Perisylvian aphasias

Introduction
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By Victor W Mark MD

Perisylvian aphasias are also known as or subsume Aphemia, Broca aphasia, Conduction aphasia, Expressive aphasia, Fluent aphasia, Global aphasia, Motor aphasia, Nonfluent aphasia, Phonemic aphasia, Primary progressive aphasia, Receptive aphasia, Recurring utterances, Semantic aphasia, Sensory aphasia, and Wernicke aphasia. -ed.

The perisylvian aphasias are common language disorders that follow focal injury to the cerebral cortex or subcortical structures in the area of the sylvian fissure (areas supplied by the middle cerebral artery), most prominently after damage to the left side of the brain. These disturbances constitute the most familiar and historically influential language disorders, including global aphasia, Broca aphasia, and Wernicke aphasia. The perisylvian aphasias share the inability to repeat (in contrast to the transcortical aphasias) but vary in the extent to which speech production and comprehension are differentially affected. These disorders are most often seen after stroke, but increasing attention is being directed to their occurrence in certain neurodegenerative disorders, particularly primary progressive aphasia. An emerging form of therapy for these disorders comes from the area of transcranial magnetic or direct current stimulation, with initially promising findings. Dr. Victor Mark of the Department of Physical Medicine and Rehabilitation at the University of Alabama at Birmingham School of Medicine explores contemporary and potential future approaches to treatment. The article also provides video vignettes from patients whom Dr. Mark has personally evaluated to demonstrate these language disturbances.

Key Points

  • Aphasia is a disturbance of only the symbolic aspects of language, whether expressive or receptive. The term does not apply to purely motor speech disorders (such as dysarthria) or to auditory processing disorders (such as hearing loss) that are not specific to language. Hence, as a central communication disturbance, aphasia disrupts not only speech but also reading and writing.
  • Although aphasia is typically considered to follow stroke in adults, increasing attention is being paid to neurodegenerative disorders that also cause aphasia, particularly the forms of primary progressive aphasia.
  • Aphasia is usually considered to follow left hemispheric injury rather than right hemispheric injury. Nonetheless, aphasia can follow right hemispheric injury. The clinician should not automatically consider a patient with focal brain illness not to have aphasia simply because the illness involves the right cerebral hemisphere.
  • Evidence is gradually increasing to demonstrate several successful forms of intervention for aphasia. Among the most vigorously pursued at present is transcranial electrical or magnetic stimulation to portions of the surviving cerebral cortex to improve left perisylvian function.