Alexia (condition): Difference between revisions
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FelixRosch (talk | contribs) ICD-10 rewrite. Diagnosis absorbed into diagnostic category for Dyslexia. Redirect posted following ICD-10 integration to Dyslexia. |
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#REDIRECT [[Dyslexia]] |
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{{Medref|date=January 2015}} |
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{{Infobox disease | |
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Name = Alexia | |
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ICD10 = {{ICD10|R|48|0|r|47}} | |
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ICD9 = {{ICD9|315.01}}, {{ICD9|784.61}} | |
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ICDO = | Image = | Caption = |OMIM = |OMIM_mult = | MedlinePlus = | eMedicineSubj = | |
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eMedicineTopic = | DiseasesDB = | |
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MeshID = D004410 }} |
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'''Alexia''' ({{ety|gre|ἀ- (a-)|absence of, without||λέξις (lexis)|word}}) is a brain disorder in which a person is unable to understand written words. It refers specifically to the loss, usually in adulthood, of a previous ability to read.<ref name="Leff 2001">{{cite journal |author=Leff AP, Crewes H, Plant GT, Scott SK, Kennard C, Wise RJ |title=The functional anatomy of single-word reading in patients with hemianopic and pure alexia |journal=Brain |volume=124 |issue=Pt 3 |pages=510–21 |date=March 2001 |pmid=11222451 |doi=10.1093/brain/124.3.510 |url=http://brain.oxfordjournals.org/content/124/3/510.long }}</ref><ref name="Ahlsén 2006">{{Cite book | last1 = Ahlsén | first1 = Elisabeth. | title = Introduction to neurolinguistic | year = 2006 | publisher = John Benjamins | location = Amsterdam ; Philadelphia, PA | isbn = 978-90-272-3233-5 |oclc=803100368| pages=115- |url=http://books.google.co.uk/books?id=ziC_Dbl4KnIC&pg=PA115&redir_esc=y#v=onepage&q&f=false }}</ref> |
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Alexia is most often associated with damage to the cortex in the [[temporal lobe]], [[parietal lobe]] or [[occipital lobe]], which may arise from brain injury, stroke, or a progressive illness. [[dyslexia|"Developmental dyslexia"]], in contrast, has genetic origins. However, both alexia and developmental dyslexia share similar symptoms. |
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Alexia may be accompanied by [[expressive aphasia]] and/or [[receptive aphasia]], which is the acquired inability to produce (expressive aphasia) and / or comprehend (receptive aphasia) spoken language. Alexia can also co-occur with [[agraphia]], the specific loss of the ability to produce written language even when the necessary [[motor skills]] seem to be intact. |
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There are two subgroups of alexia: central alexias and peripheral alexias.<ref name="Bub 2003">{{cite journal|last1=Bub|first1=Daniel|title=Alexia and related reading disorders|journal=Neurologic Clinics|volume=21|issue=2|year=2003|pages=549–568|PMID=12916491|doi=10.1016/S0733-8619(02)00099-3 |url=http://cnbc.cmu.edu/~plaut/VisCog/papers/Bub03NeurolClin.alexia.pdf}}</ref><ref name="Cherney 2004">{{cite journal |author=Cherney LR |title=Aphasia, alexia, and oral reading |journal=Top Stroke Rehabil |volume=11 |issue=1 |pages=22–36 |year=2004 |pmid=14872397 |doi=10.1310/VUPX-WDX7-J1EU-00TB |url=http://go.galegroup.com/ps/i.do?id=GALE%7CA114168257&v=2.1&u=vol_m58c&it=r&p=AONE&sw=w&asid=87aca52b54b8be7ac9bca33518edef74}}</ref> Basically, central alexia is alexia as a part of aphasia, or alexia with agraphia, whereas peripheral alexia is an isolated impairment, without agraphia.<ref>{{cite web | url=http://www.acnr.co.uk/pdfs/volume4issue3/v4i3cogprimer.pdf | title=Alexia | publisher=ACNR | work=VOLUME 4 NUMBER 3 JULY/AUGUST 2004 | accessdate=3 December 2013 | author=Alexander Leff}}</ref> |
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== Central alexias== |
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Central alexias include [[surface dyslexia|surface alexia]], [[semantic dyslexia|semantic alexia]], [[phonological dyslexia|phonological alexia]], and [[deep dyslexia|deep alexia]].<ref name="Bub 2003"/><ref name="Cherney 2004"/><ref>{{cite book | last = Harley | first = Trevor A. | title = The psychology of language: from data to theory | publisher = Taylor & Francis | year = 2001 | isbn = 978-0-86377-867-4 }}</ref><ref name="Coslett 2000">{{cite journal |author=Coslett HB |title=Acquired dyslexia |journal=Semin Neurol |volume=20 |issue=4 |pages=419–26 |year=2000 |pmid=11149697 |doi=10.1055/s-2000-13174 |url=https://www.thieme-connect.de/DOI/DOI?10.1055/s-2000-13174}}</ref> |
