Transcranial approaches

Probably the most popular method of reconstructing the anterior skull base today is the use of the pericranial flap. After skin incision is performed, a scalp flap is elevated in the subgaleal plane to the level of the supraorbital rims [5]. At this point, the pericranium is incised and the dissection is carried forward in this plane, preserving the blood supply from the supratrochlear and supraorbital arteries (Fig. 2a). After the craniofacial resection is completed, the pericranial flap may even be sutured to the posterior remnant of the dura. It therefore may be used to repair dural defects or can be used to augment the intact or reconstructed dura by providing support, mainly because of its vascularity.

On the other hand, if the frontal sinus is entered during a subfrontal craniotomy, the posterior wall and all sinus mucosa are carefully removed by cranialization. Subsequently, a galeal periosteal flap from the forehead, sealed with fibrin glue, can be used to cover the basal parts of the frontal sinus. The frontal sinus may also be closed with autologous fat (Fig. 2b).

Moreover, autogenous wet bone powder collected during skull trephination may be useful for cranial reconstruction to fill in the dead space left after the craniotomy.

In cases of extensive bone removal, a titanium mesh can be used to support the anterior skull base reconstruction.

Coagulation of the dural edge should be avoided, as this generates its retraction and complicates a watertight closure. A clearance of several millimeters during dural opening should be allowed between the bone margin and the dural incision, to facilitate its final closure.

Endonasal approaches

When performing an endonasal approach [1], the use of specific reconstructive techniques is based upon many factors apart from the corridor and target area: the size and shape of the skull base defect, the condition of the surrounding bone and remaining dura, whether or not a CSF leak was encountered intraoperatively, the nature of the CSF leak encountered (high- or low-flow), the extent of communication between the nasal and intracranial cavities, the anticipated postoperative intracranial pressure (ICP), the nature of any resected lesion, the status of the nasal septum and lateral nasal wall, a history of previous surgery or radiation therapy, and the anticipated need for adjuvant therapies (i.e., irradiation or chemotherapy). Currently, pedicled flaps offer the most reliable reconstruction of large skull base defects, ensuring the successful isolation of the intracranial space from the sinonasal tract, to prevent complications such as meningitis, intracranial abscesses, encephaloceles, CSF leaks, and tension pneumocephalus. Pedicled flaps, such as the posterior pedicle nasoseptal flap (i.e., the Hadad-Bassagaisteguy flap) have revolutionized the endoscopic repair of the skull base, as their axial blood supply can irrorate a large surface area with a small and relatively long pedicle. In this view, it is mandatory to save the vascularization coming from the sphenopalatine artery during the nasal phase of the surgical procedure.

Furthermore, a free middle turbinate flap may be useful to reinforce the reconstruction; this has to be saved at the beginning of the procedure (Fig. 3).