Fluctuating cognition, visions and one dose of haloperidol
A 77-year-old retired accountant is brought by his daughter because of two years of 'not being himself'. He has episodes of staring blankly for minutes and then carrying on as if nothing happened, and his alertness varies from day to day. For 18 months he has described small children playing in the garden at night in vivid detail, and once saw his dead brother sitting in the kitchen; he is not frightened and at times seems amused. His wife says he shouts and kicks in his sleep and has fallen out of bed twice. He has become slow, with a shuffling gait and frequent falls. Examination shows symmetrical rigidity and a quiet voice, but no rest tremor. MMSE 22/30 with poor clock drawing and copying. He takes amitriptyline 50 mg for back pain and oxybutynin for urinary urgency. Because of night-time agitation the on-call doctor gives haloperidol 1.5 mg. The next morning he is drowsy, rigid, unable to swallow his tablets, with temperature 37.6 °C and creatine kinase 900 U/L.
1. What is the most likely underlying diagnosis, and how do you distinguish it from its closest rivals?
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Dementia with Lewy bodies (DLB). The central features are all present: fluctuating cognition and arousal, recurrent well-formed and detailed visual hallucinations that are non-threatening, REM sleep behaviour disorder (dream enactment, kicking, falling out of bed), and spontaneous parkinsonism. Supporting features include repeated falls, autonomic dysfunction (urinary urgency), and pronounced visuospatial impairment with relatively preserved naming on the MMSE.
Rivals
- Parkinson's disease dementia: the 'one-year rule' - if parkinsonism has been present for more than 12 months before cognitive decline, label it PDD. Here the cognitive, hallucinatory and sleep features appear early and together, favouring DLB.
- Alzheimer's disease: usually presents with prominent amnesia and language impairment; early vivid hallucinations, REM behaviour disorder and parkinsonism are atypical. Mixed pathology is common, so this is a probabilistic judgement.
- Vascular dementia: stepwise course, focal signs, vascular risk factors on imaging.
- Delirium: the acute deterioration overnight is delirium superimposed on dementia, not the underlying disease; look for the cause (the haloperidol itself, urinary infection, constipation, dehydration, pain).
- Other: progressive supranuclear palsy (vertical gaze palsy, falls early), corticobasal syndrome, drugs (anticholinergics here), and depression with cognitive impairment.
Arrange CT or MRI to exclude structural causes, and consider FP-CIT SPECT or MIBG if the diagnosis remains unclear - but the clinical picture here is strong enough to act on.
2. Explain what happened after the haloperidol and set out your management of the acute deterioration.
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Explanation. Up to half of patients with DLB are exquisitely sensitive to dopamine-blocking drugs: they develop severe rigidity, sedation, immobility, dysphagia, fever and raised CK, sometimes full neuroleptic malignant syndrome, and have a doubled mortality risk with antipsychotics. The 1.5 mg dose was small but enough. The amitriptyline and oxybutynin add a heavy anticholinergic load, which worsens cognition, causes urinary retention and contributes to delirium. This is an iatrogenic deterioration, not a progression of dementia.
Immediate management
- Stop haloperidol permanently and record a documented antipsychotic-sensitivity alert; also stop amitriptyline and oxybutynin, reviewing analgesia and bladder symptoms.
- Supportive care: hydration, monitoring of temperature, CK, renal function and electrolytes, and treat the delirium non-pharmacologically - orientation, daylight, sleep hygiene, hearing aids and glasses, family presence, mobilisation.
- Look for a precipitant: urine dipstick and culture, chest examination, constipation, pain, dehydration.
- If he becomes dangerously agitated, use a very low dose of quetiapine (12.5–25 mg) with caution, and only after cardiology review; clozapine is the evidence-based option for severe psychosis in Parkinsonian disease but requires blood monitoring and should be a specialist decision.
- Escalate to the medical team if fever exceeds 38 °C, CK rises steeply or renal function deteriorates.
Do not restart any typical antipsychotic. Deprescribe systematically and tell the family and the GP in writing what must never be given.
3. Outline the long-term plan, including drug treatment, driving, capacity and support for the family.
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Cholinesterase inhibitor. Start rivastigmine (or donepezil) - the evidence for cognitive and neuropsychiatric benefit in DLB is reasonable, and it may reduce hallucinations. Titrate slowly for nausea and bradycardia, and check pulse and weight.
- Memantine is an option if there is significant behavioural disturbance or the cholinesterase inhibitor is not tolerated.
- REM sleep behaviour disorder: melatonin 3–6 mg at night, or clonazepam at low dose if falls are not a problem; make the bedroom safe (mattress on the floor, remove sharp furniture).
- Falls and autonomic features: physiotherapy, home safety assessment, treat constipation and postural hypotension; avoid anticholinergics and sedatives systematically.
Driving. DLB with fluctuating attention and visuospatial impairment is a driving risk. Advise him to stop now, notify the licensing authority as local law requires, and document the advice; do not rely on him to self-report.
Capacity. Assume capacity until tested decision by decision: he may be unable to manage finances safely while still able to decide about his own residence or treatment. Assess formally when there is a specific decision, and involve the family with his consent.
Family. The wife is the main carer and is at risk of exhaustion and depression; refer to a carers' service, give written information about DLB and the antipsychotic warning, and discuss advance care planning while he can participate. Warn them that hallucinations may be tolerable and do not need to be treated if he is not distressed.