reintegrated and fixed to reconstruct the osseous frontal region. Simultaneously, the midface fractures are repositioned and fixed with titanium miniplates. An existing pseudo-hyperteleorism is corrected.

Subcranial approach to the upper craniofacial and frontobasal fractures (Vuillemin et al. 1988; Lädrach et al. 1999).

•Subcranial approach through coronal incision, temporary removal of the fronto-nasal fragments, selective craniotomy, subsequent ethmoidectomy and revision of the frontal base

•Osseous frontobasal reconstruction, dural repair with fascia lata and reconstruction of the anterior wall of the frontal sinus

8.5.4  Advantages, Disadvantages,

and Risks Associated with

the Subcranial Approach

The major advantage of the subcranial-transethmoidal approach is avoiding the retraction of the frontal cerebral lobe with potential collateral edema formation. Subdural exploration also reduces the risk of lesions of the olfactory fibers (Raveh and Vuillemin 1988). Thus, the subcranial approach offers an important alternative to the traditional neurosurgical approach to the frontal skull base (Vuillemin et al. 1988; Raveh et al. 1993). The smaller wound and superior evaluation of the olfactory nerve groove speak in favor of the subcranial approach where indicated (Lehmann et al. 1998).

The danger of skull base instability exists (Samii 1987, 1989) in cases of extensive debridement when the subcranialtransethmoidalapproachisused.Furthermore, the limited exposure offered by the subcranial approach is not free of risks in the strongly traumatized midface. Fractures in the region of the lateral and central orbital roofs cannot be reliably inspected and treated.

The access to the lateral sections of the anterior cranial fossa is strongly limited. Injuries to the orbital walls with orbital laceration and formation of orbital hematomas endangering the optic nerve have been described (Hosemann et al. 1991; Rohrich and Hollier 1992).

Loss of osseous structures from the medial orbital walls may lead to prolapse of the orbital contents into the interorbital space and, thus, to increase of the orbital

volume with loss of muscular balance, disturbed eye motility, enophthalmus, and infection.

It may, therefore, be necessary to reconstruct the orbital walls during the primary treatment as long as there is no polyfragmentation. A secondary reconstruction of residual, medial defects is technically challenging with inferior results.

Unnoticed dural tears may appear as an iatrogenic consequence of a radical ethmoidectomy and basal debridement with possible danger of recurrent liquorrhea.

The subcranial approach only allows modified treatment of cerebral injuries and multiple dural tears (Probst 1986).

Further disadvantages of the subcranial approach are the limited possibility to adequately treat accessory neurosurgical injuries, such as accompanying suband epidural hematomas and cerebral injuries, which are not accessible from this approach (Samii et al. 1989).

Reconstruction of the orbital roofs with exact fragment placement is more difficult to realize from a subcranial approach than from using the intracranial extradural procedure. Frequently, extensive dislocations of the frontal region, the frontoorbital or frontocranial compartments exist, make an intracranial, extradural procedure inevitable.

Moreover, the healing process of the interorbital bony skeleton with radical removal of all mucous membranes has not entirely been cleared (Hosemann et al. 1991).

The outstanding self-healing potential of injured ethmoid cells and the regenerative capacity of the paranasal sinus mucosa, with the recovery of spontaneous ventilation and drainage, brings to question the necessity of a primary radical clearance of the ethmoid cells to access the skull base (Hosemann et al. 1991; Kessler and Hardt 1998a, b).

8.6  Transfacial Approach

The transfacial-frontoethmoidal approach allows clear and sufficient extradural exploration of the frontal sinus, the ethmoid region and the sphenoid sinus as well as the medial orbit; however, with limited access to the medial orbital roof and orbital content.

It offers sufficient space to cover dural defects and placement of drains (Dieckmann and Hackmann 1977; Calcaterra 1985; Ewers et al. 1995; Lange et al. 1995; Schwab 1995; Donald 1998; Schroth et al. 1998).

Using this approach, debridement in the region of the paranasal sinuses and frontal base can be carried out efficiently with microscopic support. This is particularly the case when dealing with fractures in the regions of the cribriform plate, ethmoid roof and sphenoid (Pirsig and Treeck 1977; Draf 1995).

8.6.1  Indications

The indications are in particular localized skull base fractures of types Escher II, III, and Oberascher I, IIa. Fractures in the region of the anterior and middle ethmoid radiating into the frontal sinus can be managed transfacially. This also applies to fractures of the frontal sinus wall in case of limited bony defects in the posterior wall. Due to the narrow anatomical position, fractures of the posterior section of the ethmoid are difficult to approach transfacially (Oberascher IIb) and are, therefore, preferably treated using the endonasal approach. Dural injuries with liquorrhea in the region of the sphenoid sinus (Oberascher III), often in combination with uniand bilateral fractures of the petrous part of the temporal bone, should be treated endonasally using endoscopic techniques.

Extensive craniofacial or fronto-cranial injuries with ethmoidand frontal sinus fractures in combination with complex midfacial fractures, which necessitate the transfrontal or subcranial-extradural approach in order to reconstruct the facial architecture, are not suited for this approach (Prein 1998).

•Fractures in which lesions of the paranasal sinuses are predominant — as opposed to dura or cerebral injuries — are generally suited for the transfacial treatment; especially those in which facial soft tissue injuries offer a possibility of access (Theissing 1996; Schwab 1995).

8.6.2  Surgical Principle

There are differing concepts in treating ethmoidal cell fractures with and without skull base involvement:

Primary radical clearance of the ethmoid cells is an alternative to the conservative-surgical procedure.

Both variations have a high priority to reestablish ventilation and drainage of the paranasal sinuses.

