Extrasylvian aphasias

Alfredo Ardila PhD (Dr. Ardila of Florida International University has no relevant financial relationships to disclose.)
Victor W Mark MD, editor. (Dr. Mark of the University of Alabama at Birmingham has no relevant financial relationships to disclose.)
Originally released June 14, 1999; last updated March 18, 2016; expires March 18, 2019

This article includes discussion of extrasylvian aphasias, transcortical motor aphasia, transcortical sensory aphasia, transcortical mixed aphasia (or isolation syndrome), extrasylvian motor aphasia (transcortical motor aphasia), extrasylvian sensory aphasia (transcortical sensory aphasia), mixed extrasylvian aphasia (transcortical mixed aphasia, isolation syndrome), subcortical aphasia, and cerebellar language disorders. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Language disturbances observed in cases of damage outside of the “brain language area” are known as extrasylvian or transcortical aphasia. Preserved language repetition is its distinguishing characteristic. Two major subtypes of extrasylvian aphasia have been traditionally distinguished: extrasylvian motor aphasia and extrasylvian sensory aphasia, each 1 presenting rather different clinical manifestations. Additionally, striatocapsular and thalamic damage can result not only in speech, but also in some language, defects. It has been hypothesized that the cerebellum contributes to cognitive processing, particularly the processing of linguistic information because the cerebellum has reciprocal connections not only with the left inferior frontal gyrus, but also the left lateral temporal cortex.

Key points

 

• Aphasia observed in cases of damage outside the “brain language area” (perisylvian area of the left hemisphere) is known as extrasylvian aphasia.

 

• Usually an extrasylvian motor aphasia and extrasylvian sensory aphasia are distinguished.

 

• Sometimes aphasia can be found associated with striatocapsular and thalamic pathology.

 

• Right cerebellar damage may lead to some verbal deficits, such as impaired grammar and decreased verbal fluency.

Historical note and terminology

Wernicke and Lichtheim introduced the term "transcortical aphasia" (Wernicke 1881; Lichtheim 1885). Wernicke initially described 2 distinct types of aphasia, motor and sensory, as well as the anatomical demonstration to support this division (Wernicke 1874). Wernicke's original proposal was expanded during the following years. Lichtheim, in his paper "On Aphasia," presented a simple diagrammatic illustration of Wernicke's model of language functions (Lichtheim 1885). This model, usually known as the Wernicke-Lichtheim aphasia model, includes 7 different types of language disturbances associated with brain pathology. According to the model, aphasia can be subcortical, cortical, and transcortical. Each 1 includes 2 subtypes: motor and sensory. Finally, conduction aphasia represents a relatively isolated defect in language repetition, observed when the sensory language area becomes disconnected from the motor language area. Preserved language repetition represents the distinguishing characteristic of transcortical aphasias. The term "transcortical" represents 1 area of the Wernicke-Lichtheim aphasia model of the cortical networks involved in language and ideation, in which the exact phonological reproduction could be accomplished by the aphasic patient, but the meaning (idea) could not be extracted and reproduced.

Goldstein analyzed several varieties of aphasia gathered under the title of transcortical aphasia. The term, as originally proposed, draws a distinction between aphasias with or without repetition defects. Goldstein, in his book Die Transkortikalen Aphasien, noted that the term "transcortical" was archaic and misleading (Goldstein 1917). "Transcortical aphasia," however, remained the most widely used designation for a distinctive group of aphasic syndromes (Berthier 1999). The term "extrasylvian," instead of "transcortical," has been proposed to designate this group of language disorders (Benson and Ardila 1996). For the purpose of this article, the term "extrasylvian" will also refer to aphasias that arise from injury to either subcortical areas or areas outside of the cerebral hemispheres (eg, the cerebellum). A description of perisylvian aphasias may be found elsewhere.

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