CBL: Corticobasal Degeneration (CBD)

Asymmetric limb rigidity/apraxia in a 58-year-old — localize, differentiate, and plan care.

Topic: Movement Disorders Level: Resident Tags: CBD, atypical parkinsonism, apraxia, alien-limb

Vignette

PG, a 58-year-old right-handed man, reports 6 months of painless stiffness in the left arm interfering with dressing and eating. No tremor, sensory loss, or involuntary movements. He denies gait change or cognitive symptoms; review of systems only notes mild constipation. PMH: CAD s/p stent (aspirin, metoprolol).

Exam: Vitals normal. Alert and fluent with intact naming, memory, and writing. Cranial nerves normal. Increased tone in left wrist/finger flexors and extensors without weakness or tremor. Reflexes symmetric; toes downgoing. Sensation intact. Coordination limited on the left by rigidity; right side normal. Gait normal.

Question 1

Which localization best fits the presentation?

  • A. Cerebellar hemispheres
  • B. Right corticospinal tract with upper motor neuron weakness
  • C. Basal ganglia–cortical networks affecting the left upper limb
  • D. Peripheral nerve entrapment

Question 2

What is the most appropriate leading diagnosis and key mimics?

  • A. Parkinson disease; no mimics
  • B. CBD; mimics include PD, PSP, dystonia, stroke
  • C. Multiple sclerosis; mimics include PD and PSP
  • D. Motor neuron disease; mimic is FTD

Question 3

Which statement about diagnosis is most accurate?

  • A. MRI and biomarkers provide a definitive diagnosis
  • B. CBD is diagnosed mainly by clinical history and examination
  • C. PET always distinguishes CBD from PSP
  • D. Genetic testing confirms CBD in most cases

Question 4

Which management plan is most appropriate to start?

  • A. High-dose levodopa only; therapies rarely help
  • B. Multidisciplinary care: PT/OT/speech; trial levodopa; symptomatic meds for rigidity/behavior; caregiver support
  • C. Immediate disease-modifying therapy with tau inhibitor
  • D. Deep brain stimulation (DBS) is first-line for CBD

Teaching Points

  • CBD: asymmetric limb rigidity/apraxia → mixed motor–cognitive syndrome within 2–3 years.
  • Key exam: rigidity without weakness or tremor; alien limb or myoclonus may appear later.
  • Diagnosis is clinical; MRI/PET may show asymmetric cortical/basal-ganglia changes but are not definitive.
  • Care is supportive: PT/OT/speech, consider trial levodopa, manage behavior/cognition, plan for function and safety.

References

  1. Armstrong MJ, et al. Criteria for the diagnosis of corticobasal degeneration (2013 consensus). Research framework.
  2. Contemporary reviews on corticobasal syndrome, imaging patterns, and symptomatic management.