Introduction: Pneumosinus dilatans (PD) of the frontal sinus is a rare entity, especially in the pediatric population, with an etiology that remains unclear. Terminology used to describe abnormal expansion of the frontal sinus has been confusing and overlapping, and the term PD is often used interchangeably with other entities such as hypersinus and pneumocele. These patients are often referred to craniofacial surgeons for care. Therefore, a clear understanding of PD, including the etiology, diagnostic workup, and treatment plan, is relevant to plastic surgeons.

Objective: To present a pediatric patient with progressive right frontal bossing secondary to PD. In addition, to review previously reported cases of pnuemosinus dilatans of the frontal sinus, summarize these results, and formulate a treatment algorithm.

Participants: One case of a pediatric patient referred to craniofacial surgery by otolaryngology, found to have a diagnosis of PD. Also included are all cases of pnuemosinus dilatans of the frontal sinus reported in the English literature since 1955.

Results: Pneumosinus dilitans is distinguished in the literature from hypersinus and pneumocele. PD is an abnormal expansion of the aerated frontal sinus, with sinus walls of normal thickness. The expansion of the bone may be generalized or focal. The entity is mainly found in males in the 20-40 age range, though the literature includes reports of cases in patients aged 12 to 72 years. Presenting symptoms typically correspond to which structures are displaced. CT scan will not necessarily distinguish between pneumocele and pneumosinus dilitans, but will distinguish this from any soft tissue tumor resulting in abnormal expansion of the sinus or overlying soft tissue. Of note, the sinus mucosa is normal without secretion or signs of inflammation. Treatment of pneumosinus dilatans frontalis is directed at correcting the bony deformity, and in many cases obliteration of the involved sinus. If nasofrontal duct blockage is suspected, treatment must also address reestablishment of appropriate drainage.

Surgical Management

Abnormal expansion of frontal sinus without focal thinning (PD)

Nasofrontal duct obstruction no duct obstruction

+ frontal bossing - frontal bossing +frontal bossing no cosmetic deformity

Open procedure endoscopic restoration Open procedure no surgical treatment

+/- strip mucosa of nasal drainage to correct deformity

+/- obliterate sinus

Conclusion: While PD most commonly involves the frontal sinus, overall it is a very rare entity that should be differentiated from other paranasal sinus lesions. Diagnostic evaluation is of utmost importance, as it will dictate the extent of surgical intervention.