Individual Three-dimensional Digital Model For Endoscopic Panoramic Anatomy Of The Lateral Skull Base

Chapter1Individual three-dimensional digital model forendoscopic panoramic anatomy of pterygopalatine fossa,infratemporal fossa and its related regionsObjective In order to guide the surgical approach,broaden the surgical indications,and make a comprehensive understanding of pterygopalatine fossa, infratemporalfossa, middle cranial fossa and its related regions, we report an endoscopic transnasaltransmaxillary transpterygoid approach and subtemporal approach to these regionswith individual3D digital model assisted.Methods Twelve adult cadaveric heads were used to develop the endoscopicapproach and to identify the salient surgical landmarks. Red and blue silicone rubberdyes were respectively injected into the great vessels of the neck.Digital data (inDICOM format)acquired from a high resolution320-slice spiral CT scan was importedto a3DView software for reconstruction of the internal carotid artery,maxillaryartery and its final branch, bone of middle cranial fossa.Then,integrated thesestructures for individual3D-DM.Finally,the3D-DM was used to simulate transnasaltransmaxillary transpterygoid approach and subtemporal dissection of thepterygopalatine fossa, infratemporal fossa and the related regions,to identify thesalient surgical landmarks and anatomic variations.With the guide of 3D-DM,endoscopic endonasal and subtemporal dissection of these regions wererespectively completed under conditions that mimicked our operating suite. Then,wecompared the relevant measurement data and vision of3D-DM and endoscopicanatomy.Additionally,we compared exposure range,advantages and disadvantages ofthe two endoscopic approaches.Results The endoscopic endonasal approach was divided into three stages: entryinto the maxillary sinus, entry into the infratemporal fossa,infratemporal fossa and theother related strutures, and entry into the middle cranial fossa. Endoscopicsubtemporal approach can expose infratemporal fossa20mm below the foramen ovaleas well as the upper part of the pterygopalatine fossa,without damaging thetemporomandibular joint and mandibular nerve. When coupled with pre-operationsimulation of individual3D-DM guidance,the endoscopic endonasal approachwouldn’t injure internal maxillary artery and its final branches while openningposterior wall of the maxillary sinus.Additionally,the endonasal approach can providethe flexibility to tailor the size and location of the middle fossa craniotomy. Duringendoscopic dissection,anatomic landmarks such as sphenopalatine foramen, pterygoidcanal, foramen ovale and foramen rotundum can locate each other guided byindividual3D-DM. Pterygoid canal can be used to locate the genu of internalcarotid artery.3D-DM provided the same vision as endoscopic anatomy, quantitativemeasurements of the related structures in3D-DM are also consistent with the actualendoscopic measurement.Conclusions The endoscopic transnasal transmaxillary transpterygoid approachprovides safe and direct access to the infratemporal fossa,infratemporal fossa,middlecranial fossa and the other related structures,eliminating the need for brain retraction,temporalis muscle manipulation, or an external incision. Endoscopic subtemporalapproach can expose infratemporal fossa20mm below the foramen ovale as well asthe upper part of the pterygopalatine fossa. Some relevant neurovascular structuresmay limit the extension of the approach and the view via both routes. Assisted byindividual3D-DM, we can preoperatively understand the three-dimensionalvision,measure the bone and vascular structures.Then,the data can be used to assist endoscopic dissection. Incorporating the endoscopic endonasal transmaxillary andsubtemporal perspectives ensures a better understanding of the intracranial andextracranial neurovascular relationships. The combination of the2approaches mayimprove the visualization and may be helpful for preservation of the neurovascularduring surgery in or around this challenging area.The anatomic advantages andlimitations have been considered to evaluate the appropriate selection of each of theabove-mentioned approaches. The comparison of these2routes may provide usefulintraoperative information in the case of staged or combinedendonasal/subtemporal approaches. Chapter2Individual three-dimensional digital model forendoscopic panoramic anatomy of petrous apexObjective The aims of this study were to apply a individual three-dimensionaldigital model to endoscopic endonasal approach and subtemporal approach to analyzethe bony and artery anatomy of this area, quantify preoperatively bone removal,measure the distance of related structures and optimize surgicalplanning.Meanwhile,to evaluate the feasibility of the purely endoscopic extraduraltranscranial approach to petrous apex through a subtemporal keyhole and endonasalapproaches, and to understand potential distortions of the related anatomy better viaendoscopy.Methods Investigators dissected12human cadaveric