Connectional anatomy of the cerebellum: dentate nucleus and cerebellar peduncles from a surgical perspective

OBJECTIVE: The neuron-rich cerebellum and the fourth ventricle are the primary surgical targets in the infratentorial space, and irreversible neurological morbidities resulting from damage to the cerebellar nuclei and peduncles continue to pose a significant surgical risk. The aim of this study was to elucidate the connectional anatomy of the cerebellum from a surgical perspective. METHODS: Fiber microdissections of the cerebellum and the lower brainstem (BS) were performed in 10 postmortem human brains to disclose the deep nuclei and peduncles. Novel fiber dissection results were compared to those of tractography. RESULTS: This study revealed two distinct pathways of pontocerebellar fibers-deep and superficial-based on their relationship with the corticospinal tract. A deep course of pontocerebellar fibers typically surrounded the inferior surface of the dentate nucleus (DN). A fiber-dense and delicate surgical area-the peduncular mass-was defined at the junction of the three cerebellar peduncles along the superolateral recess of the fourth ventricle. A constant dentate tubercle, formed by the inferomedial extension of the ventral surface of the DN, was defined at the intersection between the superior cerebellar peduncle and inferior cerebellar peduncle (ICP) near the peduncular mass at the superolateral recess. The upper medial part of the tonsillar peduncle (TP) covered the inferior part of the ventral surface of the DN, and any manipulation at this point may carry the risk of injury to the nucleus. The floccular peduncle (FP), located just medial to the TP at the lateral recess of the fourth ventricle, was intimately related to the ICP. During a possible FP transgression to access BS lesions, the ICP, inferior part of the ventral DN, and cochlear nuclei may be compromised. CONCLUSIONS: Surgical approaches to the cerebellum or the fourth ventricle should take into account its white matter connections and the DN. Gaining a clear 3D understanding of the DN and the cerebellar peduncles from a surgical perspective, and recognizing key surgical landmarks around the fourth ventricle in relation to the connectional anatomy of the cerebellum and BS, may prove valuable during surgeries in the infratentorial space.