Endoscopic endonasal approaches to the cavernous sinus: surgical approaches

OBJECTIVE: After completion of an earlier endoscopic transsphenoidal anatomic study, we studied various endoscopic transsphenoidal approaches using cadaveric specimens to develop endoscopic endonasal surgical approaches to the cavernous sinus. METHODS: Ten cavernous sinuses in five artery-injected adult cadaveric heads were studied with 0-, 30-, and 70-degree angled 4-mm rod-lens endoscopes. The extent of the surgical exposure, the skewed endoscopic anatomic view, and the maneuverability of surgical instruments through their relative operating spaces were studied after various endoscopic endonasal approaches via one nostril. RESULTS: The paraseptal approach was used between the nasal septum and the middle turbinate and provided exposure at the anteromedial portion of the cavernous sinus. The contralateral paraseptal approach rendered a slightly more medial view at the cavernous sinus than did the ipsilateral approach. This approach offered limited surgical access to the lateral vertical compartment. The middle turbinectomy approach allowed surgical access to the lateral wall of the cavernous sinus, except for the superior orbital fissure and the orbital apex. The middle meatal approach, which was made between the middle turbinate and the lateral nasal wall, revealed the entire lateral vertical compartment of the cavernous sinus, including the orbital apex and the superior orbital fissure. However, its lateral tangential surgical trajectory and the absence of dedicated surgical tools limited the surgeon's surgical maneuverability. A combination of the middle turbinectomy and middle meatal approaches increased the operating space. CONCLUSION: Various endoscopic endonasal surgical approaches to the cavernous sinus were studied using adult cadaveric head specimens.     

Endoscopic endonasal cavernous sinus surgery: an anatomic study

OBJECTIVE: The endoscopic surgical anatomy of the cavernous sinus was studied to establish an anatomic basis for endoscopic endonasal cavernous sinus surgery. METHODS: Five adult cadaveric heads were studied with 0-, 30-, and 70-degree 4-mm rod-lens endoscopes. The posterior wall of the sphenoidal sinus was approached via a paraseptal, middle turbinectomy, or middle meatal approach. RESULTS: The posterior bony wall of the sphenoidal sinus is subdivided into five vertical compartments: midline, bilateral paramedian, and bilateral lateral. The midline vertical compartment consists of the planum sphenoidale, tuberculum sellae, sella, and clival indentation. The paramedian vertical compartment is composed of the medial third of the optic canal and the carotid artery protuberance. The lateral vertical compartment contains four bony protuberances (optic, cavernous sinus apex, maxillary, and mandibular) and three depressions (carotico-optic, ophthalmomaxillary [V1-V2], and maxillomandibular [V2-V3]). The three depressions form anatomic triangles at the lateral vertical compartment: the optic strut triangle, which is bordered by the optic nerve, carotid artery, and oculomotor nerve (IIIrd cranial nerve); the V1-V2 triangle; and the V2-V3 triangle. The internal carotid artery at the posterior wall of the sphenoidal sinus can be subdivided into two main segments: the parasellar and the paraclival. The vidian canal is a landmark that leads to the foramen lacerum, the mandibular nerve, and the pterygopalatine fossa. CONCLUSION: Endoscopic anatomy of the cavernous sinus has been studied via an endonasal route in cadaveric specimens to provide an anatomic basis for endoscopic endonasal cavernous sinus surgery.     

Endoscopic endonasal skull base surgery: Part 3--The clivus and posterior fossa.

OBJECT: As a minimally invasive surgical strategy, endonasal endoscopy has been implemented for the surgical treatment of clival and midline posterior fossa lesions which conventionally require radical and extensive surgical exposures. A cadaver study was performed and, subsequently, this technique was adopted into patient treatment. METHODS: Six cadaver head specimens were used in this study. Anterior sphenoidotomy was attained by either a paraseptal or middle turbinectomy approach. The ideal head positioning was measured. The clival bone was removed with a high-speed drill from sella to foramen magnum in the vertical dimension and from carotid artery to carotid artery in the transverse dimension. The width of the clival bony window between the carotid arteries was measured at the level of the sellar floor and the caudal end of the carotid artery. The surgical anatomy was studied. RESULTS: Although the middle turbinectomy approach provided a wider surgical corridor, exposure with the paraseptal approach was sufficiently ample. Ideal head positioning was at 15-degree flexion of the forehead-chin line. The average width between carotid arteries at the sellar floor level was 16 mm (range 12-22 mm) and at the lower end of the carotid arteries it was 19 mm (range 14-23 mm). When the dura mater was opened, the anterior view of the pons and medulla with corresponding cranial nerves and vasculature was encountered. Four illustrative patient cases are presented. CONCLUSIONS: This endonasal endoscopy provided excellent surgical exposure from the sella to the foramen magnum at the midline clivus and posterior fossa. Surgical techniques and illustrations of four patients are presented.     