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===Surface alexia=== |
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{{Main|Surface dyslexia}} |
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In surface alexia, words whose pronunciations are 'regular' (highly consistent with their spelling e.g. ''mint'') are read more accurately than words with irregular pronunciation, such as ''colonel''.<ref name="Friedman Hadley 1992">{{cite journal|last1=Friedman|first1=Rhonda B.|last2=Hadley|first2=Jeffrey A.|title=Letter-by-letter surface alexia|journal=Cognitive Neuropsychology| volume=9|issue=3 year=1992|pages=185–208 |url=http://www9.georgetown.edu/faculty/friedmar/pdfs/Friedman%20%281992%29%20Letter%20by%20Letter.pdf| doi=10.1080/02643299208252058}}</ref> Difficulty distinguishing [[homophones]] is diagnostic of some forms of surface alexia.<ref name="Friedman Hadley 1992" /> |
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This disorder is usually accompanied by (surface) agraphia and fluent aphasia.<ref name="Friedman Hadley 1992" /> |
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Surface alexia is associated with [[lesions]] in the [[temporo-parietal]] region of the left hemisphere, especially the [[superior temporal gyrus]].{{medical citation needed}} Some research shows that the most dramatic cases of surface alexia are caused by lesions in the inferolateral left temporal regions, which are considered to involve semantic processing.{{medical citation needed}} |
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===Phonological alexia=== |
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{{Main|Phonological dyslexia}} |
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In phonological alexia, patients can read familiar words but have difficulty reading unfamiliar words (such as invented pseudo-words). It is thought that they can recognize words by accessing lexical memory orthographically but cannot 'sound out' novel words. |
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Phonological alexia is associated with lesions in varied locations within the territory of the middle [[Cerebral arteries|cerebral artery]]. The superior temporal lobe is often also involved. Research has pointed towards the theory that phonological alexia is a development of deep alexia.{{medical citation needed}} |
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A treatment for phonological dyslexia is the Lindamood Phoneme Sequencing Program (LiPS). This program is based on a three way sensory feedback process. The subject uses their auditory, visual, and oral skills to learn to recognize words and word patterns. This is considered letter-by-letter reading using a bottom-up processing technique. Case studies with a total of three patients found a significant improvement in spelling and reading ability after using LiPS.<ref name="Kendall Conway 2003">{{cite journal|last1=Kendall| first1=Diane| last2=Conway| first2=Tim| last3=Rosenbek| first3=John |last4=Gonzalez‐Rothi |first4=Leslie|title=Case study Phonological rehabilitation of acquired phonologic alexia| journal=Aphasiology| volume=17| issue=11|year=2003|pages=1073–1095|doi=10.1080/02687030344000355}}</ref><ref name="Beeson 2010">{{Cite journal | last1 = Beeson | first1 = PM. | last2 = Rising | first2 = K. | last3 = Kim | first3 = ES. | last4 = Rapcsak | first4 = SZ. | title = A treatment sequence for phonological alexia/agraphia. | journal = J Speech Lang Hear Res | volume = 53 | issue = 2 | pages = 450–68 |date=Apr 2010 | doi=10.1044/1092-4388(2009/08-0229) | PMID=20360466 |pmc=3522177 }}</ref> |
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===Deep alexia=== |
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{{See also|Deep dyslexia}} |
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Patients with deep alexia experience semantic paralexia, which happens when the patient reads a word, and says a related meaning instead of the denoted meaning.<ref name="Friedman Hadley 1992"/> Deep alexia is more recently seen as a severe version of phonological alexia. |
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Deep alexia is caused by lesions that are often widespread and include much of the left frontal lobe.<ref name="Friedman Hadley 1992"/> Research suggests that damage to the left perisylvian region of the frontal lobe causes deep alexia, as both the phonological and lexical routes of language are impaired.{{medical citation needed}} |
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==Peripheral alexias== |