heads at the Laboratory ofSurgical NeuroAnatomy of Third Hospital of Sun Yat-sen University.Before andafter each dissection, a320-slice computed tomography (CT) scan was performed tocreate a three-dimensional digital model of the endoscopic endonasal approach andsubtemporal approach performed in the dissection room. The procedures were asfollows:(1) a preliminary exploration of each specimen using the preoperative CTscan,(2) creation of a computer-generated three-dimensional digital model of the twoapproaches, simulation of petrous apex bone resection,and location of ICA;(3)cadaveric anatomic dissection of petrous apex via endonasal and subtemporal routes,and (4) compare predissection and postdissection digital imaging，3D-DM images andendoscopic ones， to evaluate the value of individual3D-DM in preoperativesimulation for endoscopic petrous apex dissection.Results Endoscopic endonasal transsphenoidal approach can expose the area ofrostral petrous apex, while the caudal petrous apex can be exposed throughendoscopic endonasal transmaxillary transpterygoid approache by removal of partialbones of sphenoid and pterygoid. The cerebellopontine angle and ventromedialbrainstem structures come into view after petroclival dura mater incision. Someanatomic landmarks,such as pterygoid canal, clivus recess,process of ICA and optic nerve-internal carotid artery recess, can be used to locate the internal carotid arteryjointly.The inferior wall of sphenoid sinus can be used to locate the VBJ.However,thespecific anatomic landmarks for ICA or VBJ should be decided individually by3D-DM simulation preoperatively.Endoscopic infratemporal approach can expose the structure of the middle cranialfossa.After removing the bone in “Day rhombus area”,the corridor can visit middle/upper clivus,as well as posterolateral brainstem. Assisted by individual3D-DM,wecan “lock” the horizontal ICA segment through the foramen spinosum,foramenovale and/or facial nerve hiatus. Likewise,we can locate the internal auditory meatusby superficial petrosal nerve,arcuate eminence,foramen spinosum,tensor tympanimuscle and malleus.Individual3D-DM can be a good indication of the structure of skull base aroundpetrous apex, and can be use to simulate bone window formation of petrousapex.There was no statistically significant difference between the three-dimensionalmeasurement data in3D-DM and endoscopic intraoperative anatomical measurementdata by paired T-test. Endoscopic vision was highly consistent with preoperativesimulation by individual3D-DM.The three-dimensional digital model was useful todefine the exact boundaries of the endoscopic endonasal craniectomy of petrous apex.Conclusions:Aside from laboratory anatomic dissection itself, this model is veryeffective in providing a depiction of bony landmarks and visual feedback of theamount of bone removed, improving the design of the craniectomy of petrous apexin endoscopic endonasal approach and endoscopic subtemporal approach. Endoscopicapproach to the petrous apex is anatomically feasible via the two corridor, and, aidedby individual3D-DM,could extend the scope to access highly-selected lesions in theposterior cranial fossa and cerebellopontine angle.The combination of anatomic landmarks can improve the accuracy of thepositioning of the internal auditory canal.The individualized3D-DM can be used to"lock" the horizontal segment of ICA accurately.Incorporating the endoscopic endonasal and subtemporal perspectives ensures abetter understanding of the neurovascular relationships in petrous apex. The combination of the2approaches may improve the visualization and may be helpfulfor preservation of the neurovascular during surgery around this area. Chapter3Individual three-dimensional digital model forendoscopic panoramic anatomy of jugular tubercle and upperparapharyngeal regionsObjective: The main aim of our study was to analyze and compare the surgicalanatomy of jugular tubercle and upper parapharyngeal pertinent to theendoscopic-assisted far lateral approach to that of the endoscopic endonasalapproaches, to provide useful landmarks by comparing transnasal perspectives withexternal ones, and to identify safe corridors through the endonasal route to providemore lateral exposure of the inferior third of the clivus and craniocervicaljunction.To apply an individual three-dimensional digital model to various endoscopicapproaches to analyze the bony anatomy of these areas, quantify preoperatively boneremoval, and optimize surgical planning.Methods Red and blue silicone dyes were respectively injected into the greatvessels of the neck of12cadaveric specimens. Digital data acquired from a highresolution320-slices CT scan was imported to a3DView system to form individual3D-DM. With the data and view of3D-DM support,An endoscopic endonasaldissection of the jugular tubercle and upper parapharyngeal regions were completedunder conditions that mimicked our operating suite.Likewise, the same spaces weredissected through endoscopic-assisted far lateral approach.Then,to