On ``Evaluation of the Contribution of CAS in Combination with the Subcranial/Subfrontal Approach in Anterior Skull Base Surgery'' (Skull Base 2001;11:59-76)

We greatly respect the surgical skills of Laedrach and coworkers (Evaluation of the contribution of CAS in combination with the subcranial/ subfrontal approach in anterior skull base surgery. Skull Base 2001;11:59-76) in performing the complex surgeries described in their article. Doubtless, their well-known subcranial and subfrontal approach is very suitable and allows a safe and radical resection of complex pathologies by the inherent large exposure of anatomical structures. This approach also is suitable for correcting craniofacial deformations and malformations. However, reading the paper left us dissatisfied regarding a few issues.

The authors performed a set of surgeries through the subcranial/subfrontal approach. Not surprisingly, they found limited usefulness and benefit from a modern computer-assisted surgery (CAS) system. Inherently, a large access route provides enough anatomical landmarks for intraoperative orientation. Therefore, we do not understand the real purpose for the study: Was it to prove the usefulness of navigational aids or the opposite? From our reading, we suspect that costly navigational equipment is of no benefit. CAS systems were intended to aid surgeons during minimally invasive surgeries; in such settings, their value is evident to the scientific community. If the authors had chosen the now widely accepted endoscopic approach via the endonasal route, a totally different picture would have arisen.

The authors report a ``measured accuracy'' of 0.25 to 1.5 mm but no hint of how and what they measured: Was it a root-mean-square error as delivered by the system, or was it a clinical error?[1] [2] What anatomical landmarks were chosen?[3]

Finally, we must point out that we were among the first to report the development and use of an upper dental splint for frameless computer-assisted ENT surgery.[4] [5] This device is now widely used in ENT,[6] radiology,[7] radiotherapy,[8] and neurosurgery.[9] We have used the same mouthpiece to carry three-dimensional sensing equipment intraoperatively since 1997 (see Fig. 4A in Gunkel et al.).[10]

REFERENCES

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• 8 Sweeney R A, Bale R, Auberger T, Vogele M, Foerster S, Nevinny-Stickel M, Lukas P. A simple non-invasive vacuum mouthpiece-based head fixation system for high precision radiotherapy.   Strahlenther Onkol   2001;  177 43-47
• 9 Bale R J, Burtscher J, Eisner W, Obwegeser A A, Rieger M, Sweeney R A, Dessl A, Giacomuzzi S M, Twerdy K, Jaschke W. Computer-assisted neurosurgery by using a noninvasive vacuum-affixed dental cast that acts as a reference base: Another step toward a unified approach in the treatment of brain tumors.   J Neurosurg   2000;  93 208-213
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