Causes
Aphasia usually results from lesions to the language-relevant areas of the frontal, temporal and parietal lobes of the brain, such as Broca's area, Wernicke's area, and the neural pathways between them. These areas are almost always located in the left hemisphere, and in most people this is where the ability to produce and comprehend language is found. However, in a very small number of people, language ability is found in the right hemisphere. In either case, damage to these language areas can be caused by a stroke, traumatic brain injury, or other brain injury.
Aphasia may also develop slowly, as in the case of a brain tumor or progressive neurological disease, e.g., Alzheimer's or Parkinson's disease. It may also be caused by a sudden hemorrhagic event within the brain. Certain chronic neurological disorders, such as epilepsy or migraine, can also include transient aphasia as a prodromal or episodic symptom.
Aphasia can result from Herpes Simplex virus (HSV) encephalitis. The (HSV) affects the frontal and temporal lobes, subcortical structures and the hippocampal tissue which can trigger aphasia.
Aphasia is also listed as a rare side effect of the fentanyl patch, an opioid used to control chronic pain. Adverse side effects including chronic aphasia can be caused by cortico-steroids.
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