The second largest intracranial specialization of the dura mater, the tentorium cerebelli, is a transverse fold that partially separates the cerebellum and cerebral hemispheres. During routine dissection of the posterior cranial fossa, a left-sided hypoplastic region of the tentorium cerebelli was observed. This fenestration was seen at the posterior portion of the tentorium as a posteromedial strip of tissue rising vertically to interface with the falx cerebri. Although isolated cases of tentorial hypoplasia have been reported in, for example, cases of Chiari II malformation, we believe isolated fenestration of this membrane is very rare, especially in the absence of the Chiari II malformation. The current case adds to the sparse literature on isolated tentorial defects and might be of interest to neurosurgeons or clinicians who review intracranial imaging.
Keywords: cadaver; chiari malformation; clinical anatomy; isolated tentorial hypoplasia; tentorium cerebelli.