Anatomic Study Of The Extended Endoscopic Endonasal Transsphenoidal Approach Tothe Cavernous Sinus

BackgroundCavernous sinus is at both sides of the sella turcica, with complex anatomy, deep location. It has a close relationship with the pituitary gland, internal carotid artery, theⅡ-Ⅵcranial nerves and other important structures. It is a predilection site of invasive pituitary adenoma,chordoma,meningioma,nerve sheath tumors and other diseases, which is difficult for the conventional surgical approach to reach, bringing great difficulties to the surgical treatment tumors of this region. Researches on different surgical approaches for cavernous sinus are the hot spots in skull base surgery and clinical applied anatomy in recent years. Although there are many surgical approaches to the cavernous sinus, no surgical approach is applicable to all cases so far. Understanding the form and adjacent relationship of the cavernous sinus and its surrounding anatomy structures is great significance for the selection of the best surgical approach. Therefore a large number of scholars studied cavernous sinus anatomy and surgical approach.The emergence of endoscopic techniques brings a huge step forward for minimally invasive neurosurgery development. Since Lespinasse's first report of hydrocephalus surgery using endoscope in 1910, a large number of scholars have reported the endoscopic transsphenoidal approach for treatment of sellar tumors. However, due to the limitations of surgical instruments and complex anatomy structures of skull base, clinical application of endoscopic transsphenoidal approach has not been widely carried out. In recent years, with the improvement of endoscopic equipments and instruments, there are more and more transnasal endoscopic skull base surgeries, which has become the first choice for clinical treatment of pituitary adenomas. Since Weiss first named and described the "extended transsphenoidal approach" in 1987, the application scope of the approach gradually expanded. As the endoscopic imaging technology becomes more perfect and mature, many scholars did cavernous sinus tumor resection with endoscope. This study aims to investigate cavernous sinus endoscopic anatomy by expanded transnasal approach, provide anatomical basis for application of the approach.ObjectiveIn this paper, we study anatomy of the cavernous sinus, to provide anatomical basis for endoscopic expanded transnasal approach cavernous sinus surgery. Establish the anatomical landmarks of the surgical approach, understand the endoscopic cavernous sinus vascular, nerve structure and safe operation range. Reduce surgical risks and complications.1. Investigate the revealed scope with extended endoscopic endonasal transsphenoidal approach, extended endoscopic endonasal transmiddle nasal concha approach, transsphenoidal-transethmoidal (far lateral) approach. to provide anatomical basis for the surgical approach selection of cavernous sinus lesions .2. Describe and measure important anatomic landmarks in endoscopic expanded transnasal approach, understand endoscopic anatomical characteristics of these anatomic landmarks, to provide anatomical basis to enhance surgical success rate and security of endoscopic expanded transnasal approach resection of cavernous sinus lesions.3. Observe and measure cranial nerves course and blood supply within the cavernous sinus, and describe the lateral wall triangle of cavernous sinus, to provide anatomical information to expand to the middle cranial fossa .4. Investigate the safety margin of bone management and the method to protect the carotid artery and its branches.Materials and methods1. Ten formalin-fixed specimens of intact head and neck, arteries perfused with red latex, veins perfused with blue latex. Dissection was performed using 4mm diameter, 18cm length, 0°and 30°rod lens rigid endoscope and part of endoscopic instruments, fully analog endoscopic endonasal transsphenoidal approach, transmiddle nasal concha approach, transsphenoidal-transethmoidal (far lateral) approach, anatomically observe anatomical characteristics of nasal surgical approach to the cavernous sinus, establish surgical signs. Understand anatomical characteristics of endoscopic surgery regions.2. Use vernier caliper (accuracy 0.02mm) and compasses, measure related important anatomic structures in surgical approach in this region. Measure the distance between the anterior nasal spine and sphenoidal sinus opening, sphenopalatine mouth, former port of pterygoid canal, Dorello tube dural entrance. Measure the distance between both sides of the sphenopalatine foramen, pterygoid canal former ports, the medial orbital walls, sphenoidal sinus opening to sphenopalatine foramen, Dorello tube dural entrance. Measure the distance between inside edge of bilateral internal carotid artery, the diameter of the beginning part of the branch of the internal carotid artery cavernous segment and the distance between cranial nerve of cavernous segment to the midline.3. Observe the course of the cavernous segment of internal carotid artery and branches, course and blood supply of cavernous segment of cranial nerves and the triangle of the cavernous sinus lateral wall. Statistical analysis with SPSS13. 