Understanding the Brain

Alexia (condition)

From Cognopedia
Jump to: navigation, search
Alexia (acquired dyslexia)
Classification and external resources
ICD-10 R48.0
ICD-9 315.01, 784.61
MeSH D004410

Alexia (from the Greek , privative, expressing negation, and λέξις = "word") is a type of aphasia[1] where damage to the brain causes a patient to lose the ability to read.[2] It is also called word blindness, text blindness or visual aphasia.[3]

Those who suffer from "alexia" and "dyslexia" can have similar difficulties, however, "alexia" refers to an acquired reading disability, where reading ability had previously been developed, usually occurring in adulthood conditions, while "dyslexia" refers to developmental reading disability.[4][5]

Classification

There are two groups of alexia.

Causes

Alexia typically occurs following damage to the dominant hemisphere of the brain which is usually the left. It can also occur with lesions to the occipital and/or parietal lobes, which are responsible for processing auditory, phonological and visual aspects of language. The region at the junction of occipital and temporal lobes (sometimes called the occipito-temporal junction) coordinates information that is gathered from visual and auditory processing and assigns meaning to the stimulus. Alexia can also occur following damage to the inferior frontal. Damage to these different areas of the cortex result in somewhat different patterns of difficulty in affected individuals. In some cases, a stroke can cause alexia.[2][8]

Presentation

Alexia may be accompanied by expressive and/or receptive aphasia (the inability to produce or comprehend spoken language). Alexia can also co-occur with agraphia, the specific loss of the ability to produce written language even when other manual motor abilities are intact. In other cases, damage is restricted to areas responsible for input processing. The result is known as pure alexia. In this scenario, an individual's ability to produce written language is spared even though they are unable to understand written text.

Alexia without agraphia results from a left occipital splenium of the corpus callosum lesion.

Treatment

One patient with damage to areas responsible for visual processing was able to regain the ability to read by using motor processing (tracing the shapes of letters).[9]

See also

References

  1. "alexia" at Dorland's Medical Dictionary
  2. 2.0 2.1 Damasio, Antonio R. (1977). "Varieties and Significance of the Alexias". Archieves of Neurology 34 (6): 325–326. http://archneur.ama-assn.org/cgi/content/summary/34/6/325?ijkey=61bffa67ae619306dd7a7934040c014df59fbf2c&keytype2=tf_ipsecsha. Retrieved 2010-07-08. 
  3. http://medical-dictionary.thefreedictionary.com/visual+aphasia American Heritage Medical Dictionary
  4. Elisabeth Ahlsén (2006). Introduction to neurolinguistics. John Benjamins Publishing Company. pp. 115–. ISBN 9789027232335. http://books.google.com/books?id=ziC_Dbl4KnIC&pg=PA115. Retrieved 28 June 2010. 
  5. Leff AP, Crewes H, Plant GT, Scott SK, Kennard C, Wise RJ (March 2001). "The functional anatomy of single-word reading in patients with hemianopic and pure alexia". Brain 124 (Pt 3): 510–21. doi:10.1093/brain/124.3.510 url=http://brain.oxfordjournals.org/cgi/content/full/124/3/510?ijkey=0605739debdd37816078356fcf41ef44d5a60b79. PMID 11222451. 
  6. Harley, Trevor A. (2001). The psychology of language: from data to theory. Taylor & Francis. ISBN 978-0863778674. 
  7. 7.0 7.1 Coslett HB (2000). "Acquired dyslexia". Semin Neurol 20 (4): 419–26. doi:10.1055/s-2000-13174. PMID 11149697. https://www.thieme-connect.de/DOI/DOI?10.1055/s-2000-13174. 
  8. Sacks, Oliver (June 28, 2010). "A Man of Letters". The New Yorker (New York, New York: Condé Nast Publications) 86 (18): 22–28. ISSN 0028792X. 
  9. "The Writer Who Couldn't Read". 2010-06-21. http://www.npr.org/templates/story/story.php?storyId=127745750. Retrieved 2010-07-21.