Endoscopic endonasal skull base surgery: Part 1--The midline anterior fossa skull base.

OBJECTIVE: An endonasal endoscopic surgery to the anterior fossa skull base was developed in cadaver dissection as a minimally invasive surgical technique and, subsequently, used in patient treatment. METHODS: Six cadaver head specimens were used. Ideal head positioning and various surgical routes were studied. To estimate the extent of surgical exposure provided by this technique, the width of the exposed anterior cranial fossa was measured between the medial margin of the orbits, the optic nerves and the carotid arteries. Three demonstrative patient cases are presented. RESULTS: Ideal head positioning was discovered to be at 15-degree extension of the forehead-chin line. Paraseptal, middle meatal and middle turbinectomy approaches were developed. The average width between the medial orbits was measured to be 24 mm (range 22-29 mm) at the crista galli level, 27 mm (range 24-30 mm) at the planum sphenoidale, 18 mm (range 15-22 mm) between the optic nerves, and 17 mm (range 13-21 mm) between the rostral carotid siphons. This technique, when it was applied in patient care, proved to be minimally invasive. CONCLUSIONS: This endoscopic endonasal approach provided a direct "short-cut" access to the midline anterior fossa skull base. This technique can be used for the surgical treatment of cerebrospinal fluid (CSF) leak, meningiomas, craniopharyngiomas, pituitary adenomas, and other midline intracranial anterior skull base lesions. This is the first report in the English literature describing endonasal endoscopy for the surgical treatment of primary intracranial anterior fossa skull base lesions.     

Endoscopic Endonasal Approach to the Middle Cranial Fossa through the Cavernous Sinus Triangles: Anatomical Considerations

The lateral limit of endoscopic endonasal surgery has yet to be defined. The aim of this study was to investigate the lateral limit of endoscopic endonasal surgery at the level of the sphenoid sinus. Access from the sphenoid sinus to the middle cranial fossa through the cavernous sinus triangles was evaluated by cadaver dissection. Anatomical analysis demonstrated that the medial temporal dura mater was exposed through the anterior area of the clinoidal triangle, anteromedial triangle, and superior area of the anterolateral triangle, indicating potential corridors to the middle cranial fossa. This study suggests that the cavernous sinus triangles are applicable in selected cases to manage middle cranial fossa lesions by endoscopic endonasal surgery.     

Dual-Port 2D and 3D Endoscopy: Expanding the Limits of the Endonasal Approaches to Midline Skull Base Lesions with Lateral Extension

Objective To investigate a novel dual-port endonasal and subtemporal endoscopic approach targeting midline lesions with lateral extension beyond the intracavernous carotid artery anteriorly and the Dorello canal posteriorly. Methods Ten dual-port approaches were performed on five cadaveric heads. All specimens underwent an endoscopic endonasal approach from the sella to middle clivus. The endonasal port was combined with an anterior or posterior endoscopic extradural subtemporal approach. The anterior subtemporal port was placed directly above the middle third of the zygomatic arch, and the posterior port was placed at its posterior root. The extradural space was explored using two-dimensional and three-dimensional endoscopes. Results The anterior subtemporal port complemented the endonasal port with direct access to the Meckel cave, lateral sphenoid sinus, superior orbital fissure, and lateral and posterosuperior compartments of the cavernous sinus; the posterior subtemporal port enhanced access to the petrous apex. Endoscopic dissection and instrument maneuverability were feasible and performed without difficulty in both the anterior and posterior subtemporal ports. Conclusion The anterior and posterior subtemporal ports enhanced exposure and control of the region lateral to the carotid artery and Dorello canal. Dual-port neuroendoscopy is still minimally invasive yet dramatically increases surgical maneuverability while enhancing visualization and control of anatomical structures.     

