Aphasia is language dysfunction that may involve impaired comprehension or expression of words or nonverbal equivalents of words. It results from dysfunction of the language centers in the cerebral cortex and basal ganglia or of the white matter pathways that connect them. Diagnosis is clinical, often including neuropsychologic testing, with brain imaging (CT, MRI) to identify cause. Prognosis depends on the cause and extent of damage and on patient age. There is no specific treatment, but speech therapy may promote recovery.
In right-handed people and about two thirds of left-handed people, language function resides in the left hemisphere. In the other third of left-handed people, much of language function resides in the right hemisphere. Cortical areas responsible for language function include
Damage to any part of this roughly triangular area (eg, by infarct, tumor, trauma, or degeneration) interferes with some aspect of language function. Prosody (quality of rhythm and emphasis that adds meaning to speech) is usually influenced by both hemispheres but is sometimes affected by dysfunction of the nondominant hemisphere alone.
Aphasia is distinct from developmental disorders of language and from dysfunction of the motor pathways and muscles that produce speech (dysarthria). It is broadly divided into receptive and expressive aphasia.
There are other types of aphasia (see see Types of Aphasia), which may overlap considerably. No aphasia classification system is ideal. Describing the types of deficits is often the most precise way to describe a particular aphasia.
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Symptoms and Signs
Wernicke aphasia: Patients speak normal words fluently, often including meaningless phonemes, but do not know their meaning or relationships. The result is a jumble of words or “word salad.” Patients are typically unaware that their speech is incomprehensible to others. A right visual field cut commonly accompanies Wernicke aphasia because the visual pathway is near the affected area.
Broca aphasia: Patients can comprehend and conceptualize relatively well, but their ability to form words is impaired. Usually, the impairment affects speech production and writing (agraphia, dysgraphia), greatly frustrating patients' attempts to communicate. Broca aphasia may include anomia (inability to name objects) and impaired prosody.
Verbal interaction can typically identify gross aphasias. However, the clinician should try to differentiate aphasias from communication problems that stem from severe dysarthria or from impaired hearing, vision (eg, when assessing reading), or motor writing ability.
Initially, Wernicke aphasia may be mistaken for delirium. However, Wernicke aphasia is a pure language disturbance without other features of delirium (eg, fluctuating level of consciousness, hallucinations, inattention).
Bedside testing to identify specific deficits should include assessment of the following:
Formal cognitive testing by a neuropsychologist or speech and language therapist may detect finer levels of dysfunction and assist in planning treatment and assessing potential for recovery. Various formal tests for diagnosing aphasia (eg, Boston Diagnostic Aphasia Examination, Western Aphasia Battery, Boston Naming Test, Token Test, Action Naming Test) are available.
Brain imaging (eg, CT, MRI; with or without angiographic protocols) is required to characterize the lesion (eg, infarct, hemorrhage, mass). Further tests are done to determine the etiology of the lesion (eg, stroke evaluation) as indicated (see Diagnosis and see Diagnosis ).
Recovery is influenced by cause, size and location of lesions; extent of language impairment; response to therapy; and, to a lesser degree, the age, education, and general health of the patient. Children < 8 yr often regain language function after severe damage to either hemisphere. After that age, most recovery occurs within the first 3 mo, but improvement continues to a variable degree up to a year.
Treatment of certain lesions can be very effective (eg, corticosteroids if a mass lesion causes vasogenic edema). The effectiveness of treating aphasia itself is unclear, but most clinicians think that treatment by qualified speech therapists helps and that patients treated soon after onset improve the most.
Patients who cannot recover basic language skills and caregivers of such patients are sometimes able to convey messages with augmentative communication devices (eg, a book or communication board that contains pictures or symbols of a patient's daily needs, computer-based devices).
Last full review/revision July 2013 by Juebin Huang, MD, PhD
Content last modified July 2013