Spontaneous drainage of an ethmoidal mucocele: a possible cause of pneumosinus dilatans.

Idiopathic expansion of a paranasal sinus containing air and without an associated mass has been termed pneumosinus dilatans [1] . This rare disorder has been known to occur in all the paranasal sinuses, but it most commonly affects the frontal sinus. Clinical symptoms include pain , visual loss, proptosis, galactorrhea, and hypopituitarism [2-4]. Proposed mechanisms of origin include developmental, inflammatory, and obstructive. We present a 17 -year-old girl with pneumosinus dilatans of the left ethmoidal sinus. Previous CT studies, obtained 3 months prior to evaluation at our institution, demonstrated an expansile soft-tissue mass in the same lett ethmoidal sinus. Interim history included a single episode of massive rhinorrhea. We hypothesize that spontaneous drainage of a mucocele was the causative agent in our case of pneumosinus dilatans and represents a plausible mechanism of origin tor this otherwise idiopathic disorder.