Endoscopic endonasal approach to the pterygopalatine fossa: anatomic study

OBJECTIVE: The pterygopalatine fossa is a relatively small anatomic region. Because of its rich vasculonervous contents and its connections with several intracranial and extracranial compartments, it is of particular surgical interest. Because of its deep localization and despite its small size, however, it can require extensive anatomic approaches, especially for invasive cranial base lesions. We performed a cadaveric study through a minimally invasive endoscopic endonasal approach to the pterygopalatine fossa. METHODS: We studied 16 pterygopalatine fossae in eight adult cadaveric heads in which the arteries and veins were injected with latex. For visualization, we used rod-lens endoscopes, 4 mm in diameter and 18 cm in length, with 0-, 30-, 45-, and 70-degree lenses. An endonasal middle meatal transpalatine approach, an endonasal middle meatal transantral approach, and an endonasal inferior turbinectomy transantral approach were used. RESULTS: The middle meatal transpalatine approach allows for medial exposure of the pterygopalatine fossa contents, the middle meatal transantral approach allows a lateral view, and the inferior turbinectomy transantral approach allows the widest view and room for surgical maneuvering in the medial and lateral compartments of the pterygopalatine fossa and the infratemporal fossa. CONCLUSION: Our anatomic study shows that this approach can be considered a valid minimally invasive option to approach pterygopalatine fossa lesions.     

Exposure of the intracavernous carotid artery in aneurysm surgery

The pterional intradural approach was used in five cases of large and giant carotid-ophthalmic aneurysms and in two cases of intracavernous aneurysms that arose from the anterior siphon knee in the cavernous sinus (CS) and extended into the carotid cistern. In four cases of large carotid-ophthalmic aneurysms removal of the anterior clinoid process and the roof of the optic canal gave easy access to the pericarotid ring. The anteromedial part of the pericarotid ring was dissected to expose the extradural portion of the internal carotid artery (ICA) proximal to the neck and to make enough room between the wall of the CS and the extradural portion of the ICA, thus allowing easy clipping of the neck. In one case of a giant carotid-ophthalmic aneurysm extending into the CS with an extradural origin of the ophthalmic artery and in two cases of an intracavernous aneurysm arising from the siphon knee, neck clipping was performed by opening the lateral wall and roof of the CS after removal of the optic strut. The opening of the lateral wall anterior to the 3rd nerve facilitated wide exposure of the anterior siphon knee. The horizontal portion of the intracavernous ICA as well as the whole aspect of the aneurysm could be exposed as a result of the extended opening of the cavernous roof anterior to the posterior clinoid process. Successful operative results were obtained in all seven patients. A visual field detect as an operative complication was noted in one patient. No disturbance of ocular movements was noted.     

Endoscopic transsphenoidal pituitary surgery: various surgical techniques and recommended steps for procedural transition

Various techniques in pituitary endoscopy are reviewed in the attempt to assemble the transitional steps necessary to take a neurosurgeon from traditional microscopic transsphenoidal surgery to endoscopic endonasal pituitary surgery. The senior author's (HDJ) experiences of endonasal endoscopy in more than 200 operations as well as the reports in the literature on pituitary endoscopy are reviewed. Two distinct advantages that an endoscope has over an operating microscope are its ability to visualize through a narrow surgical corridor and its ability to provide angled, close-up views. An endoscope can be used to assist the operating microscope (endoscope-assisted microsurgery). Endoscopy can also be used for endonasal retractor placement when microscopic surgery is preferred (endoscopic sphenoidotomy). When endonasal endoscopy is chosen, the surgical approach can be made with a deep-transseptal, a paraseptal, a middle turbinectomy or a middle meatal approach (endonasal transsphenoidal endoscopy). Endonasal endoscopy can be performed via either one or two nostrils. Working-channel endoscopy can be performed for restricted purposes. When a neurosurgeon desires to adopt endoscopy into pituitary surgery, the author recommends endoscope-assisted microsurgery as the first step followed by endoscopic sphenoidotomy as a combined effort between an endoscopic rhinologist and the neurosurgeon as the next step leading finally to endonasal pituitary endoscopy. Various methods of transsphenoidal endoscopy and the authors' recommendations for transitional steps are reported based on the authors' personal experience and literature review.     

