Dementia with Lewy bodies (DLB) is the second most common cause of dementia following Alzheimer's disease. It usually affects patients aged > 50 years. The hallmark of DLB is the presence of Lewy bodies, which are intracytoplasmic inclusion bodies that contain synuclein proteins located in the cortical and subcortical neurons. However, these findings are not specific to DLB and may similarly be present in other neurodegenerative diseases. Although the majority of DLB cases are due to sporadic development, DLB may be familial, suggesting a genetic predisposition. Clinically, DLB is characterized by the development of a triad of features, namely cognitive, neurological, and psychiatric symptoms. The diagnosis of DLB is difficult, given the absence of distinguishing features on imaging and neuropathology. Instead, physicians should rely exclusively on the presence of core and suggestive clinical features that may distinguish DLB from other neurodenegerative disorders that cause dementia and symptoms of parkinsonism, such as Alzheimer's disease (AD) and Parkinson's disease with dementia (PDD). Distinguishing features of DLB include the presence of dementia followed by early parkinsonism symptoms within less than 1 year of symptoms-onset, vivid and detailed visual hallucinations, depressive symptoms, REM sleep disorders, neuroleptic sensitivity, early-onset postural instability and falls, and prominent visuospatial and verbal learning impairment. There is currently no cure for DLB, but management is generally aimed at improving quality of life via pharmacologic and non-pharmacologic interventions. Cholinesterase inhibitors, such as rivastigmine and memantine, have demonstrated efficacy in the treatment of behavioral symptoms among patients with DLB, and they are the first-line pharmacologic agents for the management of DLB. The prognosis of DLB is poor with a median survival time comparable to that of AD (3-8 years), but more aggressive forms have also been described.
Lewy body dementia (LBD) was named after Frederich Heinrich Lewy, a German-American neurologist who discovered the characteristic intracytoplasmic inclusions in 1912.[1][2]
In 1961, Okazaki suggested that the presence of cortical Lewy bodies in brain tissue was associated with the development of dementia.[1]
In 1984, Kosaka and colleagues hypothesized that the presence of Lewy bodies may correspond to a new disease entity, which was eventually named "diffuse Lewy body disease".[3] The disease name was then changed in 1996 at the First International Workshop of the Consortium on Dementia with Lewy Bodies to become "dementia with Lewy bodies" (DLB).[4]
DLB was not considered a diagnosis of dementia in the first 4 versions of the Diagnostic and Statistical Manual (DSM) for Mental Disorders. In 2013, DSM-5 incorporated DLB as a differential diagnosis for dementia.[5][2]
Familial predisposition to DLB has been frequently described in observational studies, suggesting the role of genetics in the development of DLB. To date, genetic mutations that are exclusively implicated in DLB have not been described; genetic determinants of DLB have also been frequently reported in Parkinson's disease.
