Receptive aphasia
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Template:DiseaseDisorder infobox
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Receptive aphasia, or Wernicke’s aphasia, fluent aphasia, or sensory aphasia is the most common type of aphasia, often (but not always) caused by neurological damage (stroke) to Wernicke’s area in the brain (Broddman area 22, in the posterior part of the superior temporal gyrus of the dominant hemisphere). This is not to be confused with Wernicke’s encephalopathy or Wernicke-Korsakoff syndrome. The aphasia was first described by Carl Wernicke and its understanding substantially advanced by Norman Geschwind. Patients with this type of aphasia are usually not aware of the errors they may be making while speaking, or that it may not be logical.
Wernicke's aphasia may present with other deficits such as dysarthria, and severity depends on the lesion present though usually without motor dysfunction. This leads to proper stringing of words together to form fluent speech even though it is often without meaning. Language expression deficits can be accompanied with memory deficits, impaired understanding of language along with impaired reading and writing.[1][2]
Historical Perspective
- Receptive aphasia was first discovered by Carl Wernicke, a German neuropathologist studying with Mynert in 1874. Wernicke published Der Aphasische Symptomencomplex. He described sensory aphasia as a distinct entity from motor aphasia (Brocas aphasia).
- Early in the 15th century the development of basic aphasia treatment started considering it as a form of memory impairment. However it was in the 18th century that Gall developed his language and speech localisation theory, and Broca, Hughlings, Jackson and Bastian noticed that recovery could be due to some sort of reorganization, meaning therapy could be beneficial. After the First World War, Goldstein, Luria and the Viennese phoniatricians Hermann Gutzmann and Emil Froeschels pioneered systematic treatments. Between the wars the focus turned to the New World and a more objective approach was developed based on identifiable behaviors. Following World War II, the theory of localisation returned, developing an approach based on the Boston School and stimulation methods of Wepman and Schuell. In the latter part of the 20th century new methods based on linguistics, psycholinguistics, modular cognitive models and psychosocial and social models were formed.[3]
Classification
- Aphasia can be broadly classified according into :
- expressive aphasia or motor aphasia
- receptive or sensory aphasia
- anomic aphasia
- global aphasia
- conduction aphasia
Pathophysiology
- Aphasia is a symptom of damage to the language areas of the brain, as such the pathogenesis of receptive aphasia is characterized by damage to the Wernicke's area (left posterior temporal area of the brain) and consequent loss of understanding of speech. The extent of damage typically guides the severity and prognosis of the resulting aphasia. Post stroke aphasia presents acutely while progressive sensory aphasia is insidious in onset, with the degree of aphasia related to the underlying disease process.
- On gross pathology, signs of damage to the Wernicke area are usually seen, which can include acute signs of stroke (ischemic or hemorrhagic), or lesions indicating a previous cerebrovascular accident. Gross atrophy of the brain parenchyma indicates workup of the patient for dementia. A growth causing compressive effects may also cause aphasia. In patients with loss of Wernicke area, a permanent loss of comprehension was noted, and recent studies have found loss of blood flow to this area leads to loss of single word understanding. New research however shows that loss of the conventional Wernicke area in the superior temporal gyrus is not the independent source of Wernicke aphasia. It has more to do with phonemic representations, and damage to this area might cause more typical conduction aphasia. This is because comprehension involves more anterior temporal regions. Comparable or exact lesions can produce different syndromes of aphasia at various points in the disease process.
- In rare cases Herpes encephalitis has been reported as a cause of aphasia
Clinical Features
Speech is preserved, but language content is incorrect. This can range from the inclusion of a few inappropriate or nonexistent words to a torrent of jargon. Grammar, intonation, stress, syntax and rate are normal. Substitutions of one word for another (paraphasias, e.g. “telephone” for “television”) are common. In severe cases, this can be confused with the psychiatric signs of “pressure of speech” and “word salad.” Comprehension may be poor and repetition is also inadequate.
Example:
- I called my mother on the television and did not understand the door. It was too breakfast, but they came from far to near. My mother is not too old for me to be young.
