Letter to the Editor. Rendering unto Caesar: mini-pterional and mini-orbitozygomatic approaches.

TO THE EDITOR: We have read with great attention the article by Yağmurlu and colleagues9 (Yağmurlu K, Safavi-Abbasi S, Belykh E, et al: Quantitative anatomical analysis and clinical experience with mini-pterional and mini-orbitozygomatic approaches for intracranial aneurysm surgery. J Neurosurg 127:646–659, September 2017). It is indeed a very interesting paper, and we agree with many of the authors’ statements, including the fact that these two approaches have become standard cranial exposures for many surgeons who perform cerebrovascular and neuro-oncological procedures.1–8 However, we also noticed many methodological incongruencies that we think are worth discussing. First, the concept of surgical freedom as adopted by the authors is different from that previously defined.7,8 Surgical freedom is classically described as a measure of the maneuverability of surgical instruments in the superficial area of exposure provided by a particular approach.7 The authors innovated and utilized this concept in a different manner. However, they do not explicitly describe how surgical freedom was measured. Why should surgical freedom depend on anatomical targets as an intrinsic variable of the approach? This point needs further explanation. A figure illustrating the authors’ idea would surely clarify their points. Second, in studies like this, a source of error is the degree of retraction that is applied when the measurements are taken. It is necessary to maintain a similar degree of retraction when the measurements are performed. This is achieved by maintaining the same extent of retraction while converting the approaches (usually using miniplates and screws) in order to prevent bias in the measurements. Nonetheless, it seems that this strategy was not used in their study. The extent to which this fact may have biased the results was not discussed. Third, the results clearly showed that the mini-pterional approach was significantly superior to the mini-orbitozygomatic (OZ) approach in many parameters, including surgical freedom for access to the internal carotid artery (ICA), middle cerebral artery (MCA) bifurcations, ipsilateral posterior cerebral artery (PCA), and the basilar artery (BA) tip. No differences were noticed for access to other anatomical targets. In addition, when the angular exposures were analyzed, the mini-pterional approach was statistically superior to the OZ approach for horizontal (ipsilateral MCA bifurcation) and vertical (ipsilateral ICA, posterior clinoid process, ipsilateral MCA bifurcation, ipsilateral PCA, ipsilateral superior cerebellar artery, BA tip) angles. In fact, the mini-OZ approach was not statistically superior to the mini-pterional approach in any of the evaluations. Thus, discussion seems to be biased in favor of the mini-OZ approach, despite the eloquence of the results to the contrary. Real statistical differences that favor the mini-pterional approach have not been emphasized while the authors claim that there are “trends” in some measurements that may favor the mini-OZ approach. However, as we all know, such trends may only represent statistical artifacts that reflect a small sample size.