Approaching deep-seated lesions in or around the thalamus/hypothalamus or mesencephalon is challenging to even the most experienced neurosurgeon. Numerous surgical corridors, all carefully planned, patient-tailored and surgeon-tailored, have been used, including the basal anterior interhemispheric approach used in the current paper by Teramoto and Bertalanffy [10]. An inherent limitation common to all approaches, be it variants of the anterior interhemispheric approach (via unilateral subfrontal or bilateral basal corridors [5, 7, 9]) or the interhemispheric, trans-callosal, subchoroidal approach [1, 3, 4, 6, 8], is the limited exposure due to critical neurovascular structures. Please check "(ref)".This refers to the article in Acta that my comments refers to - please insert here to replace the (ref).

In the anterior interhemispheric approach, the anterior communicating artery (ACOM) is one of these critical neurovascular structures that limit exposure. Previously, several eminent Japanese neurosurgeons [2, 7, 9] have demonstrated how a controlled ACOM division can obtaining a wider surgical exposure in the anterior interhemispheric fissure, but the method has failed to gain widespread use, probably due to the risk of serious complications related to ACOM perforator infarcts, as well as lack of documented effects on the surgical exposure of an ACOM sacrifice and lack of specific preoperative predictors of the need for ACOM division during a surgical procedure.

In their paper, Teramoto and Bertalanffy [10] sought to identify key factors that allow for predicting the necessity of controlled ACOM division in the bifrontal basal anterior interhemispheric approach (BBAIA). A total of 22 patients were operated using the BBAIA, of whom only eight required ACOM sacrifice. ACOM sacrifice was performed in two out of three thalamic lesions (67%), in two out of five midbrain lesions (40%), and in four out of 11 suprasellar or sellar-suprasellar lesions (36%), but in none of the hypothalamic lesions. There were 14 central and eight lateral tumors. ACOM division was associated with tumor depth for centrally located tumors, and tumor laterality for lateral tumors. However, tumor size was not associated with a need for ACOM division in neither scenario. Please check "(ref)".This refers to the article in Acta that my comments refers to - please insert here to replace the (ref).

As the total number of cases is low, we should interpret the results with caution and refrain from making generalizations. For instance, the lack of effect of tumor size could be true, or merely a type II statistical error given the low number of cases. Furthermore, one inherent risk of the BBAIA is olfactory nerve damage and the state of postoperative olfaction is not reported. Thus, the article is more a proof of concept than a claim to “gold standard status”.

Regrettably, the manuscript focused solely on the BBAIA and thus fails in describing or discussing alternative approaches to some of the lesions, something that would have been very useful when coming from an expert neurosurgeon like Prof. Bertalanffy.

The surgical results are, in general, excellent, and the authors document that no adverse effects of ACOM sacrifice were encountered in the eight patients. In this regard, the authors are to be congratulated. However, as the authors themselves point out, it was impossible to precisely identify perforating ACOM branches or an anomalous ACOM on general angiograms preoperatively and the assessment of a hypoplastic A1 segment or other variations was performed by direct inspection only intraoperatively. Consequently, it may well be that the authors’ findings may predict the necessity for ACOM division preoperatively, but there is currently no way of determining the feasibility to do so preoperatively.

Lastly, I would welcome a cadaveric study, in the spirit of our late Dr. Rhoton, that measures and documents the increase in total area of surgical exposure of the suprasellar, hypothalamic and mesencephalic regions achieved by an ACOM division.