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Peripheral alexias have been described by Bub as "impairment to processes that convert letters on the page into an abstract representation of visual word forms".<ref name="Bub 2003" /> These include [[#hemianopic alexia|hemianopic alexia]], neglect alexia, attentional alexia, and [[pure alexia]] (also known as alexia without [[agraphia]]).<ref name="Bub 2003"/><ref name="Cherney 2004"/><ref name="Coslett 2000"/> |
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===Pure alexia=== |
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{{Main|Pure alexia}} |
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'''Pure alexia''', also known as '''agnosic alexia''', '''alexia without agraphia''', and '''pure word blindness'''; is alexia due to difficulty recognizing written sequences of letters (such as words), or sometimes even letters.<ref name="Cherney 2004"/> It is 'pure' because it is not accompanied by other (significant) language-related impairments. Pure alexia does not include speech, hand writing style, language, or comprehension impairments.<ref name="Starrfelt 2013">{{Cite journal | last1 = Starrfelt | first1 = R. | last2 = Olafsdóttir | first2 = RR. | last3 = Arendt | first3 = IM. | title = Rehabilitation of pure alexia: a review. | journal = Neuropsychol Rehabil | volume = 23 | issue = 5 | pages = 755–79 | month = | year = 2013 | doi = 10.1080/09602011.2013.809661 | PMID = 23808895 | pmc=3805423}}</ref> |
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Pure alexia is caused by lesions on the [[visual word form area|visual word form area (VWFA)]]. The VWFA is composed of the left [[lateral occipital sulcus]] and is activated during reading. A lesion in the VWFA stops transmission between the [[visual cortex]] and the left [[angular gyrus]]. It can also be caused by a lesion involving the left occipital lobe and the splenium of the corpus callosum. It is usually accompanied by a [[homonymous hemianopsia]] in the right side of the visual field.<ref name="Friedman Hadley 1992"/> |
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Multiple oral re-reading (MOR) is a treatment for pure alexia. It is considered a top-down processing technique in which patients read and re-read texts a predetermined number of times or until reading speed and/or accuracy improves a predetermined amount. The idea behind MOR is to learn how to use context, syntax, and semantics of the text to process written information rather than using bottom-up processing techniques in which letter by letter (LBL) reading is necessary. The theory that the MOR technique only uses top-down processing has been questioned and some studies have shown that in fact, bottom-up processing is in part responsible for reading improvement. This has been proven by reading tests that are engineered to use as few of the same words as possible that are used in training texts during MOR treatment. In these studies, patients did not significantly improve in reading speed or accuracy when reading untrained passages. Untrained passages are defined by having differing vocabulary from the texts used in reading practice. This supports the findings that MOR also has bottom-up processing components.<ref name="Starrfelt 2013"/> In addition to tactile and kinesthetic reading techniques, other therapies that are aimed to improve letter-level reading include: timed semantic and lexical association tasks and limited-time single word identification.<ref name="Starrfelt 2013"/> |
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===Hemianopic alexia=== |
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Commonly considered to derive from [[visual field]] loss due to damage to the [[primary visual cortex]]. Sufferers may complain of slow reading but are able to read individual words normally. This is the most common form of peripheral alexia, and the form with the best evidence of the (possibility of) effective treatment.{{medical citation needed}} |
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===Neglect alexia=== |
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In neglect alexia, some letters are neglected (skipped or misread) during reading - most commonly the letters at the beginning or left side of words. This alexia is associated with right parietal lesions. |
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Use of prism glasses in treatment has been demonstrated to produce substantial benefit.<ref name="Angeli 2004"> |
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{{ cite journal |
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| last1=Angeli | first1=V |
