View source for Medicine:Posterior cortical atrophy

{{Infobox medical condition (new)
| name            = Posterior cortical atrophy
| synonyms        = Biparietal Alzheimer disease
| image           = LobesCaptsLateral.png
| alt             =
| caption         = Lobes of the human brain
| pronounce       =
| field           = neurology
| symptoms        =
| complications   =
| onset           =
| duration        =
| types           =
| causes          =
| risks           =
| diagnosis       =
| differential    =
| prevention      =
| treatment       =
| medication      =
| prognosis       =
| frequency       =
| deaths          =
}}

'''Posterior cortical atrophy''' ('''PCA'''), also called '''Benson's syndrome''', is a rare form of [[Medicine:Dementia|dementia]] which is considered a visual variant or an atypical variant of [[Medicine:Alzheimer's disease|Alzheimer's disease]] (AD).<ref name="Schott">{{cite journal |vauthors=Schott JM, Crutch SJ |title=Posterior Cortical Atrophy |journal=Continuum (Minneap Minn) |volume=25 |issue=1 |pages=52–75 |date=February 2019 |pmid=30707187 |pmc=6548537 |doi=10.1212/CON.0000000000000696 }}</ref><ref name=":0">{{Cite web|url=http://eyewiki.aao.org/Visual_variant_of_Alzheimer%E2%80%99s_disease|title=Visual variant of Alzheimer's disease - EyeWiki|website=eyewiki.aao.org|language=en|access-date=2017-11-07}}</ref><ref>{{cite journal | vauthors = Nestor PJ, Caine D, Fryer TD, Clarke J, Hodges JR | year = 2003 | title = The topography of metabolic deficits in posterior cortical atrophy (the visual variant of Alzheimer's disease) with FDG-PET | url= | journal = J Neurol Neurosurg Psychiatry | volume = 74 | issue = 11| pages = 1521–1529 | doi=10.1136/jnnp.74.11.1521| pmid = 14617709 | pmc = 1738241 }}</ref> The disease causes [[Medicine:Atrophy|atrophy]] of the posterior part of the [[Biology:Cerebral cortex|cerebral cortex]], resulting in the progressive disruption of complex [[Biology:Visual processing|visual processing]].<ref name="ucsf">{{cite web| url= http://memory.ucsf.edu/education/diseases/pca | title=Posterior Cortical Atrophy | work= UCSF Memory and Aging Center| publisher= [[Organization:University of California, San Francisco|University of California, San Francisco]] | access-date= 2011-10-22}}</ref> PCA was first described by D. Frank Benson in 1988.<ref>{{cite journal|vauthors= Benson DF, Davis RJ, Snyder BD |date=July 1988 |title= Posterior Cortical Atrophy |journal= Archives of Neurology |volume= 45 | issue=7 |pages=789–793 |pmid= 3390033|doi= 10.1001/archneur.1988.00520310107024}}</ref><ref name="nmrharv">{{cite web| url= http://www.nmr.mgh.harvard.edu/~bradd/pca.html | title= Posterior Cortical Atrophy | date= 2009-01-19 | work= Martinos Center for Biomedical Imaging| publisher= [[Organization:Harvard University|Harvard University]]| access-date= 2011-10-22}}</ref>

PCA usually affects people at an earlier age than typical cases of Alzheimer's disease, with initial symptoms often experienced in people in their mid-fifties or early sixties.<ref name="ucsf"/>  This was the case with writer Terry Pratchett (1948–2015), who went public in 2007 about being diagnosed with PCA.<ref>{{cite web |url=http://www.alzheimersresearchuk.org/terry-pratchett-donates-one-million/ |title=Terry Pratchett pledges $1 million to Alzheimer's research |publisher=Alzheimer's Research Trust |date=2011-07-29 |access-date=2011-07-29 |archive-date=2013-01-14 |archive-url=https://web.archive.org/web/20130114084313/http://www.alzheimersresearchuk.org/terry-pratchett-donates-one-million/ |url-status=dead }}</ref> In rare cases, PCA can be caused by [[Medicine:Dementia with Lewy bodies|dementia with Lewy bodies]] and [[Medicine:Creutzfeldt–Jakob disease|Creutzfeldt–Jakob disease]].<ref name="nmrharv"/><ref name="ucsf"/>

