Aphasia

Aphasia

Aphasia, or dysphasia, is an acquired loss or impairment of language (as opposed to speech) function. Language may be defined as the complex system of symbols used for communication (including reading and writing), encompassing various linguistic components (viz. phonology, semantic/lexical, syntax), all of which are dependent on dominant hemisphere integrity. Nonlinguistic components of language (emotion, inflection, cadence), collectively known as prosody, may require contributions from both hemispheres. Language is distinguished from speech (oral communication), disorders of which are termed dysarthria or anarthria. Dysarthria and aphasia may coexist but are usually separable.

Clinical assessment of aphasia requires analysis of the following features, through listening to the patient’s spontaneous speech, asking questions or giving commands, and asking the patient to repeat, name, read, and write:

• Fluency: is output effortful, labored, with agrammatism and dysprosody (nonfluent); or flowing, with paraphasias and neologisms (fluent)?
• Comprehension: spared or impaired?
• Repetition: preserved or impaired?
• Naming: preserved or impaired?
• Reading: evidence of alexia?
• Writing: evidence of agraphia?

These features allow definition of various types of aphasia (see Table and specific entries). For example, motor ("expressive") aphasias are characterized by nonfluent verbal output, with intact or largely unimpaired comprehension, whereas sensory ("receptive") aphasias demonstrate fluent verbal output, often with paraphasias, sometimes jargon, with impaired comprehension. Conduction aphasia is marked by relatively normal spontaneous speech (perhaps with some paraphasic errors) but a profound deficit of repetition. In transcortical motor aphasia spontaneous output is impaired but repetition is intact.

Aphasias most commonly follow a cerebrovascular event: the specific type of aphasia may change with time following the event, and discrepancies may be observed between classically defined clinicoanatomical syndromes and the findings of everyday practice. Aphasia may also occur with space-occupying lesions and in neurodegenerative disorders, often with other cognitive impairments (e.g., Alzheimer’s disease) but sometimes in isolation (primary progressive aphasia, semantic dementia).

Summary of findings in aphasia syndromes

	Broca	Wernicke	Conduction	Transcortical: Motor/Sensory
Fluency	↓↓	N	N	↓/N
Comprehension	N	↓↓	N	N/↓
Repetition	↓	↓	↓↓	N/N
Naming	↓	↓	↓	N?/N?
Reading	↓	↓	↓	N?/N?
Writing	↓	↓	↓	N?/N?

References
Basso A. Aphasia and its therapy. Oxford: OUP, 2003
Benson DF, Ardila A. Aphasia: a clinical perspective. New York: OUP, 1996
Caplan D. Aphasic syndromes. In: Heilman KM, Valenstein E (eds.). Clinical neuropsychology (4th edition). Oxford: OUP, 2003: 14-34 Damasio AR. Aphasia. New England Journal of Medicine 1992; 326: 531-539
Saver JL. Approach to the patient with aphasia. In: Biller J (ed.). Practical neurology (2nd edition). Philadelphia: Lippincott Williams & Wilkins, 2002: 27-39
Spreen O, Risser AH. Assessment of aphasia. Oxford: OUP, 2003 Willmes K, Poeck K. To what extent can aphasic syndromes be localized? Brain 1993; 116: 1527-1540

 

Cross References

Agrammatism; Agraphia; Alexia; Anomia; Aprosodia, Aprosody; Broca’s aphasia; Circumlocution; Conduction aphasia; Conduit D’approche; Crossed aphasia; Dysarthria; Jargon aphasia; Neologism; Optic aphasia; Paraphasia; Transcortical aphasias; Wernicke’s aphasia