Démence à corps de Lewy

Dementia is a clinical syndrome where there is progressive and widespread impairment of mental function. There are a number of types of dementia, with Maladie d'Alzheimer being the most common. Dementia with Lewy bodies (DLB) is varyingly quoted as the second or third most common type of dementia, and shares characteristics with Alzheimer's disease and la maladie de Parkinson.

How does dementia with Lewy bodies develop? (Pathogenesis)

This type of dementia is characterised by eosinophilic intracytoplasmic neuronal inclusion bodies (Lewy bodies) in the brainstem and neocortex.

There is a spectrum of Lewy body disorders, which may overlap, that include DLB, Parkinson's disease and Parkinson's disease-associated dementia.

How common is dementia with Lewy bodies? (Epidemiology)

DLB is a common type of dementia which is estimated to affect more than 100,000 people in the UK.¹ It is rare under the age of 65. DLB and dementia in Parkinson's disease together may be the cause of up to 15% of cases of dementia.²

Typical presentation

• Dementia is usually the presenting feature, with memory loss, decline in problem solving ability and spatial awareness difficulties.

• Characteristically there are fluctuating levels of awareness and attention.

• Signs of mild Parkinsonism (tremor, rigidity, poverty of facial expression, festinating gait). Falls frequently occur.

• Visual hallucinations.

• Sleep disorders including rapid eye movement sleep disorder, restless legs syndrome, nocturnal cramps.

• Fainting spells.

Diagnosis of dementia with Lewy bodies

The international consensus criteria should be used.^{3 4} Accurate diagnosis is important as it affects management.

Criteria for diagnosis of probable DLB are based on the presence of dementia in addition to core features and biomarkers.

• Core clinical features:
  

  • Fluctuating cognition with pronounced variations in attention and alertness.

  • Recurrent visual hallucinations which are typically well formed and detailed.

  • Spontaneous Parkinsonism with one or more features - these can include bradykinesia, rest tremor or rigidity.

  • REM sleep behaviour disorder, which may precede cognitive decline.

• Indicative biomarkers:
  

  • Low dopamine transporter uptake in basal ganglia demonstrated by single photon emission computed tomography (SPECT) or positron emission tomography (PET) imaging (see 'Investigations', below).

  • Abnormal (low uptake) ¹²³iodine-MIBG myocardial scintigraphy.

  • Polysmnographic confirmation of REM sleep without atonia.

Probable DLB can be diagnosed where there are two or more core clinical features, with or without indicative biomarkers, or one core clinical feature with one or more indicative biomarkers.

Possible DLB can be diagnosed if there is one core clinical feature with no indicative biomarkers, or one or more indicative biomarkers, with no core clinical features.

The criteria also give a list of supportive clinical features and biomarkers.

Supportive clinical features:

• Severe sensitivity to antipsychotic agents.

• Postural instability.

• Repeated falls.

• Syncope or other transient episodes of unresponsiveness.

• Severe autonomic dysfunction - eg, constipation, orthostatic hypotension, urinary incontinence.

• Hypersomnia.

• Hyposmia.

• Hallucinations in other modalities.

• Systematised delusions.

• Apathy, anxiety and depression.

Supportive biomarkers:

• Relative preservation of medial temporal lobe structures on CT/MRI scan.

• Generalised low uptake on SPECT/PET perfusion/metabolism scan with reduced occipital activity +/- the cingulate island sign on FDG-PET imaging.

• Prominent posterior slow-wave activity on EEG with periodic fluctuations in the pre-alpha/theta range.

DLB is less likely in the presence of other physical illness or brain disorder, including cerebrovascular disease, sufficient to account for the clinical picture in part or in full. However this does not fully exclude DLB, which may exist in combination with other pathologies. It is also less likely if Parkinsonian features are the only core clinical feature and appear for the first time at a stage of severe dementia.

DLB should be diagnosed when dementia occurs before or concurrently with parkinsonism, whereas if the dementia is diagnosed in the context of previously diagnosed Parkinson's disease, the term Parkinson disease dementia (PDD) should be used.

Clinical cognitive assessment is made using one of the standardised tools mentioned by National Institute for Health and Care Excellence (NICE) or Scottish Intercollegiate Guidelines Network (SIGN) guidance:³

• 6-item Cognitive Impairment Test (6-CIT).