==Symptoms==

The main symptom resulting from posterior cortical atrophy is a decrease in [[Philosophy:Visuospatial function|visuospatial and visuoperceptual capabilities]], since the area of atrophy involves the [[Biology:Occipital lobe|occipital lobe]] responsible for [[Biology:Visual processing|visual processing]].<ref name="Mendez 2002 33–40"/> The atrophy is progressive; early symptoms include difficulty reading, blurred vision, light sensitivity, issues with depth perception, and trouble navigating through space.<ref name="Crutch 2012 170–178"/><ref name="Borruat 2013">{{cite journal|last=Borruat|first=François-Xavier|title=Posterior Cortical Atrophy: Review of the Recent Literature|journal=Neuro-Ophthalmology|date=18 October 2013|volume=13|issue=12|pages=406|doi=10.1007/s11910-013-0406-8|pmid=24136454|s2cid=45579994|url=http://doc.rero.ch/record/319068/files/11910_2013_Article_406.pdf}}</ref>  Additional symptoms include [[Engineering:Apraxia|apraxia]], a disorder of movement planning, alexia, an impaired ability to read, and [[Biology:Visual agnosia|visual agnosia]], an object recognition disorder.<ref name="Goenthals 2001 115–119"/> In the [[Biology:Two-streams hypothesis|two-streams hypothesis]], damage to the [[Biology:Two-streams hypothesis#Ventral stream|ventral, or "what" stream]], of the [[Biology:Visual system|visual system]], located in the [[Biology:Temporal lobe|temporal lobe]], leads to the symptoms related to general vision and object recognition deficits; damage to the [[Biology:Two-streams hypothesis#Dorsal stream|dorsal, or "where/how" stream]], located in the [[Biology:Parietal lobe|parietal lobe]], leads to PCA symptoms related to impaired movements in response to visual stimuli, such as navigation and apraxia.<ref name="Goenthals 2001 115–119"/><ref name="Borruat 2013" /> 
[[Image:Ventral-dorsal streams.svg|thumb|right|The dorsal stream (green) runs through the parietal lobe, and the ventral stream (purple) runs through the temporal lobe. Both streams originate in the occipital lobe (blue) located posteriorly.]]

As [[Medicine:Neurodegeneration|neurodegeneration]] spreads, more severe symptoms emerge, including the inability to recognize familiar people and objects, trouble navigating familiar places, and sometimes visual hallucinations.<ref name="Mendez 2002 33–40"/><ref name="Crutch 2012 170–178"/>  In addition, difficulty may be experienced in making guiding movements towards objects, and a decline in literacy skills including reading, writing, and spelling may develop.<ref name="Crutch 2012 170–178"/><ref name="Crutch 2013 463–465"/><ref>{{cite journal|last=Tsunoda|first=Ayami|author2=Shuji Iritani |author3=Norio Ozaki |title=Presenile dementia diagnosed as posterior cortical atrophy|journal=Psychogeriatrics|date=17 March 2011|volume=11|issue=3|pages=171–176|doi=10.1111/j.1479-8301.2011.00366.x|pmid=21951958|doi-access=}}</ref>  Furthermore, if neural death spreads into other anterior cortical regions, symptoms similar to [[Medicine:Alzheimer's disease|Alzheimer's disease]], such as memory loss, may result.<ref name="Crutch 2012 170–178"/><ref name="Crutch 2013 463–465"/> In PCA where there is significant [[Medicine:Atrophy|atrophy]] in one hemisphere of the brain [[Medicine:Hemispatial neglect|hemispatial neglect]] may result – the inability to see stimuli on one half of the visual field.<ref name="Borruat 2013" /> [[Medicine:Anxiety|Anxiety]] and [[Medicine:Depression (mood)|depression]] are also common symptoms.<ref>{{cite journal|last=Crutch|first=Sebastian|author2=Manja Lehmann |author3=Jonathan Schott |author4=Gil Rabinovici |author5=Martin Rosser |author6=Nick Fox |title=Posterior cortical atrophy|journal=The Lancet Neurology|date=February 2012|volume=11|issue=2|pages=170–178|doi=10.1016/s1474-4422(11)70289-7|pmid=22265212|pmc=3740271}}</ref>

