[Arachnoid granulations as cause of tegmen tympani defects].

A woman aged 73 presented with a four-week history of hypoacusis and low-density clear discharge from her right ear, with no history of traumatic or surgical events. Physical examination showed right middle ear invasion and discharge of a clear liquid, which was suggestive of CSF caused by tympani defects. Left middle ear invasion presented with no other condition. Computerised tomography (CT) was requested of the cranium, with multiplanar reconstruction to detect hearing disturbances and defects in the petrous bone. The CT scan study (Fig. 1) showed partial invasion of both middle ears and mastoid cells with no ossicular chain or scutum defects. There was no observation of post-traumatic lesions or pathological contrast enhancement. Multiple erosive bony lesions (arrows) existed throughout the internal table at the base of the cranium, predominantly in the middle anterior cranial fossa (Fig. 1B) and temporal bones, including the bilateral tegmen tympani. We decided to complete the study with magnetic resonance (MR) imaging. Fig. 1C and D (coronal CT) confirmed marked thinning with focal interruption of the bilateral tegmen tympani