Lewy body pathology involves the olfactory cells in Parkinson's disease and related disorders

Background The “dual‐hit” and propagation hypotheses of α‐synuclein suggests that the olfactory cells of the olfactory epithelium are among the earliest sites of involvement in Parkinson's disease (PD). We investigated the olfactory epithelium in consecutive cases that had been registered with a brain bank. Objectives This study was undertaken to check the presence or absence of Lewy body pathology in olfactory cells. Methods Thirty‐six male and 11 female patients were examined, including eight with PD, two with dementia with Lewy bodies, 11 with incidental Lewy body disease, and 26 with no Lewy‐related alpha‐synucleinopathy. The olfactory epithelium was sampled by craniotomy followed by resection of the cribriform plate, which was fixed in formalin and decalcified with ethylenediaminetetra‐acetate. Coronal paraffin‐embedded sections of the plate were stained with hematoxylin and eosin or immunohistochemically stained with antibodies against phosphorylated α‐synuclein to detect Lewy body pathology and neuronal markers of protein gene product 9.5, phosphorylated neurofilament, and tyrosine hydroxylase. Results Lewy body pathology was detected in the olfactory cells of the olfactory epithelium in a single patient with incidental Lewy body disease and in six patients with PD, but it was not detected in patients who had dementia with Lewy bodies. Conclusions We detected Lewy body pathology in the olfactory epithelium in six of the eight patients with Parkinson's disease and in one patient with incidental Lewy body pathology. © 2016 International Parkinson and Movement Disorder Society