Fig. 9.2  Exposure of the frontal skull base after cranialisation of the frontal sinus, obliteration of the nasofrontal duct and debridement of the anterior and middle ethmoidal cells (mod. a. Imhof 2000). 1 Frontal sinus (after cranialization), 2 ethmoid cells (2.1 post-ethmoidectomy, 2.2 closure with muscle patch and fibrin sealant), 3 nasofrontal duct (obliteration with muscle patch and fibrin sealant), 4 superior sagittal sinus

In comminuted fractures of the anterior and posterior walls of the frontal sinus or extensive damage to the posterior wall of the sinus, reconstruction of the anterior wall and resection of the entire osseous posterior wall, including meticulous removal of the entire mucous membrane, is carried out with a diamond trephine. Inverted closure of the naso-frontal duct avoids postoperative complications of ascending infections (Fig. 9.2).

9.3.3  Skull Base Repair

9.3.3.1  Extradural Skull Base Repair

• Muscle/fascia patch

Following debridement of bony fragments and the loose parts of the mucous membrane in the region of the ethmoid cells, all osseous defects of the skull base are routinely covered with an autogenous free muscle or fascial graft (Draf und Samii 1977; Probst 1986; Derome 1988; Sundaresan and Shah 1988; Probst and Tomaschett 1990; Ewers et al. 1995).

Small fronto-ethmoidal defects are covered with a fasciaor neuro-patch and a pedicled, pericranial flap.

In larger defects — particularly following ethmoid cell debridement — the basal defect coverage initially consists of one to two layers of hemostyptic gauze (e.g., Tabotamp), followed by an autogenous muscle patch,

Fig. 9.3  Closure of the medial anterior skull base area: obliteration of the nasofrontal duct with muscle patch and fibrin sealant (arrow) after cranialisation of the frontal sinus and ethmoidectomy

which is fixed with fibrin glue and then covered with a pedicled pericranial flap (Probst 1986) (Fig. 9.3).

Closure of the nasofrontal ducts after cranialization of the frontal sinus is obligatory. Their mucous membranes are circularly peeled off, pushed downwards, invaginated, and sealed with fibrin glue. Final coverage of the duct and floor of the frontal sinus is achieved in the same way as described above using fibrin glue, a muscle patch and optionally a pericranial flap (Stanley and Schwartz 1989) (Fig. 9.4).

Fig. 9.5  Schematic diagram illustrating extradural treatment of fractures of the frontal skull base. Cranialization of the frontal sinus, obliteration of the nasofrontal duct, closure of the skull base defects with bone grafts and pericranial flap. The pericranial flap is inserted through a slot beneath the inferior rim of the frontal bone flap (mod. a. Imhof 2000). 1 Obliterated nasofrontal duct with muscle patch, 2 bone fragments/bone grafts/chips, 3 inserted pericranial flap, 4 dura mater, 5 galea, 6 cranialized frontal sinus

• Pericranial flap

To provide a secure occlusion of any skull base defect, a vascularized, pedicled pericranial flap is swung over the osseous border of the frontofacial compartment, spread out over the reconstructed floor of the anterior cranial fossa over an area as extensive as possible and fixed with sutures.

If necessary, a supplementary pedicled temporal fascia-flap can be inserted unior bilaterally approaching from lateral (Jackson et al. 1982, 1986; Kessler 1983; Price et al. 1988; Weerda 1995; Imhof 2000).

In the subsequent reconstruction of the frontal bone, an inferior, transverse bone-slit is left to avoid any compression to the wrapped-over, vascularized pericranial flap (Figs. 9.5 and 9.6).

• Bone grafts

Under certain circumstances there is an indication for a simultaneous closure of osseous skull base defects with autogenous cancellous or cortico-cancellous bone grafts (Probst and Tomaschett 1990).

•Increased liquorrhea from a CSF fistula (e.g., oncoming cerebral atrophy, opening of the basal cisternae and the ventricular system).

•Unfavorable fistula localization (in the region of a low positioned cribriform plate)

•In very wide bony fracture gaps, an additional autogenous bone graft is integrated to bridge the defect; the region is subsequently covered with an autogenous muscle patch. Particularly in the case of large osseous skull base defects with the risk of necrosis of the above-lying duraplasty (e.g., after extensive ethmoidectomy) a stabilizing layer of autogenous bone should be inserted to avoid herniation of the orbital gyri (Samii and Draf 1989; Stoll 1993; Frodel 2002).

Either calvarial bone from the inner table of the skull or cancellous bone may be used as bone grafts (Stanley and Schwartz 1989) (Figs. 9.7-9.9).

Fig. 9.8  Cranialization of the frontal sinus after fracture of the midface with frontal skull base fragmentation. The posterior wall of the frontal sinus has been removed. The brain slowly

expands and partially fills the additional space. The residual space is filled with fat and scar tissue (arrow). Calcifications at the level of the dura