Incidental Tentorial Cerebelli Hypoplasia: A Case Report and Comprehensive Literature Review of Its Clinical and Imaging Characteristics

Background: Tentorial hypoplasia is a rare congenital condition characterized by underdevelopment or absence of the tentorium cerebelli, a dural structure separating the cerebrum from the cerebellum. It is often detected incidentally on computed tomography (CT) or magnetic resonance imaging (MRI) and may be associated with conditions such as Dandy-Walker syndrome and Chiari malformation, although many cases remain asymptomatic. Imaging plays an essential role in identifying associated abnormalities when present. Case Presentations: Case 1: A 16-year-old male presented with a left subdural hematoma following a road traffic accident. Neuroimaging incidentally revealed tentorial hypoplasia with brain herniation into the quadrigeminal cistern, though he remained asymptomatic. Case 2: A 3-year-old child with metastatic neuroblastoma had incidentally discovered tentorial hypoplasia with brain herniation on CT and MRI, with no neurological deficits. Conclusion: Tentorial hypoplasia is often an incidental finding with a favorable prognosis, though early imaging is essential for identifying associated central nervous system (CNS) malformations and guiding management.