Posterior cortical atrophy: Primary occipital variant.

Area of Science:

• Neurology
• Neuroscience
• Medical Imaging

Background:

• Posterior cortical atrophy (PCA) is an atypical Alzheimer's disease variant.
• PCA is characterized by visuospatial and visuoperceptual deficits.
• Established dorsal and ventral subtypes exist, with a potential primary occipital (caudal) variant suggested.

Purpose of the Study:

• To define the demographics, clinical features, and biomarker profile of the primary occipital variant of PCA.
• To differentiate the primary occipital PCA from other PCA subtypes.

Main Methods:

• Investigated 52 PCA patients using neuropsychological assessment, MRI, and PET scans (FDG-PET, amyloid-PET, tau-PET).
• Classified patients into "primary occipital" and "other PCA" subgroups based on FDG-PET criteria.
• Analyzed regional FDG-PET z-scores, global amyloid-PET, temporo-parietal FDG-PET, and temporal tau-PET.

Main Results:

• Identified 9 patients with primary occipital PCA; they were older and had more education.
• Primary occipital PCA patients showed worse color perception (Ishihara test) but less severe ideomotor apraxia (WAB praxis scale).
• Primary occipital PCA had higher FDG-PET meta-ROI but no differences in amyloid- or tau-PET compared to other PCA.

Conclusions:

• Primary occipital PCA is characterized by older age at onset and impaired color perception.
• This variant exhibits less severe ideomotor apraxia and reduced temporo-parietal hypometabolism.
• Findings differentiate primary occipital PCA from established PCA phenotypes.