Wernicke's aphasia
Wernicke's aphasia is a language disorder primarily caused by damage to Wernicke's area in the brain, often due to stroke, head trauma, brain tumors, or infections. Individuals with this condition typically experience significant difficulties with auditory comprehension and word retrieval, resulting in fluent but nonsensical speech. They may produce long strings of words with frequent phonemic errors and semantic substitutions, while their ability to articulate speech remains intact. Unlike non-fluent aphasias, where speech production is hindered, those with Wernicke's aphasia can speak effortlessly but struggle to convey meaningful content.
Recovery from Wernicke's aphasia can occur, especially within the first six months post-injury, although improvements can be noted for up to two years. Treatment focuses on enhancing auditory comprehension through tailored tasks and may include pharmacological support alongside speech therapy. Despite its classification, the symptoms and severity of Wernicke's aphasia can vary widely among individuals, necessitating personalized rehabilitation strategies. A modern approach to understanding this disorder emphasizes the need to analyze the specific linguistic processes affected, allowing for more effective and customized therapeutic interventions.
Wernicke's aphasia
Disease/Disorder
Also known as: Sensory aphasia or fluent aphasia
Anatomy or system affected: Brain
Definition: An acquired language disorder that mostly causes difficulties in comprehension of oral language.
Key terms:
Brodmann areas: areas of the brain that are differentiated based on the cellular structure of the cerebral cortex
paragrammatism: confused or incomplete use of grammatical structures, as in case of substitution of function words and grammatical morphemes (e.g., "the man are singing" instead of "the man is singing")
paraphasia: a type of partial aphasia that is characterized by using words incorrectly
phonological/phonemic error: a phoneme substitution or omission in the target word (e.g., "boat" or "oat" instead of "goat"); also called phonological paraphasia
semantic error: the use of a word that resembles in meaning the target word (e.g., "cat" instead of "dog"); also called semantic paraphasia
Causes and Symptoms
Wernicke's aphasia is generally caused by a focal brain damage due to stroke, head trauma, brain tumor, or brain infection. People suffering from Wernicke's aphasia show a lesion in the middle-posterior tract of the first left temporal circonvolution, known as Wernicke's area or Brodmann area 22, and in the adjacent cortico-subcortical areas.
The classical definition of aphasic syndromes consists of various categorization systems. Some authors categorize according to the type of language errors. Others take into consideration language production and related impairments in spontaneous speech. However, in past decades a classification has been suggested on the basis of specific clusters of aphasic disorders. In particular, aphasia syndromes are differentiated in two groups: fluent and non-fluent. Wernicke's aphasia, anomic aphasia, transcortical sensory aphasia, and conduction aphasia are considered fluent aphasias, while Broca's aphasia, global aphasia, and transcortical motor aphasia are non-fluent aphasias. Fluent aphasias are characterized by difficulties in auditory comprehension or repetition and the presence of paraphasias, but speech is otherwise fluent, with no articulation disorders. Non-fluent aphasias are characterized by difficulties in articulation and spoken language with relatively preserved auditory comprehension.
In Wernicke's aphasia, auditory comprehension is impaired, generally both at the level of sentences and discourse and at the level of single words. Repetition is also compromised, as is naming that is affected by semantic and phonological omissions and substitutions, due to problems finding and retrieving words. Spontaneous speech is well articulated, connected, and effortlessly produced, but phonemic errors and semantically and non-semantically related substitutions are frequent.
Treatment and Therapy
People who become aphasic after a stroke or a traumatic brain injury generally undergo a variable degree of recuperation or spontaneous recovery in the period following injury. This effect is maximal in the first six months, although there is evidence that improvement can be observed up to two years post-onset. While all studies indicate that the initial severity, defined with global impairment measures, is the strongest predictor of recovery, the type of aphasic syndrome is not a good independent predictor. Many other factors influence spontaneous recovery, including etiology, handedness, age, multilingualism, hemispheric asymmetries, social support, and mood. The occurrence of spontaneous recovery suggests that neuroplasticity could be allowing the damaged brain to regain previously lost functionality.
Despite the importance of spontaneous recovery, treating language deficits is essential. When planning and setting the therapeutic goals for aphasia therapy, it is important to use diagnostic tools that provide an overview of an aphasic person's abilities and disabilities in both the language and associated cognitive domains in order to guarantee an impairment-specific training. Generally, in the case of Wernicke's aphasia, it is important to first treat auditory comprehension deficits through different tasks, such as matching photos or pictures with words and sentences. Concerning pharmacological treatments, in the subacute to chronic phases, drugs may provide useful adjuvant therapy, but only in the presence of specific language and speech therapies.
Perspective and Prospects
Even if a diagnostic label such as “Wernicke's aphasia” can be useful to communicate information among different clinicians, there are several limits to the classic approach: only roughly defined linguistic parameters and tasks are employed, an enormous variability is seen in the relative severity of each of the constituting symptoms in each syndrome, and many observed cases would not unambiguously fit one classic aphasia type. As a result, what is considered in one hospital to be one type of aphasia may be classified otherwise in another hospital.
A more modern approach to the study of language disorders has been influenced by theoretical linguistics, cognitive neuropsychology, and the interdisciplinary field of neurolinguistics. Each clinical condition should be described in terms of damage to representation and processes involved in a given task. The content and the format of concerned representations should be specified. Thus, the description of aphasic disorders would overcome the traditional classification of Wernicke's aphasia, global aphasia, and so on in order to take into consideration the different levels of grammar: the phonological, the morpho-syntactic, and the lexico-semantic. Moreover, for each of these levels, it is necessary to distinguish between production impairments and comprehension deficits. Only this description and analysis of deficits helps clinical neuropsychologists and speech therapists construct specific rehabilitation protocols for each patient. Impairment-specific training aims primarily at relearning degraded linguistic knowledge; reactivating impaired linguistic modalities, such as oral and written comprehension; and learning explicit compensatory linguistic strategies.
Bibliography
Berthier, Marcelo L. “Poststroke Aphasia: Epidemiology, Pathophysiology and Treatment.” Drugs & Aging 22.2 (2005): 163–82. Print.
Denes, Gianfranco, and Luigi Pizzamiglio, eds. Handbook of Clinical and Experimental Neuropsychology. Hove: Psychology, 1999. Print.
Hillis, Argye E., ed. The Handbook of Adult Language Disorders: Integrating Cognitive Neuropsychology, Neurology, and Rehabilitation. New York: Psychology, 2002. Print.
Papathanasiou, Ilias, Patrick Coppens, and Constantin Potagas, eds. Aphasia and Related Neurogenic Communication Disorders. Burlington: Jones, 2013. Print.
Whitworth, Anne, Janet Webster, and David Howard. A Cognitive Neuropsychological Approach to Assessment and Intervention in Aphasia: A Clinician's Guide. 2nd ed. New York: Psychology, 2014. Print.
Yule, George. The Study of Language. 5th ed. New York: Cambridge UP, 2014. Print.