When conversation discloses virtually no abnormalities, other tests may still be revealing. The most important of these are reading, writing, repetition, and naming. Reading aloud single letters, words, and text may disclose the dissociative syndrome of pure word blindness. Except for this syndrome and isolated mutism (aphemia; see earlier), writing is disturbed in all forms of aphasia. Literal and verbal paraphasic errors may appear in milder cases of Wernicke aphasia as the patient reads aloud from a text or from words in the examiner’s handwriting. Similar errors appear even more frequently when the patient is asked to explain the text, read aloud, or give an explanation in writing.
Testing the patient’s ability to repeat spoken language is a simple and important maneuver in the evaluation of aphasic disorders. As with other tests of aphasia, it may be necessary to increase the complexity of the test from digits and simple words to complex words, phrases, and sentences to disclose the full disability. Defective repetition occurs in all the major forms of aphasia (Broca, Wernicke, and global) because of lesions in the perisylvian language areas. The patient may be unable to repeat what is said to him, despite relatively adequate comprehension—the hallmark of conduction aphasia. Contrariwise, normal repetition in an aphasic patient (transcortical aphasia) indicates that the perisylvian area is largely intact. In fact, the tendency to repeat may be excessive (echolalia). Preserved repetition is also characteristic of anomic aphasia and occurs occasionally with subcortical lesions. Disorders confined to naming, other language functions (reading, writing, spelling) being adequate, are diagnostic of amnesic, or anomic, aphasia and referable usually to lower temporal lobe lesions.
These deficits can be quantified by the use of any one of several examination procedures. Those of Goodglass and Kaplan (Boston Diagnostic Aphasia Examination [BDAE]) and of Kertesz (Western Aphasia Battery [WAB]) are the most widely used in the United States. The use of these procedures will enable one to predict the type and localization of the lesion in approximately two-thirds of the patients, which is not much better than detailed bedside examination. Using these tests, aphasia of the Broca, Wernicke, conduction, global, and anomic types accounted for 392 of 444 unselected cases studied by Benson.
In analyzing disorders of speech and language in the clinic or at the bedside, the first objective is to separate dysarthria, or slurred speech with preservation of language, from a genuine impairment in language function, aphasia. Here, we offer a practical approach to aphasia. Dysarthria is addressed in a later section. To recapitulate, the features of a language disorder that are used to advantage by the examiner in determining the type of aphasia are • Natural sounding fluency, including normal cadence, the use of prepositions, and correct grammar • Comprehension of language • The proper selection, use, and relationships between words • Naming of displayed objects • The ability to repeat in comparison to spontaneous speech