Predisposition to DLB may be caused by autosomal dominant genetic mutations of the Synuclein gene family.[6][7] Synuclein proteins are members of a pre-synpatic protein family located in the central and peripheral nervous systems. Although the majority of reports describe defects of the α-synuclein protein overexpression in DLB, the β- and γ-synuclein protein variants have also been associated with development of DLB. Mutations of α-synuclein (SNCA) gene have been classically associated with Parkinson's disease with dementia (PDD), but triplication defects and mutations of the E46K and A53T loci within the SNCA gene have been described in patients with DLB.[8][9][10][10]
The hallmark of dementia with Lewy bodies (DLB) is the presence of Lewy bodies (LB) that are accompanied by dystropic Lewy neurite (LN) in cortical, brainstem, and limbic system neurons. Lewy bodies are eosinophilic, filamentous, intracytoplasmic inclusion bodies composed of the following components:[15][16][17][18][19][20]
Figure: A. Lewy bodies (synuclein-positive, eosinophilic, neuronal inclusions) in brain tissue of patient with dementia with Lewy bodies (DLB); B. Immunohistochemical staining of Lewy Neurites; C. Immunhistochemical staining of frontal cortex in DLB demonstrates alpha-Synuclein positive inclusions (Images courtesy of user:Jensflorian from http://commons.wikimedia.org/ licensed under the Creative Commons Attribution-Share Alike 3.0 Unported under the terms of GNU Free Documentation License)
Classically, Lewy bodies in DLB are initially present in the amygdala. As the disease advances, these bodies spread to the limbic cortex and then to the neocortex. These findings may explain the predominance of dementia in patients with early DLB and the consequent development of parkinsonism symptoms.[21] The clinical features of DLB are directly associated with the severity of Lewy-related pathology. In turn, severity is measured by the pattern of regional involvement of Lewy bodies rather than the number of Lewy bodies.[22]
Dementia with Lewy bodies (DLB) should be distinguished from other disorders that cause memory impairment, recurrent hallucinations, and Parkinsonism. The most important differential diagnoses of DLB are Alzheimer's disease (AD) and Parkinson's disease with dementia (PDD) due to the overlapping clinical features with absence of distinguishing radiographic or neuropathological features across the 3 diseases. Generally, the distinction between the 3 disease is exclusively clinical based on key findings during history-taking and physical examination.
Alzheimer's Disease (AD) and Parkinsons's Disease with Dementia (PDD)[edit | edit source]
DLB is the 2nd most common cause of dementia following Alzheimer's disease (AD) and is the underlying etiology of approximately 1.7-30.5% of dementia cases. DLB generally affects patients older than 50 years of age and has a slight male predilection.
100% of patients with DLB eventually develop dementia early during the course of the disease.[65]
Similarly, the development of parkinsonism symptoms has also been reported in up to 50-100% of patients.[65]
In advanced disease, DLB symptoms eventually include cognitive fluctuation (45-90%), depression (12-89%), visual hallucinations (13-80%), and falls (22-50%).[65]
Dementia with Lewy bodies (DLB) is characterized by the triad of progressive cognitive impairment, parkinsonism, and neuropsychiatric disturbances. The diagnosis of the DLB is usually made clinically based on history-taking and findings on physical examination in the absence of metabolic, vascular, and degenerative disoders. Unfortunately, the clinical features of DLB frequently overlap with other neurodegenerative diseases, namely Alzheimer's disease and Parkinson's disease, and some experts consider DLB to be part of the Alzheimer's/Parkinsonism spectrum.
There are several distinguishing clinical features that suggest the diagnosis of DLB:
Dementia in DLB precedes parkinsonism symptoms.
The progression of signs and symptoms in DLB is relatively rapid compared to other neurodegenerative diseases. The occurrence of parkinsonism is frequently observed within less than one year of onset of dementia. Classically, patients with DLB report postural instability (eg. frequent falls and bone fractures) early in the disease compared to the delayed onset of postural instability observed in Parkinson's disease.
Postural instability in DLB manifests early. Unlike patients with Parkinson's disease, patients with DLB report frequent falls that may be present as early as a few months after onset of symptoms.[26]
Sleep disturbances in DLB are often due to REM sleep disorder. While other neurodegenerative diseases are associated with sleep disorders, REM sleep disorders have been frequently associated with DLB.
Sensitivity to neuroleptic agents and to antiparkinsonian drugs. As many patients with DLB are diagnosed with psychosis or Parkinson's disease due to the presence of overlapping features, symptoms in DLB paradoxically exacerbate upon administration of neuroleptics and antiparkinsonian drugs. Patients often experience worse psychotic symptoms (antiparkinsonian drugs) and parkinsonism symptoms (neuroleptics).[69][26]
DSM-V Diagnostic Criteria for Major or Mild Neurocognitive Disorder With Lewy Bodies[66][edit | edit source]
“
A.The criteria are met for major or mild neurocognitive disorder.
AND
B.The disorder has an insidious onset and gradual progression.
