Neurosurg Rev 2014 37 597 608 DOI 10 1007 s10143 014 0552 8 ORIGINAL ARTICLE A combined dual port endoscope assisted pre and retrosigmoid approach to the cerebellopontine angle an extensive anatomo surgical study Antonio Bernardo Davide Boeris Alexander I Evins Giulio Anichini Philip E Stieg Received 28 May 2013 Revised 6 December 2013 Accepted 7 December 2013 Published online 8 May 2014 Springer Verlag Berlin Heidelberg 2014 Abstract The use of the endoscope in the cerebellopontine angle CPA has been suggested to minimize cerebellar retraction and reduce the size of the craniotomy 3D endoscopy combines the benefits of conventional 2D endoscopy with the added benefit of stereoscopic perception though improved visualization alone does not guarantee improved surgical maneuverability and a better surgical outcome We propose a new combined dual port endoscope assisted pre and retrosigmoid approach to improve visualization and accessibility of the CPA with shortened distances and increased surgical maneuverability of neurovascular structures We analyze surgical exposure and maneuverability of this approach and compare it with the surgical microscopic and a conventional single port endoscope assisted retrosigmoid approach This combined pre and retrosigmoid approach was performed on eight cadaveric heads 16 sides The endoscopic probe was inserted through the presigmoid surgical port while surgical manipulation was performed through the retrosigmoid corridor The CPA was divided into three compartments from medial to lateral the anteromedial and the middle and the posterolateral The microscope provided good visualization of the posterolateral and middle compartments whereas poor visualization was offered of the anteromedial compartment The dual port endoscopic approach dramatically improved visualization and surgical maneuverability of the anteromedial compartments clivus and related neurovascular structures Additionally the 3D endoscope allowed for a better understanding of the surgical anatomy of the CPA and improved visualization of structures located in the anteromedial compartments towards the midline This approach allowed for A Bernardo D Boeris A I Evins G Anichini P E Stieg Department of Neurological Surgery Weill Cornell Medical College Cornell University 1300 York Avenue Baker F2212 New York NY 10065 USA e mail anb2029 med cornell edu full realization of the benefits of endoscopic assisted technique by improving surgical access and maneuverability Keywords 3D Endoscopy Microsurgical anatomy Retrosigmoid approach Presigmoid approach Cerebellopontine angle Introduction The primary method of surgical access to the cerebellopontine angle CPA is the classic retrosigmoid approach 16 Surgical interventions in this region are most commonly used in the treatment of vestibular schwannomas and to resolve neurovascular conflicts of cranial nerves CN V and VII 1 4 6 8 14 17 The use of the endoscope has been mainly suggested to minimize cerebellar retraction and reduce the size of the craniotomy in order to obtain better reconstruction and improve postoperative prognosis 9 The endoscope provides valuable assistance in tumor removal and microvascular decompression and allows the surgeon to obtain a better view of the medial structures 15 In spite of the recent excitement derived by the use of this tool surgeons still face considerable difficulty in inserting the endoscopic probe in the narrow passages available in most skull base approaches that provide very little space for surgical manipulation The use of a novel combined dual port endoscope assisted pre and retrosigmoid approach to the CPA may provide extra space and unobstructed surgical corridors necessary for optimal surgical manipulation We propose a new surgical approach that combines endoscopic visualization through a presigmoid port with surgical access through a retrosigmoid corridor Fig 1 We evaluate the degree of exposure and surgical maneuverability achieved with this modified surgical technique and discuss optimal 598 Neurosurg Rev 2014 37 597 608 inferior to the level of the digastric groove Using an Anspach XMax surgical drill an initial burr hole was made 1 cm inferior to the asterion A craniotomy was then performed extending superiorly to the transverse sinus anteriorly to the sigmoid sinus and caudally to the inferior nuchal line where the dura plane turned downward The diameter of the bone opening measured 4 cm on its anteroposterior aspect Sigmoid sinus skeletonization and presigmoid dissection Fig 1 The combined dual port endoscope assisted pre and retrosigmoid approach Complete skeletonization of the sigmoid sinus is achieved Endoscopic visualization is provided through a presigmoid port with surgical access achieved through a retrosigmoid corridor indications for the use of the 3D endoscope in surgically accessing this area The sigmoid sinus was located and uncovered anteriorly The area between the sigmoid sinus and the middle fossa plate or the sinodural angle was fully evacuated of air cells to provide adequate exposure of the presigmoid area The sigmoid sinus was completely skeletonized and the mastoid air cells were removed medially along the posterior petrous face to expose the presigmoid dura Fig 2 The endolymphatic sac was located 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 petrosal sinus superiorly to the jugular bulb inferiorly and medially and from the sigmoid sinus laterally to the labyrinth medially Fig 3 Thorough knowledge of the temporal bone anatomy allowed for maximal drilling without injury the labyrinth and or facial nerve Proper bone removal at this point provided optimal space for insertion of the endoscopic probe Fig 4 Presigmoid dural incision Methods A combined pre and retrosigmoid approach to access the CPA was performed on eight preserved cadaveric heads 16 sides previously injected with colored latex red colored for arteries blue for veins The presigmoid dura was incised at the sinodural angle between the sigmoid sinus and the endolymphatic sac towards the jugular bulb exposing the CPA Fig 5a The resulting opening provided an optimal area for insertion of the endoscopic probe Fig 5b Retrosigmoid dural incision Retrosigmoid approach Each head was placed in the lateral position with the mastoid surface at the highest point A curvilinear incision was made starting 3 cm
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