Pneumosinus dilatans associated with orbital neurilemmona

Background. Pneumosinus dilatans (PSD) is a rare condition. It has been reported in association with spheno-orbital meningioma, optic nerve sheath meningioma, orbital fibro-osseous diseases and intracranial meningioma, but never with orbital neurilemmoma. We report 4 cases of orbital neurilemmomas in association with PSD, and stress the importance of PSD in cases of orbital neurilemmomas. Methods. We reviewed the hospital chart, and found 324 orbital tumors were found from 1974 to 1996. Eight consecutive cases of pathology-proven primary orbital neurilemmoma were studied. Clinical features, especially computed tomography (CT) scan, were completely reviewed to find the co-existence of orbital neurilemmoma and pneumosinus dilatans. Results. Four cases (50%) among 8 cases of pathology-proven orbital neurilemmomas were found to have pneumosinus dilatans in their CT scan. All these four cases were extraconal tumors. Representative CT scan showed enlarged, aerated sinus with thinning of the affected sinus walls. Ethmoidal, frontal and maxillary sinuses were the most frequently affected. Conclusions. Pneumosinus dilatans is commonly associated with primary orbital neurilemmoma.