In aphasia, a person may be unable to comprehend or unable to formulate language because of damage to specific brain regions. The major causes are stroke and head trauma; prevalence is hard to determine but aphasia due to stroke is estimated to be 0.1–0.4% in the Global North. Aphasia can also be the result of brain tumors, epilepsy, brain damage and brain infections, or neurodegenerative diseases.
Wernicke's aphasia, also known as receptive aphasia, sensory aphasia or posterior aphasia, is a type of aphasia in which individuals have difficulty understanding written and spoken language. Patients with Wernicke's aphasia demonstrate fluent speech, which is characterized by typical speech rate, intact syntactic abilities and effortless speech output. Writing often reflects speech in that it tends to lack content or meaning. In most cases, motor deficits do not occur in individuals with Wernicke's aphasia. Therefore, they may produce a large amount of speech without much meaning. Individuals with Wernicke's aphasia are typically unaware of their errors in speech and do not realize their speech may lack meaning. They typically remain unaware of even their most profound language deficits.
A communication disorder is any disorder that affects an individual's ability to comprehend, detect, or apply language and speech to engage in dialogue effectively with others. The delays and disorders can range from simple sound substitution to the inability to understand or use one's native language.
Aphasiology is the study of language impairment usually resulting from brain damage, due to neurovascular accident—hemorrhage, stroke—or associated with a variety of neurodegenerative diseases, including different types of dementia. These specific language deficits, termed aphasias, may be defined as impairments of language production or comprehension that cannot be attributed to trivial causes such as deafness or oral paralysis. A number of aphasias have been described, but two are best known: expressive aphasia and receptive aphasia.
Anomic aphasia is a mild, fluent type of aphasia where individuals have word retrieval failures and cannot express the words they want to say. By contrast, anomia is a deficit of expressive language, and a symptom of all forms of aphasia, but patients whose primary deficit is word retrieval are diagnosed with anomic aphasia. Individuals with aphasia who display anomia can often describe an object in detail and maybe even use hand gestures to demonstrate how the object is used, but cannot find the appropriate word to name the object. Patients with anomic aphasia have relatively preserved speech fluency, repetition, comprehension, and grammatical speech.
Neuropsychological tests are specifically designed tasks that are used to measure a psychological function known to be linked to a particular brain structure or pathway. Tests are used for research into brain function and in a clinical setting for the diagnosis of deficits. They usually involve the systematic administration of clearly defined procedures in a formal environment. Neuropsychological tests are typically administered to a single person working with an examiner in a quiet office environment, free from distractions. As such, it can be argued that neuropsychological tests at times offer an estimate of a person's peak level of cognitive performance. Neuropsychological tests are a core component of the process of conducting neuropsychological assessment, along with personal, interpersonal and contextual factors.
Wernicke's area, also called Wernicke's speech area, is one of the two parts of the cerebral cortex that are linked to speech, the other being Broca's area. It is involved in the comprehension of written and spoken language, in contrast to Broca's area, which is primarily involved in the production of language. It is traditionally thought to reside in Brodmann area 22, which is located in the superior temporal gyrus in the dominant cerebral hemisphere, which is the left hemisphere in about 95% of right-handed individuals and 70% of left-handed individuals.
Conduction aphasia, also called associative aphasia, is an uncommon form of difficulty in speaking (aphasia). It is caused by damage to the parietal lobe of the brain. An acquired language disorder, it is characterised by intact auditory comprehension, coherent speech production, but poor speech repetition. Affected people are fully capable of understanding what they are hearing, but fail to encode phonological information for production. This deficit is load-sensitive as the person shows significant difficulty repeating phrases, particularly as the phrases increase in length and complexity and as they stumble over words they are attempting to pronounce. People have frequent errors during spontaneous speech, such as substituting or transposing sounds. They are also aware of their errors and will show significant difficulty correcting them.
