Anomic aphasia has been associated with lesions in different parts of the language area, typically in the left temporal lobe. In these cases, the lesion has been deep to the posterior temporal lobe, particularly in the left thalamus, or in the middle temporal convolution, in a location to interrupt connections between sensory language areas and the hippocampal regions concerned with learning and memory. Mass lesions, such as a tumor, herpes encephalitis, or an abscess, are the most frequent causes; as these lesions enlarge, a contralateral upper quadrantic visual field defect or a Wernicke aphasia is added. Occasionally, anomia appears with lesions caused by occlusion of the temporal branches of the posterior cerebral artery, and it is in these instances that we have seen the most pronounced cases of anomia, usually associated with a right hemianopia and alexia but normal writing ability. Anomia may be a prominent manifestation of transcortical motor aphasia (see later) and may be associated with the Gerstmann syndrome, in which case the lesions are found in the frontal lobe and angular gyrus, respectively.
An anomic type of aphasia is often an early sign of Alzheimer and Pick disease (minor degrees of it are common in old age) and is a principal feature of one type of degenerative lobar cerebral atrophy in the category of the primary progressive aphasias (see Chap. 39). Finally, anomic aphasia may be the only residual abnormality after partial recovery from Wernicke, conduction, transcortical sensory, or (rarely) Broca aphasia (Benson).
This rare and somewhat amusing condition defies classification but is worthy of comment because it may be mistaken for hysteria or psychosis. An accent that is distinctly foreign but vague in actual region of origin replaces the patient’s native speech pattern. The syndrome arises after a left-sided lesion, most often a stroke with a mild associated Broca aphasia. Although the accent may be interpreted by the listener as compatible with German, Spanish, French, Asian, or another nationality, authoritative analysis indicates that the alterations are not specific to any genuine language and are simply attributed by the listener to a known foreign accent. The syndrome is also encountered as a transient phenomenon during recovery from stroke. The relation to disorders of prosody, which is produced by lesions of the nondominant hemisphere, is unclear. LeCours and Lhermitte made an analysis of the disorder based on the obligate use of diphthongs in certain languages; these were not properly pronounced in the foreign accent syndrome and made French listeners detect an English accent. An extensive examination of one case and references to additional ones can be found in the article by Kurowski and colleagues.
Writing is, of course, an integral part of language function, but a less essential and universal component, for a segment of the world’s population speaks but does not read or write. It might be supposed that all the rules of language derived from the study of aphasia would be applicable to agraphia. In large part, this is true. One must be able to formulate ideas in words and phrases in order to have something to write as well as to say; hence, disorders of writing, like disorders of speaking, reflect all the basic defects of language. But there is an obvious difference between these two expressive modes. In speech, only one final motor pathway coordinating the movements of lips, tongue, larynx, and respiratory muscles is available, whereas if the right hand is paralyzed, one can still write with the left one, or with a foot, and even with the mouth by holding a pencil between the teeth (a contrivance used by individuals whose arms are paralyzed by cervical root avulsion from motorcycle accidents). An accurate general statement is that written language is disordered similarly to spoken language in the Broca and Wernicke aphasias and in most of their derivatives. When comprehension is impaired, writing to dictation is often impossible. Paraphasias appear in the writings of aphasics much the same as they do in speech.