Dementia with Lewy Bodies

In the late 1970s an entity called diffuse Lewy body disease (DLBD) was first described, with LBs 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 AD but is often shorter.

In 1995, an international consensus conference was held, establishing clinical criteria for a diagnosis of a new nosologic entity, DLB. Parkinsonism preceding dementia by an arbitrary interval of 1 year or more is termed PD-D, 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).

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 antiparkinsonian medications.

Rapid eye movement sleep behavior 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.

Diagnostic Criteria for DLB and PDD
Lewy Body Dementia Association	www.lbda.org/
NIH information Page	https://www.ninds.nih.gov/Disorders/All-Disorders/Dementia-Lewy-Bodies-Information-Page

Central feature required for a diagnosis of DLB

A progressive cognitive decline of sufficient magnitude to interfere with normal social or occupational function. Prominent or persistent memory impairment may not necessarily occur in the early stages but is usually evident with progression. Deficits on tests of attention and of frontal-subcortical skills and visuospatial ability may be especially prominent.

Core Features for DLB:

Two of the three core features are essential for a diagnosis of probable DLB

One of the three core features is essential for possible DLB

a. Fluctuating cognition with pronounced variations in attention and alertness

b. Recurrent visual hallucinations that are typically well formed and detailed

c. Spontaneous motor features of parkinsonism

Features supportive of the diagnosis

Repeated falls

Syncope

Transient loss of consciousness

Neuroleptic sensitivity

Systematized delusions

Hallucinations in other modalities

A diagnosis of DLB is less likely in the presence of:

Stroke disease, evident as focal neurologic signs or on brain imaging

Evidence on physical examination and investigation of any physical illness or other brain disorder sufficient to account for the clinical picture