Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write.
Aphasia disorders usually develop quickly as a result of head injury or stroke, but can develop slowly from a brain tumor, infection, or dementia, or can be a learning disability such as dysnomia.
The area and extent of brain damage determine the type of aphasia and its symptoms. Aphasia types include Broca's aphasia, non-fluent aphasia, motor aphasia, expressive aphasia, receptive aphasia, global aphasia and many others (see Category:Aphasias).
Medical evaluations for the disorder range from clinical screenings by a neurologist to extensive tests by a language pathologist.
Most aphasia patients can recover some or most skills by working with a speech and language therapist. 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. Patients with a learning-disorder aphasia such as dysnomia can learn coping skills, but cannot recover abilities that are congenitally limited.
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.
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 don't exist. The neural organization of language is complicated; language is a comprehensive and complex behavior and it makes sense that it isn't 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.
People with aphasia may experience any of the following behaviors due to an acquired brain injury, although some of these symptoms may be due to related or concomitant problems such as dysarthria or apraxia and not primarily due to aphasia.
- inability to comprehend language
- inability to pronounce, not due to muscle paralysis or weakness
- inability to speak spontaneously
- inability to form words
- inability to name objects
- poor enunciation
- excessive creation and use of personal neologisms
- inability to repeat a phrase
- persistent repetition of phrases
- paraphasia (substituting letters, syllables or words)
- agrammatism (inability to speak in a grammatically correct fashion)
- dysprosody (alterations in inflexion, stress, and rhythm)
- uncompleted sentences
- inability to read
- inability to write
- limited verbal output
- difficulty in naming
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. Aphasia is also listed as a rare side effect of the fentanyl patch, an opioid used to control chronic pain.
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.
A multi-disciplinary team, including the doctor, psychologist, 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.
Treatment techniques mostly fall under two approaches:
- Substitute Skill Model - an approach that uses an aid to help with spoken language, i.e. a writing board
- Direct Treatment Model - an approach which targets deficits with specific exercises
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.
- Other - i.e. drawing as a way of communicating, trained conversation partners.
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. 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.
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". The most prominent writers on this topic have been Harold Goodglass and Edith Kaplan.
* Individuals with Broca's aphasia (also termed expressive aphasia) were once thought to have ventral temporal damage, though more recent work by Dr. Nina Dronkers using imaging and 'lesion analysis' has revealed that patients with Broca's 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. Individuals with Broca's aphasia often have right-sided weakness or paralysis of the arm and leg, because the frontal lobe is also important for body movement. Video clips showing patients with Broca-type aphasia can be found here.
* In contrast to Broca's aphasia, damage to the temporal lobe may result in a fluent aphasia that is called Wernicke's aphasia (also termed sensory aphasia). These individuals usually have no body weakness, because their brain injury is not near the parts of the brain that control movement. A video clip with a patient exhibiting Wernicke's aphasia can be found here
* 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. Pure word deafness
2. Conduction aphasia
3. Apraxia of speech (now considered a separate disorder in itself)
4. Transcortical motor aphasia
5. Transcortical sensory aphasia
* Anomia is another type of aphasia proposed under what is commonly known as the Boston-Neoclassical model, which is essentially a difficulty with naming. A final type of aphasia, 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.
The different types of aphasia can be divided into three categories: fluent, non-fluent and "pure" aphasias.
* Fluent aphasias, also called receptive 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: Wernicke's aphasia, Transcortical sensory aphasia, Conduction aphasia, Anomic aphasia
* Nonfluent aphasias, also called expressive aphasias are difficulties in articulating, but in most cases there is relatively good auditory verbal comprehension. Examples of nonfluent aphasias are: Broca's aphasia, Transcortical motor aphasia, Global aphasia
* "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, Pure word deafness