Fig 1. A, The axial HRCT image of the right temporal bone in case 1 shows an erosion in the posterior temporal bone wall (arrow). The erosion does not contain calcifications or bone spicules and was identified as an arachnoid granulation.

B, On the axial HRCT image obtained 3 mm below A, the normal endolymphatic duct (black arrowhead) is identified anterior to the arachnoid granulation (black arrow). Tympanosclerosis is present (white arrowhead).

C, The axial 0.7-mm-thick T2-weighted image of the posterior fossa confirms the right (arrowhead) and left (arrow) arachnoid granulation. On the right side, the internal fibrous structure is seen as hypointense lines within the granulation.