Table 1 Revised criteria for the clinical diagnosis of probable and possible DLB

Essential for a diagnosis of DLB is dementia, defined as a progressive cognitive decline of sufficient magnitude to interfere with normal social or occupational functions, or with usual daily activities. Prominent or persistent memory impairment may not necessarily occur in the early stages but is usually evident with progression. Deficits on tests of attention, executive function and visuo-perceptual ability may be especially prominent and occur early.

Core clinical features

  (the first three typically occur early and may persist throughout the course)

  Fluctuating cognition with pronounced variations in attention and alertness.

  Recurrent visual hallucinations that are typically well formed and detailed.

  REM sleep behaviour disorder (RBD) which may precede cognitive decline.

  One or more spontaneous cardinal feature of parkinsonism – these are bradykinesia (defined as slowness of movement and decrement in amplitude or speed), rest tremor, or rigidity.

Supportive clinical features

  Severe sensitivity to antipsychotic agents ; postural instability ; repeated falls ; syncope or other transient episodes of unresponsiveness.; severe autonomic dysfunction e.g. constipation, orthostatic hypotension, urinary incontinence ; hypersomnia; hyposmia; hallucinations in other modalities; systematized delusions; apathy, anxiety and depression.

Indicative biomarkers

  Reduced dopamine transporter (DaT) uptake in basal ganglia demonstrated by SPECT or PET

  Abnormal (low uptake) MIBG myocardial scintigraphy

  Polysomnographic confirmation of REM sleep without atonia

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

Probable DLB can be diagnosed if:

  a) two or more core clinical features of DLB are present, with or without the presence of indicative biomarkers or

  b) only one core clinical feature is present, but with one or more indicative biomarkers

Probable DLB should not be diagnosed on the basis of biomarkers alone

Possible DLB can be diagnosed if:

  a) only one core clinical feature of DLB is present, with no indicative biomarker evidence, or

  b) one or more indicative biomarkers is present but there are no core clinical features

DLB is less likely:

  a) in the presence of any other physical illness or brain disorder including cerebrovascular disease, sufficient to account in part or in total for the clinical picture, although these do not exclude a DLB diagnosis and may serve to indicate mixed or multiple pathologies contributing to the clinical presentation.

  or

  b) 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. The term Parkinson’s disease dementia (PDD) should be used to describe dementia that occurs in the context of well-established Parkinson’s disease. In a practice setting the term that is most appropriate to the clinical situation should be used and generic terms such as LB disease are often helpful. In research studies in which distinction needs to be made between DLB and PDD the existing one-year rule between the onset of dementia and parkinsonism continues to be recommended.