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Lewy body dementia (LBD) is characterised by the triad of cognitive fluctuation, visual hallucinations, and parkinsonism. REM sleep behaviour disorder often precedes other symptoms by years. Neuroleptic sensitivity is a critical risk; Antipsychotics can cause severe, life-threatening reactions.
Key Knowledge
● LBD is the second most common neurodegenerative dementia, after Alzheimer’s
● Core features: fluctuating cognition, visual hallucinations, parkinsonism, REM sleep behaviour disorder
● Differs from Parkinson’s disease dementia by timing: in LBD, cognitive symptoms occur within one year of motor symptoms (or before)
● Severe neuroleptic sensitivity (avoid typical and most atypical antipsychotics)
● Supportive features include autonomic dysfunction, falls, syncope, severe sensitivity to antipsychotics
● Diagnosis is clinical (Diamond Lewy Toolkit is a useful aid to assess core features); DaT scan can support diagnosis and if diagnostic uncertainty persists then an MIBG scan.
What is Lewy Body Dementia?
Dementia with Lewy bodies is a neurodegenerative disorder characterised by the abnormal accumulation of alpha-synuclein (Lewy bodies) in the brain, particularly affecting cortical and subcortical structures.
Core clinical features (at least two required for probable diagnosis):
● Fluctuating cognition: Pronounced variations in attention and alertness, day-to-day, or even hour-to-hour. The individual may be lucid one moment and confused the next. Daytime drowsiness and episodes of reduced responsiveness are common.
● Recurrent visual hallucinations: Typically well-formed, detailed, often of people or animals. Usually non-threatening initially, but can cause distress. Partial insight that they are not real may be present.
● REM sleep behaviour disorder (RBD): Acting out dreams during REM sleep, e.g. shouting, punching, kicking, typically reported by a partner. This may precede other symptoms by years. Note this can cause risk due to assaulting people in their sleep.
● Spontaneous parkinsonism: Bradykinesia, rigidity, tremor (rest tremor less common than in Parkinson’s disease). Gait disturbance and postural instability are common.
Other possible features:
● Severe neuroleptic sensitivity (life-threatening reactions to antipsychotics)
● Postural instability and falls
● Syncope and autonomic dysfunction (orthostatic hypotension, urinary incontinence, constipation)
● Hypersomnia
● Hyposmia (reduced sense of smell)
● Delusions (often paranoid)
● Apathy, anxiety, low mood
Cognitive profile:
● Early and prominent deficits in attention, executive function, and visuospatial abilities
● Memory may be relatively preserved early on (unlike Alzheimer’s)
● Decline is progressive but fluctuating
Relationship to Parkinson’s disease dementia (PDD):
The “one-year rule” differentiates LBD from PDD: if dementia occurs before or within one year of motor symptoms, it’s LBD; if motor symptoms precede dementia by more than one year, it’s PDD. The underlying pathology and treatment is similar.
Differential Diagnosis for Lewy Body Dementia
1. Alzheimer’s disease
Key distinctions: Alzheimer’s presents with early, prominent memory impairment and gradual, steady decline. Visual hallucinations, parkinsonism, and RBD are uncommon. Fluctuations are less marked. Neuroleptic sensitivity is not a feature.
2. Parkinson’s disease dementia (PDD)
Key distinctions: In PDD, motor symptoms (bradykinesia, rigidity, tremor) precede cognitive decline by more than one year. In LBD, cognitive symptoms occur within one year of motor symptoms or before them.
3. Vascular dementia
Key distinctions: Stepwise deterioration related to cerebrovascular events. Cognitive profile depends on location of infarcts. Parkinsonism and hallucinations are less common. Neuroimaging shows evidence of cerebrovascular disease.
4. Delirium
Key distinctions: Delirium is acute or subacute, with an identifiable medical precipitant (infection, medication, metabolic disturbance). It is potentially reversible. LBD has chronic, progressive fluctuation rather than acute onset.
5. Late-onset psychotic disorder or schizophrenia
Key distinctions: Psychotic disorders do not involve progressive cognitive decline, parkinsonism, or RBD. Onset of schizophrenia after age 60 is rare
6. Frontotemporal dementia (FTD)
Key distinctions: FTD presents with prominent behavioural changes (disinhibition, apathy, loss of empathy) or language deficits. Visual hallucinations and parkinsonism are uncommon early on.
7. Depression with pseudodementia
Key distinctions: In depression, cognitive complaints exceed objective impairment. Mood symptoms predominate. Response to antidepressant treatment improves cognition. However, note depression can co-exist with LBD.
Risk Assessment in Lewy Body Dementia
As with every risk assessment, you must consider risk to self, to others and from others.
