Perisylvian aphasias

Victor W Mark MD (Dr. Mark of the University of Alabama at Birmingham has no relevant financial relationships to disclose.)
Originally released April 23, 1998; last updated August 13, 2016; expires August 13, 2019

This article includes discussion of perisylvian aphasias, aphemia, Broca aphasia, conduction aphasia, expressive aphasia, motor aphasia, phonemic aphasia, primary progressive aphasia, receptive aphasia, semantic aphasia, sensory aphasia, Wernicke aphasia, fluent aphasia, global aphasia, nonfluent aphasia, primary progressive aphasia, and recurring utterances. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

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. Evidence from different sources points to overactivity of the right inferior frontal lobe as inhibiting recovery from post-stroke aphasia. In this article, the author explores contemporary and potential future approaches to treatment. The article also provides video vignettes from patients the author 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 disorders (such as hearing loss) that are not specific to language. Hence, as a central communication disturbance, aphasia disrupts not only speech, but also (but not invariably) 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.

 

• Evidence has begun to support the use of speech therapy to treat 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 interventions 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.

Historical note and terminology

Aphasia is the disordered use of words or sentences due to the impaired processing of their intrinsic information content. The term is preferred when language disturbance is noticeably more severe than any other concurrent cognitive disorder in the same individual. It is distinguished from disturbances of hearing, voluntary oral control, memory, and attention that only secondarily impair communication. The term also does not apply to nonverbal aspects of verbal communication, such as emotional or musical intonation. Aphasia is used preferentially to describe impaired, immediately interactive communication involving speech or sign language (Chiarello et al 1982), rather than recorded exchange (eg, written communication).

This article emphasizes aphasia in the adult (ie, following a typical adult-level acquisition of word knowledge and proficiency in sentence comprehension and production). The perisylvian aphasias, ie, those that follow cerebral damage at or near the Sylvian fissure, have most frequently been described following stroke. Indeed, as many as 40% of stroke patients may be aphasic (Boller 1981). Therefore, this overview emphasizes aphasic disturbances commonly encountered in clinical practice. However, the disturbances reviewed here may occur with other cerebral disorders as well, including brain tumors (Anderson et al 1990), dementia, and multiple sclerosis (Friedman et al 1983).

Aphasia has been described for centuries (Benton and Joynt 1960; Sondhaus and Finger 1988; Brown and Chobor 1992). Formal clinical reports of aphasia appeared in the Russian literature in the late 18th and early 19th centuries (Glozman 2007). In the 1860s, French anthropologist Paul Broca associated expressive speech impairments with left frontal lobe injury that was evident at autopsy. He suggested, for the first time, that the left frontal lobe was essential for language (Berker et al 1986). Marc Dax may have independently concluded the same, but refrained from publishing his findings (Critchley 1979). Subsequently, the German neurologists Meynert and Wernicke reported patients who spoke fluently but comprehended poorly (Wernicke 1874; Whitaker and Etlinger 1993). Wernicke distinguished receptive from expressive disorders. At about the same time, the English neurologist John Hughlings Jackson regarded the aphasic brain as a glass not partly empty, but partly filled. He was impressed by the retained language functions in even profoundly aphasic individuals, their considerable performance fluctuation during a single examination, and especially the preservation of "automatic" speech (ie, well-learned expressions such as greetings and curses prompted by the particular context) relative to "propositional" speech (the creation of new expressions) (Critchley and Critchley 1998). Subsequently, Jackson learned that François Baillarger in France had independently, and somewhat earlier, identified the same phenomenon; therefore, he termed this the “Baillarger principle” (Freeman 1970).

Broca's and Wernicke's findings inspired other investigators, many of whom were German, to develop language models based on the interaction among spatially and functionally discrete cerebral regions. However, interest in the 19th century German aphasia models faltered by the early 20th century, perhaps due to the stigma of Germany's defeat in the first World War (Geschwind 1964). Simultaneously, Jackson's writings failed to gain greater acceptance, perhaps because his works were difficult to read (Critchley and Critchley 1998). The advent of psychoanalysis and personality theories, and the abandonment of surgery for mental illness later in the 20th century, may have overshadowed interest in human focal cognitive disturbances in general. Inspired by Myers and Sperry's finding of specific cognitive disorders in laboratory animals following experimental interhemispheric disconnection, the American neurologist Norman Geschwind revived Wernicke's intrahemispheric disconnection model in an extensive review (Geschwind and Kaplan 1962; Geschwind 1965). Through his influential cognitive disorders training program, aphasia became a leading neurologic topic in the present era. A comprehensive historical overview of research on aphasia, including technological advances in understanding its neurologic mechanisms and recovery, is provided by Hillis (Hillis 2007).

By the 1890s European case studies began to appear that described progressive rather than static forms of aphasia (Harciarek and Kertesz 2011). These early reports were described with respect to dementia rather than aphasia itself. The earliest report of a relatively purely progressive aphasia appears to have been by Sérieux (Serieux 1893). Because the term dementia connotes multiple as opposed to solitary progressive cognitive disturbances within the same individual, the concept of progressive aphasia did not itself become crystallized until Mesulam's seminal observations in the late 20th century (Mesulam 1982). Mesulam coined the term “primary progressive aphasia” (Mesulam 1987) to indicate dementing illnesses in which language decline was the most noticeable disturbance.

Broca termed the language disturbance "aphemia." However, in 1864, his more esteemed colleague Armand Trousseau criticized the term due to its Greek connotation of "infamy" and advocated "aphasia" instead (Finger 1994; Samuels et al 2002), which from then on became the standard term for acquired language disorder. Today "aphemia" is seldom used, but generally describes chronically impaired speech with intact comprehension and writing (Albert et al 1981; Schiff et al 1983; Alexander et al 1989). “Dysphasia” is a frequently used alternate term for aphasia, particularly among British scholars.

Numerous classifications and terminologies have been proposed for aphasia subtypes, without universal acceptance. Generally, clinicians understand the following classifications, despite the controversies. Fluent aphasia refers to a language disorder with effortless speech production; nonfluent aphasia indicates a language disorder with halting, effortful speech production. Both may involve impaired comprehension and speech. Therefore, the terms receptive (or sensory) aphasia and expressive (or motor) aphasia should be discouraged (Mesulam 1990; Willmes and Poeck 1993), because seldom (if ever) does one identify a purely expressive or receptive disorder (Kimura and Watson 1989). Broca aphasia describes effortful production, loss of grammatical modifications, and relatively preserved comprehension. Wernicke aphasia denotes fluent speech typified by circumlocution and neologisms, and is classically associated with more severe comprehension impairment. Conduction aphasia indicates minimally disturbed comprehension and expression, but with relatively impaired repetition. Global aphasia (or severe aphasia, total aphasia) indicates profoundly impaired general language functions with minimally deficient other cognitive functions. Anomic aphasia, the most common disturbance of primary progressive aphasia (Deramecourt et al 2010), indicates a deficit primarily of word retrieval.

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