Unified staging system for Lewy body disorders: correlation with nigrostriatal degeneration, cognitive impairment and motor dysfunction.

The two current major staging systems in use for Lewy body disorders fail to classify up to 50% of subjects. Both systems do not allow for large numbers of subjects who have Lewy-type alpha-synucleinopathy (LTS) confined to the olfactory bulb or who pass through a limbic-predominant pathway that at least initially bypasses the brainstem. The results of the current study, based on examination of a standard set of ten brain regions from 417 subjects stained immunohistochemically for alpha-synuclein, suggest a new staging system that, in this study, allows for the classification of all subjects with Lewy body disorders. The autopsied subjects included elderly subjects with Parkinson's disease, dementia with Lewy bodies, incidental Lewy body disease and Alzheimer's disease with Lewy bodies, as well as comparison groups without Lewy bodies. All subjects were classifiable into one of the following stages: I. Olfactory Bulb Only; IIa Brainstem Predominant; IIb Limbic Predominant; III Brainstem and Limbic; IV Neocortical. Progression of subjects through these stages was accompanied by a generally stepwise worsening in terms of striatal tyrosine hydroxylase concentration, substantia nigra pigmented neuron loss score, Mini Mental State Examination score and score on the Unified Parkinson's Disease Rating Scale Part 3. Additionally, there were significant correlations between these measures and LTS density scores. It is suggested that the proposed staging system would improve on its predecessors by allowing classification of a much greater proportion of cases.

Olfactory bulb alpha-synucleinopathy has high specificity and sensitivity for Lewy body disorders.

Involvement of the olfactory bulb by Lewy-type alpha-synucleinopathy (LTS) is known to occur at an early stage of Parkinson's disease (PD) and Lewy body disorders and is therefore of potential usefulness diagnostically. An accurate estimate of the specificity and sensitivity of this change has not previously been available. We performed immunohistochemical alpha-synuclein staining of the olfactory bulb in 328 deceased individuals. All cases had received an initial neuropathological examination that included alpha-synuclein immunohistochemical staining on sections from brainstem, limbic and neocortical regions, but excluded olfactory bulb. These cases had been classified based on their clinical characteristics and brain regional distribution and density of LTS, as PD, dementia with Lewy bodies (DLB), Alzheimer's disease with LTS (ADLS), Alzheimer's disease without LTS (ADNLS), incidental Lewy body disease (ILBD) and elderly control subjects. The numbers of cases found to be positive and negative, respectively, for olfactory bulb LTS were: PD 55/3; DLB 34/1; ADLS 37/5; ADNLS 19/84; ILBD 14/7; elderly control subjects 5/64. The sensitivities and specificities were, respectively: 95 and 91% for PD versus elderly control; 97 and 91% for DLB versus elderly control; 88 and 91% for ADLS versus elderly control; 88 and 81% for ADLS versus ADNLS; 67 and 91% for ILBD versus elderly control. Olfactory bulb synucleinopathy density scores correlated significantly with synucleinopathy scores in all other brain regions (Spearman R values between 0.46 and 0.78) as well as with scores on the Mini-Mental State Examination and Part 3 of the Unified Parkinson's Disease Rating Scale (Spearman R -0.27, 0.35, respectively). It is concluded that olfactory bulb LTS accurately predicts the presence of LTS in other brain regions. It is suggested that olfactory bulb biopsy be considered to confirm the diagnosis in PD subjects being assessed for surgical therapy.