Technical Strategies for Superior Petrosal Vein Preservation in Microvascular Decompression

Background: Eponymously known as the vein of Dandy, the superior petrosal vein (SPV) is a key vascular structure of the posterior fossa, with outsize clinical impact due to its frequent obstruction of the working corridor for cerebellopontine angle (CPA) surgery, including microvascular decompression (MVD). The mandate to preserve SPV is a long-standing source of debate in neurosurgery, with reports of serious complications including venous infarction resulting from SPV sacrifice varying widely, from < 1% to 30%. Given that no reliable predictors have been established to identify those patients at increased risk of complications from SPV sacrifice, our practice has been to preserve the SPV whenever possible, particularly during MVD, where normal anatomy is anticipated. Correspondingly, the goal of this study was to present a video review of MVDs to emphasize the technical nuances that have enhanced our ability to preserve SPV in nearly all such cases.

Methods: Retrospective chart review and microsurgical video analysis of 8 MVD operations.

Results: Four patients each underwent MVD for trigeminal neuralgia (TN) or hemifacial spasm (HFS), with SPV preservation in all cases, and confirmatory postoperative MRI demonstrating no evidence of infarct, hemorrhage, cerebellar congestion, or other complication or sign of venous injury. In all cases, we gently modified the rotation of the patient’s neck, attempting to achieve horizontal orientation of sigmoid sinus in TN, versus 5–10 degrees of rotation toward the contralateral side in hemifacial spasm, which optimizes access to the root entry zone while encouraging SPV displacement anterolaterally. During bony exposure, we broadly identify the entire edge of the transverse-sigmoid sinus junction and sinuses, optimal light entry and a sufficiently large dural opening to allow for variable angulation without SPC sacrifice. Once the dura is open, care is taken to maximize CSF drainage, typically via dissection of the great horizontal fissure and wide microsurgical removal of the superficial CPA arachnoid for ideal posterior fossa relaxation and further opening of the operative corridor. Finally, a dynamic approach is taken to optimizing the microscope’s working axis and leveraging the mobility of the operating table, particularly in cases of unusual anatomy not fully accommodated by our preferred positioning. Video review demonstrated that, even with considerable individual variations in vein configuration, temporal bone angulation, and positioning of the aberrant vascular loops, by carrying out the steps of optimized positioning, maximal bony and dural exposures, careful and thorough arachnoid dissection, and thoughtful positioning of the microscope and operating table, SPV was preserved without obstruction in all eight cases, as we have noted in our MVD practice more broadly.

Conclusion: Preservation of SPV is feasible but requires a detail-oriented approach to positioning, exposure, arachnoid dissection, and operator ergonomics to allow for a facile operation without impediment in all anatomic variants. Although the true incidence of a meaningful clinical consequence from SPV sacrifice is likely very low, it is clearly a defined entity, and we recommend adopting these techniques to eliminate a source of avoidable and potentially severe complications.

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No conflict of interest has been declared by the author(s).