To self:
● Falls and injury – Parkinsonism, orthostatic hypotension and autonomic dysfunction increase fall risk
● Aspiration and choking – Swallowing difficulties in later stages
● Severe neuroleptic reactions – Life-threatening if antipsychotics are prescribed
● Wandering and getting lost – Disorientation during fluctuations
● Self-neglect – Inability to manage ADLs, nutrition, hygiene
● Accidents – Due to cognitive impairment (e.g., leaving oven on)
● Depression and suicide – Insight into decline can lead to low mood
To others:
● Generally low
● RBD may cause unintentional injury to partner during sleep
From others:
● Vulnerability to financial exploitation or abuse due to cognitive impairment
Communication Tips
LBD often presents with hallucinations or confusion, so a detailed collateral history is essential. Focus on fluctuations, hallucinations, motor symptoms and sleep.
Opening and collateral history:
● “I’d like to understand what’s been happening. Can you tell me what you’ve noticed?”
● (To carer/relative) “Can you describe a typical day? What changes have you noticed?”
Exploring cognitive fluctuations:
● “Does their alertness vary from day-to-day or even during the day?”
● “Are there times when they seem very drowsy or ‘switched off’?”
● “Do they have good days or bad days?”
● “Can they hold a conversation sometimes but seem confused at other times?”
Exploring hallucinations:
● “Have you noticed them seeing or hearing things that aren’t there?”
● “What do they see? Can they describe it?”
● “How do they react to these experiences? Are they frightened or unbothered?”
● “Do they happen more at certain times of day?”
Exploring motor symptoms:
● “Have you noticed any slowness in their movements?”
● “Do they have stiffness, shakiness or difficulty walking?”
● “Have they had any falls?”
Exploring sleep:
● (To partner) “Do they act out their dreams at night, including shouting, thrashing, punching?”
● “Have you been hit or kicked during the night?”
● “When did this start?” (May predate other symptoms)
Exploring autonomic symptoms:
● “Do they get dizzy when they stand up?”
● “Any problems with bladder or bowel control?”
● “Any excessive daytime sleepiness?”
Impact on functioning:
● “How are they managing day-to-day tasks such as washing, dressing, cooking?”
● “Do they need help with these now?”
● “Can they still recognise family members?”
Screen for mood and behavioural symptoms:
● “Have you noticed any changes in mood or anxiety?”
● “Any paranoia or unfounded suspicions?”
● “Any loss of interest in things they previously enjoyed?”
Medications (critical):
● “What medications are they taking?”
● “Have they been prescribed any antipsychotics?” (Flag neuroleptic sensitivity risk)
CASC Scenario: Lewy Body Dementia
Setting: Memory clinic (outpatient)
Candidate Instructions:
You are the SpR in the memory clinic. You are seeing Mrs Joan Whitaker, an 82-year-old retired librarian, with her daughter Susan. Mrs Whitaker was referred by her GP following concerns about memory problems and confusion over the past 14 months. ACE-III score last week was 68/100 (attention 12/18, memory 16/26, fluency 8/14, language 24/26, visuospatial 8/16). MRI brain showed generalised atrophy with no focal lesions or significant vascular disease. Blood tests including TFTs, B12, FBC, CRP and glucose were normal.
Please take a collateral history from Susan regarding her mother’s presentation.
Scenario Summary:
Joan Whitaker is an 82-year-old woman with a 14 month history of cognitive decline consistent with Lewy body dementia. She has prominent day-to-day fluctuations in cognition and alertness, recurrent well-formed visual hallucinations (seeing children in the house, animals), spontaneous parkinsonism (stooped posture, shuffling gait, falls), and REM sleep behaviour disorder, predating other symptoms by two years (acting out dreams, shouting at night). She has had several falls, episodes of syncope, and demonstrates prominent visuospatial deficits. Her daughter manages her care and is exhausted. Joan has mild insight into her memory problems but not into her hallucinations. There is significant concern about falls risk and caregiver burden.
Actor Brief:
You are Susan Whitaker, a 56-year-old office manager living in Guildford. You’re here today with your mother, Joan, who is 82 and a retired librarian. You live about thirty minutes away and visit three times a week, but you’re increasingly worried about her safety living alone in her bungalow alone.
The memory problems started about 14 months ago. At first, it was small things, such as forgetting appointments, repeating herself, losing her keys. But it’s gotten much worse. What’s really striking is how much she varies from day to day, even hour to hour. Some days she seems quite sharp; she’ll chat normally, remember things, follow conversations. Other days, especially in the afternoons, she’s completely confused, doesn’t know what day it is, asks the same question over and over, and seems “miles away.” You can have a conversation with her in the morning and by lunchtime, it’s like she’s a different person; vacant, staring into space, not really responding.
About six months ago, she started seeing things that weren’t there. She tells you there are children in the house, usually two or three of them, playing in the living room. She’ll talk to them, such as asking them if they want food. She also sees cats and dogs that aren’t there. She’s not frightened by these visions, in fact, she seems quite matter-of-fact about them. When you tell her there’s no one there, she looks confused but doesn’t seem distressed. It happens most days now.
