Definition and epidemiology
Aphasia is an acquired impairment of language processing affecting speech production, comprehension, reading, or writing, resulting from focal injury to language networks (classically left perisylvian cortex in right-handed individuals). It is distinct from dysarthria (motor speech articulation problem) and from developmental language disorders coded under F80.x, which arise in childhood rather than being acquired.
Stroke is the leading cause, with aphasia present in roughly 20-40% of acute stroke patients at presentation. Prevalence rises with age because stroke incidence rises with age; it affects men and women at similar rates. Traumatic brain injury, brain tumors, CNS infections, and neurodegenerative conditions (primary progressive aphasia) are other important causes.
Coding note
- R47.0: acquired aphasia/dysphasia, used for stroke- and lesion-related cases in adults
- F80.1: expressive language disorder (developmental)
- F80.2: receptive language disorder (developmental, often with expressive involvement)
- F80.0: specific speech articulation disorder (not true aphasia, but often grouped in coding sets)
- Broca's aphasia: non-fluent, effortful speech with relatively preserved comprehension; often with contralateral hemiparesis
- Wernicke's aphasia: fluent but meaningless/paraphasic speech with impaired comprehension; patients often unaware of deficit
- Conduction aphasia: disproportionately impaired repetition from arcuate fasciculus damage, fluency and comprehension relatively spared
- Global aphasia = large perisylvian lesion affecting both Broca's and Wernicke's areas plus connections
- Transcortical aphasias spare repetition because the perisylvian core is isolated, not destroyed, by watershed infarcts
- Aphasia must be distinguished from dysarthria (motor articulation problem, language itself intact)
- MRI with diffusion-weighted imaging is the most sensitive test for acute ischemic lesion localization
- Primary progressive aphasia is a frontotemporal dementia variant presenting with isolated, gradually worsening language decline
Etiology and risk factors
- Ischemic or hemorrhagic stroke involving the middle cerebral artery territory - by far the most common cause in adults
- Traumatic brain injury with focal left-hemisphere contusion or diffuse injury
- Brain tumors (primary or metastatic) compressing or infiltrating language cortex
- CNS infections - herpes simplex encephalitis classically involves temporal lobes
- Neurodegenerative disease - primary progressive aphasia (a frontotemporal dementia variant) presents with gradually worsening language with relatively preserved memory early on
- Migraine with aura and seizure/postictal (Todd's) paralysis can cause transient aphasia
- Risk factors mirror stroke risk factors: hypertension, atrial fibrillation, diabetes, smoking, hyperlipidemia, prior TIA/stroke
Pathophysiology
Language is lateralized to the left hemisphere in about 95-99% of right-handed people and roughly 70% of left-handed people. Core language regions include Broca's area (posterior inferior frontal gyrus, language production and grammar), Wernicke's area (posterior superior temporal gyrus, language comprehension), and the arcuate fasciculus connecting them (repetition).
Damage disrupts specific components of the language network:
- Broca's area damage impairs fluent speech output while comprehension is relatively preserved
- Wernicke's area damage impairs comprehension while fluent (but often nonsensical) speech output is preserved
- Arcuate fasciculus damage impairs repetition disproportionately (conduction aphasia)
- Large perisylvian lesions involving both areas and the connecting pathways cause global aphasia
- Watershed/border-zone infarcts sparing the perisylvian core but isolating it produce transcortical aphasias, in which repetition is preserved despite poor fluency or comprehension
Clinical features
Bedside evaluation tests four domains: fluency, comprehension, repetition, and naming. The pattern across these domains defines the clinical subtype.
| Type | Fluency | Comprehension | Repetition | Lesion site |
|---|---|---|---|---|
| Broca's | Non-fluent, effortful | Relatively intact | Impaired | Posterior inferior frontal gyrus |
| Wernicke's | Fluent but paraphasic | Impaired | Impaired | Posterior superior temporal gyrus |
| Conduction | Fluent | Relatively intact | Markedly impaired | Arcuate fasciculus |
| Global | Non-fluent | Impaired | Impaired | Large perisylvian lesion |
| Transcortical motor | Non-fluent | Relatively intact | Preserved | Anterior to Broca's (watershed) |
| Transcortical sensory | Fluent | Impaired | Preserved | Posterior to Wernicke's (watershed) |
| Anomic | Fluent | Intact | Intact | Variable; naming deficit predominates |
Associated findings depend on the vascular territory: Broca's aphasia often accompanies right face/arm weakness (anterior MCA involvement); Wernicke's aphasia often occurs without hemiparesis (posterior MCA territory) but patients may lack awareness of their deficit (anosognosia) and appear agitated or paranoid due to frustration with miscommunication.
Diagnosis
Diagnosis is clinical, supported by neuroimaging to identify the underlying lesion.
Bedside assessment
- Spontaneous speech (fluency, grammar, paraphasias)
- Comprehension (yes/no questions, following commands)
- Repetition (phrases, especially complex ones)
- Naming (confrontation naming of objects)
- Reading and writing
Standardized tools
- Western Aphasia Battery, Boston Diagnostic Aphasia Examination for detailed characterization
- NIH Stroke Scale item for language in the acute stroke setting
Neuroimaging
- CT head (non-contrast) acutely to rule out hemorrhage and guide thrombolysis decisions
- MRI brain with diffusion-weighted imaging for sensitive detection of acute infarct and precise lesion localization
- MRI with contrast or further workup if tumor, abscess, or encephalitis suspected
Additional workup
- Vascular imaging (CTA/MRA, carotid duplex) and cardiac evaluation when stroke is confirmed, per standard stroke workup
- EEG if seizure-related aphasia suspected
- Neuropsychological and speech-language pathology (SLP) evaluation to characterize severity and guide therapy, especially for primary progressive aphasia where imaging/PET and biomarker workup for underlying neurodegenerative pathology may be pursued
Differential diagnosis
- Dysarthria - motor speech articulation disorder with normal language content and comprehension; often from cranial nerve, cerebellar, or brainstem dysfunction
- Apraxia of speech - impaired motor planning for speech sounds, language itself intact
- Confusion/delirium - disorganized thought affecting speech content broadly, with fluctuating attention, unlike the stable language-specific deficit of aphasia
- Psychiatric speech disturbance (e.g., formal thought disorder in schizophrenia) - lacks a focal lesion and specific fluency/comprehension/repetition pattern
- Developmental language disorders (F80.1, F80.2) - childhood onset, not acquired
- Hearing loss - can mimic comprehension deficits but language processing itself is intact
Management
Management addresses the underlying cause and the language deficit itself.
