Pneumocephalus associated with ethmoidal sinus osteoma--case report.

A 35-year-old female suffered sudden onset of severe headache upon blowing her nose. No rhinorrhea or signs of meningeal irritation were noted. Computed tomography (CT) with bone windows clearly delineated a bony mass in the right ethmoid sinus, extending into the orbit and intracranially. Conventional CT demonstrated multiple air bubbles in the cisterns and around the mass in the right frontal skull base, suggesting that the mass was associated with entry of the air bubbles into the cranial cavity. T1- and T2-weighted magnetic resonance (MR) imaging showed a low-signal lesion that appeared to be an osteoma but did not show any air bubbles. Through a wide bilateral frontal craniotomy, the cauliflower-like osteoma was found to be protruding intracranially through the skull base and the overlying dura mater. The osteoma was removed, and the dural defect was covered with a fascia graft. Histological examination confirmed that the lesion was an osteoma. The operative procedure resolved the problem of air entry. CT is superior to MR imaging for diagnosing pneumocephalus, by providing a better assessment of bony destruction and better detection of small amounts of intracranial air.