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Posterior Cortical Atrophy (PCA)

Summary

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  • Neurodegenerative syndrome characterised by progressive decline in visual processing and other posterior cortical functions
  • Typically presents with visual complaints despite intact primary visual pathways
  • Imaging shows atrophy of parietal, occipital, and occipitotemporal cortices

Pathophysiology

  • Underlying pathology is most commonly Alzheimer's disease (AD) in 80-100% of cases
  • Other causes include:
    • Dementia with Lewy bodies
    • Corticobasal degeneration
    • Prion disease
  • Selective vulnerability of posterior brain regions, particularly visual association areas
  • Neuronal loss and accumulation of amyloid plaques and neurofibrillary tangles in affected areas

Demographics

  • Typically affects individuals in their 50s or 60s
  • Mean age of onset: 58-60 years
  • No clear gender predilection
  • Rare disorder, estimated to account for 5-10% of early-onset dementia cases

Diagnosis

  • Clinical presentation:
    • Progressive visual dysfunction (e.g., difficulty reading, recognising objects, or navigating)
    • Preserved memory and insight in early stages
    • Later development of other cognitive deficits
  • Neuropsychological testing:
    • Impairments in visuospatial and visuoperceptual tasks
    • Relatively preserved memory and language functions
  • Diagnostic criteria:
    • Proposed by Crutch et al. (2017)
    • Core features include insidious onset, gradual progression, and prominent visual deficits

Imaging

  • Structural MRI:
    • Atrophy of parietal, occipital, and occipitotemporal cortices
    • Relative sparing of medial temporal lobes and hippocampi in early stages
    • Progressive atrophy with disease progression
  • Functional imaging (PET/SPECT):
    • Hypometabolism/hypoperfusion in posterior cortical regions
    • Asymmetry common, with right hemisphere often more affected
  • Advanced techniques:
    • Diffusion tensor imaging: white matter tract degeneration in posterior regions
    • Amyloid PET: positive in AD-related PCA cases

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  • A 65-year-old patient presented with memory impairment, visual hallucinations and apraxia.
  • MRI showed relatively mild hippocampal atrophy on the right but severe symmetrical atrophy of the parietal and occipital lobes.
  • CSF biomarkers were compatible with Alzheimer's disease.

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  • A 60-year-old patient presented with logopenic aphasia and memory impairment.
  • MRI showed marked widening of parietal and, to a lesser extent, occipital sulci.
  • Hippocampal volume loss was less pronounced (MTAS 2).
  • CSF biomarkers were consistent with Alzheimer's disease.

Treatment

  • No disease-modifying treatments currently available
  • Symptomatic management:
    • Acetylcholinesterase inhibitors (e.g., donepezil) may provide modest cognitive benefit
    • Memantine for moderate to severe cases
  • Non-pharmacological interventions:
    • Occupational therapy to address visual and spatial deficits
    • Environmental modifications to improve safety and function
    • Cognitive rehabilitation strategies
  • Support and education for patients and caregivers
  • Regular monitoring and adjustment of care plan as disease progresses