Preoperative Image Evaluation Of Endoscopic Endonasal Approach To The Skull Base And Anatomic Study Of The Endoscopic Endonasal Approach To The Cavernous Sinus

PartⅠThe preoperative image evaluation of the endoscopic endonasal approach to the skull baseObjective:With the development of the endoscopic endonasal surgery, the drawbacks also begin to emerge gradually. The limited operating space, hemorrhage control and reconstructive techniques need more elaborative preoperative evaluation and planning. This study focused on the newly developed MR sequence and CT techniques in the evaluation of the endoscopic endonasal approach to the skull base.Methods:13 patients with skull base lesions were given the lamellar imaging examination and CT angiogram. The data was collected and we used navigator guide software for post processing. The turbinate, nasal septum, the landmarks in the sphenoid ethmoidal sinus were evaluated and compared with the endoscope in the operation.22 patients undergo regular MR sequence (T1, T2, T1+C),3D-FIESTA (Three dimensional fast-imaging employing steady acquisition) sequence and 3D-MPRAGE (three dimensional magnetization prepared rapid acquisition with gradient echo) sequence, The 3D-MIP and MPR were used to evaluate the vital structures in and around the sellar region. Comparisons among these sequences were made.Results:CTVE can show the deviation of the nasal septum and the development of the turbinate. It was helpful in the preparation for the pedicled nasoseptal flap. The ratio of manifestation of the sphenoid ostium, sphenoid septation, carotid protuberance, optic protuberance, opticocarotid recess were 100%,215%,61.5%,53.8%,84.6%,53.8%. The ratio of the coincidence with operation was 90%. The manifestation ratio of 3D-FIESTA (90.9%) about the chiasma and pituitary stalk was higher than 3D-MPRAGE (68.2%) and normal MR (54.5%).3D-FIESTA and 3D-MPRAGE sequence can be more useful than normal MR sequence to discern the cranial nerves (Ⅲ-Ⅵ). As compared to intraoperative findings,3D-MPRAGE(79.2%) and 3D-FIESTA(83.3%) MR images were superior for delineation medial CS wall especially in the knosp gradeⅡ-Ⅲ. Conclusions:CTVE can be helpful to show the anatomic structures stereoscopically in the endonasal approach. It also can raise a precise operation plan.3D-FIESTA images can be useful in the assessment of vital structures in and around the sellar region with tumor involvement and may be helpful to the suprasellar lesions' new classification based on the EEA.3D-MPRAGE and 3D-FIESTA MR images may be more useful to discern the medial CS wall and can raise a precise definition on the pituitary adenoma invasion CS. PartⅡAnatomic study of image-guided endoscopic endonasal approach to the cavernous sinusObjective:This study aimed to investigate the anatomic characteristics of endoscopic endonasal approach to the cavernous sinus, which include searching respective anatomic landmarks in different steps and the blood supply to the mucosal flap, comparing different endonasal routes to the cavernous sinus. To establish an anatomic basis for clinical applications of endoscopic endonasal approach to cavernous sinusMethods:Four (eight sides) fresh cadaver heads, in which the common carotid artery and vertebral artery were inject with red latex, the internal jugular vein were inject with blue latex, were dissected using an endoscopic endonasal approach to expose the cavernous sinus. During the course, we located the sphenopalatine foramen and followed the path of the sphenopalatine artery; the vidian canal was also investigative. The observing was completed with 0-degree lens and 30-degree lens. Extended endoscopic endonasal transsphenoidal approach, endonasal ethmoido-pterygo-sphenoidal approach (far lateral) and contralateral endoscopic endonasal transsphenoidal approach were compared. Anatomic structures of the cavernous sinus were measured. Five adult dry skulls were analyzed for location of the SPF on lateral nasal wall. The distances of these bone marks were all measured.Results:①The inferior border of the sphenoid ostium has been situated 4.75 mm±0.4mm above the nasal septal artery. The distance between the superior border of the choanal and the inferior border of the sphenoid ostium was 13.2±3.0 mm. We should protect the the horizontal part of the middle turbinate base when we resect the middle turbinate.②The sphenopalatine foramen (SPF) has been located on the lateral nasal wall at the root of the bone structures of middle turbinate. The sphenopalatine artery passes through the sphenopalatine foramen. It provided two major branches:the posterior lateral nasal artery and the nasal septal artery. The anterior border of the SPF is characterized by an easy recognizable sharp bony crest.③The vidian protuberance, carotid protuberance, optic protuberance, opticocarotid recess and maxillary trigeminal prominence showed as 25%,62.5%,62.5%,37.5%, 25%.The ratio of the sphenoid septations was 125%.The distance between the lateral opticocarotid recess and midline was 15.1±1.2 mm.④In all cases, the medial part of the cavernous sinus can be easily recognized. The cavernous segment of the ICA can be divided into 6 segments and has 4 vessel branches. The rate of meningohypophyseal trunk was 100%.25% originated from the tip of the hidden segment,37.5% originated from the medial wall of the hidden segment,37.5% originated from the anterior wall of the hidden segment, Its branches:tentorial artery, inferior hypophyseal artery and dorsalis meningeal artery. We found two cases of common source of inferior hypophyseal artery and dorsalis meningeal artery.63.5% of the infero-lateral trunk originated from the inferior horizontal segment, the other from the anterior vertical segment.⑤Oculomotor nerve, trochlear nerve, ophthalmic nerve, abducens nerve were lining up in the lateral wall of the cavernous sinus. The abducens nerve passed through the angle created by inferolateral trunk and internal carotid artery. The inferlateral trunk also supply to the oculomotor nerve, trochlear nerve and the Meckel's capsule.Conclusions:The anatomic study of the endoscope endonasal approach to the cavernous sinus can show the relationship between the branches of the internal carotid artery and the cranial nerves in the cavernous sinus. We should protect the the horizontal part of the middle turbinate base when we resect the middle turbinate. The pedicled nasal septal flap was supplied by the branch of the sphenopalatine artery. The main blood supply to the cranial nerves in the cavernous sinus was the inferlateral trunk. The safety limits in bone of skull base removal must contain the ipsilateral internal carotid artery canal.