Translabyrinthine approach and the sigmoid sinus: a quantitative 3D analysis of exposure in cadaveric specimens.

Abstract

Introduction: Perioperative sigmoid sinus compression and sinus injury might be associated with various post-operative complication (e.g., CFS leakage, headache, intracranial hypertension, cerebellar infarct). This study was designed to quantify the effect of the sigmoid sinus (SS) on the operative exposure obtained in the translabyrinthine approach. Furthermore, it quantifies the ancillary exposure due to retraction of a skeletonized sinus. It is hypnotized that in selected cases a dorsally mobilized skeletonized SS will provide sufficient exposure to perform a translabyrinthine resection of cerebellopontine angle tumours. Method: Twelve translabyrinthine proper approaches were performed on fresh frozen cadaveric heads. The position of the sigmoid sinus was varied in three procedures: stationary (TL-S), posterior retraction (TL-R), and collapsing of the sinus (TL-C). Based on the post-operative CT-scans, a high-definition 3D reconstruction of the visualize the resection cavity was obtained. The primary outcome, ‘surgical freedom’ (mm2), was the area at the level of the craniotomy from which the internal acoustic porus could be reached in an obstructed straight line. Secondary outcomes include the ‘exposure angle’ (degrees), ‘angle of attack’ (degrees) and pre-sigmoid depth (mm2). Results: When retraction of the SS was performed during TL-R, surgical freedom increased by a mean of 41% (range: 9-92%, SD: 28) when compared to no retraction (TL-S). Collapsing the SS in TL-C provided a mean increase of 52% (range: 19-95%, SD: 22) compared to TL-S. In some specimens, the TL-R provided a greater surgical freedom than the TL-C; however, on average an increase of 10% (range: -10–30%, SD: 12) in favour of the TL-C is observed when compared to TL-R. In most cases the exposure is the greatest when the sigmoid sinus is collapsed. However, in 40% of the specimens the provided exposure while retracting (TL-R) instead of collapsing (TL-S) this sinus is equal or greater than 50% of other specimens in which the sinus is collapsed. Conclusion: It is concluded that in cases with favourable anatomy, the translabyrinthine resection while retracting a skeletonized sinus provides sufficient exposure to the cerebellopontine angle. However, further research is necessary to evaluate the translatability of manoeuvre from cadaveric specimens to a clinical setting. Keywords: Skull Base, Microsurgery, Cerebellopontine, Vestibular Schwannoma, 3D modelling, Quantitative Anatomy.