What are the causes of aphasia?

Causes of Aphasia

Stroke is the predominant cause of aphasia, accounting for the vast majority of cases, with left hemispheric strokes being almost exclusively responsible for this language disorder. 1

Primary Etiology

Stroke (Most Common)

• Ischemic stroke affecting the left hemisphere is the leading cause, with aphasia occurring in 21-38% of acute stroke patients 1, 2
• More recent data suggests approximately 30% of stroke survivors develop aphasia 1
• Left hemispheric strokes are almost exclusively responsible for aphasia presentation 1
• Both acute and chronic phases of stroke can manifest with aphasia 1

Specific Stroke-Related Mechanisms

• Subcortical strokes involving basal ganglia, thalamus, and/or deep white matter can produce aphasia, often characterized by word fluency, motor speech output, or sentence generation impairments 3
• Hemorrhagic stroke can cause aphasia, though spontaneous recovery is slower (occurring from fourth to eighth week) compared to ischemic stroke (most intensive recovery in first two weeks) 4
• Thromboembolism during invasive cardiovascular procedures accounts for 70-80% of procedure-related strokes that may result in aphasia 1

Secondary Causes

Neurodegenerative Conditions

• Frontotemporal lobar degeneration (FTLD) causes primary progressive aphasia variants 5:
  • Semantic variant (svPPA) - associated with TDP-43 type C pathology 5
  • Non-fluent/agrammatic variant (nfvPPA) - associated with tauopathy 5
• Alzheimer's disease pathology commonly causes logopenic variant aphasia (lvPPA) 5

Other Neurological Damage

• Traumatic brain injury affecting language-processing brain regions 4, 6
• Brain tumors causing dysfunction in specific language areas 6
• Infections affecting language centers 6
• Any brain damage or dysfunction affecting language-processing regions can result in aphasia 4, 6, 7

Key Anatomical Considerations

Left hemisphere dominance for language means that lesions in this hemisphere are responsible for aphasia in the overwhelming majority of cases 1, 4. Specific vulnerable areas include:

• Frontal language regions (Broca's area) 4
• Temporal language regions (Wernicke's area) 4
• Deep white matter tracts including the arcuate fasciculus 1
• Subcortical structures (basal ganglia, thalamus) 3

Clinical Context

The presence of aphasia is associated with:

• Decreased response to stroke rehabilitation interventions 1
• Increased mortality risk 1
• Significant impact on quality of life and functional communication 1
• High short- and long-term morbidity and healthcare expenditure 2