Posterior cortical atrophy

Abstract

Posterior cortical atrophy (PCA) is a neurodegenerative syndrome that is characterised by progressive decline in visuospatial, visuoperceptual, literacy, and praxic skills. The progressive neurodegeneration affecting parietal, occipital, and occipitotemporal cortices that underlies PCA is attributable to Alzheimer's disease in most patients. However, alternative underlying causes, including dementia with Lewy bodies, corticobasal degeneration, and prion disease, have also been identified, and not all patients with PCA have atrophy on clinical imaging. This heterogeneity has led to inconsistencies in diagnosis and terminology and difficulties in comparing studies from different centres, and has restricted the generalisability of findings from clinical trials and investigations of factors that drive phenotypic variability. Important challenges remain, including the identification of factors associated not only with the selective vulnerability of posterior cortical regions but also with the young age of onset of PCA. Greater awareness of the syndrome and agreement over the correspondence between syndrome-level and disease-level classifications are needed to improve diagnostic accuracy, clinical management, and the design of research studies.

Figure 1

Visual dysfunction in posterior cortical atrophy Individuals with posterior cortical atrophy have difficulty identifying objects and faces, particularly when they consist of many parts or are viewed from an unfamiliar (non-canonical) perspective. Eye-tracking studies contrasting scene perception in healthy individuals (A) and people with posterior cortical atrophy (B) suggest that patients have poor top-down guidance and control of oculomotor function. Circles represent fixation locations and circle size represents fixation duration. Patients with posterior cortical atrophy fixate prominent features initially (eg, dome on pier), but subsequently fixate relatively uninformative aspects of the scene (eg, sea or sky) and miss important contextual details (eg, beachfront or near the end of the pier). Images from Tim Shakespeare and Sebastian Crutch (unpublished).

Figure 2

Neurological testing (A) and brain imaging (B) of a 62-year-old woman with visuospatial dysfunction. Images are in neurological orientation. See the panel for a description of the case history and imaging findings.

Figure 3

Registered serial MR images showing axial views of an individual with PCA at four time points (ages 59–63 years old). Repeat scans were fluid-registered to the baseline image and colour-coded voxel-compression maps were produced. The scale shows the percentage volume change per voxel (−20 to 20%) with green and blue representing contraction and yellow and red representing expansion.