| Anomic aphasia | |
|---|---|
| Classification and external resources | |
Diffusion tensor imaging image of the brain showing the right and left arcuate fasciculus (Raf & Laf). Also shown are the right and left superior longitudinal fasciculus (Rslf & Lslf), and tapetum of corpus callosum (Ta). Damage to the Laf is known to cause anomic aphasia. |
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| ICD-9 | 784.69 |
| MeSH | D000849 |
Nominal aphasia (anomic aphasia, amnesic aphasia) is a severe problem with recalling words or names.
Dysnomia refers to a less severe form of this word-recall dysfunction. Learning disabilities caused by name-recall problems are usually diagnosed as dysnomia rather than anomia.
Contents |
Anomic aphasia (anomia) is a type of aphasia characterized by problems recalling words or names. Subjects often use circumlocutions (speaking in a roundabout way) in order to express a certain word for which they cannot remember the name. Sometimes the subject can recall the name when given clues. In addition, patients are able to speak with correct grammar; the main problem is finding the appropriate word to identify an object or person.
Sometimes subjects may know what to do with an object, but still not be able to give a name to the object. For example, if a subject is shown an orange and asked what it is called, the subject may be well aware that the object can be peeled and eaten, and may even be able to demonstrate this by actions or even verbal responses - however, they can not recall that the object is called an "orange."
Averbia is a specific type of anomic aphasia in which the person has trouble remembering only verbs. This is caused by damage to the frontal cortex, in or near Broca's area. Although people suffering from averbia cannot recall or produce action words, they also have problems naming objects as well.[1]
Alexia is another form of anomic aphasia when the person has trouble reading in their head, reading aloud, and reading comprehension.[2] Lesions in alexia patients are in the left posterior inferior temporal area.[2]
Another type of anomia is color anomia, where the patient can distinguish between colors but cannot identify them by name or name the color of an object.[3] They can separate colors into categories, but they cannot name them.
Anomia is caused by damage to various parts of the parietal lobe or the temporal lobe of the brain. These damages can be brain trauma, such as an accident, stroke, or tumor. This type of phenomenon can be quite complex, and usually involves a breakdown in one or more pathways between various regions in the brain.
Although the main causes are not specifically known, many researchers have found contributing factors to anomic aphasia. It is known that people with damage to the left hemisphere of the brain are more likely to have anomic aphasia. Broca’s area, the speech production center in the brain, was linked to being the source for speech execution problems, and with the use of functional magnetic resonance imaging (fMRI), Broca’s area was connected with speech repetition problems, which is commonly used to study anomic patients.[4] Other experts believe that damage to Wernicke's area, which is the speech comprehension area of the brain, is connected to anomia because the patients cannot comprehend the words that they are hearing.[5]
Although many experts have believed that damage to Broca’s area or Wernicke's area are the main causes of anomia, current studies have shown that damage in the left parietal lobe is the epicenter of anomic aphasia.[6] One study was conducted using a word repetition test as well as magnetic resonance imaging (MRI) in order to see the highest level of activity as well as where the lesions are in the brain tissue.[6] Fridrikkson, et al. saw that damage to neither Broca’s area nor Wernicke's area were the sole sources of anomia in the subjects. Therefore, the original model, which showed that damage occurred on the surface of the brain on the grey matter for anomia, was debunked and it was found that the damage was done in the white matter deeper in the brain on the left hemisphere.[6] More specifically, the damage was done to a part of the nerve tract called the arcuate fasciculus, which the mechanism of action is unknown but it is shown to connect the posterior (back) of the brain to the anterior (front) and vice versa.[7]
New data has shown that although the arcuate fasciculus’s main function does not include connecting Wernicke's area and Broca’s area, damage to the tract does create speech problems because the speech comprehension and speech production areas are connected by this tract.[6] Some studies have found that in right-handed people the language center is 99% in the left hemisphere; therefore, anomic aphasia almost exclusively occurs with damage to the left hemisphere. However, in left-handed people the language center is about 60% in the left hemisphere; thus, anomic aphasia can occur with damage to the right hemisphere in left-handed people.[8] Therefore, the specific cause of anomia is unknown; however, research is bringing the answer into focus.
The best way to see if anomic aphasia has developed is by using verbal as well as imaging tests. The combination of the two tests seem to be most effective. Either test done alone will give false positives or false negatives. For example, the verbal test is used to see if there is a speech disorder and whether it is a problem in speech production or comprehension. However, patients with Alzheimer’s disease have speech problems that are linked to dementia rather than anomia.[8] The imaging test, mostly MRI, is ideal for lesion mapping or viewing deterioration in the brain. However, imaging cannot diagnose anomia on its own because the lesions may not be located deep enough to damage the white matter or damaging the arcuate fasciculus. However, anomic aphasia is the most difficult to associate with a specific lesion location in the brain.[9] Therefore the combination of speech tests and imaging tests has the highest sensitivity and specificity.[10]
However, it is also important to do a hearing test in case that the patient cannot hear the words or sentences needed in the speech repetition test.[11] In the speech tests, the person is asked to repeat a sentence with common words and if the person cannot identify the word but he or she can describe it then the person is highly likely to have anomic aphasia. However, to be completely sure, the test is given as a person is in an MRI and the exact location of the lesions and areas activated by speech are pinpointed.[6] Although no simpler or cheaper option is available as of now, lesion mapping and speech repetition tests are the main ways of diagnosing anomic aphasia.
Unfortunately, there is no method available to completely cure the anomic aphasia. However, there are treatments that help improve word-finding skills. Although a person with anomia may find it difficult to recall many types of words such as common nouns, proper nouns, verbs, etc., many studies have shown that treatment for object words, or nouns, have shown promise in rehabilitation research.[11] The treatment includes visual aid, such as pictures, and the patient is asked to identify the object or activity. However, if that is not possible, then the patient is shown the same picture surrounded by words associated with the object or activity.[12] Throughout the process positive encouragement is provided. The treatment shows an increase in word-finding during treatment; however, word identifying decreased two weeks after the rehabilitation period.[11] Therefore, it shows that rehabilitation needs to be continuous for word-finding abilities to improve from the baseline. The studies show that verbs are harder to recall or repeat even with rehabilitation.[11]
This disorder may be extremely frustrating for people with and without the disorder. Although the person with anomic aphasia may know the specific word, they may not be able to recall it and this can be very difficult for everyone in the conversation. However, it is important to be patient and work with the person so that he or she gains confidence with his or her speech. Positive reinforcements are helpful.[11]
Although there are not many literary cases about anomic aphasia, there are many books out there about life with aphasia. One of the most notable books on aphasia is The Man Who Lost His Language by Sheila Hale. It is the story of Sheila Hale’s husband, John Hale, who was a very prestigious scholar who suffered a stroke and lost speech formation abilities. Sheila Hale does a great job explaining the symptoms and mechanics behind aphasia and speech formation. She also adds in the emotional components of dealing with a person with aphasia and how to be patient with the speech and communication.
There are many institutes and universities that are working to gain a better understanding of anomic aphasia so that people suffering from anomia have more information on their disorder. One of the leading departments in the United States is the Department of Aphasia in the University of South Carolina. The lead researcher, Dr. Julius Fridrikkson, has done extensive research on aphasia and other communication disorders using neuroimaging <http://www.sph.sc.edu/comd/fridriks/index.htm>.