Operative Procedure

The surgical procedure commences with a bifrontal craniotomy. The bicoronal skin incision in the scalp is deepened to a level just superficial to the pericra-mum which is then incised approximately 5 cm posterior to the scalp incision. The galea and pericranium are elevated to the level of the supraorbital rims and the nasofrontal suture line, preserving the neurovascular (supraorbital) pedicle as it emerges from the supraorbital notch (Figure 12-2). Once this

Figure 12-2. A, Incision for bifrontal craniotomy. B and C, Galeal-pericranial flap.

flap has been successfully elevated, a frontal cran-iotomy is performed. We utilize a single burr hole on either side of the saggital sinus and a side-cutting craniotome for the bone flap with the inferior osteotomy located subfrontally at approximately the level of the nasion. The dura overlying the frontal lobe is then carefully explored and, based upon the tumor's extent, the decision whether to proceed by an extradural or intradural route is made. Upon dissection of the anterior cranial fossa floor, the olfactory bulbs are sharply divided and their dural sleeves i *

Figure 12-2. A, Incision for bifrontal craniotomy. B and C, Galeal-pericranial flap.

are oversewn to prevent a CSF leak. Once an adequate degree of frontal lobe relaxation is achieved, the bony anterior fossa floor can be fully visualized and the superior bone cuts made (Figure 12-3). These cuts frequently involve a posterior cut at approximately the level of the anterior sphenoid wall, variable portions of the superior orbital roof, and the entire cribriform plate and superior ethmoid complex. This frontal bone flap is later cranialized by removing the posterior bony sinus wall and stripping the mucosa from the anterior sinus wall to prevent the formation of a frontal sinus mucocele.

We have found this bifrontal cranial approach to offer outstanding access with minimal morbidity and good cosmesis.1314 In an effort to minimize the morbidity associated with this bifrontal craniotomy, the use of less extensive subcranial exposures have been described.15-17 While some of these approaches may, in selected circumstances, offer adequate access and permit visualization of the full superior extent of a tumor, their potential for inadequate exposure outweighs any perceived cosmetic benefit.

Once the tumor has been adequately encompassed from above, and all bone cuts at the anterior cranial base performed, facial exposure of the tumor is obtained. Depending upon the extent of the tumor, this is accomplished via either an isolated lateral rhinotomy or a Weber-Ferguson approach (Figure 12-4). If significant lateral extension of the tumor is present, the Weber-Ferguson approach can be modified through a lateral extension which we prefer to

Figure 12-3. Exposure of cribriform plate/anterior base of skull.
Figure 12-4. Incision for lateral rhinotomy.

carry out through a transconjunctival incision into the ipsilateral fornix of the conjunctiva (rather than through a subciliary incision). With this exposure, tumor can be successfully mobilized encompassing complete anatomic units (maxilla/orbit/sinus) en bloc with the bony skull base. Once the tumor has been resected with tumor-free margins, reconstruction of the anterior skull base defect can proceed. When orbital exenteration and/or total maxillectomy are performed and a significant soft tissue defect is present, free tissue transfer offers the best option for satisfactory reconstruction. However, if a significant soft tissue defect has not been created, reconstruction focuses on establishing a water-tight seal around the intracranial contents and isolating the sinonasal tract. In order to achieve this, the scalp flap that includes both galea and pericranium is now dissected in a plane superficial to the galea, leaving galea on each side of the incision to allow for closure. This well-vascularized galeal-pericranial flap is then sutured to the basal dura and the perimeter of the bony defect (Figure 12-5).121418

We have recently adopted additional reconstructive nuances in an effort to minimize the postoperative morbidity and sequelae of craniofacial resection. While many descriptions of craniofacial surgical techniques indicate that the nasofrontal duct can be transsected and marsupialized to the surrounding soft tissue,6 our experience with postoper-

Figure 12-5. Repair of anterior base of skull defect with galeal-pericranial flap.

ative nasolacrimal duct stenosis and epiphora would argue otherwise.14 We currently stent the naso-lacrimal duct after it has been transsected (Figure 12-6), and remove this stent after the completion of radiotherapy. In addition to nasolacrimal duct stent-ing, we have also focused attention on the accurate repositioning of the medial canthus. A permanent suture is placed in the divided medial canthal tendon and it is overcorrected in both the superior and posterior planes in anticipation of postoperative laxity of the tendon (Figure 12-7). If this overcorrection is not performed, variable degrees of orbital dystopia and telecanthus can occur and occasionally result in visual disturbances. These two technical aspects of craniofacial reconstruction are critical, as Andersen and colleagues19 noted that nearly 50 percent of patients undergoing craniofacial resection for tumors of the anterior skull base develop ocular sequelae from their treatment.

Tumors of the anterior skull base can extend laterally and closely approach (if not directly invade) the orbital periosteum and orbital soft tissues. In these cases, resection of the majority of the bony and fascial support of orbit may be required, although the globe is preserved. The loss of support for an otherwise normal eye (especially when most/all of the orbital floor is resected) was recently addressed by Stern and colleagues,20 who noted a decrease in the likelihood of eventual eye function when the orbital floor was resected for sinonasal cancer, espe cially when postoperative radiotherapy was employed. The authors used this data to make the case that orbital exenteration should be more strongly considered at the time of the initial surgical resection if major loss of eye support and postoper-

Figure 12-6. Placement of nasolacrimal duct stent.
Figure 12-7. Repair of medial canthal tendon.

ative radiotherapy were anticipated. However, most would not resect an eye unless gross invasion of the orbital contents (fat, muscle, or globe) and/or significantly decreased ocular function were present. This conservative approach is supported by a recent meta-analysis by Carrau and colleagues21 that could not document any increase in local recurrences with such an approach. An alternative solution to the issue of eye function following the loss of the orbit's physical support was recently offered by Cordeiro and col-leagues.22 These authors noted improved eye function (as well as cosmesis) when the resected orbital floor was reconstructed using a combination of a bone graft (either split calvarium or rib) and a vascularized flap (either pedicled or free) regardless of whether postoperative radiotherapy was administered.

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