Regarding speech and comprehension, people with Wernicke’s aphasia may:
- Sequence words together to make illogical sentences
- Form new words which may be senseless
- Be able to deliver words in a normal melodic line
- Articulate words
- Face hardship or add words while repeating phrases
- Interrupt others and speak too fast
- Have impaired reading and writing capacity
- Understand visual materials better than written or spoken words
- Preserve cognitive abilities different than those related with language
- Be oblivious of spoken mistakes, and subsequently rectify them. These mistakes include
- Jargon: Incoherent but structurally intact speech that may be composed of invented words or incoherently arranged known words.
- Neologisms: Newly invented words
- Paraphasias: Substitution of the target word with one that is similar, or addition of unintended syllables, entire words or phrases into speech. Paraphasias can be divided according to:
- Phonemic,
- Verbal,
- Neologistic,
- Perseverative.
Damage to the Wernicke's area in the non-dominant hemisphere results in sensory dysprosody, in which the ability to perceive the pitch, rhythm, and emotional tone of speech is lost. Patients who recover from Wernicke’s aphasia describe that they experienced others speech to be incomprehensible and, despite knowing they were speaking, did not recognize their own words or were able to stop themselves from speaking. The ability to understand and repeat songs is generally unaffected, as these are processed by the opposite hemisphere. "Melodic intonation therapy" had been attempted with aphasic patients as therapy to help them speak normally, but in 2003 this was found to be ineffective.[4]
"Neighbourhood signs", for example visual changes, headaches, sensory or motor deficits in other areas of the body are suggestive of involvement of areas of the cortex adjacent to language areas. A detailed history is needed to assess whether the aphasia is isolated or part of a larger neurodegenerative condition involving multiple areas of the brain. "Neighborhood signs include a superior quadrantanopsia due to involvement of optic radiations, limb apraxia due to involvement of the inferior parietal lobule or its connections to the premotor cortices, finger agnosia, acalculia, or agraphia (components of the Gerstmann syndrome) due to involvement of the angular gyrus. The key neighborhood sign is a negative one; patients with Wernicke aphasia usually have no hemiparesis."
Aphasia is different from a disease like Alzheimer’s, in which many of the brain’s functions diminish over time. Interestingly, patients were able to recite from memory, a key difference from Alzheimer's Dementia. The patient is still able to express obscenity, however typically they have no control or knowledge of their spoken obscenities. Patients' written expression is fluent, however their choice and spelling of words is highly irregular. Thus, regressing writing skills can be an early indicator of Wernickes aphasia.
Patients are usually physically independent in the absence of other focal neurological deficits.
Luria's theory on Wernicke's aphasia
Luria proposed that this type of aphasia has three characteristics.[5]
- A deficit in the categorization of sounds. In order to understand what is said, one must be able to perceive subtle sounds of spoken language. For example, differentiating between bad and bed is simple for native English speakers. The Dutch language however, makes no difference between these vowels, and therefore the Dutch experience trouble with these sounds. This is exactly what patients with Wernicke’s aphasia experience even in their own dialect: they can't isolate notable sound characteristics and organize them into known arrangements.
- A defect in speech. A patient with Wernicke's aphasia can and may be able to speak a great deal, though confusing sound characteristics, producing “word salad”: separately comprehensible words that make no sense together.
- An impairment in writing. Those who cannot differentiate sounds cannot be predicted to write.
Differentiating Receptive aphasia from other diseases
- Receptive aphasia must be differentiated from other diseases that cause language deficits and memory impairment such as:
- Brocas Aphasia
- Global Aphasia
- Dementia
- Alzheimers
- Agraphia
Epidemiology and Demographics
- About 750,000 strokes occur each year in the USA.
- About 1 third (225,000) of strokes result in aphasia.
- There are at least 2,000,000 people in the USA with aphasia.
- There are at least 250,000 people in Great Britain with aphasia.
Age
- Aphasia after stroke is more common for older adults than younger adults (Ellis & Urban, 2016). Fifteen percent of individuals under the age of 65 experience aphasia after their first ischemic stroke; this percentage increases to 43% for individuals 85 years of age and older (Engelter et al., 2006).
