出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2016/09/06 11:07:10」(JST)
Dementia with Lewy bodies | |
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Lewy bodies are the pathomorphological characteristic of the disease
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Classification and external resources | |
Specialty | Neurology |
ICD-10 | G31.8 |
ICD-9-CM | 331.82 |
OMIM | 127750 |
DiseasesDB | 3800 |
eMedicine | neuro/91 |
MeSH | D020961 |
[edit on Wikidata]
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Dementia with Lewy bodies (DLB), also known as Lewy body dementia (LBD), diffuse Lewy body disease, cortical Lewy body disease, and senile dementia of Lewy type, is a type of progressive neurodegenerative dementia closely associated with Parkinson's disease primarily affecting older adults. Its primary feature is a more rapid cognitive decline than with Parkinson's, which may lead to hallucinations, as well as varied attention and alertness when compared to a person's baseline function.[1]
People with LBD display an inability to plan or a loss of analytical or abstract thinking and show markedly fluctuating cognition. Wakefulness varies from day to day, and alertness and short-term memory rise and fall. Persistent or recurring visual hallucinations with vivid and detailed imagery often are an early diagnostic symptom. The disorder is characterized anatomically by the presence of Lewy bodies, clumps of alpha-synuclein and ubiquitin protein in neurons, detectable in post mortem brain histology.[medical citation needed]
While the specific symptoms in a person with LBD may vary, core features of LBD are: fluctuating cognition with great variations in attention and alertness from day to day and hour to hour, recurrent visual hallucinations (observed in 75% of people with LBD), and motor features of Parkinson's disease. Suggestive symptoms are rapid eye movement (REM)-sleep behavior disorder and abnormalities detected in PET or SPECT scans.[2] REM sleep behavior disorder (RBD) often is a symptom first recognized by the patient's caretaker. RBD includes vivid dreaming, with persistent dreams, purposeful or violent movements, and falling out of bed.[3] Benzodiazepines, anticholinergics, surgical anesthetics, some antidepressants, and over-the-counter drug (OTC) cold remedies may cause acute confusion, delusions, and hallucinations.
Tremors are less common in LBD than in Parkinson's Disease.[4] Parkinsonian features may include shuffling gait, reduced arm-swing during walking, blank expression (reduced range of facial expression), stiffness of movements, ratchet-like cogwheeling movements; low speech volume, sialorrhea, and difficulty swallowing. Also, LBD patients often experience problems with orthostatic hypotension, including repeated falls, syncope (fainting), and transient loss of consciousness. Sleep-disordered breathing, a problem in multiple system atrophy, also may be a problem.[5]
One of the most critical and distinctive clinical features of the disease is hypersensitivity to neuroleptic and antiemetic medications that affect dopaminergic and cholinergic systems.[medical citation needed] In the worst cases, a patient treated with these medications could become catatonic, lose cognitive function, or develop life-threatening muscle rigidity. Some commonly used medications that should be used with great caution, if at all, for people with LBD, are chlorpromazine, haloperidol, or thioridazine.[6]
Visual hallucinations in people with LBD most commonly involve perception of people or animals that are not there, and may reflect Lewy bodies or AD pathology in the temporal lobe.[7][8] Delusions may include reduplicative paramnesia and other elaborate misperceptions or misinterpretations.[medical citation needed] These hallucinations are not necessarily disturbing and, in some cases, the person with LBD may have insight into the hallucinations and even be amused by them or, be conscious they are not real. People with LBD also may have problems with vision, including double vision,[6] and misinterpretation of what they see, for example, mistaking a pile of socks for snakes or a clothes closet for the bathroom.[9]
The major cause of LBD is not well understood yet, but a genetic link with the PARK11 gene has been described.[10] As with Alzheimer's disease and Parkinson's disease, most cases of LBD appear sporadically and LBD is not thought to have a strong hereditary link.[11] As with Alzheimer's disease, the LBD risk is heightened with inheritance of the ε4 allele of the apolipoprotein E (APOE).[12]
In LBD, loss of cholinergic (acetylcholine-producing) neurons is thought to account for degeneration of cognitive function (similar to Alzheimer's), while the death of dopaminergic (dopamine-producing) neurons appears to be responsible for degeneration of motor control (similar to Parkinson's) – in some ways, therefore, LBD resembles both disorders.
