Alpha-synuclein aggregates in the parotid gland of idiopathic REM sleep behavior disorder

Background The neuropathological hallmark of Parkinson's disease (PD) is the presence of aggregates of phosphorylated alpha-synuclein (pAS) in the nervous system. Method We report a patient with video-polysomnography-confirmed idiopathic REM sleep behavior disorder that underwent parotidectomy because of parotid gland cancer. Immunohistochemistry of the gland tissue revealed abundant pAS deposits. One year after surgery the patient was diagnosed with PD. Prompted by this observation we examined the parotid gland in 10 consecutive individuals that underwent elective parotidectomy irrespective of their clinical condition. Results One had PD and another had mild parkinsonian signs plus reduced dopamine transporter uptake in the striatum. Both had pAS deposits in the parotid gland. The remaining eight subjects had no neurological signs and pAS was found in one of them. Conclusion Our study shows that the parotid gland may contain pAS pathology in the prodromal stage of PD and in manifested PD.