[Arachnoid granulations of the posterior temporal bone wall: report of two cases].

Arachnoid granulations play a role in CSF drainage. They are primarily located adjacent to cerebral venous sinuses. They may arise on a bony surface causing progressive bony erosion. We report two cases of arachnoid granulations eroding the posterior wall of the temporal bone. The aim of this paper was to illustrate the clinical presentation, and the imaging findings of arachnoid granulation of the posterior wall of the temporal bone. They remain asymptomatic in most cases, but they might cause a communication between the subarachnoid space and mastoid air cells, increasing the risk of bacterial meningitis, subdural empyema, and other intracranial infections. Differential diagnoses are also described, including endolymphatic sac tumours.