===Connection to Alzheimer's disease===

Studies have shown that PCA may be a variant of [[Medicine:Alzheimer's disease|Alzheimer's disease]] (AD), with an emphasis on visual deficits.<ref name=":0" /><ref name="Goenthals 2001 115–119"/> Although in primarily different, but sometimes overlapping, brain regions, both involve progressive neural degeneration, as shown by the loss of neurons and synapses, and the presence of neurofibrillary tangles and [[Medicine:Senile plaques|senile plaques]] in affected brain regions; this eventually leads to [[Medicine:Dementia|dementia]] in both diseases.<ref name="Kennedy 2011 248–257"/><ref name="Hof 1997 3609–3625"/> In PCA there is more cortical damage and [[Biology:Grey matter|gray matter]] (cell body) loss in posterior regions, especially in the occipital, parietal, and temporal lobes, whereas in Alzheimer's there is typically more damage in the [[Biology:Prefrontal cortex|prefrontal cortex]] and [[Biology:Hippocampus|hippocampus]].<ref name="Crutch 2013 463–465"/><ref name="Kennedy 2011 248–257"/><ref>{{cite journal|last=Tsunoda|first=Ayami|author2=Shuji Iritani |author3=Norio Ozaki |title=Presenile dementia diagnosed as posterior cortical atrophy|journal=Psychogeriatrics|date=17 March 2011|volume=11|issue=171–176|doi=10.1111/j.1479-8301.2011.00366.x|pmid=21951958|pages=171–176|doi-access=}}</ref> PCA tends to impair [[Working memory|working memory]] and anterograde memory, while leaving [[Biology:Episodic memory|episodic memory]] intact, whereas in AD there is typically impaired episodic memory, suggesting some differences still lie in the primary areas of cortical damage.<ref name="Crutch 2012 170–178"/><ref name="Kennedy 2011 248–257"/>

Over time, however, atrophy in PCA may spread to regions that are commonly damaged in AD, leading to shared AD symptoms such as deficits in memory, language, learning, and cognition.<ref name="Goenthals 2001 115–119">{{cite journal|last=Goenthals|first=Maartin|author2=Patrick Santens|title=Posterior cortical atrophy. Two case reports and a review of the literature|journal=Clinical Neurology and Neurosurgery|date=20 February 2001|volume=103|issue=2|pages=115–119|doi=10.1016/s0303-8467(01)00114-7|pmid=11516556|s2cid=46582748}}</ref><ref name="Crutch 2013 463–465">{{cite journal|vauthors=Crutch SJ, Schott JM, Rabinovici GD, Boeve BF, Cappa SF, Dickerson BC, Dubois B, Graff-Radford NR, Krolak-Salmon P, Lehmann M, Mendez MF, Pijnenburg Y, Ryan NS, Scheltens P, Shakespeare T, Tang-Wai DF, van der Flier WM, Bain L, Carrillo MC, Fox NC|title=Shining a light on posterior cortical atrophy|journal=Alzheimer's & Dementia|date=Jul 2013|volume=9|issue=4|pages=463–5|pmid=23274153|doi=10.1016/j.jalz.2012.11.004|s2cid=16404876}}</ref><ref name="Kennedy 2011 248–257">{{cite journal|last=Kennedy|first=Jonathan|author2=Manja Lehmann |author3=Magdalena J. Sokolska |author4=Hilary Archer |author5=Elizabeth K. Warrington |author6=Nick C. Fox |author7=Sebastian J. Crutch |title=Visualizing the emergence of posterior cortical atrophy|journal=Neurocase: The Neural Basis of Cognition|date=25 October 2011|volume=18|issue=3|pages=248–257|doi=10.1080/13554794.2011.588180|pmid=22026812|s2cid=20617012}}</ref><ref name="Hof 1997 3609–3625">{{cite journal|last=Hof|first=Patrick|author2=Brent Vogt |author3=Constantin Bouras |author4=John Morrison |title=Atypical Form of Alzheimer's Disease with Prominent Posterior Cortical Atrophy: a Review of Lesion Distribution and Circuit Disconnection in Cortical Visual Pathways|journal=Vision Res.|date=December 1997|volume=37|issue=24|pages=3609–3625|doi=10.1016/s0042-6989(96)00240-4|pmid=9425534|doi-access=free}}</ref> Although PCA has an earlier onset, a diagnosis with Alzheimer's is often made, suggesting that the degeneration has simply migrated anteriorly to other cortical brain regions.<ref name="Mendez 2002 33–40">{{cite journal|last=Mendez|first=Mario|author2=Mehdi Ghajarania |author3=Kent Perryman |title=Posterior cortical atrophy: Clinical characteristics and differences compared to Alzheimer's disease|journal=Dementia and Geriatric Cognitive Disorders|date=14 June 2002|volume=14|issue=1|pages=33–40|doi=10.1159/000058331|pmid=12053130|s2cid=12291848}}</ref><ref name="Goenthals 2001 115–119"/>

