Dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is a type of dementia accompanied by changes in behavior, cognition, and movement. As a progressive illness, it is usually diagnosed when cognitive decline interferes with normal daily functioning. A core feature is REM sleep behavior disorder (RBD), in which people lose normal muscle paralysis during REM sleep and act out their dreams. Memory loss is not always an early symptom, RBD may appear years or decades before other symptoms. Other frequent symptoms include visual hallucinations, marked fluctuations in attention or alertness, and slowness of movement, trouble walking, or rigidity. The autonomic nervous system is usually affected, resulting in changes in blood pressure, heart and gastrointestinal function, with constipation as a common symptom. Mood changes such as depression and apathy are common.    —B. Tousi (2017), Diagnosis and Management of Cognitive and Behavioral Changes in Dementia With Lewy Bodies.    —B.P. Boot (2015), Comprehensive treatment of dementia with Lewy bodies Dementia with Lewy bodies (DLB) is a type of dementia accompanied by changes in behavior, cognition, and movement. As a progressive illness, it is usually diagnosed when cognitive decline interferes with normal daily functioning. A core feature is REM sleep behavior disorder (RBD), in which people lose normal muscle paralysis during REM sleep and act out their dreams. Memory loss is not always an early symptom, RBD may appear years or decades before other symptoms. Other frequent symptoms include visual hallucinations, marked fluctuations in attention or alertness, and slowness of movement, trouble walking, or rigidity. The autonomic nervous system is usually affected, resulting in changes in blood pressure, heart and gastrointestinal function, with constipation as a common symptom. Mood changes such as depression and apathy are common. The exact cause is unknown, but involves widespread deposits of abnormal clumps of alpha-synuclein protein known as Lewy bodies in neurons, as well as Lewy neurites. DLB is not usually inherited, but there is a genetic association in a small number of families. A probable diagnosis is made based on symptoms and biomarkers; which may include blood tests, neuropsychological tests, medical imaging, and polysomnography. Other conditions that share some symptoms of DLB include Alzheimer's disease (AD), Parkinson's disease, delirium, and rarely, psychosis. There is no cure, and no medication can modify its progression. Treatments aim to relieve some of the symptoms and reduce the burden on caregivers. Acetylcholinesterase inhibitors, such as donepezil and rivastigmine, are effective at improving cognition and overall functioning, and melatonin can be used for sleep-related symptoms. Antipsychotics are usually avoided, even for hallucinations, because people with DLB are sensitive to them, and their use can result in death. Medications for one symptom may worsen another. DLB is one of the three most common types of dementia, along with Alzheimer's, and vascular dementia. Together with Parkinson's disease dementia, it is one of two dementias classified as the Lewy body dementias. It typically begins after the age of 50, and about 0.4% of people over 65 are affected. People in the latter stages of DLB may be unable to care for themselves. Life expectancy following diagnosis is about eight years. The abnormal deposits of protein that are the underlying mechanism of the disease were discovered in 1912 by Frederic Lewy, and diffuse Lewy body disease was first described by Kenji Kosaka in 1976. Dementia with Lewy bodies (DLB) is a progressive neurodegenerative dementia. Together with Parkinson's disease dementia, it is one of the Lewy body dementias, which are also classified as atypical parkinsonian syndromes. It is one of the synucleinopathies—neurodegenerative diseases that are due to an abnormal accumulation of alpha-synuclein protein in the brain—along with Parkinson's disease, multiple system atrophy, and other rarer conditions. The alpha-synuclein protein deposits causing DLB can damage different regions of the nervous system, including multiple brain regions in the central nervous system, and the autonomic nervous system. This widespread damage can affect several domains of functioning, resulting in a disease that is more complex than many other dementias, with widely varying symptoms. The symptoms can be divided into essential, core, and supportive features. An identifiable prodromal phase occurs in DLB; the earliest signs are constipation and dizziness from autonomic dysfunction, reduced ability to smell, visual hallucinations, and REM sleep behavior disorder (RBD). DLB is distinguishable from AD even in the prodromal phase. According to the 2017 Fourth Consensus Report of the DLB Consortium, dementia is diagnosed on the occurrence of a 'progressive cognitive decline of sufficient magnitude to interfere with normal social or occupational functions, or with usual daily activities.” While dementia is an essential feature of DLB, it does not always appear early on, and is more likely to present as the condition progresses—typically after age 55—and memory loss is not always noticeable in the early stages. In contrast to AD, where the hippocampus is among the first brain structures affected, and episodic memory loss related to encoding of memories is typically the earliest symptom, memory impairment occurs later in DLB. Memory loss in DLB has a different progression from AD because frontal structures are involved earlier, with later involvement of temporoparietal brain structures. Deterioration in memory function occurs because new memories may be encoded, but not retrieved. Verbal memory is not as severely affected as in AD.