Aphasia

Aphasia, also known as dysphasia, is an acquired disorder that impairs an individual’s ability to comprehend, formulate or use language due to damage to specific regions of the brain. Although the condition affects the mechanisms of language, a person’s intelligence remains intact. Aphasia interferes with spoken and written communication, and in some cases, the understanding and production of visual language forms such as sign language. The severity of symptoms can vary widely, from mild word-finding difficulties to profound impairment of all language modalities.

Background and Causes

Aphasia most frequently results from stroke, with a significant proportion of individuals experiencing language disturbances following acute cerebrovascular events. In developed countries, the prevalence of post-stroke aphasia is estimated to fall between 0.1 and 0.4 per cent. Traumatic brain injury is another major cause, particularly when the frontal or temporal lobes are affected.
Additional causes include brain tumours, epilepsy, autoimmune neurological disorders, infectious diseases affecting neural tissue and neurodegenerative conditions. Herpesviral encephalitis, for example, can damage temporal lobe structures and lead to marked language impairment. Progressive forms of aphasia emerge in the context of degenerative diseases, in which a noticeable decline in language occurs over time.
Aphasia is distinct from motor speech disorders such as dysarthria, as it arises from disruptions in language processing rather than muscle weakness or sensory loss. However, both conditions may coexist when larger or multiple regions of the brain are compromised.

Core Aspects of Language Impairment

Diagnosis typically requires impairment in at least one of the four fundamental components of communication:
• Spoken language production• Spoken language comprehension• Written language production• Written language comprehension
Across all types of aphasia, anomia, or difficulty retrieving words, is one of the most common symptoms. Both expressive and receptive language abilities may be compromised. While language is disrupted, formulaic and automatic expressions—such as greetings or well-learned songs—are often preserved, demonstrating that some language networks may remain functional.

Signs, Symptoms and Common Behaviours

Symptoms depend on the precise location and extent of brain damage. Individuals with aphasia may experience:
• Difficulty naming familiar objects• Impaired comprehension of spoken or written language• Production of incomplete or grammatically incorrect sentences• Errors in pronunciation not attributable to muscle weakness• Substitution of letters, sounds or words• Inability to repeat words or phrases• Limited verbal output or speech resembling gibberish• Difficulty reading or writing• Trouble following simple verbal commands
Secondary behaviours may also arise. Self-repairs, for instance, occur when individuals attempt to correct mistakes but inadvertently disrupt fluency further. Those with non-fluent aphasia often display significant effort and frustration during speech attempts. By contrast, automatic phrases and habitual utterances may be produced with relative ease compared to novel or spontaneous speech.

Subcortical Aphasia

Subcortical aphasia arises from damage to deep brain structures, such as the thalamus, basal ganglia or internal capsule. Although these regions are not primarily responsible for language, they support large-scale language networks, and lesions can lead to disruptions in fluency, comprehension or repetition. Symptoms vary depending on the site and size of the subcortical lesion.

Cognitive Deficits and Their Role

Although aphasia is defined by linguistic difficulties, many individuals exhibit additional cognitive deficits. Research indicates that:
• Short-term and working memory deficits are common, affecting both verbal and visuospatial domains.• Attention impairments frequently co-occur and may influence language performance.• Executive functions such as planning, flexibility and self-monitoring can be disrupted.• Individuals with mild aphasia may still show slower processing speed and greater susceptibility to interference in attention tasks.
The relationship between these cognitive deficits and language impairment remains a subject of discussion. Some researchers propose that attention and memory deficits play a contributing role in aphasia, while others view them as general consequences of brain injury rather than direct causes of language breakdown.
Cognitive difficulties influence rehabilitation outcomes and quality of life. They may affect learning during therapy and are linked to reduced functional independence. Assessing these deficits requires careful selection of tools, as many cognitive tasks rely partly on language and may not accurately reflect non-linguistic functioning.

Types and Characteristics of Aphasia

Aphasia is typically classified according to patterns of impairment across expressive and receptive domains. Common forms include:
• Broca’s aphasia: Non-fluent, effortful speech with relatively preserved comprehension.• Wernicke’s aphasia: Fluent but often nonsensical speech, accompanied by impaired comprehension.• Global aphasia: Severe impairment across all language modalities.• Anomic aphasia: Predominantly characterised by word-finding difficulty.• Conduction aphasia: Marked by impaired repetition with otherwise fluent speech and relatively good comprehension.• Primary progressive aphasia: A degenerative condition involving gradual language decline.• Subcortical aphasias: Arising from damage beneath cortical language regions.
Each of these types reflects disruption within specific components of the broader language network.

Implications and Functional Impact

Aphasia significantly influences everyday activities. It can limit social interactions, affect employment, reduce academic performance and disrupt family communication. Individuals often develop compensatory strategies such as gesture use, circumlocution, pointing, drawing or reliance on communication aids. Emotional responses including frustration, embarrassment and withdrawal are common.
Rehabilitation focuses on enhancing remaining language abilities, building compensatory strategies and improving communication environments. Early, individualised therapy provides the best outcomes. Many individuals experience meaningful improvements, though recovery is influenced by factors such as the cause of aphasia, lesion size, cognitive function and access to treatment.
Aphasia also affects families and caregivers, who may require guidance on communication techniques and support for the psychological and social challenges associated with the condition. Despite its far-reaching effects, with appropriate intervention and environmental support, many people with aphasia continue to participate actively in personal, social and professional aspects of life.