Clinical Screening for Posterior Cortical Atrophy

Abstract

Background: Posterior cortical atrophy (PCA) is a progressive neurologic syndrome that presents with complex visual deficits. Although PCA is most commonly a form of Alzheimer disease (AD), its early diagnosis is usually delayed due to a lack of understanding for how best to clinically screen for the syndrome. Objective: To identify neurobehavioral screening tasks for PCA—beyond simple visual constructions—that can be administered in clinic or at bedside. Method: We compared the performance of 12 individuals who met neuroimaging-supported consensus criteria for PCA with that of 12 matched individuals with typical AD (tAD) and 24 healthy controls (HC) on clinic/bedside tasks measuring (a) complex figure copying, (b) Balint syndrome, (c) visual object agnosia, (d) color identification, (e) figure–ground discrimination, (f) global–local processing, (g) dressing apraxia, (h) ideomotor apraxia, and (i) Gerstmann syndrome. Results: All of the individuals with PCA were impaired on the figure–ground discrimination task compared with half of the tAD group and no HC. Approximately half of the PCA group had Balint syndrome, dressing apraxia, and ideomotor apraxia compared with none in the tAD group. Difficulty copying a complex figure, global–local processing impairment, and Gerstmann syndrome did not distinguish between the two dementia groups. Conclusion: The figure–ground discrimination task can be used successfully as an overall screening measure for PCA, followed by specific tasks for Balint syndrome and dressing and limb apraxia. Findings reinforce PCA as a predominant occipitoparietal disorder with dorsal visual stream involvement and parietal signs with spatiomotor impairments.