A 72-year-old man develops progressive dementia, prominent visual hallucinations of children and animals, marked day-to-day fluctuations in cognition, and REM sleep behaviour disorder. He falls after starting haloperidol for the hallucinations. What is the diagnosis, and what is the critical management implication of the fall?
- A Alzheimer's disease; start an NMDA antagonist
- B Vascular dementia; antiplatelet therapy
- C Dementia with Lewy bodies; extreme neuroleptic sensitivity — antipsychotics cause severe parkinsonian rigidity and increased mortality; avoid typical and most atypical antipsychotics ✓
- D Frontotemporal dementia; use SSRIs for behavioural symptoms
Explanation
The clinical triad of fluctuating cognition, recurrent visual hallucinations, and parkinsonism, along with REM sleep behaviour disorder (an additional core feature), is pathognomonic of dementia with Lewy bodies (DLB). A critical and potentially fatal characteristic is severe neuroleptic sensitivity — typical antipsychotics and some atypicals (olanzapine, risperidone) can cause profound, irreversible parkinsonism, autonomic instability, and accelerated cognitive decline, with mortality risk 2–3 times higher than in non-DLB patients. The fall after haloperidol reflects acute drug-induced rigidity. Quetiapine (low dose) or clozapine are relatively safer options if behavioural treatment is absolutely necessary.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.