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| last2=Benassi | first2=MG |
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| last3=Ladavas | first3=E |
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| year=2004 |
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| title=Recovery of oculo-motor bias in neglect patients after prism adaptation |
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| journal=Neuropsychologia |
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| volume=42 | issue=9 | pages=1223–34 | doi=10.1016/j.neuropsychologia.2004.01.007 |
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}} |
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</ref> |
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===Attentional Alexia=== |
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Patients with attentional alexia complain of letter crowding or migration, sometimes blending elements of two words into one. The lesion usually affects the left parietal lobe (Warrington et al., 1993). Patients perform better when word stimuli are presented in isolation rather than flanked by other words and letters. Using a large magnifying glass may help as this should reduce the effects of flanking interference from nearby words; however, no trials of this or indeed any other therapy for left parietal syndromes have been published.{{medical citation needed}} |
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==Dual-route cascaded model of reading== |
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{{Main|Dual-route hypothesis to reading aloud}} |
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The dual-route theory of [[Reading (process)|reading]] aloud was first described in the early 1970s.<ref name="Pritchard 2012">{{cite journal |author=Pritchard SC, Coltheart M, Palethorpe S, Castles A |title=Nonword reading: comparing dual-route cascaded and connectionist dual-process models with human data |journal=J Exp Psychol Hum Percept Perform |volume=38 |issue=5 |pages=1268–88 |date=October 2012 |pmid=22309087 |doi=10.1037/a0026703 }}</ref> This theory suggests that two separate mental mechanisms, or cognitive routes, are involved in reading aloud, with output of both mechanisms contributing to the [[pronunciation]] of a written stimulus.<ref name="Pritchard 2012" /><ref name=coltheart1>{{cite journal|last=Coltheart|first=Max|author2=Curtis, Brent|author3= Atkins, Paul|author4= Haller, Micheal|title=Models of reading aloud: Dual-route and parallel-distributed-processing approaches.|journal=Psychological Review|date=1 January 1993|volume=100|issue=4|pages=589–608|doi=10.1037/0033-295X.100.4.589}}</ref><ref name="Yamada 1990">{{cite journal |author=Yamada J, Imai H, Ikebe Y |title=The use of the orthographic lexicon in reading kana words |journal=J Gen Psychol |volume=117 |issue=3 |pages=311–23 |date=July 1990 |pmid=2213002 }}</ref> One mechanism is the ''lexical route'', which is the process whereby skilled readers can recognize known words by sight alone, through a “dictionary” lookup procedure.<ref name="Pritchard 2012" /><ref name="Zorzi Houghton 1998">{{cite journal|last1=Zorzi|first1=Marco|last2=Houghton|first2=George|last3=Butterworth|first3=Brian|title=Two routes or one in reading aloud? A connectionist dual-process model.|journal=Journal of Experimental Psychology: Human Perception and Performance |volume=24| issue=4| year=1998| pages=1131–1161|issn=1939-1277|doi=10.1037/0096-1523.24.4.1131}}</ref> The other mechanism is the ''nonlexical'' or ''sublexical route'', which is the process whereby the reader can “sound out” a written word. This is done by identifying the word's constituent parts (letters, [[phonemes]], [[graphemes]]) and, applying knowledge of how these parts are associated with each other, for example how a string of neighboring letters sound together.<ref name="Pritchard 2012" /><ref name="Zorzi Houghton 1998" /><ref name = "Coltheart 2005">{{cite book | last1 = Coltheart | first1 = Max | title = Word recognition processes in reading. Modeling reading : the dual-route approach | editors = Margaret J Snowling; Charles Hulme | work = The science of reading : a handbook | publisher = Blackwell Pub., | year = 2005 | location = Malden, MA | pages = 6–23 | url = http://www.pitt.edu/~perfetti/PDF/Coltheart%2005.pdf | oclc = 57579252 | isbn = 9781405114882}}</ref> |
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==History== |
