bandeau) and after carefully extradurally raising the frontal cerebral lobe, one obtains a subfrontal tangential view of the whole frontal skull base – if possible, selectively protecting the olfactory fibers.

This osteotomy provides an improved exposure of the dural injuries without undue retraction of the frontal lobe (Hardt et al. 1992; Kessler and Hardt 1998a, b; Kuttenberger and Hardt 2001). With regard to the level of

access, this procedure is approximately equivalent to that of the subcranial-subdural approach (Figs. 8.15–8.17).

8.4.2.3  Skull Base Exposition

One differentiates between an extradural and an intradural exposition, depending on whether or not the dura

Fig. 8.15  Osteotomy of the nasofrontal segment to facilitate horizontal exposure of the medial frontobasal region without traumatic brain retraction. The horizontal and vertical osteotomies are performed using a microsaw (arrow)

is raised from the basal bone. The decision as to whether to operate intraor extradurally, or even through both approaches if necessary, must be made by the neurosurgeon intraoperatively. Crucial criteria are extent and

localization of the dural injuries. If there is no intradural pathology or trauma in need of revision, then fractures in the region of the skull base, frontal sinus or the orbital roofs are revised via a transfrontal-extradural approach.

• Extradural exposition of the skull base

Extradural exploration is particularly applicable in all basal injuries in the vicinity of the frontal sinus, anterior, and mid-ethmoid and orbital roof with no cerebral injury. Debridement of the anterior and mid-ethmoid region and consequently the frontal sinus can be carried out from the epidural space (Giuliani et al. 1997).

Technical Aspects

After removing the skull bone and the fronto-facial fragments, one can expose the floor of the anterior cranial fossa. Using light-enforced dura dissectors and bipolar Malis forceps, the dura is carefully peeled off from the floor of the anterior cranial fossa and the orbital roofs as far as the edge of the greater wing of the sphenoid bone.

In doing so the dura is also relieved antero-medially towards the crista galli. Should it be necessary to expose the cribriform plate bilaterally, then the falx must also be removed, possibly in combination with resection of the crista.

Fig. 8.16  Craniotomy and additional frontofacial osteotomy to facilitate horizontal exposure of the medial frontobasal region. (a) Intraoperative view after bifrontal craniotomy and frontofa-

cial osteotomies. (b) Frontal bone flap and frontofacial segment. (c) Extended horizontal approach to the frontobasal area after removal of the frontofacial segment. Pericranium flap reflected

The dura often rips when removing it from the ethmoid/nasal roof, as it is very thin but strongly adherent in this area (Imhof 2000). The olfactory fibers must be resected in order to expose posterior fractures.

Bleeding from small dural vessels is carefully controlled by applying H2O2 cotton pads, with the bipolar Malis forceps and a temporary coverage of minor bleeding spots with a thin layer of resorbable collagen fleece. Dural tack-up sutures are essential as hemorrhage prophylaxis (Figs. 8.18 and 8.19).

After complete exposure of the basal area, the frontal lobe of the brain is carefully retracted, so providing an unhindered view of the posterior wall of the frontal sinus, orbital roof and the anterior skull base.

Due to intraoperative manipulation of the anterior skull base, there may be hemorrhage from the frontobasal dura. This is can be stopped by coagulation and the application of adrenaline-soaked pads, so omitting further neurosurgical measures (Imhof 2000).

For protection, the frontal lobe of the brain is covered with a moist membrane (Merocel) and retracted with flexible brain spatulas. Excessive pressure to the frontal lobe can rapidly result in secondary cerebral edema with respective swelling and thus impede or even inhibit its exposure.

In frontobasal fractures, small nondislocated bony fragments are, if possible, left in the position. Larger fragments are sometimes difficult to mobilize and reduce, without injuring vessels or neural structures. Large, loose fragments are placed into antibiotic solution and later used to reconstruct the osseous skull base. If defects of the frontal base result, autogenous bone grafts have to be used for reconstruction (Imhof 2000).

• Intradural exposition of the skull base

If frontobasal fractures are combined with cerebral injuries which need revision or if extensive fronto­basal fractures with dural tears lie in the vicinity of the nasal roof

Fig. 8.17  Craniotomy with additional frontofacial osteotomy. (a) Bifrontal osteotomy. (b) After removal of the frontofacial segment excellent exposure of the frontobasal area is archieved without extensive brain retraction. (c) The frontal flap and the

frontofacial segment. (d) Reintegration and fixation of the frontofacial segment and the bone flap. Burr holes and bony gaps are filled with bone dust