Pathologically, LBD is characterized by the development of abnormal collections of (alpha-synuclein) protein within the cytoplasm of neurons (known as Lewy bodies). These intracellular collections of protein have similar structural features to "classical" Lewy bodies, seen subcortically in Parkinson's disease. Additionally, those affected by LBD experience a loss of dopamine-producing neurons (in the substantia nigra) in a manner similar to that seen in Parkinson's disease. A loss of acetylcholine-producing neurons (in the basal nucleus of Meynert and elsewhere) similar to that seen in Alzheimer's disease also is known to occur in those with LBD. Cerebral atrophy also occurs as the cerebral cortex degenerates. Autopsy series have revealed the pathology of LBD is often concomitant with the pathology of Alzheimer's disease. That is, when Lewy body inclusions are found in the cortex, they often co-occur with Alzheimer's disease pathology found primarily in the hippocampus, including senile plaques (deposited beta-amyloid protein), and granulovacuolar degeneration (grainy deposits within and a clear zone around hippocampal neurons). Neurofibrillary tangles (abnormally phosphorylated tau protein) are less common in LBD, although they are known to occur, and astrocyte abnormalities[vague] are also known to occur.[13][14][15][16] Presently, it is not clear whether LBD is an Alzheimer's variant or a separate disease entity.[17][18][19][20] Unlike Alzheimer's disease, the brain may appear grossly normal with no visible signs of atrophy.[21]
LBD symptoms overlap clinically with Alzheimer's disease and Parkinson's disease, but are associated more commonly with the latter.[17] Because of this overlap, LBD in its early years often is misdiagnosed. The overlap of neuropathological and presenting symptoms (cognitive, emotional, and motor) may make an accurate differential diagnosis difficult. In fact, LBD often is confused in its early stages with Alzheimer's disease and/or vascular dementia (multi-infarct dementia), although, whereas Alzheimer’s disease usually begins gradually, LBD frequently has a rapid or acute onset, with especially rapid decline in the first few months. Thus, LBD tends to progress more rapidly than Alzheimer’s disease.[6] Despite the difficulty, a prompt diagnosis is important because of the risks of sensitivity to certain neuroleptic (antipsychotic) medications and because appropriate treatment of symptoms may improve life for both the person with LBD and the person's caregivers.[6]
LBD is distinguished from the dementia that sometimes occurs in Parkinson's disease by the time frame in which dementia symptoms appear relative to Parkinson symptoms.[22] Parkinson's disease with dementia (PDD) would be the diagnosis when dementia onset is more than a year after the onset of Parkinson's. LBD is diagnosed when cognitive symptoms begin at the same time or within a year of Parkinson symptoms.
There is no cure for LBD. Treatment may offer symptomatic benefit but remains palliative in nature. Current treatment modalities are divided into pharmaceutical and caregiving.
Pharmaceutical management, as with Parkinson's disease, involves striking a balance between treating the motor and emotive/cognitive symptoms. Motor symptoms appear to respond somewhat to the medications used to treat Parkinson's disease (e.g. levodopa) while cognitive issues may improve with medications for Alzheimer's disease such as donepezil. Medications used in the treatment of Attention deficit/hyperactivity disorder (e.g. methylphenidate) might improve cognition or daytime sleepiness; however, medications for both Parkinson's disease and ADHD increase levels of the chemical dopamine in the brain and therefore, increase the risk of hallucinations with those classes of pharmaceuticals.[23]
Treatment of the movement and cognitive portions of the disease may worsen hallucinations and psychosis, while treatment of hallucinations and psychosis with anti-psychotics may worsen parkinsonian or ADHD symptoms in LBD, such as tremor or rigidity and lack of concentration or impulse control.[24][25] Physicians may find the use of cholinesterase inhibitors represents the treatment of choice for cognitive problems and donepezil (Aricept), rivastigmine (Exelon), and galantamine (Reminyl) may be recommended as a means to help with these problems and to slow or prevent the decline of cognitive function.[6] Reports indicate Lewy body dementia may be more responsive to donepezil than Alzheimer's disease.[26] Memantine also may be useful.[27] Levocarb may help with movement problems, but in some cases, as with dopamine agonists, may tend to aggravate psychosis in people with LBD. Clonazepam may help with rapid eye movement behavior disorder; table salt or antihypotensive medications may help with fainting and other problems associated with orthostatic hypotension. Botulinum toxin injections in the parotid glands may help with sialorrhea. Other medications, especially stimulants such as the ADHD drug methylphenidate (Ritalin) and modafinil, may improve daytime alertness, but as with the anti-parkinsonian drug Levocarb, anti-hyperkinetics such as Ritalin increase the risk of psychosis.[17] Experts advise extreme caution in the use of antipsychotic medication in people with LBD because of their sensitivity to these agents. When these medications must be used, atypical antipsychotics are preferred to typical antipsychotics; a very low dose should be tried initially and increased slowly and, patients should be carefully monitored for adverse reactions to the medications.
