A 68-year-old man develops progressive cognitive decline over 2 years with prominent early visual hallucinations of children in his room, marked day-to-day fluctuation in alertness, and mild parkinsonian rigidity. His family notes he acts out his dreams at night, thrashing and shouting during sleep. A single dose of an antipsychotic produced severe rigidity and collapse. Which finding best supports the diagnosis over Parkinson disease dementia?

• A Cognitive decline beginning more than one year after motor symptoms
• B Good response to levodopa
• C Presence of bradykinesia and rigidity
• D REM sleep behavior disorder preceding cognitive decline ✓

Explanation

Dementia with Lewy bodies is diagnosed when cognitive decline occurs before or within one year of parkinsonism; cognitive decline starting beyond one year after established motor symptoms indicates Parkinson disease dementia instead. REM sleep behavior disorder, fluctuating cognition and early hallucinations all favor Lewy body dementia. Severe neuroleptic sensitivity, as seen here, is also characteristic. Bradykinesia and rigidity occur in both conditions, so option C does not discriminate between them.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.