APHASIA

Aphasia (/əˈfeɪʒə/, /əˈfeɪziə/ or /eɪˈfeɪziə/; from ancient Greek: 'aphatos' meaning[1] ἀφασία (ἄφατος, ἀ- + φημί), "speechlessness"[2]) is a disturbance of the comprehension and formulation of language caused by dysfunction in specific brain regions.[3] This class of language disorder ranges from having difficulty remembering words to losing the ability to speak, read, or write. This also affects visual language such as sign language.[4] Aphasia is usually linked to brain damage, most commonly by stroke. Brain damage linked to aphasia can also cause further brain diseases such as cancer, epilepsy and Alzheimer's disease.[5]

Acute aphasia disorders usually develop quickly as a result of head injury or stroke, and progressive forms of aphasia develop slowly from a brain tumor, infection, or dementia.[6][7] The area and extent of brain damage or atrophy will determine the type of aphasia and its symptoms. Aphasia types include expressive aphasia, receptive aphasia, conduction aphasia, anomic aphasia, global aphasia, primary progressive aphasias and many others (see Category:Aphasias). Medical evaluations for the disorder range from clinical screenings by a neurologist to extensive tests by a Speech-Language Pathologist.[6][8]

Most acute aphasia patients can recover some or most skills by working with a Speech-Language Pathologist. This rehabilitation can take two or more years and is most effective when begun quickly. Only a small minority will recover without therapy, such as those suffering a mini-stroke. Improvement varies widely, depending on the aphasia's cause, type, and severity. Recovery also depends on the patient's age, health, motivation, handedness, and educational level.[6]

Classification [edit]

Classifying the different subtypes of aphasia is difficult and has led to disagreements among experts. The localizationist model is the original model, but modern anatomical techniques and analyses have shown that precise connections between brain regions and symptom classification do not exist. The neural organization of language is complicated; language is a comprehensive and complex behavior and it makes sense that it is not the product of some small, circumscribed region of the brain.

No classification of patients in subtypes and groups of subtypes is adequate. 

Only about 60% of patients will fit in a classification scheme such as fluent/nonfluent/pure aphasias. There is a huge variation among patients with the same diagnosis, and aphasias can be highly selective. For instance, patients with naming deficits (anomic aphasia) might show an inability only for naming buildings, or people, or colors.[9]

Localizationist model [edit]

Cortex

The localizationist model attempts to classify the aphasia by major characteristics and then link these to areas of the brain in which the damage has been caused. The initial two categories here were devised by early neurologists working in the field, namely Paul Broca and Carl Wernicke. Other researchers have added to the model, resulting in it often being referred to as the "Boston-Neoclassical Model".

• Individuals with expressive aphasia (also called Broca's aphasia) were once thought to have frontal lobe damage, though more recent work by Dr. Nina Dronkers using imaging and 'lesion analysis' has revealed that patients with Expressive aphasia have lesions to the medial insular cortex. Broca missed these lesions because his studies did not dissect the brains of diseased patients, so only the more temporal damage was visible. Dronkers and Dr. Odile Plaisant scanned Broca's original patients' brains using a non-invasive MRI scanner to take a closer look.[10] Damage to a region of the motor association cortex in the left frontal lobe (Broca's area) disrupts the ability to speak.[11] Individuals with Expressive aphasia often have right-sided weakness or paralysis of the arm and leg, because the frontal lobe is also important for body movement.
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• In contrast to Expressive aphasia, damage to the temporal lobe may result in a fluent aphasia that is called receptive aphasia (also known as Sensory aphasia and Wernicke's aphasia). Patients suffering from receptive aphasia, unlike Broca's aphasia patients, produce speech without any grammatical problem. However, because the Wernicke's area which is responsible for language comprehension is damaged, receptive aphasia patients cannot convey the meaning. These individuals usually have no body weakness, because their brain injury is not near the parts of the brain that control movement.
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• Working from Wernicke's model of aphasia, Ludwig Lichtheim proposed five other types of aphasia, but these were not tested against real patients until modern imaging made more in-depth studies available. The other five types of aphasia in the localizationist model are:

1. Auditory verbal agnosia (also known as Pure Word Deafness)
2. Conduction aphasia
3. Apraxia of speech (now considered a separate disorder in itself)
4. Transcortical motor aphasia (also known as Adynamic aphasia and Extrasylvian motor aphasia)
5. Transcortical sensory aphasia

• Anomic aphasia, also known as anomia or dysnomia, is another type of aphasia proposed under what is commonly known as the Boston-Neoclassical model, which is essentially a difficulty with naming.

