Capgras Delusion in Posterior Cortical Atrophy-A Quantitative Multimodal Imaging Single Case Study

Area of Science:

• Neurology
• Neuroimaging
• Psychiatry

Background:

• Alzheimer's disease (AD) typically presents with memory loss, but atypical variants exist.
• Posterior Cortical Atrophy (PCA) is an AD variant causing severe visuospatial and visuoperceptual deficits.
• Capgras delusion, a rare misidentification syndrome, has not been previously reported in PCA.

Purpose of the Study:

• To report the first case of Capgras delusion in a patient diagnosed with PCA.
• To investigate the neuroanatomical correlates of Capgras delusion in PCA using multimodal neuroimaging.
• To elucidate the brain-behavior relationship in this rare presentation.

Main Methods:

• Case study of a 57-year-old female patient with PCA who developed Capgras delusion.
• Multimodal neuroimaging: structural MRI (voxel-based morphometry) and FDG-PET, F18-florbetaben PET.
• Analysis of gray matter volume changes and glucose hypometabolism.
• Functional connectivity analysis to assess network involvement.

Main Results:

• The patient developed Capgras delusion 8 years after initial PCA symptoms.
• Voxel-based morphometry revealed progressive gray matter atrophy in occipital, temporoparietal, and frontal regions, predominantly in the right hemisphere.
• FDG-PET showed parietooccipital and right frontotemporal hypometabolism.
• Amyloid accumulation was detected in the neocortex, confirming underlying AD.
• Capgras delusion onset correlated with atrophy in the right posterior cingulate gyrus/precuneus and right middle frontal gyrus/frontal eye field.

Conclusions:

• This case demonstrates a link between specific patterns of brain atrophy in PCA and the development of Capgras delusion.
• Right frontal and posterior cingulate/precuneus regions appear critical for the manifestation of Capgras delusion in PCA.
• Findings suggest involvement of default mode and dorsal attention networks in this delusion.