Gender
- Receptive aphasia affects men and women equally, though some data suggests that differences may exist by type and severity of aphasia. For example, Wernicke’s aphasia and global aphasia occur more commonly in women, and Broca's aphasia occurs more commonly in men (Hier, Yoon, Mohr, & Price, 1994).
Race
- There is no racial predilection for Receptive Aphasia.
Risk Factors
Natural History, Complications and Prognosis
- If the underlying cause is left untreated, progressive neurological weakness leads to greater deficits. Prognosis depends on the size of the lesion, the volume of Wernicke area that is involved, patients age, education of the patient and the condition of the contralateral hemisphere. Smaller lesions have generally better prognosis than larger ones, however the etiology is a major factor. It was found that severity of the initial aphasia correlated with overall recovery, with more severe disease causing greater permanent disability. Patients benefit from therapy in initial phases of the disease and in cases of severe deficits, however the benefits are limited and progress slows to a crawl after 10-12 months of therapy. For post stroke aphasia it was found that language improved with reperfusion of the affected area over time. With therapy, recovery can be complete, however depending on the underlying disease the aphasia can progress to conduction or anomic aphasia.
Diagnosis
Diagnostic Criteria
- The diagnosis of aphasia is usually made by the primary care physician treating the patient for brain injury. The lesion is located precisely using imaging modalities, commonly Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans. A speech-language pathologist then carries out a comprehensive analysis of the patients ability to communicate and understand effectively, along with investigating his or her reading, writing and cognitive ability. Other known deficits must be corrected before detailed examination takes place. If the individual with aphasia wears prescription glasses or hearing aids, and prescriptions are still appropriate, the glasses or aids should be worn during assessment. "If additional hearing and/or visual deficits resulted from the neurological event—and physical or environmental modifications (e.g., large-print material, modified lighting, amplification devices) are not sufficient to compensate for these changes—then the individual should be referred for complete audiologic and/or vision assessments prior to testing."[6] In the case of multilingual patients, it is important to factor in the language, native or second language, premorbid use of each language, and relevance of the language to the patients surroundings. Sometimes second languages are affected much more significantly than native. Clinicians should try to assess deficits across all languages spoken, as testing in only one language can be incomplete. Together with a detailed case history and examination, these tests are used to guide the treatment and rehabilitation of patients with aphasia.
- Boston Diagnostic Aphasia Examination (BDAE): diagnoses the presence and type of aphasia, with special attention to location of the lesion and its role in normal functioning.
- Western Aphasia Battery - Revised (WAB): determines the presence, type and severity of aphasia. Can also be used to establish a baseline for the patient.
- Communication Activities of Daily Living - Second Edition (CADL-2): measures functional communication abilities with focus on reading, writing, social interactions with multiple degrees of communication.
- Revised Token Test (RTT): gauge understanding of verbal instruction; focuses on patient's ability to follow directions.
Laboratory Findings
- There are no specific laboratory findings associated with Aphasia.
Treatment
Before aphasia treatment can start, it is important to try and remove the underlying disease. In cases where the aphasia is caused by a neoplastic process or buildup of fluid in the parenchyma, there is rapid recovery after removal of the mass. Infection control is also key to prevent further complications. In cases of Landau-Kleffner syndrome, where aphasia is linked to epilepsy, adequate control of seizures is the cornerstone of treatment. Therapy for aphasia is mainly comprised of speech and language exercises. There is no consensus on whether to start therapy as soon as possible or letting there be a short lag between onset of aphasia and initiation of therapy to allow for spontaneous resolution. The aim of treatment is to enable the patient to make best use of their remaining language function, improve language skill, and learn how to communicate in other possible ways so their wants and needs can be articulated and addressed.[7] It often involves group therapy, and retraining of the individual to deliver their thoughts in alternate ways, along with repetition of common words and phrases. This reorganization is referred to as neuroplasticity, wherein the brain rearranges itself to lay different pathways after damage to existing ones. Thomson noted,"Portions of the right hemisphere, extended left brain sites, or both have been shown to be recruited to perform language functions after brain damage".
