Hypertrophy of the inferior olivary nucleus in corticobasal degeneration: A neuropathological study.

Corticobasal degeneration (CBD) is a rare neurodegenerative disorder. The status of the inferior olivary nucleus (ION) in CBD has been inadequately investigated. In this study, we conducted a pathological investigation of the ION in CBD. We reviewed the data of Japanese patients with pathologically confirmed CBD who underwent consecutive autopsies between 1985 and 2020 at our institute. We retrospectively examined clinical data from medical records and clinicopathological conferences and semi-quantitatively assessed the ION, central tegmental tract, superior cerebellar peduncle, and dentate nucleus. Of the 32 patients included, 14 (43.8%) had hypertrophy of the ION (HION), of whom 6 showed laterality. In the 14 HION cases, with or without laterality, except in 1 unevaluable case, atrophy/myelin pallor of the central tegmental tract was observed on the same side as the hypertrophy. Ten patients with HION, with or without laterality, had atrophy/myelin pallor of the superior cerebellar peduncle on the contralateral side to the hypertrophy. The ION presents with hypertrophic changes in CBD. The lesion is a primary degeneration in CBD and is related to the degeneration of the Guillain-Mollaret triangle. This finding contributes to the elucidation of the specific pathological characteristics of CBD.