AND
C.The disorder meets a combination of core diagnostic features and suggestive diagnostic features for either probable or possible neurocognitive disorder with Lewy bodies.
For probable major or mild neurocognitive disorder with Lewy bodies, the individual has two core features, or one suggestive feature with one or more core features.
For possible major or mild neurocognitive disorder with Lewy bodies, the individual has only one core feature, or one or more suggestive features.
1.Core diagnostic features:
a.Fluctuating cognition with pronounced variations in attention and alertness.
b.Recurrent visual hallucinations that are well formed and detailed.
c.Spontaneous features of parkinsonism, with onset subsequent to the development of cognitive decline.
2.Suggestive diagnostic features;
a.Meets criteria for rapid eye movement sleep behavior disorder.
b.Severe neuroleptic sensitivity.
AND
D.The disturbance is not better explained by cerebrovascular disease, another neurodegenerative disease, the effects of a substance, or another mental, neurological, or systemic disorder.
Non-pharmacologic interventions are the mainstay of DLB management, given the lack of efficacy and at at times, paradoxical responses induced by some pharmacologic agents.[71]
Neuroleptics (first generation antipsychotic agents) and antiparkinsonian agents are generally not recommended in patients with DLB, given the high rates of sensitivity to these drugs. When administered neuroleptics, patients often report worsening motor symptoms. When administered antiparkinsonian agents, some patients reported exacerbations of hallucinations.
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↑Murayama S (2008). "[Neuropathology of frontotemporal dementia]". Rinsho Shinkeigaku (in Japanese). 48 (11): 998. PMID19198143.CS1 maint: Unrecognized language (link)
↑Hodges JR, Patterson K (1996). "Nonfluent progressive aphasia and semantic dementia: a comparative neuropsychological study". J Int Neuropsychol Soc. 2 (6): 511–24. PMID9375155.
↑Helkala EL, Laulumaa V, Soininen H, Riekkinen PJ (1988). "Recall and recognition memory in patients with Alzheimer's and Parkinson's diseases". Ann. Neurol. 24 (2): 214–7. doi:10.1002/ana.410240207. PMID3178177.
↑Metzler-Baddeley C (2007). "A review of cognitive impairments in dementia with Lewy bodies relative to Alzheimer's disease and Parkinson's disease with dementia". Cortex. 43 (5): 583–600. PMID17715794.
↑Uversky VN (2008). "Alpha-synuclein misfolding and neurodegenerative diseases". Curr. Protein Pept. Sci. 9 (5): 507–40. PMID18855701.
↑Bennett DA, Schneider JA, Wilson RS, Bienias JL, Arnold SE (2004). "Neurofibrillary tangles mediate the association of amyloid load with clinical Alzheimer disease and level of cognitive function". Arch. Neurol. 61 (3): 378–84. doi:10.1001/archneur.61.3.378. PMID15023815.
↑Tsolaki M, Kokarida K, Iakovidou V, Stilopoulos E, Meimaris J, Kazis A (2001). "Extrapyramidal symptoms and signs in Alzheimer's disease: prevalence and correlation with the first symptom". Am J Alzheimers Dis Other Demen. 16 (5): 268–78. doi:10.1177/153331750101600512. PMID11603162.
↑McGuinness B, Barrett SL, Craig D, Lawson J, Passmore AP (2010). "Executive functioning in Alzheimer's disease and vascular dementia". Int J Geriatr Psychiatry. 25 (6): 562–8. doi:10.1002/gps.2375. PMID19810010.
↑ 72.072.172.272.372.472.572.6Shea C, MacKnight C, Rockwood K (1998). [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?
dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9785144 "Donepezil for treatment of dementia with Lewy bodies: a case series of nine patients"] Check |url= value (help). Int Psychogeriatr. 10 (3): 229–38. PMID9785144. line feed character in |url= at position 54 (help)CS1 maint: Multiple names: authors list (link)