Aphasia

[Oralee]

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

Posterosuperior temporal lobe (which contains the Wernicke area)
Adjacent inferior parietal lobe
Posteroinferior part of the frontal lobe just anterior to the motor cortex (Broca area)
Subcortical connections between those regions

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).

[Lizzy Liz]

Loss of ability to understand or express speech, caused by brain damage.

[Tracie Lynn]

a medical condition that makes a person unable to speak, write, or understand speech or writing because of damage to the brain