammatical structure of speech is disrupted; the patient transposes or substitutes letters in words. Voluntary speech (narration, conversational speech) suffers more than repetition or automatic speech. This form of aphasia is combined with the impairment of writing—agraphia.

Sensory aphasia occurs when focuses of disease are present in the surface zones of the temporal lobe of the brain. It is manifested by the impairment of impressive speech to the point of complete incomprehension and also the impairment of expressive speech as a result of the absence of auditory control over the words uttered. When paraphasic errors occur, one word is replaced by another that is similar in sound but different in meaning. In severe cases speech becomes completely unintelligible. This form is often combined with the impairment of reading (alexia).

Amnesic aphasia consists in forgetting the names of objects and attempting to substitute descriptions of the objects for their names. It is often combined with sensory aphasia.

The other forms of aphasia, total and conduction, are more rarely observed. Total aphasia is manifested by the impairment of expressive, as well as impressive, speech. Conduction aphasia occurs when there are large focuses of disease in the white matter of the hemispheres of the cerebral cortex. Aphasias have been described that are caused by disease not only of the cortical but also of the deeper formations, which testifies to the complex architecture of the functional system that provides for speech.

Causes of aphasia are vascular diseases of the brain, en-cephalitides, traumas, and brain tumors. Treatment is directed at the illness causing the aphasia. Speech processes impaired in aphasia may be restored as a result of prolonged training based on the fact that the performance of acts of speech, writing, and reading can be reconstructed and that these acts include the processes of visual and kinesthetic analysis which are supported by the remaining sections of the cortex.

When aphasia occurs in childhood, it disrupts the course of the child’s general development. When sensory aphasia appears between the ages of five and seven years, it most often leads to the gradual disappearance of speech. Restorative work in this form of aphasia is extremely complicated. The child usually does not achieve normal speech development. Other forms of aphasia in children have a more favorable prognosis. Children suffering from aphasia are trained together with alalia patients. Systematic drill in speech and writing are very important.