Authors' Response

We believe that the outcome and surgical management of the cases reported in our study were criticized by inappropriate arguments and statements as follows

First, the above letter evokes an impression that we negate the usefulness of computer-assisted surgery (CAS). In contrast, our article emphasizes that the contribution of CAS, in general, and to anterior skull base surgery, in particular, is undisputed. We attempted to define and identify the indications for CAS in open anterior skull base surgery in relation to the subcranial-subfrontal approach compared to traditional approaches to extensive lesions, which were 23% of the cases. The comments by Dr. Häusler and colleagues that our article ``overlooks the key concerns of image-guided surgery,'' that it ``trivially'' concludes that navigation was not useful, and that they were surprised that CAS was found to be useful at all by using such ``wide open approaches'' are inadequate. They appear to have missed our point. Their extensive description of the usefulness of CAS for different regions and indications, including the comparison to facial nerve monitoring, is also irrelevant to our article.

Second, their declarations that the subcranial approach is ``extensive,'' requires a ``large coronal'' skin incision, is ``wide open,'' and requires ``painstaking osteosynthesis'' are inappropriate and suggest that they are neither acquainted with this approach nor the related literature. The opposite is true: The coronal incision is neither larger nor different from the classic incision. The major advantages of the subcranial approach are that it is less invasive and less extensive than combined traditional craniofacial and transcranial approaches. It thereby enables a broad exposure (not the approach!) under direct visualization of all planes, avoiding frontal lobe retraction and facial skin incisions. Thus, radical en bloc tumor resection or adequate management of other extensive lesions located in this area is feasible through the same access (for details see our article and the associated literature). Accordingly, the popularity of the subcranial approach has increased (furthermore, see our article).[1] [2] [3] [4] [5] [6] After the involved bone is removed, defects are reconstructed using osteosynthesis, a process that is anything but ``painstaking'' in experienced hands. As reflected by their comments, Häusler and coworkers are neither in charge of nor experienced with craniomaxillofacial or open anterior skull base surgery.

Third, stating that the subcranial approach should have been avoided by using endonasal-endoscopic CAS procedures is an obvious overestimation, particularly with respect to the extent of the lesions in this study. Lesions manifesting intracranial and complex involvement of the diverse skull base planes (see Fig. 1 in our article), bone resorption, or extensions involving the orbital-maxillary regions imply extensive resection and reconstruction, including bone grafts (see Fig. 6 in our article) and mandate adequate exposure. One of the tumor cases (see Fig. 5 in our article) demonstrates the pitfalls related to endoscopic procedures; tumor left in the sphenoid and parasellar area effaced the intracavernous portion of the internal carotid artery along with the extensions in the pterygopalatine fossa. Their statement that by ``today's state of the art, mucoceles . . . are no longer treated by external but through endonasal endoscopic'' procedures far exceeds reality. The mucoceles in our series were extensive lesions with concomitant intracranial or ethmoidal-orbital involvement and frontal bone defects that mandated reconstruction with bone grafts and allografts. When a broad exposure to anterior skull base tumors and lesions is indicated, the approach must be selected meticulously to insure that oncological guidelines (i.e., avoiding piecemeal removal, simple debulking resulting in palliative treatment, or insufficient management) are followed. The implication that ``conventional surgeons''-whatever is meant by that-defend open approaches is essentially incorrect. The correct evaluation of the indications and limitations for endoscopic or open procedures implies adequate experience with the techniques of skull base surgery. Only then is the selection of an adequate method possible.

In their letter, Dr. Häusler and coworkers refer to their experience and publications (specifically Caversaccio et al., their references 6 and 7). A review of these and other articles of his (see our article) shows that most of the cases included in one category-anterior skull base/paranasal surgery-mainly concern paranasal sinus procedures while the true anterior skull base cases are referred to as single examples of cerebrospinal fluid leak, removal of inverted papillomas, and ``even'' a palliative management of a malignancy. Actually, we managed most of the skull base cases mentioned in their papers (as alluded there), which is why Laedrach was included in the list of authors. Their repetitive papers provide no statistical data concerning the extent or location of the lesions, outcomes, recurrence rates, or follow-up information about the skull base or other regions in these cases; they mainly describe the usefulness of CAS. Their lack of experience with external and endoscopic anterior skull base surgery underlies their unjustified and misleading comments.

Finally, we respond to their criticism of the first author Laedrach concerning the splint and the corresponding photo (see Fig. 3B in our article) and his contribution. The letter alludes to the CAS Medivison SynthesStratec System with the term ``Bernese.'' This system was developed by the Maurice Mueller Institute, Bern and the Orthopedic Departments in Bern and in Michigan in the United States. The application of this system in skull base surgery has already been described by Fernandez et al.[7] and was not mentioned in Caversaccio's publications and letter.

Drs. Caversaccio and Häusler did not develop the system. They promoted its acquisition by the hospital in 1997 for four disciplines: ENT; neuroradiology; neurosurgery; and craniofacial, skull base, facial plastic and reconstructive surgery. Dr. Caversaccio was nominated by those involved to coordinate this project among these disciplines. Dr. Laedrach was officially integrated into the group: He was not ``asked'' to participate and ``realize'' a maxillary splint. Rather, it was suggested that he develop the splint reinforcing the buccal wall, enabling the rod attachment for the light-emitting diodes and screws for edentulous patients. The construction differs from the devices as alluded to in their letter and their references 9 and 10. The splint per se is not an issue. It has been in use for more than 20 years for multiple indications and was not described as an innovative development. At the outset Laedrach developed, produced, and placed these splints in each patient individually-primarily for ENT cases-because we mostly used a carrier fixed to the skull in our cases. The upper jaw splint shown in Fig. 3B is merely representative: The draping of the patient shows that this is not an anterior skull base case, and, correctly, it was not referred to as one of our cases. We are currently using the Stryker Leibinger Navigation System, obviating the need for the splint.

In conclusion, criticizing a method and advocating different procedures imply adequate experience based on a convincing statistical evaluation after the management of similar lesions and achieving the same or better results. Only then can a relevant contribution be made.

REFERENCES

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