In Reply: Absence of Ischemic Injury After Sacrificing the Superior Petrosal Vein During Microvascular Decompression.

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To the Editor: Thank you for your response1 to our evaluation of sacrificing the superior petrosal vein (SPV) in microvascular decompressions (MVDs),2 and we appreciate the opportunity to discuss this important topic further. As a principle, we agree with the neurosurgical adage that “no structure should be taken unless absolutely necessary,” and we apply that to the SPV as much as to other adjacent neurovascular structures during the retrosigmoid approach for MVDs.3 Indeed, we emphasize the importance of the SPV in our discussion and point out that it is a major infratentorial vein that drains nearly half of the petrosal draining complex.4,5 However, there arise situations where taking the vein will improve visualization or reduce the risk of bleeding (ie, cerebellopontine angle [CPA] tumors). It is these situations that led to our question on the safety of taking the SPV. Data from our study and other large-scale analyses in the MVD literature (such as McLaughlin et al6) show a significantly low rate of complications despite sectioning the SPV. In our study, this was directly evaluated between cohorts with and without SPV sacrifice and led to our thoughts that there may be other unexplained contributing factors that have led to the complications that have been reported in case reports and series, not necessarily directly tied to sacrificing the SPV. Ultimately, the decision to sacrifice any neurovascular structure is a risk-benefit decision. We would argue that the SPV, if it does significantly obscure direct visualization of a nerve to be decompressed during a retrosigmoid MVD, may be worth taking. Though there is a nonzero risk reported in the literature of complications, the low magnitude of this risk must be weighed against the chances of inadvertently harming another neurovascular structure due to poor visualization or insufficiently decompressing the pathological nerve. Additionally, we mentioned violating a small branch of the SCA as the true cause of a complication in our discussion not to imply that it is a common cause but rather a potential cause. This detail stemmed from the impressive dissection of cadavers to explore the SPV in Matsushima et al,7 which noted that nearly all 30 cadaveric cerebellopontine angles they analyzed had branches of the SCA “intertwined with the superior petrosal veins and their tributaries.” In rare circumstances, it is conceivable that electrocautery through a segment of arachnoid and SPV can fully occlude a minor arterial vessel as well. Overall, the success rate of MVDs for trigeminal neuralgia is roughly 70% pain-free without medication at t = 10 yr post-MVD.8 However, revision MVDs have higher complication rates and morbidity rates in and of themselves, on top of the risks of undergoing a subsequent surgical procedure that a patient must endure.9,10 We agree that surgeons should avoid taking the SPV ad libitum, but, when necessary, the SPV may be sacrificed when the benefits outweigh the risks. In our cohort of over 200 patients who underwent MVDs with SPV sacrifice, we felt that it was safe to do so. We certainly do not condone freely taking neurovascular structures and always encourage critical analyses of every step in surgery—before, during, and after an operation. Funding This study did not receive any funding or financial support. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.