Up until the late 1970s, literature references recommended radical clearance of injured naso-ethmoidal cells, even without verified dural injuries. More recent publications (Theissing 1996) only speak of a relative indication for debridement in strongly dislocated ethmoid cell fractures. Experimental and clinical research by Hosemann et al. (1991, 1993) has had fundamental consequences on the treatment of naso-ethmoidal fractures.

According to anatomical differences, Hosemann et al. (1991) differentiated between the therapy for anterior and posterior ethmoid cells. Fractures of the posterior ethmoid cell region generally legitimate an expectative conservative treatment. In the anterior ethmoid cell region there is only a relative indication for radical clearance.

Hosemann et al. (1991) stress the significant selfhealing potential and regeneration ability of the ethmoidal cell mucosa with recovery of spontaneous ventilation and drainage of the ethmoidal system, even with extensive fracture comminution. Regeneration of the ethmoidal cell system even in stongly dislocated and comminuted fractures of the interorbital complex were demonstrated by means of a retrospective study based on CT scans (Kessler and Hardt 1998a, b).

A comparison of craniofacial fractures treated with cranial ethmoid cell debridement with subcranial midfacial and NOE fractures treated without ethmoid cell debridement showed no relevant postoperative differences in the subsequent long-term CT follow-up (Kessler and Hardt 1998a, b).

•These results question the necessity of primary radical ethmoidal clearance in comminuted anterior skull base fractures (Hosemann et al. 1991, 1992, 1993; Kessler and Hardt 1998a, b) (Figs. 8.23 and 8.24)

8.6.3  Transfacial Surgical Approaches (Denecke et al. 1992; Schwab 1995; Theissing 1996; Ernst et al. 2004)

For a unilateral transfacial approach the paranasal semicircular incision according to Kilian and for a bilateral approach the butterfly-incision according to Siebenmann are used (Ewers et al. 1995; Boenninghaus 1971, 1974).

As is often the case in frontobasal injuries, there are facial soft tissue injuries which make it necessary to

modify the classical approaches (Dieckmann and Hackmann 1977).

If the butterfly incision is continued laterally via the zygomatic bone, a cranially based bipedicled flap can be created and used in craniotomies for treating skull base fractures with the intraand extradural approach (Ewers et al. 1995).

1.The semicircular incision takes its course below the inner border of the eyebrow, continues caudally between the bridge of the nose and the medial corner of the eye and ends at the height of the inferior orbital margin (Schwab 1995). The incision may also be combined with a primary Z-plasty in the corner of the eye.

Fig. 8.25  Different transfacial approaches for exposure and revision of the frontal sinus, ethmoid, orbit, and sphenoid (mod. a. Probst 1971). (a) Unilateral subbrow incision (frontoorbital

(d) Coronal incision combined with a median subbrow incision

By strictly holding the scalpel vertically the skin, the subcutaneous tissue and the periosteum are cut simultaneously through to the bone. Bleeding from the supraorbital artery must be carefully controlled. Whilst performing the incision the lacrimal sac and the lacrimal canals must be protected as far as the entrance point of the nasolacrimal canal. Subsequently,­ the soft tissues and periosteum from the floor of the frontal sinus and lateral slope of the nose are dissected. It is necessary to perform a strictly subperiosteal dissection around the insertion point of the medial palpebral ligament and trochlea. Particular care must be taken to maintain the integrity of the medial palpebral ligament, in order to prevent a secondary hypertelorism. The lacrimal sac is released from its bony groove (Figs. 8.25 and 8.26).

2.Subsequently, the floor of the frontal sinus and the ethmoid can be opened through this approach, either by an osteoplasty or by a bone resection. Bone trepanation­ (lacrimal bone - anterior section of the lamina papyracea) in the medial orbital corner above the lacrimal fossa, provides access to the frontal sinus, ethmoid cells and orbital roof. If the anterior wall of the frontal sinus is comminuted, bony fragments should be removed and reimplanted at the end of the operation if possible. The fragments are preferably fixed with microplates.

3.After opening and clearing the ethmoidal cells and carefully removing the bony fragments in the region of the posterior wall of the frontal sinus, roof of the ethmoid and cribriform plate, transethmoidal removal of the anterior wall of the sphenoid sinus with exploration of the roof of the sphenoid sinus is possible.

4.Following exploration of the ethmoidal roof and the cribriform plate, the osseous defect in the skull base

is enlarged using a diamond or trepan burr under endoscopic control, so providing a good view of the dural defect. Fluorescin sodium administered intrathecally prior to surgery results in an improved intraoperative presentation of dural defects (Theissing 1996; Ernst et al. 2004).

5.In order to sufficiently seal any dural leak, it is essential to have a complete view of the entire dural tear. The dura is primarily sutured after it has been carefully lifted from the bone. In order to protect the olfactoryfibresasfaraspossible,noextensivemanipulations should be done here. A graft is then placed between bone and dura to cover the defect (Ernst et al. 2004).

In the case of a bilateral fracture, the transplant has to be extended to the opposite side to cover the complete defect. A second graft overlaps the bony defect and is fixed with fibrin glue. The reconstruction should be supported by a nasal tamponade for 7 days (Ernst et al. 2004) (Fig. 8.27).

8.6.4  Dura Treatment in the Frontal

Skull Base

8.6.4.1  Frontal Sinus

Posterior wall defects of the frontal sinus are mostly found at the point of transition to the ethmoid.

•Simple osseous defects without dural injury are covered with a patch (fascia/alloplastic material) and sealed with fibrin glue. Bony fragments can be replaced in order to reduce the size of larger defects.