"Mailbox Slot" pericranial flap for endoscopic skull base reconstruction.

INTRODUCTION Following an expanded endoscopic ethmoid resection with transnasal craniectomy, repair of cerebrospinal fluid (CSF) leakage and reconstruction of the dural defect are major challenges. Reconstruction of the bone defect is not necessary; the importance is to achieve complete separation of the intracranial cavity from the upper aerodigestive tract. Risk for postoperative CSF leak is dependent on the size and location of the defect and previous treatments (as external beam therapy [EBT]). A number of options are available for primary surgery. Small defects can be repaired with a fat graft placed in the resected area. In other cases, multilayered closure with fascia lata or composite closure using biomaterials can be used, with adequate outcomes. Alternatively, the use of the nasoseptal flap (NSF) has been advocated to provide vascularized tissue, with which the rate of postoperative leaks has been dramatically reduced to less than 5%. However, it can not be harvested for most cases of tumors after prior surgical resection or if the nasal septum is involved. In case of previous EBT, it is necessary to cover the defect with a vascularized flap harvested from a nonirradiated area. The pericranial flap (PCF) is the most versatile alternative to the NSF and has the potential for the largest area of coverage, which can be increased according to the site of the coronal incision. Several techniques have been reported, even with endoscopic PCF sampling. This flap is classically introduced into the cavities through a lateral or a low-median nasionectomy. From there, it can cover the skull base as far posteriorly as the sella. The drawback of this technique is that it may impair ventilation of the frontal sinus. Furthermore, passage through the nasion does not allow coverage of the back wall of the frontal sinus, which might be needed if the margin of the dural resection is high and anterior. We present here a procedure that allows the PCF to cover the whole anterior skull base, including the posterior wall of the frontal sinus.