Endoscopic Endonasal Approach to the Ventral Cranio-Cervical Junction: Anatomical Study

Summary. Summary.   Objective: In order to develop an endoscopic endonasal approach to the ventral cranio-cervical junction and odontoid process under the concept of a minimally invasive surgical strategy, a cadaver study was performed.   Methods: Sixteen artery-injected adult head specimens were used. Endonasal endoscopic approach was made through one- or two-nostril routes following the Jho's endonasal paraseptal technique. Rod-lens endoscopes, which were 2.7 or 4 mm in diameter, 18 cm in length with 0-, 30-, and 70-degree lenses, were used.   Results: Surgical landmarks leading to the craniocervical junction were the inferior margin of the middle turbinate, nasopharynx and Eustachian tube. The nasopharynx was readily identified following the inferior margin of the middle turbinate. The line drawn between the Eustachian tubes indicated the juncture between the clivus and atlas. With a midline mucosal incision, the ventral cranio-cervical junction was exposed. Odontoid resection was performed with removal of the anterior arch of the atlas. Clival resection can be performed as much rostral as required. Manoeuverability of the surgical instruments was better with a two-nostril technique than with a one-nostril. Although the entire midline clivus was accessible rostrally, C-2 was the caudal limit through this endonasal route. A suturing device needed to be developed for mucosal or dural closure for live operations.   Conclusion: This cadaver study demonstrates that an endoscopic endonasal approach to the ventral cranio-cervical junction and odontoid process can be a valid alternative to the conventional transoral approach.     

Identification of the internal carotid artery at the superior part of the cavernous sinus during endoscopic endonasal cavernous sinus tumor surgery

Background

Identification of the internal carotid artery (ICA) is essential for successful endoscopic endonasal cavernous sinus tumor surgery. This study aimed to develop a method for identifying the ICA in cavernous sinus tumors at the superior part of the cavernous sinus.

Methods

Ten fresh cadavers were studied with a 4-mm 0° and 30° endoscope to identify surgical landmarks of the ICA in the cavernous sinus. Clinical cases of cavernous sinus tumors were surgically treated using an endoscopic transpterygoid approach.

Results

Anatomical study indicated the ICA at the superior part of the cavernous sinus can be identified using three steps: 1) exposure of the optic nerve sheath by drilling the optic canal; 2) identification of the proximal orifice of the optic nerve sheath at the transition of the optic nerve sheath and dura mater of the tuberculum sellae; and 3) identification of the clinoid segment of the ICA at the distal dural ring just below the proximal orifice of the optic nerve sheath. Although the ICA was encased and transposed by tumors in preliminary surgical cases, the clinoid segment of the ICA was safely exposed at the superior part of the cavernous sinus using this method.

Conclusions

Dural structures around the cavernous sinus are key to identifying the ICA at the superior part of the cavernous sinus. This method is expected to reduce the risk of ICA injury during endoscopic endonasal surgery for cavernous sinus tumors.     

Extradural total petrous apex resection with trigeminal translocation for improved exposure of the posterior cavernous sinus and petroclival region

We have analyzed a strategy for improved exposure of the posterior cavernous sinus and petroclival region through an extradural subtemporal approach to be utilized in the removal of neoplastic processes with involvement of the apical petrous bone and posterior cavernous sinus. This surgical approach includes the following elements for improved exposure of the posterior cavernous sinus through the middle fossa corridor: (1) maximal extradural exposure and mobilization of the trigeminal nerve complex, allowing its elevation and anterior displacement, (2) complete extradural removal of the anterior petrous pyramid from the porus acousticus to the petrous apex under direct vision, (3) total exposure of the abducens nerve from the posterior fossa to its point of cross over the intracavernous carotid artery, and (4) wide extradural exposure of the cavernous carotid artery in the foramen lacerum region. This strategy can be combined with other related approaches; specifically, frontotemporal or posterior transpetrosal exposures for extensive lesions.Microsurgical dissection and morphometric analysis were performed in 20 fixed cadaver specimens for the purposes of validating the method for clinical application and determining the key elements to maximization of exposure. The trigeminal complex could be anteromedially retracted 4.8 mm +/- 1.3 (range = 3 to 6 mm) without skeletonization of V(2) and V(3). Liberating these two divisions from their bony canals to their first peripheral branch (10.4 mm +/- 2.5 and 5.4 mm +/- 1.1, respectively) resulted in increased mobilization an average of 9.1 mm +/- 1.7 (7 to 14 mm). Further mobilization is achieved by dividing the attachment between the trigeminal connective tissue sheath and the fibrous carotid ring at the foramen lacerum. An average of 13.0 mm +/- 3.1 (7 to 20 mm) of the posterior intracavernous carotid artery was exposed. Detailed microanatomic observations and a comprehensive morphometric analysis of the relevant anatomic relationships were made.     

