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Aphasia: causes, symptoms, diagnosis, treatment
Last reviewed: 07.07.2025
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Aphasia is a disorder or loss of speech function - a violation of active (expressive) speech and its understanding (or its non-verbal equivalents) as a result of damage to the speech centers in the cerebral cortex, basal ganglia or white matter containing conductors connecting them. The diagnosis is based on clinical symptoms, neuropsychological and imaging (CT, MRI) studies. The prognosis depends on the nature and extent of the damage, as well as the patient's age. Specific treatment for aphasia has not been developed, but active correction of speech disorders contributes to a faster recovery.
Speech functions are associated primarily with the posterior superior temporal lobe, the adjacent inferior parietal lobe, the inferior lateral frontal lobe, and the subcortical connections between these areas, usually in the left hemisphere, even in left-handers. Damage to any part of this area of the brain, conventionally united into a functional triangle (due to infarction, tumor, trauma, or degeneration), leads to certain disorders of speech function. Prosody (stress and intonation of speech, which gives it significance) is a function of both hemispheres, but sometimes disorders are observed with isolated dysfunction of the subdominant hemisphere.
Aphasia should be distinguished from speech development disorders and dysfunction of the motor pathways and muscles that provide speech articulation (dysarthria). Aphasia is, to some extent, conditionally divided into sensory and motor.
Sensory (receptive or Wernicke's aphasia) aphasia is the inability to understand words or recognize auditory, visual or tactile symbols. It is caused by damage to the posterior superior temporal lobe of the dominant hemisphere and is often associated with alexia (impaired understanding of written speech). In expressive (motor or Broca's aphasia) aphasia, understanding and comprehension of speech remain relatively intact, but the ability to produce speech is impaired. Motor aphasia is caused by damage to the posterior inferior frontal lobe. Agraphia (writing disorder) and impaired reading aloud are often observed.
[ Symptoms of aphasia
Patients with Wernicke's aphasia speak normal words fluently, often including meaningless phonemes, but have no awareness of their meaning or relationships. The result is a jumble of words or "word hash." Patients with Wernicke's aphasia are usually aware that their speech is incomprehensible to others. Wernicke's aphasia is usually accompanied by a narrowing of the right visual field because the visual pathway passes near the affected area.
Patients with Broca's aphasia can understand and comprehend words relatively well, but their ability to pronounce words is impaired. Typically, the disorder affects speech production and writing (agraphia, dysgraphia), significantly complicating patients' attempts to communicate. Broca's aphasia may be associated with anomia (inability to name objects) and impaired prosody (intonation components).
Diagnosis of aphasia
Verbal communication usually allows identification of the presence of gross aphasia. The examination conducted to identify specific disorders should include examination of spontaneous speech, naming, repetition, comprehension, speech production, reading and writing. Spontaneous speech is assessed by the following indicators: fluency, number of spoken words, ability to initiate speech, presence of spontaneous errors, pauses for word selection, hesitation, verbosity and prosody. Initially, Wernicke's aphasia may be mistaken for delirium. However, Wernicke's aphasia is an isolated speech disorder in the absence of other signs of delirium (flickering consciousness, hallucinations, inattention).
Formal cognitive testing by a neuropsychologist or speech therapist can reveal more subtle levels of dysfunction and help in treatment planning and assessment of the potential for recovery. A wide range of formal tests for diagnosing aphasia are available to specialists (e.g., the Boston Diagnostic Aphasia Examination, the Western Aphasia Battery, the Boston Naming Test, the Nominative Test, the Action Naming Test, etc.).
CT or MRI (with or without angiography) are performed to clarify the nature of the lesion (infarction, hemorrhage, space-occupying lesion). Further studies are performed to clarify the etiology of the disease in accordance with the algorithm described earlier.
Prognosis and treatment of aphasia
The effectiveness of treatment has not been reliably established, but most clinicians believe that involving a professional speech therapist in the earliest stages of the disease gives the best results: the earlier treatment is started, the greater the chance of success.
The degree of recovery also depends on the size and location of the lesion, the degree of speech disorders and, to a lesser extent, the age, level of education and general health of the patient. In almost all children under 8 years of age, speech function is fully restored after severe damage to either hemisphere. At a later age, the most active recovery occurs during the first three months, but the final stage can last up to 1 year.