• Global aphasia, results from damage to extensive portions of the perisylvian region of the brain. An individual with global aphasia will have difficulty understanding both spoken and written language and will also have difficulty speaking. This is a severe type of aphasia which makes it quite difficult when communicating with the individual.[12]

• Isolation aphasia, also known as mixed transcortical aphasia, is a type of disturbance in language skill that causes the inability to comprehend what is being said to you or the difficulty in creating speech with meaning without affecting the ability to recite what has been said and to acquire newly presented words. This type of aphasia is caused by brain damage that isolates the parts of the brain from other parts of the brain that are in charge of speech.[13] The brain damages are caused to left temporal/parietal cortex that spares the Wernicke's area. Isolation aphasia patients can repeat what other people say, thus they do recognize words but they can't comprehend the meaning of what they hear and repeat themselves. However, they can not produce meaningful speech of their own.[14]

Progressive aphasias [edit]

Primary progressive aphasia (PPA) is associated with progressive illnesses or dementia, such as frontotemporal dementia / Pick Complex Motor neuron disease, Progressive supranuclear palsy, and Alzheimer's disease; which is the gradual process of losing the ability to think. It is characterized by the gradual loss of the ability to name objects. People suffering from PPA may have difficulties comprehending what others are saying. They can also have difficulty trying to find the right words to make a sentence.[15][16][17] There are three classifications of Primary Progressive Aphasia : Progressive nonfluent aphasia (PNFA), Semantic Dementia (SD), and Logopenic progressive aphasia (LPA)[18]

Progressive Jargon Aphasia is a fluent or receptive aphasia in which the patient's speech is incomprehensible, but appears to make sense to them. Speech is fluent and effortless with intact syntax and grammar, but the patient has problems with the selection of nouns. They will either replace the desired word with another that sounds or looks like the original one, or has some other connection, or they will replace it with sounds. Accordingly, patients with jargon aphasia often use neologisms, and may perseverate if they try to replace the words they can't find with sounds. Commonly, substitutions involve picking another (actual) word starting with the same sound (e.g. clocktower - colander), picking another semantically related to the first (e.g. letter - scroll), or picking one phonetically similar to the intended one (e.g. lane - late).

Fluent, non-fluent and "pure" aphasias [edit]

The different types of aphasia can be divided into three categories: fluent, non-fluent and "pure" aphasias.[19]

• Receptive aphasias, also called Fluent aphasias, are impairments related mostly to the input or reception of language, with difficulties either in auditory verbal comprehension or in the repetition of words, phrases, or sentences spoken by others. Speech is easy and fluent, but there are difficulties related to the output of language as well, such as paraphasia. Examples of fluent aphasias are: Receptive aphasia, Transcortical sensory aphasia, Conduction aphasia, Anomic aphasia[19]

• Expressive aphasias, also called Nonfluent aphasias, are difficulties in articulating, but in most cases there is relatively good auditory verbal comprehension. Examples of nonfluent aphasias are: Expressive aphasia, Transcortical motor aphasia, Global aphasia[19]

• "Pure" aphasias are selective impairments in reading, writing, or the recognition of words. These disorders may be quite selective. For example, a person is able to read but not write, or is able to write but not read. Examples of pure aphasias are: Pure alexia, Agraphia, Auditory verbal agnosia[19]

Primary and secondary cognitive processes [edit]

Aphasias can be divided into primary and secondary cognitive processes.

• Primary aphasia is due to problems with cognitive language-processing mechanisms, which can include: Transcortical sensory aphasia, Semantic Dementia, Apraxia of speech, Progressive nonfluent aphasia, and Expressive aphasia
• Secondary aphasia is the result of other problems, like memory impairments, attention disorders, or perceptual problems, which can include: Transcortical motor aphasia, Dynamic aphasia, Anomic aphasia, Receptive aphasia, Progressive jargon aphasia, Conduction aphasia, and Dysarthria.[20]

Cognitive neuropsychological model [edit]

The cognitive neuropsychological model builds on cognitive neuropsychology. It assumes that language processing can be broken down into a number of modules, each of which has a specific function.[21] Hence there is a module which recognises phonemes as they are spoken and a module which stores formulated phonemes before they are spoken. Use of this model clinically involves conducting a battery of assessments (usually from the PALPA, the "psycholinguistic assessment of language processing in adult acquired aphasia ... that can be tailored to the investigation of an individual patient's impaired and intact abilities" [22]), each of which tests one or a number of these modules. Once a diagnosis is reached as to where the impairment lies, therapy can proceed to treat the individual module.