There is no standard definition of PCA and no established diagnostic criteria, so it is not possible to know how many people have the condition. Some studies have found that about 5 percent of people diagnosed with Alzheimer's disease have PCA. However, because PCA often goes unrecognized, the true percentage may be as high as 15 percent. Researchers and physicians are working to establish a standard definition and diagnostic criteria for PCA.<ref>{{Cite web|url=http://www.alz.org/dementia/posterior-cortical-atrophy.asp|title=Posterior Cortical Atrophy {{!}} Signs, Symptoms, & Diagnosis|website=Dementia|access-date=2016-07-25}}</ref>

PCA may also be correlated with Lewy body disease, [[Medicine:Creutzfeldt–Jakob disease|Creutzfeldt–Jakob disease]], [[Medicine:Bálint's syndrome|Bálint's syndrome]], and [[Medicine:Gerstmann syndrome|Gerstmann syndrome]].<ref name="Crutch 2012 170–178">{{cite journal|last=Crutch|first=Sebastian|author2=Manja Lehmann |author3=Jonathan Schott |author4=Gil Rabinovici |author5=Martin Rosser |author6=Nick Fox |title=Posterior Cortical Atrophy|journal=The Lancet Neurology|date=February 2012|volume=11|issue=2|pages=170–178|doi=10.1016/s1474-4422(11)70289-7|pmid=22265212|url=http://discovery.ucl.ac.uk/1337217/1/1337217.pdf |pmc=3740271}}</ref><ref name="Borruat 2013" /><ref>{{cite journal|last=Nagaratnam|first=Nages|author2=Kujan Nagaratnam |author3=Daniel Jolley |author4=Allan Ting |title=Dementia following posterior cortical atrophy—a descriptive clinical case report|journal=Archives of Gerontology and Geriatrics|date=6 June 2001|volume=33|issue=2|pages=179–190|doi=10.1016/s0167-4943(01)00179-0|pmid=15374033}}</ref> In addition, PCA may result in part from mutations in the presenilin 1 gene (PSEN1).<ref name="Borruat 2013" />

==Diagnosis==

The cause of PCA is unknown, and there are no fully accepted diagnostic criteria for the disease.<ref name=":0" /><ref name="Borruat 2013" /> This is partially due to the gradual onset of PCA symptoms, their variety, the rare nature of the disease, and the younger age of onset typically 50–60 years.<ref name="middlebury.edu">{{cite journal|last=Crutch|first=Sebastian J.|author2=Manja Lehmann |author3=Jonathan M. Schott |author4=Gil D. Rabinovici |author5=Martin N. Rossor|author5-link=Martin Rossor |author6=Nick C. Fox |title=Posterior Cortical Atrophy|journal=The Lancet Neurology|date=February 2012|volume=11|issue=2|pages=170–178|doi=10.1016/s1474-4422(11)70289-7|pmid=22265212 |pmc=3740271}}</ref> In 2012, the first international conference on PCA was held in Vancouver, Canada.  Continued research and testing will hopefully result in accepted and standardized criteria for diagnosis.<ref name="Borruat 2013" />

PCA is often initially misdiagnosed as an [[Medicine:Anxiety disorder|anxiety disorder]] or [[Medicine:Depression (mood)|depression]]. It has been suggested that depression or anxiety may result from the symptoms of decreased visual function, and the progressive nature of the disease. Early visual impairments have often led to a referral to an [[Medicine:Ophthalmology|ophthalmologist]], which can result in unnecessary cataract surgery.<ref name="middlebury.edu"/>

