Table 1: Revised [7, 121] criteria for the clinical diagnosis of probable and possible dementia with Lewy bodies (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 visuoperceptual ability may be especially prominent and occur early.

Core clinical features (The first 3 typically occur early and may persist throughout the course.)
(i) Fluctuating cognition with pronounced variations in attention and alertness
(ii) Recurrent visual hallucinations that are typically well formed and detailed
(iii) REM sleep behavior disorder, which may precede cognitive decline
(iv) One or more spontaneous cardinal features 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, for example, constipation, orthostatic hypotension, urinary incontinence; hypersomnia; hyposmia; hallucinations in other modalities; systematized delusions; apathy, anxiety, and depression

Indicative biomarkers
(i) Reduced dopamine transporter uptake in basal ganglia demonstrated by SPECT or PET
(ii) Abnormal (low uptake) 123iodine-MIBG myocardial scintigraphy
(iii) Polysomnographic confirmation of REM sleep without atonia

Supportive biomarkers
(i) Relative preservation of medial temporal lobe structures on CT/MRI scan
(ii) Generalized low uptake on SPECT/PET perfusion/metabolism scan with reduced occipital activity 6 the cingulate island sign on FDG-PET imaging
(iii) Prominent posterior slow-wave activity on EEG with periodic fluctuations in the prealpha/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 disease dementia (PDD) should be used to describe dementia that occurs in the context of well-established Parkinson disease. In a practice setting, the term that is most appropriate to the clinical situation should be used and generic terms such as Lewy body disease are often helpful. In research studies in which distinction needs to be made between DLB and PDD, the existing 1-year rule between the onset of dementia and parkinsonism continues to be recommended.

(Adapted from Ian G. McKeith et al., Neurology 89 July 4, 2017).