Diagnosis of dementia with Lewy bodies

It's always important to get dementia diagnosed, but knowing the type of dementia is particularly important if dementia with Lewy bodies is suspected. Find out who is most likely to be affected and how you can get a diagnosis.

Who is affected by dementia with Lewy bodies?

Dementia with Lewy bodies (DLB) accounts for around 4 per cent of all recorded dementia, but there is good evidence that the condition is not always diagnosed correctly. Based on studies of brain tissue after death, scientists think DLB may account for as much as 10-15 per cent of all dementia.

DLB appears to affect men and women equally. As with Alzheimer's disease and vascular dementia, DLB becomes more common over the age of 65. However, it can also affect people under 65.

Other than age, there are few risk factors (such as medical conditions or lifestyle choices) that are known to increase a person's chances of developing DLB. Most people who develop DLB have no clear family history of the condition. A few families seem to have genetic mutations that are linked to inherited Lewy body disease, but these are very rare. 

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Diagnosing dementia with Lewy bodies

Getting the right diagnosis is particularly important if DLB is suspected. This is mainly because people with DLB can benefit from some medications, but also react very badly to others.

However, DLB can be difficult to identify correctly and diagnosis should ideally be made by a specialist with experience of the condition. People with DLB are often mistakenly diagnosed as having Alzheimer’s disease or, less often, vascular dementia. Other things that can cause similar symptoms, including infections or the side effects of medication, also need to be ruled out.

The doctor will talk to the person, and someone who knows them well. They will ask about the person’s medical history, when the symptoms started, and how these are affecting their life now. The doctor will carry out mental ability tests, but these may not always give a reliable result. This is because symptoms of DLB can vary a lot over time, particularly on tasks that need attention and decision-making. A neurological examination (looking at reflexes, stiffness and balance, for example) should also be done.

Typical features of someone who is diagnosed with DLB are:

  • varying levels of attention or alertness
  • persistent detailed visual hallucinations
  • movement problems similar to those of Parkinson’s disease
  • rapid eye movement sleep behaviour disorder

If the person shows signs of DLB, brain scans are used to help to clarify the diagnosis. Computed tomography (CT) or magnetic resonance imaging (MRI) scans may rule out brain conditions (eg a brain tumour or bleed) which can have similar symptoms. They may also help to show that the person has DLB rather than vascular dementia.

If there is still doubt, a more specialised brain scan might be carried out. This can confirm a diagnosis of DLB if it shows loss of a particular type of cells (dopamine nerve cells) at the base of the brain.

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