Due to the lack of biomarkers for PCA, neuropsychological examinations are advised.<ref>{{cite journal|last=Croisile|first=MD. Bernard|author2=Alexis Brice|journal=Orphanet Encyclopedia|date=September 2004|url=https://www.orpha.net/data/patho/GB/uk-Benson.pdf|access-date=11 November 2013|title=Benson's syndrome or Posterior Cortical Atrophy|archive-date=12 November 2013|archive-url=https://web.archive.org/web/20131112161606/https://www.orpha.net/data/patho/GB/uk-Benson.pdf|url-status=dead}}</ref> [[Biology:Neuroimaging|Neuroimaging]] can also assist in the diagnosis of PCA.<ref name="middlebury.edu"/> For PCA and AD neuroimaging is carried out using MRI scans, [[Biology:Single-photon emission computed tomography|single-photon emission computed tomography]], and [[Physics:Positron emission tomography|positron emission tomography]] (PET scans).<ref>{{cite journal|last=Goldstein|first=Martin A. |author2=Iliyan Ivanov |author3=Michael E. Silverman|title=Posterior Cortical Atrophy: An Exemplar for Renovating Diagnostic Formulation in Neurosychiaty|journal=Comprehensive Psychiatry|date=May 2011|volume=52|issue=3|pages=326–333|doi=10.1016/j.comppsych.2010.06.013|pmid=21497228 }}</ref> [[Biology:Neuroimaging|Neuroimages]] are often compared to those of people with AD to assist diagnosis. Due to the early onset of PCA in comparison to AD, images taken at the early stages of the disease will vary from brain images in AD. At this early stage brain [[Medicine:Atrophy|atrophy]] will be shown to be more centrally located in the right [[Biology:Posterior lobe of cerebellum|posterior lobe]] and occipital gyrus, while AD brain images show the majority of atrophy in the medial [[Biology:Temporal lobe|temporal cortex]]. This variation within the images will assist in early diagnosis of PCA; however, as the years go on the images will become increasingly similar, due to the majority of PCA also developing to AD later in life because of continued brain [[Medicine:Atrophy|atrophy]].<ref name="Borruat 2013" /><ref>{{cite journal|vauthors=Möller C, van der Flier WM, Versteeg A, Benedictus MR, Wattjes MP, Koedam EL, Scheltens P, Barkhof F, Vrenken H|title=Quantitative Regional Validation of the Visual Rating Scale for Posterior Cortical Atrophy|journal=European Radiology|date=Feb 2014|volume=24|issue=2|pages=397–404|doi=10.1007/s00330-013-3025-5|pmid=24092044|s2cid=14187936}}</ref> A key aspect found through brain imaging of PCA patients is a loss of [[Biology:Grey matter|grey matter]] (collections of neuronal cell bodies) in the posterior and occipital temporal cortices within the right hemisphere.<ref>{{cite journal|vauthors=Migliaccio R, Agosta F, Toba MN, Samri D, Corlier F, de Souza LC, Chupin M, Sharman M, Gorno-Tempini ML, Dubois B, Filippi M, Bartolomeo P|title=Brain Networks in Posterior Cortical Atrophy: A Single Case Tractography Study and Literature Review|journal=Cortex|date=November 2012|volume=48|issue=10|pages=1298–1309|doi=10.1016/j.cortex.2011.10.002|pmid=22099855|pmc=4813795}}</ref>

For some people with PCA, neuroimaging may not give a clear diagnosis; therefore, careful observation in relation to PCA symptoms can also assist in the diagnosis.<ref name="middlebury.edu"/> The variation and lack of organized clinical testing has led to continued difficulties and delays in the diagnosis of PCA.<ref name="Borruat 2013" />

==Treatment==
Specific and accepted treatment for PCA has yet to be discovered; this may be due to the rarity and variations of the disease.<ref name="Borruat 2013" /><ref>{{cite journal|last=Caine|first=Diana|title=Posterior Cortical Atrophy: A Review of the Literature|journal=Neurocase|year=2004|volume=10|issue=5|pages=382–385|doi=10.1080/13554790490892239|pmid=15788276|s2cid=45491962}}</ref>  At times people with PCA are treated with AD treatments, such as cholinesterase inhibitors, [[Biology:Donepezil|donepezil]], [[Chemistry:Rivastigmine|rivastigmine]], [[Chemistry:Galantamine|galantamine]], and [[Chemistry:Memantine|memantine]].<ref name="Borruat 2013" /> Antidepressant drugs have also provided some positive effects.<ref name="middlebury.edu"/>

Other treatments such as [[Medicine:Occupational therapy|occupational therapy]], or help with adapting to visual changes may help.<ref name="Borruat 2013" /><ref name="middlebury.edu"/> People with PCA and their caregivers are likely to have different needs than the more typical cases of Alzheimer's disease, and may benefit from specialized support groups, or other groups for young people with dementia. No study to date has been definitive to provide accepted conclusive analysis on treatment options.<ref name="middlebury.edu"/>

== References ==
{{Reflist}}

== External links ==
* [http://www.raredementiasupport.org/pca/ Posterior Cortical Atrophy support] from the [[Biology:Dementia Research Centre|Dementia Research Centre]]

{{Medical resources
|  ICD10           = G31.1
|  ICD9            = <!--{{ICD9|xxx}}-->
|  ICDO            =
|  OMIM            =
|  DiseasesDB      =
|  MedlinePlus     =
|  eMedicineSubj   =
|  eMedicineTopic  =
|  MeSH            =
|  GeneReviewsNBK  =
|  GeneReviewsName =
|  Orphanet        = 54247
}}

{{CNS diseases of the nervous system}}

[[Category:Aging-associated diseases]]
[[Category:Unsolved problems in neuroscience]]

{{Sourceattribution|Posterior cortical atrophy}}