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.