Clinical Screening for Posterior Cortical Atrophy.

Area of Science:

• Neurology
• Neuroscience
• Ophthalmology

Background:

• Posterior cortical atrophy (PCA) is a progressive neurologic syndrome characterized by complex visual deficits.
• PCA is often an early manifestation of Alzheimer disease (AD), but diagnosis is frequently delayed due to a lack of effective clinical screening tools.
• Understanding the specific neurobehavioral deficits in PCA is crucial for timely diagnosis and management.

Purpose of the Study:

• To identify reliable neurobehavioral screening tasks for PCA beyond simple visual construction tasks.
• To develop clinic or bedside-administrable assessments for early PCA detection.
• To differentiate PCA from typical AD (tAD) and healthy controls (HC) using specific cognitive and visual-motor tasks.

Main Methods:

• Compared 12 PCA patients, 12 tAD patients, and 24 HC on tasks including figure-ground discrimination, Balint syndrome, visual object agnosia, and apraxias.
• Evaluated performance on complex figure copying, color identification, global-local processing, and Gerstmann syndrome.
• Utilized neuroimaging-supported consensus criteria for PCA diagnosis.

Main Results:

• Individuals with PCA showed significant impairment in figure-ground discrimination compared to tAD and HC groups.
• Approximately half of the PCA group exhibited Balint syndrome, dressing apraxia, and ideomotor apraxia, which were absent in the tAD group.
• Complex figure copying, global-local processing, and Gerstmann syndrome did not differentiate between PCA and tAD.

Conclusions:

• Figure-ground discrimination tasks serve as effective screening tools for PCA.
• Specific assessments for Balint syndrome and apraxias are recommended for further evaluation in suspected PCA cases.
• PCA is confirmed as an occipitoparietal disorder involving dorsal visual stream and parietal spatiomotor functions.