Chapter 5: Aphasia, Apraxia, & Agnosia

APHASIA

General Considerations

Approximately 90% of people are right-handed, and approximately 95% of them process language in the left cerebral hemisphere (ie, have left-cerebral dominance). Of the 10% of people who are left-handed, approximately 60% have left-cerebral dominance for language. Aphasia occurs with structural lesions of the language-dominant hemisphere that involve regions critical for language processing—especially the frontal, parietal, and temporal areas of the operculum (cerebral areas surrounding the sylvian fissure). Such lesions can be small but critically located (eg, cerebral contusion or infarction), or they can be part of more widespread damage (eg, Alzheimer disease).

Aphasia affects more than speech. A disturbance of language in its broadest sense, aphasia is not explained by articulatory impairment (dysarthria) or sensory loss.

Clinical Features

A. Symptoms and Signs

Language assessment involves six components: verbal expression, speech comprehension, naming, repetition, writing, and reading.

1. Verbal expression

Verbal expression refers to the speech a patient generates spontaneously, for example, full sentence responses to questions. A variety of abnormalities might be detected in an aphasic’s spontaneous speech (Table 5–1). There may be a reduction in fluency, the amount of speech produced over time. Word-finding difficulty can produce hesitations in otherwise fluent speech; by contrast, the speech of Broca aphasia (discussed later) is labored and hesitant throughout, independent of word-finding per se. Reduced prosody refers to impairment of the musical qualities of speech—rhythm, accent, and pitch. Paraphasias are word errors, either real but unintended words (semantic paraphasias, eg, “hotel” for “hospital”) or substituted syllables within words (phonemic paraphasias, eg, “hosicle” for “hospital”). Paraphasias may be occasional contaminants of speech or they may nearly replace it, rendering it incomprehensible (jargon).

Even in the absence of paraphasias, the content of aphasic speech may be difficult to grasp, with fluent prosodic sentences and seemingly intact grammar (paragrammatism) but limited or empty content. By contrast, the nonfluent, nonprosodic speech of Broca aphasia may consist only of nouns and verbs, with loss of grammatical words (ie, telegraphic speech, agrammatism). Some aphasic patients tend to repeat a single phrase or word over and over (recurrent utterance).

2. Speech comprehension

Assessment of speech comprehension must take into account abnormalities of verbal expression or other cognitive disturbance.

For example, an incorrect answer to a question could ...