In the late 1970s an entity called Diffuse Lewy body (DLB) disease was first described, after the histopathological hallmark “Lewy bodies” were seen throughout the brain, including the cortex. Once thought to be rare it is now assumed that Dementia with Lewy Bodies accounts for 15-25% of elderly demented patients. Age at onset is higher than PD, ranging from 60 to 85 years. The duration from onset of dementia to death overlaps with Alzheimer’s disease but is often shorter.

In 1995, an international consensus conference was held, establishing clinical criteria for the diagnosis of DLB. Parkinsonism preceding dementia by an arbitrary interval of 1 year or more is termed Parkinson’s disease dementia (PDD), and dementia that precedes or accompanies the onset of Parkinsonism is labeled DLB. Patients with DLB have an older age at onset and shorter disease duration than patients with typical PD. Resting tremor is less common (55% verses 85%).

Patients with DLB have deficits in memory, attention, language, executive functions, and visuospatial and visuoconstructional abilities. They typically fall in the mild range on the MMSE (22-26).

Attention typically fluctuates significantly, resulting in excessive drowsiness or even a delirium-like presentation

Visual hallucinations are reported (usually well formed, often benign, but sometimes threatening) in 40% to 75% of patients with DLB. They are usually unprovoked but may be seen in the setting of anti-Parkinsonian medications.

Rapid eye movement sleep behaviour disorder (RBD) is a sleep disturbance (acting out dreams) that has been associated with Lewy Body disorders (PD and DLB). Supranuclear gaze palsies, although uncommon, have been reported.

Current consensus criteria for the diagnosis of Dementia with Lewy Bodie, adapted from (McKeith et al., 2017).

Essential for the diagnosis of DLB is dementia defined as progressive cognitive decline of sufficient magnitude to interfere with normal social of 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)
– fluctuating cognition with pronounced variation in attention and alertness
– Recurrent visual hallucinations that are typically well-formed and detailed
– REM sleep behaviour disorder, which may precede cognitive decline
– 1 or more spontaneous cardinal features of Parkinsonism: bradykinesia (slowness of movement and decrement in amplitude or speed), resting 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, erectile dysfunction)
– Hypersomnia
– Hallucinations in other modalities
– Systemized delusions
– Apathy, anxiety and depression
Indicative biomarkers
– Reduced dopamine transporter uptake in basal ganglia demonstrated by SPECT or PET
– Abnormal (low uptake) 123-Iodine-MIBG myocardial scintigraphy
– Polysomnographic confirmation of REM sleep without atonia
Supportive biomarkers
– Relative preservation of medial temporal lobe structures on CT or MRI scan
– Generalized low uptake on SPECT perfusion or PET 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
Probably 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 for 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 (within 1 year) with Parkinsonism.

PDD should be used to describe dementia that occurs in the context of well-established Parkinson’s disease.

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