レビー小体型認知症

概念
大脳皮質,扁桃核,黒質,青斑核などに多数のLewy小体が出現し,痴呆とパーキンソニズムを主症状とする症例として日本から報告されました。認知症性の原因疾患では、アルツハイマー型認知症、脳血管性認知症についで3番目に多い疾患です。
診断特異的な検査はなく後述する診断基準を参考に総合的に診断する、あるいは経時的変化を追うことになります。

症状
通常、初老期・老年期に発病し,進行性の皮質性痴呆を示します。しかしながら、初期には記憶障害がめだたないこともあったり、注意や前頭皮質機能や視空間機能の障害が目立つこともあります。

認知機能障害に加え、以下の中核症状が特徴です。

    注意力や意識清明度の変動
    鮮明な再発性幻視体験
    特発性のパーキンソニズム

指示する特徴としては、

    繰り返す転倒や失神
    一過性の意識障害
    抗精神病薬への過敏性
    系統的な妄想
    幻視以外の幻覚

などなど。以下の診断基準を参考にしてください。
検査

    CT/MRI:特異的な所見はありません。アルツハイマー型認知症と比較すると側頭葉内側部の萎縮が比較的目立たないのが特徴です
    MIBG心筋シンチグラフィー:パーキンソン病と同様に集積低下します
    SPECT:早期アルツハイマー病では後部帯状回から楔前部と右頭頂葉にかけて血流の低下が見られますが、早期DLBでは両側の楔前回、後部帯状回、後頭葉皮質にかけて血流の低下が認められます

診断基準

Revised criteria for the clinical diagnosis of dementia with Lewy bodies (DLB) Neurology 2005

1. Central feature (essential for a diagnosis of possible or probable DLB)

    Dementia defined as progressive cognitive decline of sufficient magnitude to interfere with normal social or occupational function.
    Prominent or persistent memory impairment may not necessarily occur in the early stages but is usually evident with progression.
    Deficits on tests of attention, executive function, and visuospatial ability may be especially prominent.

2. Core features (two core features are sufficient for a diagnosis of probable DLB, one for possible DLB)

    Fluctuating cognition with pronounced variations in attention and alertness
    Recurrent visual hallucinations that are typically well formed and detailed
    Spontaneous features of parkinsonism

3. Suggestive features (If one or more of these is present in the presence of one or more core features, a diagnosis of probable DLB can be made. In the absence of any core features, one or more suggestive features is sufficient for possible DLB. Probable DLB should not be diagnosed on the basis of suggestive features alone.)

    REM sleep behavior disorder
    Severe neuroleptic sensitivity
    Low dopamine transporter uptake in basal ganglia demonstrated by SPECT or PET imaging

4. Supportive features (commonly present but not proven to have diagnostic specificity)

    Repeated falls and syncope
    Transient, unexplained loss of consciousness
    Severe autonomic dysfunction, e.g., orthostatic hypotension, urinary incontinence
    Hallucinations in other modalities
    Systematized delusions
    Depression
    Relative preservation of medial temporal lobe structures on CT/MRI scan
    Generalized low uptake on SPECT/PET perfusion scan with reduced occipital activity
    Abnormal (low uptake) MIBG myocardial scintigraphy
    Prominent slow wave activity on EEG with temporal lobe transient sharp waves

5. A diagnosis of DLB is less likely

    In the presence of cerebrovascular disease evident as focal neurologic signs or on brain imaging
    In the presence of any other physical illness or brain disorder sufficient to account in part or in total for the clinical picture
    If parkinsonism only appears for the first time at a stage of severe dementia

6. Temporal sequence of symptoms
DLB should be diagnosed when dementia occurs before or concurrently with parkinsonism (if it is present). The term Parkinson disease dementia (PDD) should be used to describe dementia that occurs in the context of well-established Parkinson disease. In a practice setting the term that is most appropriate to the clinical situation should be used and generic terms such as LB disease are often helpful. In research studies in which distinction needs to be made between DLB and PDD, the existing 1-year rule between the onset of dementia and parkinsonism DLB continues to be recommended. Adoption of other time periods will simply confound data pooling or comparison between studies. In other research settings that may include clinicopathologic studies and clinical trials, both clinical phenotypes may be considered collectively under categories such as LB disease or alpha-synucleinopathy.

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