Her movement has deteriorated. She shuffles when she walks, hunched over, taking tiny steps. She’s had five falls in the past six months; three at home, two on her road. She just seems to lose her balance. Her face looks quite blank and expressionless now, which is sad because she used to be so animated. She moves very slowly, and it takes her ages to get dressed or make a cup of tea.
She also has these episodes where she just “goes” – she’ll suddenly sway, go pale, and nearly collapse. It’s happened twice while you’ve been there. She comes round after a minute or so, but it’s terrifying. Her GP checked her blood pressure and said something about it dropping when she stands up.
There’s also something odd that started before all of this; about five years ago, your father (who died three years ago) complained that Joan would shout and thrash around in her sleep, acting out dreams. She’d kick him, punch the air, shout at people. He joked that she was “fighting off burglars” in her dreams. You didn’t think much of it at the time, but you’ve read that it might be relevant.
She’s managing basic tasks like washing and dressing, but she needs prompts. She forgets to eat if you don’t check. She can’t cook anymore and she left the gas on the hob twice and nearly caused a fire. She can’t manage her medications independently. She struggles with anything that requires planning or organisation. She can’t work the remote control for the TV anymore, which is frustrating for her.
Her mood is okay, she’s not depressed and still has moments of humour and pleasure, especially on her good days. But she’s aware something’s wrong and occasionally gets tearful about it. She’s sleeping reasonably well, though restless at night. She doesn’t drink or smoke. She’s on ramipril 5mg for blood pressure and atorvastatin 20mg for cholesterol, both of which you manage for her.
You’re exhausted. You’re working full-time, managing your mother’s care, and worried constantly about her falling or leaving the gas on. You’ve had to take time off work multiple times. Your husband, David, has been supportive, but you can feel the strain. You’re worried about what happens next and whether she can stay at home much longer.
Feedback for Scenario
Knowledge & Clinical Skills
A good candidate will:
● Elicit the core clinical features of lewy body dementia through targeted questioning: fluctuating cognition and alertness (day-to-day and hour-to-hour variation), recurrent visual hallucinations (well-formed, detailed, often of people or animals), spontaneous parkinsonism (bradykinesia, rigidity, shuffling gait, postural instability, falls), and REM sleep behaviour disorder
● Systematically assess supportive features including falls, syncope, autonomic dysfunction (orthostatic hypotension), and visuospatial deficits, which are more prominent in LBD than in Alzheimer’s disease
● Check medical history and screen for delirium (infection, constipation, pain)
● Explore functional impairment comprehensively, particularly safety concerns (falls, cooking, medication management) which are critical for determining level of support needed and capacity for independent living
● Assess caregiver burden sensitively.
● Assess risk (wandering, self-neglect, falls, risk to others)
Communication
A good candidate will:
● Demonstrate empathy for the daughter’s exhaustion and distress, explicitly acknowledging the burden of caring and the emotional toll of watching a parent decline
● Structure the collateral history efficiently, covering the key domains (cognition, hallucinations, motor symptoms, function, mood, behaviour) while remaining responsive to the daughter’s concerns
● Balance the need to gather information with addressing the daughter’s emotional needs, allowing space for her to express worry and frustration while keeping the interview focused
● Offer daughter support when distressed “this sounds like it is putting a lot of pressure on you – there are things we can do to help and it would be good to explore this with you in more detail in a future appointment.”
Authors / Reviewers
Dr Damir Rafi is a psychiatry speciality registrar in forensics, currently working in London.
Dr Leola Foscoe is a is a psychiatry speciality registrar in older adults, currently working in the North East of England.
Dr Rebecca Goodall is a is a psychiatry speciality registrar in child and adolescent psychiatry, currently working in London.
References and Resources
● World Health Organization. (2019). International classification of diseases for mortality and morbidity statistics (11th ed.). https://icd.who.int/browse11/l-m/en
● McKeith, I. G., et al. (2017). Diagnosis and management of dementia with Lewy bodies: Fourth consensus report of the DLB Consortium. Neurology, 89(1), 88-100. https://doi.org/10.1212/WNL.0000000000004058
● National Institute for Health and Care Excellence. (2018). Dementia: Assessment, management and support for people living with dementia and their carers (NG97). https://www.nice.org.uk/guidance/ng97
Disclaimer:
This article is intended for use as a learning resource for doctors training in Psychiatry in the UK. It is not intended for patients. If you are looking for information about mental health conditions, please visit www.rcpsych.ac.uk/mental-health to find readable, user-friendly and evidence-based information on mental health problems, treatments and other topics written by qualified psychiatrists, with help from patients and carers. If you are looking for help for a mental health condition, please visit https://www.mind.org.uk/ for information about where help is available.
The article was written by UK doctors and cross-checked against various published sources (see Reference list). We endeavour to keep information up to date, but it should not be relied on for clinical decision making. Consult local guidelines and senior colleagues whenever you are not sure.