DLB usually occurs sporadically, in people with no known family history of the disease. However, rare familial cases have occasionally been reported.
The central feature of DLB is progressive cognitive decline, combined with three additional defining features:
- Pronounced “fluctuations” in alertness and attention, such as frequent drowsiness, lethargy, lengthy periods of time spent staring into space, or disorganized speech
- Recurrent visual hallucinations
- Parkinsonian motor symptoms, such as rigidity and the loss of spontaneous movement
People may also suffer from depression.
The symptoms of DLB are caused by the build-up of Lewy bodies – accumulated bits of alpha-synuclein protein – inside the nuclei of neurons in areas of the brain that control particular aspects of memory and motor control. Researchers don’t know exactly why alpha-synuclein accumulates into Lewy bodies or how Lewy bodies cause the symptoms of DLB, but they do know that alpha-synuclein accumulation is also linked to Parkinson’s disease, multiple system atrophy, and several other disorders, which are referred to as the “synucleinopathies”. The similarity of symptoms between DLB and Parkinson’s disease, and between DLB and Alzheimer’s disease, can often make it difficult for a doctor to make a definitive diagnosis. In addition, Lewy bodies are often also found in the brains of people with Parkinson’s and Alzheimer’s diseases. These findings suggest that either DLB is related to these other causes of dementia or that an individual can have both diseases at the same time.
Like Alzheimer’s disease and Parkinson’s disease, DLB is a neurodegenerative disorder that results in progressive intellectual and functional deterioration. There are no known therapies to stop or slow the progression of DLB. Average survival after the time of diagnosis is similar to that in Alzheimer’s disease, about 8 years, with progressively increasing disability.
There is no cure for DLB. Treatments are aimed at controlling the cognitive, psychiatric, and motor symptoms of the disorder. Acetylcholinesterase inhibitors, such as donepezil and rivastigmine, are primarily used to treat the cognitive symptoms of DLB, but they may also be of some benefit in reducing the psychiatric and motor symptoms. Some individuals with DLB may benefit from the use of levodopa for their rigidity and loss of spontaneous movement.