0 software, the results presented as x±s.Results and discussion1. Surgery signs of the cavernous sinus surgery with endoscopic expanded transnasal approach include: choana narium, middle turbinate, sphenoid sinus openings, slope depression, internal carotid artery eminence, optic nerve eminence, internal carotid artery-optic recess, pterygoid canal. Stripping scope of anterior inferior wall of sphenoid sinus, taking bilateral pterygoid canal and foramen lacerum as boundaries. 2. The distances between the anterior nasal pine and sphenoidal ostium, sphenopalatine foramen, anterior opening of pterygoid cannal, Dorello canal entrance were (68. 05±3. 76)mm,(53. 26±2. 17)mm,(57. 86±3. 19)mm,(61. 53±2. 14)mm。3. The distance between sphenopalatine foramen was(18. 67±2. 94)mm, the anterior opening of pterygoid cannal(21. 26±1. 87)mm, the sphenoidal ostium to the sphenopalatine foramen(6. 95±1. 57)mm, the entrance of Dorello canal was (19. 68±1. 87)mm.4. Three kinds of expanded transnasal surgery approach toward the exposure range of cavernous sinus:4. 1 Endonasal transsphenoidal approach: reveal and go into sphenoid sinus from between the nasal septum and middle nasal concha. This approach can push nasal septum to the opposite side, and push ipsilateral middle nasal concha outside, open the front of the sphenoid sinus and reveal cavernous sinus. If beyond the midline in the surgery, we can not only reveal the ipsilateral cavernous sinus, but can also better reveal contralateral anterior cavernous sinus. Because of the obstruction of middle nasal concha and superior nasal concha, we can not fully reveal the ipsilateral lateral wall of the cavernous sinus. Only reveal the pituitary gland and ipsilateral part of the medial wall of the cavernous sinus structures. If remove superior nasal concha or supreme nasal concha and extend laterally, we can better reveal the back of the ipsilateral cavernous sinus. This approach better reveals the contralateral cavernous sinus and reach the abducens nerve, oculomotor nerve and the superior orbital fissure outside contralateral internal carotid artery.4. 2 Middle nasal concha resection approach: This approach has a much broader surgical path, the anterior wall of sphenoid sinus can be opened laterally to the palatine bone and inside of pterygoid process. With 0°endoscope, lateral structures of internal carotid artery in ipsilateral cavernous sinus and inside structures of contralateral cavernous sinus can be clearly revealed. The 30oendoscope can be used to observe the posterior wall of the sphenoid sinus and bilateral structures in cavernous sinus. However, due to the impact of posterior ethmoid sinus, it is difficult to reach orbital apex and superior orbital fissure. Compared with the nasal septum side approach, the middle nasal concha resection approach can reveal surgical region more sufficiently, which is suitable for revealing of pathological changes in lateral structures of ipsilateral cavernous sinus and inside structures of contralateral cavernous sinus. Like the nasal septum side approach, the middle nasal concha resection approach is better to reveal the front wall of the contralateral cavernous sinus than ipsilateral part.4. 3 transsphenoidal-transethmoidal (far lateral) approach: This approach is more lateral. Middle nasal meatus approach can push away middle nasal concha and do part of anterior and posterior group ethmoidectomy to reveal the cavernous sinus. In the surgery, open a window in the anterior wall of sphenoid sinus near cavernous sinus, and then expand the bone window, if necessary, remove the bone of petrous segment of the internal carotid artery, this approach can well observe the lateral part of sphenoid sinus, structures in the ipsilateral cavernous sinus, superior orbital fissure, inside and inferior wall of optic canal, lateral wall of the cavernous sinus, Meckel's cave, even the base of middle cranial fossa outside cavernous sinus.Endoscopic extended transnasal approach can expand toward cavernous sinus direction. Important anatomical structures within the cavernous sinus can be clearly shown after cutting open the medial wall of the cavernous sinus.