α-Synuclein Inclusions in Amygdala in the Brains of Patients with the Parkinsonism-Dementia Complex of Guam

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Abstract
We investigated by immunohistochemistry the deposition of α-synuclein in the brains of deceased patients with the parkinsonism-dementia complex (PDC) of Guam. Five of 13 PDC brains showed numerous α-synuclein positive neuronal inclusions and abnormal neurites, chiefly in the amygdala. Similar α-synuclein positive lesions were observed, although to a lesser extent, in the entorhinal cortex and the dorsal vagal nucleus. No α-synuclein positive inclusions were observed in motor cortex or locus coeruleus, and only a small number of positive inclusions were found in the Sommer's sector, temporal cortex, or substantia nigra. Some of the α-synuclein positive inclusions were reminiscent of cortical Lewy bodies (LB), but many of those in the amygdala coexisted with tau-positive pretangles and/or neurofibrillary tangles (NFT) within the same neurons. In these neurons, tau-positive shells encapsulated α-synuclein positive central cores or irregularly shaped α-synuclein-positive deposition intermingled with pretangles/NFT. Thus, the present study suggests that a common mechanism may govern aggregation of α-synuclein and tau in the amygdala, and that aggregation of α-synuclein may play some role in the neurodegenerative process of a tauopathy (i.e. PDC) in which Aβ deposition is virtually absent.