Acute/causal treatment
- Acute ischemic stroke: thrombolysis (alteplase or tenecteplase) within the eligible window and/or mechanical thrombectomy for large vessel occlusion, per American Heart Association/American Stroke Association and European Stroke Organisation guidelines
- Hemorrhagic stroke: blood pressure control and neurosurgical evaluation as indicated
- Tumor, abscess, or encephalitis: treat the specific etiology (surgery, antimicrobials, oncologic therapy)
Language rehabilitation
- Speech-language therapy is the mainstay for all aphasia types once medically stable; evidence supports starting early and continuing intensively
- Approaches include constraint-induced language therapy, melodic intonation therapy (useful in non-fluent aphasia), and computer-assisted practice
- Group therapy and communication partner training improve functional communication and quality of life
- For primary progressive aphasia, therapy focuses on compensatory strategies and augmentative communication since the underlying neurodegeneration is not reversible
Supportive measures
- Multidisciplinary rehabilitation (SLP, occupational therapy, physical therapy as needed)
- Patient and family education and counseling, since aphasia carries high psychosocial burden
- Augmentative and alternative communication devices for severe or persistent cases
Complications and prognosis
Prognosis depends heavily on etiology, lesion size/location, and time since onset. Post-stroke aphasia shows the greatest spontaneous recovery in the first 3-6 months, with continued gradual improvement possible for years with therapy; younger age and smaller lesion volume predict better recovery. Global aphasia carries the worst prognosis; anomic aphasia the best.
Complications include social isolation, depression (highly prevalent in aphasic stroke survivors), reduced employment and independence, and increased caregiver burden. Primary progressive aphasia is progressive by definition and eventually evolves into a broader dementia syndrome affecting memory and behavior in most patients.
"Broca's is BROKEN speech (non-fluent), Wernicke's is WORDY but makes no sense (fluent, impaired comprehension)."
Practice questions
1. A 68-year-old man is brought to the emergency department after his wife noticed he suddenly began speaking in short, halting phrases 2 hours ago. On exam, he says "want... go... home" with obvious effort and frustration. He follows commands correctly and can point to objects named by the examiner, but he cannot repeat the phrase "no ifs, ands, or buts." He has mild right facial droop and right arm weakness. Which of the following is most likely affected?
2. A 74-year-old woman presents with 1 day of fluent, grammatically well-formed speech that is largely nonsensical, including word substitutions like calling a "pen" a "table." She cannot follow simple one-step commands and seems unaware that anything is wrong, appearing calm despite her family's distress. She has no limb weakness. Which vascular territory is most likely involved?
3. A 61-year-old man has fluent spontaneous speech and intact comprehension of commands, but he makes frequent phonemic errors and performs very poorly when asked to repeat multi-syllabic phrases such as "Methodist Episcopal Church." MRI shows a small infarct in the left supramarginal gyrus region. Which aphasia subtype best fits this presentation?
Frequently asked questions
What causes aphasia?
Aphasia is most commonly caused by stroke affecting the left hemisphere's language areas, particularly in the middle cerebral artery territory. Other causes include traumatic brain injury, brain tumors, central nervous system infections such as herpes encephalitis, and neurodegenerative disease (primary progressive aphasia). The common thread is focal damage to brain regions responsible for producing or understanding language.
What are the first symptoms of aphasia?
Early symptoms depend on the type but often include sudden difficulty finding words, speaking in short effortful phrases, or producing fluent speech that doesn't make sense. Many patients also struggle to understand spoken or written language, or to repeat phrases accurately. When onset is sudden, it is a stroke emergency and requires immediate medical evaluation.
How is aphasia diagnosed?
Aphasia is diagnosed clinically by testing fluency, comprehension, repetition, and naming at the bedside, often using standardized batteries like the Western Aphasia Battery. Brain imaging, usually CT initially and MRI with diffusion-weighted imaging for detail, identifies the underlying lesion causing the language deficit. A speech-language pathologist typically performs a more detailed assessment to classify the type and severity.
Is aphasia curable?
Aphasia is not always curable, but significant improvement is common, especially after stroke, where the first 3-6 months show the most spontaneous recovery. Speech-language therapy, especially started early and delivered intensively, improves outcomes further and some patients regain near-normal communication. Aphasia from progressive neurodegenerative disease, however, is expected to worsen over time rather than resolve.
Broca's aphasia vs Wernicke's aphasia — what is the difference?
Broca's aphasia causes non-fluent, effortful, grammatically simplified speech with relatively preserved comprehension, and often comes with weakness on the right side of the body. Wernicke's aphasia causes fluent but often meaningless or paraphasic speech with impaired comprehension, and patients frequently lack awareness that their speech doesn't make sense. The key bedside distinguishing features are fluency of output and comprehension ability.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: F80.0
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.