the nasal-ethmoidal-sphenoidal complex is performed unilaterally or bilaterally (according to the extension of disease) to expose the lateral margins [10]. The lamina papyracea is included in the dissection when the tumor is in close proximity to or frankly involves it. When required by extension of disease, an endoscopic medial maxillectomy can be performed to achieve good control of the entire maxillary sinus [13]. Superiorly, the dissection is continued in the anteroposterior direction by resecting the olfactory fibers and the basal lamella of the ethmoidal turbinate(s) to mobilize the specimen. The entire nasal-ethmoidal-sphenoidal complex is then isolated and pushed toward the central part of the nasal fossa (centripetal technique) to remove it transorally or through the nasal vestibule. Surgical margins are checked by frozen sections and, if necessary, the resection is extended until free margins are obtained.
Skull Base Removal
According to the extension of the disease, EER can be extended to include the anterior skull base (endoscopic resection with transnasal craniectomy; ERTC). The ethmoid roof is exposed using a drill with a diamond burr. The anterior and posterior ethmoidal arteries are identified, cauterized, and divided. The crista galli is carefully detached from the dura and removed with blunt instruments, preserving the integrity of the dural layer.
Intracranial Step
The key point for subsequently performing an optimal skull base reconstruction is to properly dissect the epidural space over the orbital roofs laterally, the planum sphenoidale posteriorly, and the posterior wall of the frontal sinus anteriorly before starting the resection of the dura. The dura is then incised and circumferentially cut with angled scissors or a dedicated scalpel, far enough away from the suspected area of tumor spread. The falx cerebri is clipped or cauterized in the anterior portion before its resection, to avoid sagittal sinus bleeding; next, the posterior portion at the level of the sphenoethmoidal planum is resected. The arachnoid plane over the intracranial portion of the tumor is dissected and separated from the brain parenchyma. The specimen, including the residual tumor, anterior skull base, and the overlying dura, together with one or both of the olfactory bulbs, is removed transnasally. Dural margins are sent for frozen sections. With small tumors, dural resection can be performed by leaving the ethmoidal complex attached to the skull base at the level of the olfactory grooves in a monobloc fashion.
Table 2. Intraoperative and postoperative complications rate during sinonasal and skull base endoscopic surgery
Skull Base Reconstruction
The resulting skull base defect is reconstructed by the endoscopic endonasal multilayer technique, which is preferably performed using autologous materials. In our experience, fascia lata and/or the iliotibial tract possess the best characteristics in terms of thickness, pliability, and strength. For the first intradural layer of duraplasty, the graft has to be at least 30% larger than the dural defect and split anteriorly on the midline to adjust to the falx cerebri in case of bilateral resection. The second layer, intracranial and extradural, needs to be precisely sized and tacked between the previously undermined dura and the residual bone of the skull base. Fragments of fatty tissue are placed to eliminate the dead space between the second and third layers and to flatten the residual denuded skull base. The third extracranial layer must cover all of the exposed anterior skull base, but must not overlap the frontal sinusotomies. The borders of the second and third layers are properly fixed with small amounts of fibrin glue. No bone or cartilage grafts are used to repair the skull base to avoid radionecrosis, infection, and extrusion after postoperative radiotherapy. In the case of a tumor not involving the nasal septum and without multifocal localizations, the third layer of the skull base reconstruction can be harvested using mucoperiosteal/mucoperichondrial pedicled flaps based on the nasal branches of the sphenopalatine artery (Hadad-Bassagasteguy flap) [14] or vascularized by the septal branches of ethmoidal arteries (septal flip flap) [15, 16]. The use of local pedicled flaps facilitates rapid healing of the surgical cavity and reduces postoperative nasal crusting, which is particularly helpful in patients who require adjuvant irradiation. At the end of the procedure, in selected cases, the frontal sinusotomies can be stented with rolled polymeric silicone sheaths to allow subsequent frontal sinus debridement with no risks for duraplasty. The surgical cavity is packed for about 48 h.
Fig. 3. Complications after endoscopic endonasal surgery. a, b Left frontal lobe abscess after skull base reconstruction; coronal and sagittal views, respectively. c, d Brain herniation after endoscopic skull base reconstruction; coronal and sagittal views, respectively.
Complications
Although endoscopic surgery resection of sinonasal tumors is associated with lower morbidity, better postoperative quality of life [17, 18], and faster hospitalization days [3], as in any surgical intervention postoperative complications can occur. Nonetheless, after these procedures they are less severe and frequent compared to traditional open approaches [19]. From the reports available in the literature on endoscopic management of sinonasal tumors, it is evident that the rate of complications is 9–11% [19–30], while the mortality rate is around 0–1% [22–24]. Complications and mortality rates of open approaches, which are 36.3 and 4.5%, respectively [22], confirm that endoscopic strategy is a safer and less invasive procedure (Table 2). Of note, the analysis of retrospective series frequently has a low statistical value, since the comparison is made between cases with variable extent and histology.
In general, potential complications can be divided into five main groups (Fig. 3):
1Systemic (sepsis, fever).
2Central nervous system (meningitis, brain abscess, pneumocephalus, cranial nerves injuries, etc.).
3Orbital (orbital hematoma, pneumorbit, epiphora, etc.).
4Vascular (intraoperative bleeding from sphenopalatine, ethmoidal, frontopolar, medial orbitofrontal, or internal carotid arteries [ICA]; nasal bleeding after nasal packing removal). Although the injury of ICA during an endoscopic procedure is luckily a rare event (0.2–1%) [23], the progressively expanded indications for endoscopic surgery have led the surgeon to more and more frequently deal with lesions deeply related with the ICA. Several authors have published their experience regarding this issue [26],
