RESUMO
Osteoid osteoma is a benign tumor, which is mostly seen in the long bones but occasionally originates and grows inside the paranasal sinuses. It rarely may impinge the dura with growing upward inside the ethmoid sinus. As a result, it can cause dural rupture, CSF leak and tension pneumocephalus. This needs complete resection with dural repair as an effective treatment. In this case report, a 72 year old man with osteoid osteoma is reported who had been referred with headache, rhinorrhea, memory loss, mood disorder and mutism. Pneumo-encephalus due to injury of dura of the skull base by a left ethmoid sinus osteoma was later found by CT scan. This tumor was completely resected and dura repaired by a surgical team including neurosurgeon and otorhinolaryngologist. The signs and symptoms were disappeared during the next few days