Global aphasia is a severe form of nonfluent aphasia, caused by damage to the left side of the brain, that affects receptive and expressive language skills as well as auditory and visual comprehension. Acquired impairments of communicative abilities are present across all language modalities, impacting language production, comprehension, and repetition. Patients with global aphasia may be able to verbalize a few short utterances and use non-word neologisms, but their overall production ability is limited. Their ability to repeat words, utterances, or phrases is also affected. Due to the preservation of the right hemisphere, an individual with global aphasia may still be able to express themselves through facial expressions, gestures, and intonation. This type of aphasia often results from a large lesion of the left perisylvian cortex. The lesion is caused by an occlusion of the left middle cerebral artery and is associated with damage to Broca's area, Wernicke's area, and insular regions which are associated with aspects of language.
Transcortical sensory aphasia (TSA) is a kind of aphasia that involves damage to specific areas of the temporal lobe of the brain, resulting in symptoms such as poor auditory comprehension, relatively intact repetition, and fluent speech with semantic paraphasias present. TSA is a fluent aphasia similar to Wernicke's aphasia, with the exception of a strong ability to repeat words and phrases. The person may repeat questions rather than answer them ("echolalia").
Transcortical motor aphasia (TMoA), also known as commissural dysphasia or white matter dysphasia, results from damage in the anterior superior frontal lobe of the language-dominant hemisphere. This damage is typically due to cerebrovascular accident (CVA). TMoA is generally characterized by reduced speech output, which is a result of dysfunction of the affected region of the brain. The left hemisphere is usually responsible for performing language functions, although left-handed individuals have been shown to perform language functions using either their left or right hemisphere depending on the individual. The anterior frontal lobes of the language-dominant hemisphere are essential for initiating and maintaining speech. Because of this, individuals with TMoA often present with difficulty in speech maintenance and initiation.
Mixed transcortical aphasia is the least common of the three transcortical aphasias. This type of aphasia can also be referred to as "Isolation Aphasia". This type of aphasia is a result of damage that isolates the language areas from other brain regions. Broca's, Wernicke's, and the arcuate fasiculus are left intact; however, they are isolated from other brain regions.
Primary progressive aphasia (PPA) is a type of neurological syndrome in which language capabilities slowly and progressively become impaired. As with other types of aphasia, the symptoms that accompany PPA depend on what parts of the left hemisphere are significantly damaged. However, unlike most other aphasias, PPA results from continuous deterioration in brain tissue, which leads to early symptoms being far less detrimental than later symptoms. Those with PPA slowly lose the ability to speak, write, read, and generally comprehend language. Eventually, almost every patient becomes mute and completely loses the ability to understand both written and spoken language. Although it was first described as solely impairment of language capabilities while other mental functions remain intact, it is now recognized that many, if not most of those with PPA experience impairment of memory, short-term memory formation and loss of executive functions. It was first described as a distinct syndrome by M. Marsel Mesulam in 1982. Primary progressive aphasias have a clinical and pathological overlap with the frontotemporal lobar degeneration (FTLD) spectrum of disorders and Alzheimer's disease. However, PPA is not considered synonymous to Alzheimer's disease due to the fact that, unlike those affected by Alzheimer's disease, those with PPA are generally able to maintain the ability to care for themselves, remain employed, and pursue interests and hobbies. Moreover, in diseases such as Alzheimer's disease, Pick's disease, and Creutzfeldt-Jakob disease, progressive deterioration of comprehension and production of language is just one of the many possible types of mental deterioration, such as the progressive decline of memory, motor skills, reasoning, awareness, and visuospatial skills.
Auditory verbal agnosia (AVA), also known as pure word deafness, is the inability to comprehend speech. Individuals with this disorder lose the ability to understand language, repeat words, and write from dictation. Some patients with AVA describe hearing spoken language as meaningless noise, often as though the person speaking was doing so in a foreign language. However, spontaneous speaking, reading, and writing are preserved. The maintenance of the ability to process non-speech auditory information, including music, also remains relatively more intact than spoken language comprehension. Individuals who exhibit pure word deafness are also still able to recognize non-verbal sounds. The ability to interpret language via lip reading, hand gestures, and context clues is preserved as well. Sometimes, this agnosia is preceded by cortical deafness; however, this is not always the case. Researchers have documented that in most patients exhibiting auditory verbal agnosia, the discrimination of consonants is more difficult than that of vowels, but as with most neurological disorders, there is variation among patients.
