Corticobasal Degeneration

Corticobasal Degeneration (CBD) is a rare neurodegenerative disease affecting movement, cognition, and behavior, caused by tau protein buildup in the cerebral cortex and basal ganglia.[1] Symptoms typically begin between ages 50-70, with an average survival of 6-8 years.[2] The cause remains unknown, though research explores tau-related mechanisms for potential treatments.

CBD affects 4.9-7.3 per 100,000 people, often presenting asymmetrically, starting in one limb.[2] It’s one of the Parkinson-plus syndromes, with diagnosis complicated by overlap with Parkinson’s, PSP, and other disorders, requiring postmortem confirmation for certainty.[3]

Symptoms

CBD symptoms vary but often include:[3]

  • Slowness and stiffness (parkinsonism)
  • Dystonia (abnormal postures)
  • Myoclonus (rapid muscle jerks)
  • Difficulty concentrating or cognitive changes
  • Language issues (e.g., trouble finding words)
  • Behavioral changes (e.g., crude actions)

A common feature is “alien limb syndrome,” where an arm moves uncontrollably despite intact strength, affecting tasks like combing hair.[4] Walking and balance issues often emerge later.[2]

Cause and Pathophysiology

CBD involves tau protein misfolding into insoluble fibers, destabilizing microtubules and causing cell death in the cortex and basal ganglia.[5] Astrocytic plaques, identified via Gallyas-Braak staining, are a hallmark, particularly in the frontal and premotor cortex.[6] The exact trigger is unclear, with rare familial cases linked to genetic mutations.

Diagnosis

Diagnosis uses the 2013 Armstrong criteria, requiring gradual onset over 1+ year and specific features like limb rigidity or alien limb phenomena.[7] Overlap with PSP, Parkinson’s, and Alzheimer’s complicates clinical diagnosis, with MRI showing asymmetric cortical atrophy.[8] Definitive confirmation comes postmortem via tauopathy evidence.[9]

Management

No cure exists; treatments target symptoms. Dopaminergic drugs like levodopa offer limited relief for parkinsonism,[10] while therapies (e.g., speech, physical) and mobility aids help manage symptoms.[2] Research into tau-targeted therapies continues.

Prognosis and History

Survival averages 8 years, with death often from aspiration pneumonia or infections.[2] CBD was first described in 1967 as corticodentatonigral degeneration, with the term "corticobasal degeneration" coined in 1989.[11]

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