Due to hypersensitivity to neuroleptics, prevention of LBD patients taking these medications is of great importance. People with LBD are at risk for neuroleptic malignant syndrome, a life-threatening illness, because of their sensitivity to these medications, especially the older typical antipsychotics, such as haloperidol. Other medications, including medications for urinary incontinence and the antihistamine medication diphenhydramine (Benadryl), also may worsen confusion.
Because LBD gradually renders people incapable of tending to their own needs, caregiving is very important and must be managed carefully over the course of the disease. Caring for people with LBD involves adapting the home environment, schedule, activities, and communications to accommodate declining cognitive skills and Parkinsonian symptoms.[9]
People with LBD may swing dramatically between good days—high alertness and few cognitive or movement problems—and bad days, and the level of care they require thus may vary widely and unpredictably. Sharp changes in behavior may be due to the day-to-day variability of LBD, but they also may be triggered by changes in the schedule or home environment, or by physical problems, such as constipation, dehydration, bladder infection, injuries from falls, and other problems people with LBD may not be able to convey to caregivers. Potential physical problems always should be taken into consideration when an individual with LBD becomes agitated.
As hallucinations and delusions are not dangerous or troubling to the person with LBD, it may be best for caregivers not to disabuse patients of them. Often the best approach is benign neglect - acknowledging, but not encouraging or agreeing. Trying to talk the LBD patient out of his delusion may be frustrating to caregivers and discouraging to patients, sometimes provoking anger or dejection. When misperceptions, hallucinations, and the behaviors stemming from these become troublesome, caregivers should try to identify and eliminate environmental triggers, and perhaps, offer cues or "therapeutic white lies" to steer patients out of trouble. Physicians may prescribe low doses of atypical antipsychotics, such as quetiapine, for psychosis and agitation in LBD. A small clinical trial found that about half of LBD patients treated with low doses of quetiapine experienced a significant reduction in these symptoms. Unfortunately, several participants in the study had to discontinue treatment because of side effects, such as excessive daytime sleepiness or orthostatic hypotension.[22]
Changes in the schedule or environment, delusions, hallucinations, misperceptions, and sleep problems also may trigger behavior changes. It can help people with LBD to encourage exercise, simplify the visual environment, stick to a routine, and avoid asking too much (or too little) of them. Speaking slowly and sticking to essential information improves communication. The potential for visual misperception and hallucinations, in addition to the risk of abrupt and dramatic swings in cognition and motor impairment, should put families on alert to the dangers of driving with LBD.[12]
Currently, an estimated 60 to 75% of diagnosed dementias are of the Alzheimer's and mixed (Alzheimer's and vascular dementia) type, 10 to 15% are Lewy body type, with the remaining types being of an entire spectrum of dementias, including frontotemporal lobar degeneration (Picks Disease), alcoholic dementia, pure vascular dementia, etc. LBD is slightly more prevalent in men than women.[12]
Lewy body dementia affects about one million individuals in the United States alone.[citation needed]
Frederic Lewy (1885–1950) was first to discover the abnormal protein deposits ("Lewy body inclusions") in the early 1900s.[28] Dementia with Lewy bodies was first described by Japanese psychiatrist and neuropathologist Kenji Kosaka in 1976.[29] LBD only started to be diagnosed in the mid-1990s after the discovery of alpha-synuclein staining first highlighted Lewy bodies in the cortex of post mortem brains of a subset of dementia patients.[11] Because it was only discovered recently, LBD is not a recognized diagnosis in DSM-IV, which was published in 1994. It is, however, briefly mentioned in the DSM-IV-TR (published in 2000) under "Dementia Due to Other General Medical Conditions". In 1996, a consortium of scientists initially proposed and later, revised diagnostic guidelines. It is in DSM-5 (published in 2013) as "Major or Mild Neurocognitive Disorder with Lewy Bodies".
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Pathology of the nervous system, primarily CNS (G04–G47, 323–349)
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Both/either |
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リンク元 | 「レビー小体型認知症」「dementia with Lewy body」 |
関連記事 | 「dement」「body」 |
(以下略)
<youtube>http://www.youtube.com/watch?v=RSRbR1R4mz0</youtube>
[★] レビー小体型認知症, DLB, Lewy body dementia
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