• Le test cognitif à 10 points (10-CS).

• Le dépistage en 6 items.

• Le test de dépistage des troubles de la mémoire (MIS).

• Le Mini-Cog.

• Testez Votre Mémoire (TYM).

• Standard informant interviews may help improve sensitivity (eg, the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE).⁵

Diagnostic différentiel

• Other forms of dementia, especially dementia in la maladie de Parkinson or dementia in progressive supranuclear palsy. Normally in dementia associated with Parkinson's disease, the movement disorder has been present for at least a year before the onset of dementia and this one-year rule is used in research studies where the distinction needs to be made between DLB and PDD.

• Intracranial tumours.

• Accidents vasculaires cérébraux.

Enquêtes

• The decision to refer is usually a clinical one.

• The basic dementia screen is not specified in the NICE guideline, but many clinics ask for the following blood tests before referral:³

  • Routine haematology - FBC, ferritin, vitamin B12, folate.

  • Biochemistry (including electrolytes, calcium, glucose, and renal and liver

  • function).

  • TFTs.

  • Midstream specimen of urine (MSU).

  • CXR and ECG where clinically indicated.

• CT and MRI scanning are largely used in secondary care to exclude other causes of dementia - other scans are used as indicated in the biomarker section of the diagnostic criteria.

Management of dementia with Lewy bodies³

• Refer to a specialist with expertise in differential diagnosis - so that DLB can be identified using the appropriate criteria and investigations.

• After diagnosis, the patient and their family/carers should have access to a memory service or equivalent multidisciplinary dementia service.

• People living with dementia should have a single named health or social care professional who is responsible for co-ordinating their care and who should develop a care and support plan.

• Offer carers a psychoeducation and skills training programme which includes education, the development of personalised strategies, training in how to communicate and provide care and advice about how to look after their own physical and mental health.

• Ensure that support provided to carers is tailored to their needs and preferences and available at a location that they can get to easily.

• Offer a range of activities to promote well-being, tailored to the person's preferences.

• Offer group cognitive stimulation therapy to people living with mild or moderate dementia.

• Do not offer acupuncture, ginseng, vitamin E supplements or herbal formulations to treat dementia.

• Try to involve the psychiatric social worker and carer support workers early. They can help with the initial risk assessment, arrange appropriate financial support (allowances etc), and arrange daycare, day centre attendance, relief admissions, etc.

• Driving is a very complex task and all patients with dementia must inform the DVLA. Decisions on licensing are usually based on medical reports for those with a Group 1 licence, but a formal driving assessment may also become necessary. In early dementia with slow progression, a licence may be issued with the need for annual review. Group 2 licences will be revoked.⁶

• If a patient and/or their family/carers will not co-operate with the DVLA, then consider whether you are obligated to break confidentiality. The GMC guidelines in this area may help and it would be sensible to discuss this with your defence organisation.⁷

Médication

Behavioural and psychotic symptoms may need assessment by a psychogeriatrician, who may also assess whether drug treatment is appropriate to prevent deterioration.

• Avoid antipsychotic drugs for psychiatric and behavioural problems - these commonly induce severe sensitivity reactions in DLB patients - motor and mental impairment is worsened and mortality may be increased. Where these are used, careful monitoring for sensitivity reactions should take place and the lowest effective dose should be used for the shortest possible time. The patient and their family/carers should be involved in the decision making process if these drugs are used.

• Anti-Parkinsonian treatment may also worsen psychosis.

• NICE and SIGN guidelines advise that the cholinesterase inhibitors donepezil or rivastigmine can be used for DLB, with galantamine being used only if donepezil and rivastigmine are not tolerated.

• If cholinesterase inhibitors are not tolerated, or are contra-indicated, consider memantine.

• The most recent Cochrane review suggests that the evidence of benefit remains unclear and the NICE guideline acknowledges that it is often unclear if prescribing is appropriate, and that further randomised controlled trials in this area are needed.^{8 3}

Pronostic

As with other types of dementia, DLB is progressive, and shortens lifespan. It progresses gradually over the course of years. Average survival from onset is 5-8 years.⁹ Rate of cognitive decline appears to be faster than for those with Alzheimer's disease.¹⁰