provide usefullandmarks by comparing transnasal perspectives with external ones.Quantity boneremoval of occipital condyle by postoperatively3D-DM and compare with thepreoperative ones simulated by3D-DM,to analyze physical percent complete of boneexcision and optimize preoperative planning. Results Individual3D-DM can simulate surgical landmarks,locate importantstructures（such as VA, hypoglossal canal and jugular foramen）,and identifyanatomical variation.Three-dimensional model was useful to define the exactboundaries of the endoscopic endonasal and far lateral craniectomy. The visionacquired by3D-DM was consistent with the intraoperative findings. Preoperativemeasurement of related landmarks in3D-DM was no significant difference from themeasurement of cadaveric head specimens.Completion of a unilateral ventromedial condyle resection opens a3.5mm(transverse length)×10mm (vertical length) lateral surgical corridor, facilitatingdirect access to the vertebral artery at its dural entry point into the posterior fossa. Thesupracondylar groove is a reliable landmark for locating the hypoglossal canal inrelation to the condyle. The hypoglossal canal is used as the posterior limit of thecondyle removal to preserve more than half of the condylar mass. The transjugulartubercle approach is accomplished by drilling above the hypoglossal canal, andincreases the vertical length of the lateral surgical corridor by8mm, allowing forvisualization of the distal cisternal segment of the lower cranial nerves. Combinationof anatomic landmarks like eustachian tube,medial pterygoid plate, lateral pterygoidplate, foramen ovale and foramen spinosum were reliable way for locating theparapharyngeal space.The comparison of the2endoscopic surgical perspectives (endonasal and farlateral approach) allowed us to define2subregions over inferior third of the clivusand its relevant area (jugular tubercle and upper parapharyngeal). The definition ofthese subregions was based on the identification of some anatomic landmarks (jugulartubercle, occipital condyle and the hypoglossal canal) that limit lateral expansion viathe endonasal route and the natural well-established corridors via the far lateral route.The hypoglossal nerve, vertebral artery and hypoglossal canal divide the lower thirdof the clivus into ventromedial and dorsolateral compartments. The endonasalapproach provides significantly larger exposure of the brainstem in the ventromedialcompartment compared to the far lateral approach. The far lateral approach provides awide exposure of the brainstem in the dorsolateral compartment. The exposure of the brainstem in the dorsolateral compartment is not possible using the endonasalroute. The surgical corridor from one compartment to the other, through the lowercranial nerves, was significantly larger on the far lateral approach than on theendonasal route.Additionally,endoscopic endonasal route can provide a better showof front section of the jugular foramen in parapharyngeal space, including ICA,glossopharyngeal nerve, vagus nerve and anterolateral jugular vein. However, thefar-lateral approach provide a better show of posterolateral structures of the jugularforamen than the ventral approach,such as hypoglossal nerve, accessory nerve,vertebral artery and so on.Conclusions The endoscopic transnasal approach offers a safe, wide exposure ofjugular tubercle and upper parapharyngeal regions. The far lateral approach is mostsuitable for lesions located dorsolateral to the lower cranial nerves.The combinationof the2approaches may improve the visualization in this challenging area. Thecomplex3-dimensionality of the jugular tubercle and the upper parapharyngeal spaceneeds a sound knowledge of the surgical anatomy. The ability to orientate oneself inthis complex area is related to an accurate knowledge of its anatomy throughcomparison of endoscopic transnasal and external perspectives.The endonasal approach provides significantly larger exposure of the brainstemin the ventromedial compartment compared to the far lateral approach. The far lateralapproach provides a wide exposure of the brainstem in the dorsolateral compartment.Far-lateral approach assisted by endoscopy can increase the ventromedial structureexposed.This3D-DM is very effective in providing a depiction of surgical landmarks andvisual feedback of the amount of bone removed, improving the design of thecraniectomy in the endoscopic endonasal and endoscopic-assisted far-lateral approachapproach.The vertebral artery and hypoglossal canal are the most important landmarks toguide surgical planning. Although precise knowledge of the surgical anatomy relatedto this approaches is crucial, team experience and meticulous preoperative study ofeach patient and lesion remain to be vital for successful selection of the therapeutic strategy. A modern skull base team of surgeons must be prepared to offer eitherapproach. We should carefully selected suitable cases, not blindly carry outendoscopic endonasal approach or far lateral approach.