In a recent American Journal of Otolaryngology article by Vaezeafshar et al. titled Mucocele formation under pedicled nasoseptal flap , the authors presented a case of a 60-year-old man who was submitted to an endonasal transsphenoidal approach for a pituitary adenoma with subsequent sellar reconstruction with a multilayer technique for an intraoperative CSF leak.

Abdominal fat to fill the skull base defect, porous polyethylene implant (Porex Surgical, Inc., Newnan, GA) beneath the sellar bone margins and a pedicled nasoseptal flap to cover the sellar defect were used. The authors stated that the mucosa overlying the sphenoid cavity and clival recess was removed before the flap was placed. A layer of fibrin sealant (Tisseel; Baxter Healthcare corporation, Deerfield, IL) and several pieces of absorbable gelatin sponge (Gelfoam; Pharmacia & Upjohn, Kalamazoo, MI) were placed to stabilize the flap. Four months after surgery a postoperative MRI showed the development of a mucocele under the nasoseptal flap. A second follow-up MRI performed two years after surgery showed an enlarging mucocele, however the patient was not submitted to endoscopic marsupialization given that he was asymptomatic.

There is still a controversy if the underlying mucosa should be removed before the flap’s placement. Hadad et al. in their original article recommended wide removal of the mucosa to prevent mucocele formation. A recent study by McCoul et al. reported a case of sphenoid sinus mucocele as a complication of the nasoseptal flap. The authors assumed that this complication arose as a result of incomplete removal of the mucosa, with persistent secretion of mucus beneath the healed flap. Alternatively Bleier et al. reported routine placement of the flap without removal of the mucosa: they observed only one mucocele out of a series of 28 patients.

We are strongly convinced that incomplete removal of the mucosa may be a potential factor of mucocele formation although the article by Bleier et al. reports only a 3.6% risk when the mucosa is not removed at all. However, another possible explanation can be suggested for mucocele formation under the nasoseptal flap, which no author has taken in consideration yet. Once harvested, the flap is placed in the nasopharynx or in the maxillary sinus to be protected from the instruments and facilitate the “four hands” technique. During this step, the flap can wrap around itself and around the pedicle, which results in subsequent difficulty to identify both mucosal and mucoperichondrial/mucoperiostial sides at the end of the surgical procedure, when the flap may be covered with blood, clots and bone dust and surgeons in the beginning of their experience in endoscopic skull base procedures can be confused. This may lead to wrong placement of the flap with the mucosal side against the skull base defect and the mucoperichondrial/mucoperiostial side towards the nasal cavity. This will cause a mucocele due to persistent secretion of mucus by the mucosal side of the flap which is in contact with the bony skull base, although all the sinus mucosa has been removed accurately.

To avoid this complication, we recommend young or unexperienced surgeons to mark the mucosal side of the flap with a sterile ink pen in order to recognize this side at the end of the procedure and adequately place the flap with the mucoperichondrial/mucoperiostial side against the skull base.

In summary although the possibility of mucocele formation is relatively low, with 3.4% of probability even if the mucosa is not removed, we prefer and recommend: a) to routinely mark the flap at the beginning of the procedure in order to have a safe placement of the flap with the correct side against the skull base, b) to remove routinely the underlying mucosa, c) to smooth with a drill the bony surface around the site of the defect, d) to drill out the basisphenoid in order to improve the pedicle’s arc of rotation, e) to identify, coagulate and cut the palatovaginal (pharyngeal), vidian and discending palatine arteries in order to release laterally the pedicle of the nasoseptal flap which will offer more length and mobility to the flap and f) to place adequately the flap and the pedicle against the denuded bony surfaces without leaving dead spaces. To our view following all these expedients, the risk for mucocele formation under the nasoseptal flap will decrease to 0%.