Authors' Response

Most of the arguments in this letter are similar to those of Häusler and coworkers. It seems that our article has given rise to misunderstandings among those devoted to endonasal-endoscopic procedures. This is surprising because the objective of the study was clearly defined-to evaluate the contribution of computer-assisted surgery (CAS) using the subcranial/subfrontal approach in cases mandating a broad exposure, resection, and reconstruction of the afflicted anterior skull base locations.

Compared with other traditional external facial approaches, the less invasive subcranial approach provides broad exposure and direct visualization of anatomical landmarks and vital skull base structures, including intra- and extracranial locations, thus reducing the indication for CAS to 23% in our cases. This figure is in contrast to other external approaches that do not provide an equivalent optimal exposure-in such cases, the contribution of CAS would, as expected, be higher and even more so in endonasal approaches. These aspects were clearly depicted in our article as was the exclusion of endonasal-endoscopic procedures in this study. As emphasized in the Discussion from our article: ``The degree of the CAS contribution is highly dependent on the choice of the approach.'' The endoscopic-endonasal procedures as such are well known, as are their indications and limitations. However, these issues were not the subject of our article; further discussion is beyond the scope of this letter.

The query about the technical details of measured accuracy and further attributes, as referred to in our article (i.e., the technical aspects and the features of this CAS system), again were not the subject of the study. Accordingly, we referred readers to the related literature (see the Introduction, Material and Methods). However, the accuracy in these clinical/surgical cases was 0.25 to 1.5 mm (mean, <0.5 mm, which is clinically relevant).

To clarify: We do not oppose endonasal-endoscopic surgery given adequate indications. It simply was not the subject of our article. Actually, we neither understand the issue of this letter in relation to our article nor its message.