Dementia with Lewy bodies

5. Diagnosis

It is always important to get dementia diagnosed, but knowing the type of dementia (eg DLB, Alzheimer’s disease) 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.