Western Aphasia Battery (WAB) is an instrument for assessing the language function of adults with suspected neurological disorders as a result of a stroke, head injury, or dementia. There is an updated version, the Western Aphasia Battery-Revised (WAB-R). It helps discern the presence, degree, and type of aphasia. It also measures how the patient performed on the test to provide a baseline so they can detect changes throughout their time in therapy. This also allows to see the patient's language strengths and weaknesses so that they can figure out what to treat, and lastly, it can infer the location of the lesion that caused aphasia. Another such test is the Boston Diagnostic Aphasia Examination. The WAB targets English speaking adults and teens with a neurological disorder between the ages of 18 and 89 years old. The WAB tests both linguistic and non linguistic skills. The linguistic skills assessed include, speech, fluency, auditory comprehension, reading and writing. The non-linguistic skills tested include drawing, calculation, block design and apraxia.
Paraphasia is a type of language output error commonly associated with aphasia, and characterized by the production of unintended syllables, words, or phrases during the effort to speak. Paraphasic errors are most common in patients with fluent forms of aphasia, and come in three forms: phonemic or literal, neologistic, and verbal. Paraphasias can affect metrical information, segmental information, number of syllables, or both. Some paraphasias preserve the meter without segmentation, and some do the opposite. However, most paraphasias affect both partially.
The comprehensive aphasia test (CAT) was created by Kate Swinburn, Gillian Porter and David Howard. The CAT is a new test for people who have acquired aphasia, the impairment of language ability. The comprehensive assessment can be completed over one or two sessions. The test contains a cognitive screening, a language battery and a disability questionnaire. The authors of the comprehensive aphasia test take account of current linguistic and psychological theory and other variable that impact aphasic performance. The CAT was published in 2005 and was the first new aphasia test in English for 20 years. The test is designed to (1) screen for associated cognitive deficits,(2) assess language impairment in people with aphasia, (3) investigate the consequences of the aphasia on the individual's lifestyle and emotional well-being, and (4) monitor changes in the aphasia and its consequences over time.
The Boston Naming Test (BNT), introduced in 1983 by Edith Kaplan, Harold Goodglass and Sandra Weintraub, is a widely used neuropsychological assessment tool to measure confrontational word retrieval in individuals with aphasia or other language disturbance caused by stroke, Alzheimer's disease, or other dementing disorder. A common and debilitating feature is anomic aphasia, an impairment in the ability to name objects. The BNT contains 60 line drawings graded in difficulty. Patients with anomia often have greater difficulties with the naming of not only difficult and low frequency objects but also easy and high frequency objects. Naming difficulties may be rank ordered along a continuum. Items are rank ordered in terms of their ability to be named, which is correlated with their frequency. This type of picture-naming test is also useful in the examination of children with learning disabilities and the evaluation of brain-injured adults.
The Delis–Kaplan Executive Function System (D-KEFS) is a neuropsychological test used to measure a variety of verbal and nonverbal executive functions for both children and adults. This assessment was developed over the span of a decade by Dean Delis, Edith Kaplan, and Joel Kramer, and it was published in 2001. The D-KEFS comprises nine tests that were designed to stand alone. Therefore, there are no aggregate measures or composite scores for an examinee's performance. A vast majority of these tests are modified, pre-existing measures ; however, some of these measures are new indices of executive functions.
Language and Language Disturbances: Aphasic Symptom Complexes and Their Significance for Medicine and Theory of Language is a book on aphasia by Dr. Kurt Goldstein, published in 1948. In Language and Language Disturbances, Goldstein theorized that a loss of abstract processing was the core deficit in aphasia.
