Extended endoscopic endonasal transclival clipping of posterior circulation aneurysms--an alternative to the transcranial approach.

Abstract

Somanna et al. present a small series of four patients with basilar (BA) aneurysms who were treated partially or entirely using a purely endoscopic endonasal approach (EEA). The authors are to be commended for their brave attempt at clipping these rather complex aneurysms through the transsphenoidal transclival exposure. They should also be praised for the honest reporting of their results. Let’s start by emphasizing that the authors of this editorial are strong advocates of endoscopic endonasal skull base surgery and the lead author (AD) has significant surgical experience with complex skull base pathologies treated via an EEA. However, we have also published on the limitations of endoscopic endonasal surgery [1, 2] and believe that the enthusiasm for EEA in cerebrovascular surgery should be evaluated very cautiously so as not to compromise patient outcomes. Furthermore, application of EEA in cerebrovascular surgery, specifically in the current endovascular era, could potentially be detrimental to both expanded endocsopic endonasal surgery and open cerebrovascular surgery fields if similar outcomes are not achieved. Acknowledging the lack of access to endovascular treatment in some countries, we will hereby outline our criticism. First of all, the case selection process was suboptimal. The authors, rightfully, emphasized the importance of the “midline” positioned basilar artery (BA) but overlooked the significance of the level of the BA bifurcation. Three of the patients presented had “high” bifurcations with the neck above the dorsum sella and the dome certainly well above that. This necessitated drilling of the dorsum sella and posterior clinoid as well as a “pituitary transposition” to reach out behind the dorsum. Even after achieving the after-mentioned exposure and with the aid of the angled 30° scope, they were not able to properly visualize the perforator-rich area at the posterior aspect of the BA bifurcation. In fact, even if the perforators were visualized, dissecting them properly off the neck/dome of the aneurysm would have been difficult given the present instrumentation. This constellation of limitations in access, optics, and instrumentation resulted in perforator injuries in three of the four patients. These challenges are not surprising given that some of them have already been demonstrated [3, 4]. A cadaveric study has shown that the endoscopic endonasal exposure of the BA bifurcation was not possible in 36 % of the specimens (and we certainly realize that in that study pituitary transposition was not performed) [3]. But even when the transposition is performed and the basilar apex is at or below the level of the dorsum sella, perforator injuries using this approach remain significant [4]. The fourth patient however had a basilar trunk aneurysm where a traditional craniotomy approach would have been more challenging, and we believe the endoscopic endonasal approach was effective in this particular case and had a good outcome. Second, the authors performed three pituitary transpositions in order to access the retrosellar space but failed to comment on the technique of transposition (intradural vs. extradural vs. interdural). More significantly, there was no mention of the postoperative endocrinological status of their patients given the wellrecognized transient and/or most likely permanent pituitary dysfunction associated with transposing the pituitary gland. We believe that this is a major limitation as it may convey to novices an unrealistically low risk profile for this rather complex maneuver. Third, lateral and anterolateral open transcranial approaches would have been the appropriate option for the first three cases in the absence of the least invasive endovascular * Amir R. Dehdashti Adehdashti@NSHS.edu