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In 1892 Joseph Jules Dejerine discovered alexia after studying the case of Oscar C., an educated French merchant who lost the ability to understand written words after suffering a stroke.<ref name="Bub 2003"/> Oscar C. suddenly couldn’t interpret letters or words and saw them as obscure symbols which were devoid of meaning. According to Dejerine, the white matter of Oscar C.’s lesion had severed the connection between his interpretation of visual words and his visual cortices. The patient could therefore no longer access the stored orthography of words from vision, while his spelling capacities (from non-visual memory) had not been damaged.<ref name="Bub 2003"/> Dejerine also observed that Oscar C.’s ability to understand numbers had remained intact, although the ophthalmologist who examined the patient before turning him over to Dejerine had found that Oscar C.’s numeral reading was very slow and fraught with error.<ref name="Bub 2003"/> |
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==Notable cases== |
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Canadian novelist [[Howard Engel]] suffered from alexia (sine [[agraphia]]) following a stroke in 2000. His case was subsequently publicised by neurologist [[Oliver Sacks]].<ref>{{Cite web | last = | first = | title = Why novelist Howard Engel couldn’t read, but could write |author= Oliver Sacks | url = http://www.newyorker.com/reporting/2010/06/28/100628fa_fact_sacks | publisher =The New Yorker | year = 2010 | accessdate = 17 November 2013 }}</ref> |
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==See also== |
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{{col-begin}} |
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{{col-2}} |
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* [[Agnosia]] |
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* [[Apraxia of speech]] |
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* [[Auditory agnosia]] |
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* [[Dementia]] |
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* [[Primary progressive aphasia]] |
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{{col-2}} |
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* [[Strephosymbolia]] |
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* [[Stroke]] |
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* [[Synesthesia]] |
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* [[Visual agnosia]] |
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{{col-end}} |
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==References== |
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{{Reflist|2}} |
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==Further reading== |
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*{{cite journal |author=Henry ML, Beeson PM, Alexander GE, Rapcsak SZ |title=Written language impairments in primary progressive aphasia: a reflection of damage to central semantic and phonological processes |journal=J Cogn Neurosci |volume=24 |issue=2 |pages=261–75 |date=February 2012 |pmid=22004048 |pmc=3307525 |doi=10.1162/jocn_a_00153 |url=}} |
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*{{cite journal |author=Kim ES, Rapcsak SZ, Andersen S, Beeson PM |title=Multimodal alexia: neuropsychological mechanisms and implications for treatment |journal=Neuropsychologia |volume=49 |issue=13 |pages=3551–62 |date=November 2011 |pmid=21952194 |pmc=3221964 |doi=10.1016/j.neuropsychologia.2011.09.007 |url=}} |
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*{{cite journal |author=Seghier ML, Neufeld NH, Zeidman P, ''et al.'' |title=Reading without the left ventral occipito-temporal cortex |journal=Neuropsychologia |volume=50 |issue=14 |pages=3621–35 |date=December 2012 |pmid=23017598 |pmc=3524457 |doi=10.1016/j.neuropsychologia.2012.09.030 |url=}} |
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==External links== |
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{{Lesions of spinal cord and brain}} |
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{{Speech and voice symptoms and signs}} |
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{{dyslexia}} |
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{{DEFAULTSORT:Alexia (Condition)}} |
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<!-- Categories --> |
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[[Category:Alexia (condition)| ]] |
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[[Category:Aphasias]] |
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[[Category:Dyslexia]] |
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[[Category:Learning disabilities]] |
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[[Category:Agnosia]] |
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Revision as of 16:16, 2 January 2015
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