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Posterior cortical atrophy (PCA), also called Benson's syndrome, is a form of dementia which is usually considered an atypical variant of Alzheimer's disease.〔Nestor PJ, Caine D, Fryer TD, Clarke J, Hodges JR: (The topography of metabolic deficits in posterior cortical atrophy (the visual variant of Alzheimer's disease) with FDG-PET ). J Neurol Neurosurg Psychiatry 2003; 74:1521–1529〕 The disease causes atrophy of the back (posterior) part of the cerebral cortex, resulting in the progressive disruption of complex visual processing. PCA was first described by D. Frank Benson in 1988. In rare cases,〔 PCA "can also be due to other diseases including dementia with Lewy bodies and Creutzfeldt–Jakob disease."〔 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.〔 This was the case with writer Terry Pratchett (1948-2015), who went public in 2007 about being diagnosed with PCA.〔(【引用サイトリンク】title=Terry Pratchett pledges $1 million to Alzheimer's research )〕 In ''The Mind's Eye'', neurologist Oliver Sacks examines the case of a noted concert pianist, Lilian Kallir (1931-2004), who suffered from PCA. ==Symptoms== The main symptom resulting from PCA is a decrease in visuospatial and visuoperceptual capabilities.〔 Because the posterior region of the brain is home to the occipital lobe, which is responsible for visual processing, visual functions are impaired in PCA patients. The atrophy is progressive; early symptoms include difficulty reading, blurred vision, light sensitivity, issues with depth perception, and trouble navigating through space.〔〔 Additional symptoms include apraxia, a disorder of movement planning, alexia, an impaired ability to read, and visual agnosia, an object recognition disorder.〔 Damage to the ventral, or “what” stream, of the visual system, located in the temporal lobe, leads to the symptoms related to general vision and object recognition deficits; damage to the dorsal, or “where/how” stream, located in the parietal lobe, leads to PCA symptoms related to impaired movements in response to visual stimuli, such as navigation and apraxia.〔 As neurodegeneration spreads, more severe symptoms emerge, including the inability to recognize familiar people and objects, trouble navigating familiar places, and sometimes visual hallucinations.〔〔 In addition, patients may experience difficulty making guiding movements towards objects, and may experience a decline in literacy skills including reading, writing, and spelling.〔〔 Furthermore, if neural death spreads into other anterior cortical regions, symptoms similar to Alzheimer's disease, such as memory loss, may result.〔〔 PCA patients with significant atrophy in one hemisphere of the brain may experience hemispatial neglect, the inability to see stimuli on one half of the visual field.〔 Anxiety and depression are also common in PCA patients. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Posterior cortical atrophy」の詳細全文を読む スポンサード リンク
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