A...AbstractIntroductionMethodsRetrosigmoid approachSigmoid sinus skeletonization and presigmoid dissectionPresigmoid dural incisionRetrosigmoid dural incisionAnatomical findingsPosterolateral compartmentMiddle compartmentAnteromedial compartmentResultsDiscussionConclusionsReferencesORIGINAL ARTICLEA combined dual-port endoscope-assisted pre- and retrosigmoidapproach to the cerebellopontine angle: an extensiveanatomo-surgical studyAntonio Bernardo & Davide Boeris & AlexanderI.Evins&Giulio Anichini & Philip E. StiegReceived: 28 May 2013 /Revised: 6 December 2013 /Accepted: 7 December 2013 /Published online: 8 May 2014#Springer-Verlag Berlin Heidelberg 2014Abstract The use of the endoscope in the cerebellopontineangle (CPA) has been suggested to minimize cerebellar retrac-tion and reduce the size of the craniotomy. 3D endoscopycombines the benefits of conventional 2D endoscopy with theadded benefit of stereoscopic perception, though improvedvisualization alone does not guarantee improved surgical ma-neuverability and a better surgical outcome. We propose anew combined dual-port endoscope-assisted pre- andretrosigmoid approach to improve visualization and accessi-bility of th e CPA with shortened distances and incre asedsurgical maneuverability of neurovascular structures. We an-alyze surgical exposure and maneuverability of this approachand compare it with the surgical microscopic and a conven-tional single-port endoscope-assisted retrosigmoid approach.This combined pre- and retrosigmoid a pproach was per-formed on eight cadaveric heads (16 sides). The endoscopicprobe was inserted through the presigmoid surgical port whilesurgical manipulation was performed through theretrosigmoid corridor. The CPA was divided into three com-partments, from medial to lateral, the anteromedial, and themiddle and the posterolateral. The microscope provided goodvisualization of the posterolateral and middle compartments,whereas poor visualization was offered of the anteromedialcompartment. The dual-port endoscopic approach dramatical-ly improved visualization and surgical maneuverability of theanteromedial compartments, clivus, and related neurovascularstructures. Additionally, the 3D endoscope allowed for a betterunderstanding of the surgical anatomy of the CPA and im-proved visualization of structures located in the anteromedialcompartments towards the midline. This approach allowed forfull realization of the benefits of endoscopic-assisted tech-nique by improving surgical access and maneuverability.Keywords 3D.Endoscopy.Microsurgical anatomy.Retrosigmoid approach.Presigmoid approach.Cerebellopontine angleIntroductionThe primary method of surgical access to the cerebellopontineangle (CPA) is the classic retrosigmoid approach [16]. Surgi-cal interventions in this region are most commonly used in thetreatment of vestibular schwannomas and to resolveneurovascular conflicts of cranial nerves (CN) V and VII [1,4–6, 8, 14, 17]. The use of the endoscope has been mainlysuggested to minimize cerebellar retraction and reduce the sizeof the craniotomy in order to obtain better reconstruction andimprove postoperative prognosis [9]. The endoscope providesvaluable assistance in tumor removal and microvascular de-compression and allows the surgeon to obtain a better view ofthe medial structures [15]. In spite of the recent excitementderived by the use of this tool, surgeons still face considerabledifficulty in inserting the endoscopic probe in the narrowpassages available in most skull base approaches that providevery little space for surgical manipulation.The use of a novel combined dual-port endoscope-assistedpre- and retrosigmoid approach to the CPA may provide extraspace and unobstructed surgical corridors necessary for opti-mal surgical manipulation.We propose a new surgical approach that combines endo-scopic visualization through a presigmoid port with surgicalaccess through a retrosigmoid corridor (Fig. 1). We evaluatethe degree of exposure and surgical maneuverability achievedwith this modified surgical technique and discuss optimalA. Bernardo (*):D. Boeris:A. I. Evins:G. Anichini:P. E. StiegDepartment of Neurological Surgery, Weill Cornell Medical College,Cornell University, 1300 York Avenue, Baker F2212, New York,NY 10065, USAe-mail: [email protected] Rev (2014) 37:597–608DOI 10.1007/s10143-014-0552-8indications for the use of the 3D endoscope in surgicallyaccessing this area.MethodsA combined pre- and retrosigmoid approach to access theCPA was performed on eight preserved cadaveric heads (16sides) previously injected with colored latex (red-colored forarteries, blue for veins).Retrosigmoid approachEach head was placed in the lateral position, with the mastoidsurface at the highest point. A curvilinear incision was madestarting 3 cm superior to the asterion and terminated 2 cminferior to the level of the digastric groove. Using an AnspachXMax® surgical drill, an initial burr hole was made 1 cminferior to the asterion. A craniotomy was then performedextending superiorly to the transverse sinus, anteriorly to thesigmoid sinus, and caudally to the inferior nuchal line wherethe dura plane turned downward. The diameter of the boneopening measured 4 cm on its anteroposterior aspect.Sigmoid sinus skeletonization and presigmoid dissectionThe sigmoid sinus was located and uncovered anteriorly. Thearea between the sigmoid sinus and the middle fossa plate, orthe sinodural angle, was fully evacuated of air cells to provideadequate exposure of the presigmoid area. The sigmoid sinuswas completely skeletonized, and the mastoid air cells wereremoved medially along the posterior petrous face to exposethe presigmoid dura (Fig. 2). The endolymphatic sac waslocated in a thickened portion of the posterior fossa dura,medial to the sigmoid sinus and inferior to the posterior canal.The presigmoid dura was uncovered from the superior petro-sal sinus superiorly to the jugular bulb inferiorly and mediallyand from the sigmoid sinus laterally to the labyrinth medially(Fig. 3). Thorough knowledge of the temporal bone anatomyallowed for maximal drilling without injury the labyrinth and/or facial nerve. Proper bone removal, at this point, providedoptimal space for insertion of the endoscopic probe (Fig. 4).Presigmoid dural incisionThe presigmoid dura was incised at the sinodural angle be-tween the sigmoid sinus and the endolymphatic sac towardsthe jugular bulb, exposing the CPA (Fig. 5a). The resultingopening
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