Extradural hematoma is much less commonly seen in the posterior fossa than supratentorium (usually in the middle cranial fossa). The hematoma has the typical lentiform shape (bi-convex) of extradural hemorrhage and strips the dura anteriorly as evidenced by displacement of the transverse sinus anteriorly (arrow).  Origin of the bleeding is presumed to be due to disruption of the sinus, i.e. venous bleeding.