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The hidden truth about aphasia: Did you know the link between stroke and traumatic brain injury?
Aphasia, also known as speech disorder, is caused by damage to specific areas of the brain that impairs an individual's ability to understand or express language. Major causes of aphasia include stroke and traumatic brain injury, but their incidence is often difficult to determine. It is estimated that the prevalence of aphasia due to stroke in the northern hemisphere is between 0.1% and 0.4%.
Aphasia not only affects the production and understanding of spoken and written language, but may also affect visual languages such as sign language.
Symptoms of aphasia range from occasional difficulty finding words to a complete loss of the ability to speak, read, or write, but the individual's intellectual ability is not affected. Key features of aphasia include difficulty expressing and understanding language. Additionally, one deficit common to all people with aphasia is word-finding difficulty (i.e., difficulty finding the correct word). Aphasia is therefore defined as an impairment of one or more modes of communication in the brain, resulting in abnormal functioning.
Depending on the location of the damage in the brain, the appearance and severity of aphasia may vary. For example, when asked to name an object, a person with aphasia may use a vague word such as "thing" instead of the specific name of the object. Sometimes, they'll even explain it with a descriptive phrase like: "writing stuff."
Despite their difficulties with spoken language, people with aphasia often retain the skillful expressive words they use in daily life (such as birthday songs).
Cognitive deficits in aphasia
Although aphasia is traditionally described as a language deficit, many patients with aphasia are often accompanied by non-verbal cognitive deficits, such as problems in areas such as attention, memory, and executive function. As cognitive neural networks underpin language reorganization after stroke, although the origins of language deficits in aphasia are less clear, language-related cognitive losses remain critical to the recovery process.
For example, many patients with aphasia have deficits in short-term and working memory abilities, and these conditions are often accompanied by poor performance on language-related tasks such as object naming and sentence comprehension.
Many studies have found that performance deficits in attention and other cognitive domains in patients with aphasia are positively correlated with their language function, suggesting that multiple cognitive deficits coexist in the impact of aphasia.
Causes of aphasia
Aphasia is often caused by stroke, with about a quarter of stroke patients experiencing aphasia. Any disease or injury that causes damage to the language-controlling areas of the brain can lead to aphasia, including brain tumors, traumatic brain injury, epilepsy, or progressive neurological disease. In some rare cases, aphasia may also be caused by encephalitis.
Acute illness, such as brain injury or stroke, often causes the onset of aphasia quickly, whereas aphasia caused by brain tumors, infections, or dementia tends to develop gradually.
The underlying cause of aphasia may include any damage to the brain, not just the areas that control language.
Diagnostic methods
Diagnosis of aphasia often relies on neuroimaging methods such as magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI). These tools help determine the presence of aphasia and the extent of the impairment. Using these images, we were able to identify potential damage to language areas, specifically in the anterior and temporal lobes of the left brain.
Treatment and Rehabilitation
Many studies have shown positive results from rehabilitation efforts for aphasia. By measuring the outcome of speech recovery using functional neuroimaging techniques or diffusion tensor imaging, we are able to evaluate a patient's progress during speech therapy. These technologies help doctors gain a deeper understanding of patients’ conditions and provide personalized treatment plans.
Progress in rehabilitation of patients with aphasia may be closely related to the combination of cognitive intervention and speech therapy.
As our understanding of aphasia continues to advance, whether better outcomes can be achieved with effective therapies is an important area of discussion. Could cultivating an emphasis on language understanding and its cognitive underpinnings more effectively promote the recovery of people with aphasia?
