Posterior Cortical Atrophy

Abstract

Purpose of review: This article presents an overview of the clinical syndrome of posterior cortical atrophy (PCA), including its pathologic underpinnings, clinical presentation, investigation findings, diagnostic criteria, and management.

Recent findings: PCA is usually an atypical form of Alzheimer disease with relatively young age at onset. New diagnostic criteria allow patients to be diagnosed on a syndromic basis as having a primary visual (pure) form or more complex (plus) form of PCA and, when possible, on a disease-specific basis using biomarkers or underlying pathology. Imaging techniques have demonstrated that some pathologic processes are concordant (atrophy, hypometabolism, tau deposition) with clinical symptoms and some are discordant (widespread amyloid deposition). International efforts are under way to establish the genetic underpinnings of this typically sporadic form of Alzheimer disease. In the absence of specific disease-modifying therapies, a number of practical suggestions can be offered to patients and their families to facilitate reading and activities of daily living, promote independence, and improve quality of life SUMMARY: While rare, PCA is an important diagnostic entity for neurologists, ophthalmologists, and optometrists to recognize to allow for early accurate diagnosis and appropriate patient management. PCA provides an important opportunity to investigate the causes of selective vulnerability in Alzheimer disease.

FIGURE 3-1

Age of disease onset in posterior cortical atrophy. Data from an international study of 302 patients shows a peak between 50 and 60 years of age, with diminishing incidence with increasing age.

FIGURE 3-2

Eye tracking demonstrates preserved reading in typical Alzheimer disease (tAD) (A) and impaired reading in posterior cortical atrophy (PCA) (B, C). Blue arrows outline reading order, red arrows indicate omission of subsequent words through reading later sections of text, and yellow arrows indicate reading of earlier sections of text. Transcripts of the participants' corresponding spoken output are beneath each example (italicized text). Each hyphen in the transcript beneath each example indicates a pause of 3 seconds. Numbers refer to where words were repeated. Reprinted with permission from Yong KX et al, Neurology. © 2015 American Academy of Neurology.

FIGURE 3-3

Visual dysfunction in posterior cortical atrophy (PCA). Eye tracking studies in healthy individuals (A) and patients with PCA (B) demonstrate simultanagnosia in PCA. Circles represent fixation locations and circle size (and corresponding figure in milliseconds) indicates fixation durations. Individuals with PCA fixate on prominent features initially (eg, the dome on the pier) but subsequently fixate on relatively uninformative aspects of the scene (eg, the sea or sky), missing important contextual details (eg, the beachfront or near the end of the pier). Reprinted from Crutch SJ, et al, Lancet Neurol. © 2012 Elsevier Ltd.

FIGURE 3-4

Fragmented letters. Individuals with posterior cortical atrophy will often be able to read individual letters, but not when they are presented in degraded form (apperceptive agnosia). Reprinted with permission from Warrington EK. © 2010 National Hospital, Institute of Neurology.

FIGURE 3-5

Visual fields in posterior cortical atrophy. In patient 2 and patient 10, visual field deficits are principally limited to a hemifield; in patient 3 and patient 4, both hemifields are affected to some extent. Reprinted from Millington RS, et al, Neuroimage Clin. © 2017 The Authors.

FIGURE 3-6

Pattern of cognitive impairment in typical Alzheimer disease (A) and posterior cortical atrophy (B). Increasing impairment in a cognitive domain is represented by retreat of the color in its segment toward the center of the circle. Thus, verbal and nonverbal memory are profoundly affected in panel A but relatively preserved in panel B, while profound posterior cortical impairment is seen in panel B. Modified with permission from Warren JD, et al, Nat Rev Neurol. © 2012.

FIGURE 3-7

Typical MRI in posterior cortical atrophy. Sagittal (A) and coronal (B) MRIs show marked parietal lobe volume loss.

FIGURE 3-8

Visual rating scale for the posterior brain regions. In sagittal, axial, and coronal orientation, this rating scale rates atrophy as follows: 0 = no atrophy, 1 = minimal atrophy, 2 = moderate atrophy, and 3 = severe atrophy. PAR = parietal lobe; PCS = posterior cingulate sulcus; POS = parietooccipital sulcus; PRE = precuneus. Reprinted with permission from Koedam EL, et al, Eur Radiol. © 2011 The Authors.

FIGURE 3-9

Cortical ribboning in Heidenhain variant of Creutzfeldt-Jakob disease. Axial diffusion-weighted 1.5T MRI shows right occipital lobe cortical ribboning (arrow) in a patient presenting with the Heidenhain phenotype, which can clinically resemble posterior cortical atrophy. Reprinted with permission from Townley RA, et al, Neurocase. © 2018 Information UK Limited.

FIGURE 3-10

Multimodal imaging in posterior cortical atrophy (PCA). Single-participant axial images for one control participant and five patients with posterior cortical atrophy showing cerebral blood flow (CBF) (arterial spin labeling [ASL]), glucose metabolism (fludeoxyglucose positron emission tomography [FDG-PET]), atrophy (structural MRI), and amyloid deposition (florbetapir PET). Amyloid deposition varies between individuals but is distributed throughout the cortex in all. Cerebral blood flow, hypometabolism, and atrophy are, by contrast, all restricted to posterior cortical areas. f = female; m = male; SUVR = standardized uptake value ratio. Reprinted with permission from Lehmann M, et al, J Neurol Neurosurg Psychiatry. © 2016 British Medical Journal.

FIGURE 3-11

Tau imaging in posterior cortical atrophy. [¹⁸F]Flortaucipir positron emission tomography (PET) imaging reveals focal parietooccipital tau pathology. SUVR = standardized uptake value ratio.