Fig. 8.20  Schematic diagram of the transfrontal intradural approach to the frontobasal area and visualization of the injured dura (mod. a. Samii et al. 1989; Weerda 1995)

Fig. 8.21  Transfrontal intradural approach to the frontobasal area Intraoperative view demonstrating intradural exposure of the traumatized right frontal lobe (arrow)

8.4.3  Advantages, Disadvantages,

and Risks Associated with

the Transcranial Approach

Without doubt the extradural and intradural approaches pose a greater operative risk than the subcranial approach,­ particularly when early surgery is undertaken. The danger of postoperative cerebral edema is far greater in recent cerebral injuries (Probst and Tomaschett 1990). With approximately 3% there is a much lower mortality rate after the edema has subsided and the cerebral parameters have normalized (Loew et al. 1984).

Postponed intracranial intervention in the treatment of dural and skull base lesions, awaiting the subsidence of the cerebral edema, consequently results in a postponed primary surgical treatment of the midfacial fractures and the skull base by 2-3 weeks. As a result of delayed surgery and beginning fracture consolidation, bone reduction is complicated and hence may entail secondary surgery at a later date.

Furthermore an increased risk of ascending infection exists from deferred surgery owing to congestion and secretion in the paranasal sinuses as well as an increased risk of meningitis resulting from the untreated skull base fractures (Vuillemin et al. 1988).

A partial or total anosmia is not always avoidable. This may either be a consequence of trauma, particularly from dislocated fragments in the medial skull base region, or it may result from surgical exploration, especially if the olfactory fibers have to be transected bilaterally (Samii 1989). Olfactory dysfunction (hypor anosmia) as a result of the surgical transcranial intervention was found in 7-8% (Neidhardt 2002; Schroth et al. 2004).

Other disadvantages may arise from the compara tively large wound surface and technically from the problematic treatment of the olfactory groove, ­concerning preservation of olfactory function, the direct contact with the cerebral cortex, pontine veins and the superior sagittal sinus (Füssler et al. 1996; Rosahl et al. 1996; Lehmann et al. 1998).

The narrow access to the sphenoidal sinus and further dural tears as a consequence of surgery in areas where it is particularly adherent (medial ethmoidal roof, cribriform plate, crista galli) pose additional risks (Lehmann et al. 1998).

With a supplementary frontofacial osteotomy the frontal base can be tangentially exposed, bone fragments removed and the skull base reconstructed without excessive retraction of the cerebral structures. The surgical trauma is minimized and at the same time a radical ethmoidectomy – as in the subcranial approach – can be avoided (Kuttenberger and Hardt 2001).

8.5  Transfrontal-Subcranial Approach

The classical extracranial-transethmoidal approach is limited to the frontal sinuses and the ethmoid-­ sphenoidal region and is therefore not an adequate alternative to the neurosurgical approach (Samii and Draf 1978; Calcaterra 1980, 1985; Elies 1982; Loew

et al. 1984; Myers and Sataloff 1984; Strohecker 1984; Probst 1986).

Raveh et al. (1984) and Raveh and Vuillemin (1988, 1992) further developed the transethmoidal method and converted it to a subcranial approach, through which one can work subcranially parallel to the skull base level, so avoiding excessive iatrogenic trauma of the cerebral structures. This is especially important where cerebral edema is already present (Raveh and Vuillemin 1992; Raveh et al. 1993; Donald 1994; Lehmann et al. 1998; Fliss et al. 1999).

8.5.2  Surgical Principle

Following a transfrontal coronal approach, resection of fronto-nasal bone fragments and a selective craniotomy, the ethmoidal cells are radically cleared out and the entire median subbasal region, the medial orbital walls, medial orbital roof and orbital apex exposed from a subcranial aspect (Raveh and Vuillemin 1988, 1992; Lädrach et al. 1995, 1999; Gliklich and Lazor 1995; Raveh and Lädrach 1997; Kellman 1998; Raveh et al. 1998; Gliklich and Cheney 1998; Moore et al. 1999).

8.5.1  Indications

Based on the most frequent fracture variations in the region of the anterior cranial fossa, the subcranial approach enables the treatment and reconstruction of the frontal skull base structures along the median and medio-lateral regions of the anterior cranial fossa (Moore et al. 1999) (Fig. 8.22).

•In the majority of cases, the indications for a subcranial­ approach are limited to localized injuries of the periand interorbital regions (NOE fractures) with circumscribed median frontobasal fractures without intracranial injuries (Kellman 1998; Lädrach and Raveh 2000).

Fig. 8.22  Schematic diagram demonstrating the extent of exposure along the skull base which is possible through the extended subcranial approach (mod. a. Vuillemin et al. 1988; Lädrach et al. 1999; Lädrach and Raveh 2000)

8.5.3  Subcranial Surgical Technique

The subcranial approach to the skull base is carried out by temporary resection of the naso-fronto-cranial fragments, and occasionally to obtain a better view, an additional selective osteotomy in the naso-frontal region is performed with preservation of the osteotomized segments (Raveh and Vuillemin 1988).

The size of the collaterally removed segments depends on the extent of the fracture site and involves either only the narrow fronto-nasal or additionally the cranio-fronto- nasal region (Vuillemin et al. 1988; Raveh and Vuillemin 1992; Raveh et al. 1998; Lädrach et al. 1999; Lädrach and Raveh 2000).

Subsequently, after removing the fracture fragments and an additional fronto-nasal segment, a subbasal debridement of the ethmoidal cells is carried out with a radical ethmoidectomy and total removal of the ethmoidal mucosa, so exposing the fractured frontal base, including the sphenoid region and the medial orbital walls (Raveh and Vuillemin 1988; Vuillemin et al. 1988).

Due to the enhanced access through the transeth- moidal-extracranial approach, the medial aspects of the orbital roof and the orbital apex become visible, allowing a decompression of the optic nerve. In such cases, the medial wall of the optic canal is removed transethmoidally and the region is drained to prevent a postoperative apex syndrome (Lädrach et al. 1995; Lädrach and Raveh 2000). Following dural treatment, reconstruction of the frontobasal structures is performed along the median skull base and the medio-lateral region of the anterior cranial fossa with reconstruction of the orbital roof.

Definite dural sealing is accomplished by using autogenous fascia-lata grafts (Raveh et al. 1998). Subsequently, the extracted fronto-cranial segments are