Aphasia

What Aphasia is

Aphasia is an acquired language disorder caused by damage to the language-dominant hemisphere of the brain — most commonly the left hemisphere following ischaemic or haemorrhagic stroke. It affects production and comprehension of spoken and written language in combinations that traditionally map onto classical syndromes (Broca's, Wernicke's, conduction, transcortical, global) though contemporary practice increasingly treats aphasia as a continuum rather than a discrete taxonomy. Aphasia is distinct from dysarthria and apraxia of speech, which are motor rather than linguistic disorders, and from cognitive-communication disorders, which reflect generalised brain injury rather than focal language system damage.

Diagnostic criteria and defining features

• Acquired impairment of language (expression, comprehension, reading, or writing)
• Attributable to focal brain damage, most commonly left middle cerebral artery distribution stroke
• Language impairment disproportionate to generalised cognitive impairment
• Not explained by dysarthria, apraxia, or sensory deficit alone
• Documented through standardised aphasia battery (e.g., WAB, BDAE, CAT)

Criteria summarised from DSM-5-TR, ICD-11, and ASHA practice guidance. Always cross-reference against the diagnostic manual of record before using in a report.

How language sample analysis contributes

Language sampling in aphasia is the workhorse assessment for documenting functional communication change over time. Collect a connected-speech sample using a standardised picture description (Cookie Theft) or personal narrative, transcribe verbatim, and compute content units, words per minute, correct information units per minute (Nicholas & Brookshire 1993), and mean length of utterance. Repeat samples at admission, discharge, and follow-up to quantify spontaneous recovery and treatment response. A language sample captures functional output in a way that confrontation naming and repetition tasks cannot.

Related disorders