A 71-year-old man has had slowly progressive cognitive decline for four years. Two years after the memory problems began, he developed bradykinesia, rigidity, and a shuffling gait. There were no motor symptoms before the cognitive decline. Which diagnosis does this temporal profile best support?
- A Parkinson disease dementia ✓
- B Dementia with Lewy bodies
- C Alzheimer disease with incidental parkinsonism
- D Progressive supranuclear palsy
Correct answer: A. Parkinson disease dementia
Explanation
The accepted convention distinguishes Parkinson disease dementia from dementia with Lewy bodies by the one-year rule: when cognitive decline develops at least one year after established parkinsonism, the label is Parkinson disease dementia; when dementia precedes or appears within one year of motor symptoms, it is dementia with Lewy bodies. Here cognition came first by two years, so option A fits. Progressive supranuclear palsy shows vertical gaze palsy and falls early, not described here.
Reference: Kaplan and Sadock's Synopsis of Psychiatry, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.