A 70-year-old man presents with bradykinesia, cogwheel rigidity, unilateral resting tremor, and postural instability. He has a poor response to levodopa after 18 months. MRI shows 'hummingbird sign' (midbrain atrophy with relative pontine preservation). The most likely diagnosis is:
- A Parkinson's disease
- B Progressive supranuclear palsy (PSP) ✓
- C Multiple system atrophy (MSA-P subtype)
- D Corticobasal syndrome
Explanation
Progressive supranuclear palsy (Richardson syndrome) classically presents with vertical supranuclear gaze palsy, axial rigidity, early falls, and poor levodopa response. The 'hummingbird sign' (also called penguin sign) on MRI sagittal view reflects selective midbrain atrophy with preserved pons — the midbrain-to-pons area ratio and midbrain diameter are hallmarks of PSP on neuroimaging. MSA-P shows 'hot cross bun sign' on axial pons MRI. Corticobasal syndrome features alien limb phenomenon and asymmetric apraxia. Parkinson's disease responds to levodopa and lacks the specific MRI changes.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.