pneumosinus dilatans pneumosinus dilatans pneumosinus dilatans is a condition consisting of abnormal expansion or dilatation of one or more paranasal sinuses. it most often affects the frontal sinus, and can cause damage to vision due to pressure on the nearby optic nerve. the preferred treatment is endoscopic surgery to deflate the sinus. pneumosinus dilatanslateral view paranasal sinus sources hsu, wen-ming; et al. (2002). "pneumosinus dilatans associated with orbital neurilemmoma" (pdf). chinese medical journal. archived from the original (pdf) on 2006-01-05. retrieved 2006-06-28. carta, a.; et al. (june 1999). "neuro-ophthalmological presentation of pneumosinus dilatans". neuro-ophthalmology. retrieved 2006-06-28.