However, treatment is particularly challenging due to the fact that patients with aphasia suffer from impaired comprehension, which limits their perception of their degree of impairment. It is useful for the therapist to employ shorter phrases, direct and simple commands and to talk slowly. Due to the heterogenicity and wide spectrum of deficits that can occur, therapy is highly specific to the patient. Therapy differs according to severity of impairment and changes over time as the patient improves.
When the cause of aphasia is a stroke, recovery of language function peaks within two to six months, after which further progress is limited. However, efforts should still be made, as an improvement in aphasia has been recorded long after a stroke. Family support and social support are crucial to a positive outcome. Treatment of post-stroke depression and post-stroke cognitive issues, as well as of other neurological disorders such as neglect, agnosia, and hemiparesis, should be worked on during rehabilitation to further improve patient outcome.
Therapy is based on the particular therapists methods, with wide variations between technique. There are however some salient features of treatment that are common across the board. These can be organised into impairment based (one on one) techniques and communication based techniques (social approaches or participation-based approaches). There is a significant overlap between these methods as well. Communication based therapy focuses on alternative means of communicating. It consists of compensatory strategies, and individuals are directed to use any remaining language ability that successfully transmits information. These strategies are partly “language-based” and are likely to include impairment-based objectives.
Impairment-based techniques
Constraint-induced therapy (CIT): This therapy is modeled after physical therapy for paralysis in which a patient is directed to use an impaired side of the body, because the unaffected side is constrained. With respect to communication functions, an aphasic person may be constrained in using intact gesture so that they use and subsequently improve the affected spoken language. This is more intensive than traditional therapy schedules but it is applied for shorter duration. It is completely different from communication based therapy, in which the patient is encouraged to use intact abilities to communicate. Studies suggest enhanced results when the drug Memantine is used in conjunction with therapy.
Melodic Intonation Therapy (MIT): Established by Robert Sparks in Boston, MIT is based on an observation that that some persons with aphasia “sing it better than saying it.” It consists of patients saying regular phrases or sentences in a set melodic tune. It is recommended for people expressive aphasia with intact comprehension. This approach is however of limited benefit.
Tele-rehabilitation: Established therapy is provided over the Internet with cameras the therapist and patient can see and hear each other, being developed by William Connors in Pittsburgh.
Specific Communication-based methods
PACE therapy (Promoting Aphasics’ Communicative Effectiveness): This procedure is a slight variation of the basic picture-naming drill, with the introduction of basic conversation into the exercise. These adjustments involve the patient and the therapist taking turns conveying messages or pictures hidden from the listener, with no limitations on how to convey those messages. Developed by Jeanne Wilcox and Albyn Davis in Memphis, mostly adopted in European practice.
Conversational coaching: Developed by Audrey Holland in Arizona, this strategy uses practiced conversations to help aid real life interactions. With assistance from Leora Cherney in Chicago, this method has been integrated into a computer program. Called “AphasiaScripts,” it includes a virtual therapist to provide help for the person with aphasia.
Supported conversation: Developed by Aura Kagan in Toronto, Canada, supported conversation is a methoed employing support groups to build patient confidence through practicing everyday encounters. Volunteers engage in real conversations with patients. Similar therapies include “conversation therapy”.
See also
References
- ↑ "Aphasia".
- ↑ "Aphasia".
- ↑ TY - BOOK AU - Code, Chris PY - 2008/10/10 SP - T1 - A Short History of the Past and Future of Aphasia Therapy DO - 10.13140/2.1.3036.3840 ER -
- ↑ Hébert, S. & Racette, A., Gagnon, L. & Peretz, I. (2003). Revisiting the dissociation between speaking and singing in aphasia. Brain, 126, 1838-1850. http://brain.oxfordjournals.org/cgi/reprint/126/8/1838
- ↑ Kolb & Whishaw: Fundamentals of Human Neuropsychology (2003), pages 503-504. The whole paragraph on Luria's theory is written with help of this reference.
- ↑ "Aphasia".
- ↑ "The neurophysiology of language: Insights from non-invasive brain stimulation in the healthy human brain". Brain and Language.