Causes [edit]

Aphasia usually results from lesions to the language-relevant areas of the frontal, temporal and parietal lobes of the brain, such as Broca's area, Wernicke's area, and the neural pathways between them. These areas are almost always located in the left hemisphere, and in most people this is where the ability to produce and comprehend language is found. However, in a very small number of people, language ability is found in the right hemisphere. In either case, damage to these language areas can be caused by a stroke, traumatic brain injury, or other brain injury.

Aphasia may also develop slowly, as in the case of a brain tumor or progressive neurological disease, e.g., Alzheimer's or Parkinson's disease. It may also be caused by a sudden hemorrhagic event within the brain. Certain chronic neurological disorders, such as epilepsy or migraine, can also include transient aphasia as a prodromal or episodic symptom.[24]

Aphasia can result from herpesviral encephalitis. The herpes simplex virus affects the frontal and temporal lobes, subcortical structures and the hippocampal tissue which can trigger aphasia.[25]

Aphasia is also listed as a rare side effect of the fentanyl patch, an opioid used to control chronic pain.[26] Adverse side effects including chronic aphasia can be caused by cortico-steroids.^[citation needed^]

Management [edit]

There is no one treatment proven to be effective for all types of aphasias. 

The reason that there is no universal treatment for aphasia is because of the nature of the disorder and the various ways it is presented, as explained in the above sections. 

Aphasia is rarely exhibited identically, implying that treatment needs to be catered specifically to the individual. Studies have shown that although there isn't consistency on treatment methodology in literature, there is a strong indication that treatment in general has positive outcomes.[27]

A multi-disciplinary team, including doctors (often a physician is involved, but more likely a clinical neuropsychologist will head the treatment team), physiotherapist, occupational therapist, speech-language pathologist, and social worker, works together in treating aphasia. For the most part, treatment relies heavily on repetition and aims to address language performance by working on task-specific skills. The primary goal is to help the individual and those closest to them adjust to changes and limitations in communication.[27]

Treatment techniques mostly fall under two approaches:

1. Substitute Skill Model - an approach that uses an aid to help with spoken language, i.e. a writing board
2. Direct Treatment Model - an approach which targets deficits with specific exercises[27]

Several treatment techniques include the following:

• Visual Communication Therapy (VIC) - the use of index cards with symbols to represent various components of speech
• Visual Action Therapy (VAT) - involves training individuals to assign specific gestures for certain objects
• Functional Communication Treatment (FCT) - focuses on improving activities specific to functional tasks, social interaction, and self-expression
• Promoting Aphasic's Communicative Effectiveness (PACE) - a means of encouraging normal interaction between patients and clinicians. In this kind of therapy the focus is on pragmatic communication rather than treatment itself. Patients are asked to communicate a given message to their therapists by means of drawing, making hand gestures or even pointing to an object.[28]
• Other - i.e. drawing as a way of communicating, trained conversation partners[27]

More recently, computer technology has been incorporated into treatment options. A key indication for good prognosis is treatment intensity. A minimum of 2–3 hours per week has been specified to produce positive results.[29] The main advantage of using computers is that it can greatly increase intensity of therapy. These programs consist of a large variety of exercises and can be done at home in addition to face-to-face treatment with a therapist. However, since aphasia presents differently among individuals, these programs must be dynamic and flexible in order to adapt to the variability in impairments. Another barrier is the capability of computer programs to imitate normal speech and keep up with the speed of regular conversation. Therefore, computer technology seems to be limited in a communicative setting, however is effective in producing improvements in communication training.[29]

Several examples of programs used are StepByStep, Linguagraphica, Computer-Based Visual Communication (C-VIC), TouchSpeak (TS), and Sentence Shaper.[29]

Melodic intonation therapy is often used to treat non-fluent aphasia and has proved to be very effective in some cases.[30]

Zolpidem, a drug with the trade name of Ambien, may provide short-lasting but effective improvement in symptoms of aphasia present in some survivors of stroke. The mechanism for improvement in these cases remains unexplained and is the focus of current research by several groups, to explain how a drug which acts as a hypnotic-sedative in people with normal brain function, can paradoxically increase speech ability in people recovering from severe brain injury. Use of zolpidem for this application remains experimental at this time, and is not officially approved by any pharmaceutical manufacturers of zolpidem or medical regulatory agencies worldwide.