The extradural subtemporal keyhole approach to the sphenocavernous region: anatomic considerations.

Fourteen cadaver specimens (28 sides) and twelve dry human skulls (24 sides) were used to study the anatomic relationships between bony, neurovascular and foraminal landmarks in the floor of the middle fossa in preparation for performing the extradural subtemporal keyhole approach to the sphenocavernous region. The interforaminal distance was largest between the foramina rotundum (FR) and ovale (FO) and was smallest between the FO and foramen spinosum (FS). The largest angle between exit foramen was the FR to FO. The greater superficial petrosal nerve (GSPN) was always found to overlie and run parallel to the petrous internal carotid artery, however, its location over the artery and its separation from it by bone was variable. With a subtemporal "keyhole" placed above the posterior zygomatic root (PZR), a 0 degrees endoscope allowed easy visualization of the middle meningeal artery (MMA) and the mandibular nerve (V 3 ) however, a 30 degrees endoscope was more useful for visualizing the maxillary nerve (V 2 ) and the ophthalmic nerve (V 2 ). With a sphenoidotomy performed between V 1 and V 2, the 30 degrees endoscope was found to be the most useful for visualizing the carotid siphon and the contralateral wall of the sphenoid sinus, while the 70 degrees endoscope was the most useful for visualizing of the floor of the sella and the walls of the sphenoid sinus. Two venous concerns with respect to performing endoscopic approaches to the region were identified: a fibrous layer overlies a heavy venous plexus that encircles the petrous carotid artery, and the foramen Vesalius, which transmits a large emissary vein draining the cavernous sinus, was identified medial to the FO in 30 % of our dissected sides.     

Anatomical study of the cavernous sinus emphasizing operative approaches and related vascular and neural reconstruction

The efficacy of three operative approaches to the cavernous sinus (CS) and the possibilities of vascular and cranial nerve reconstruction in and around the CS were studied in 50 cadaver specimens (25 heads). The lateral operative approach was through the lateral wall, between Cranial Nerves V1 and IV, or between Cranial Nerves V1 and V2. The superior approach was through the superior wall of the CS after removing the anterior clinoid process and unroofing the optic canal. The inferior approach followed the petrous internal carotid artery (ICA) into the CS after an extradural subtemporal exposure or after a combined subtemporal and infratemporal fossa exposure. The different exposures of the spaces of the CS and of the intracavernous structures provided by the superior and the lateral approaches were complementary. The exposure provided by the inferior approach was minimal; however, the junction of the petrous and cavernous ICA was best exposed by this route. The combined subtemporal and infratemporal fossa approach exposed the petrous ICA (for proximal control or for reconstruction) with the greatest ease and with the least temporal lobe retraction. The combination of the superior and lateral approaches and the complete mobilization of the intracavernous ICA facilitated its repair after experimental lacerations. Lacerations of either the inferior and the inferomedial aspects of any portion of the cavernous ICA or of the anterior surface of the posterior vertical segment of the artery were the most difficult to repair. End-to-end anastomosis was more difficult with the posterior third of the artery than with the anterior two-thirds. A vein graft with an average length of 3.5 cm could be sutured from the petrous to the supraclinoid ICA to bypass the cavernous ICA, with an average occlusion time of 45 minutes. End-to-end technique was judged better for the proximal anastomosis, but end (graft)-to-side anastomosis was easier to perform at the distal end because of the location of the ophthalmic artery. Resuture of Cranial Nerves III and VI could not be performed in fresh cadavers if the gap exceeded 0.3 cm. In 3 specimens, the exposure of Cranial Nerve VI in the posterior fossa through the petrous apex and in the orbital apex was followed by graft placement (bypassing the CS). The complex anatomy of the cranial nerves at the apex of the CS was also defined in 10 specimens. Surgeons who perform operations in and around the CS for neoplastic and vascular lesions will find these studies useful.     

Extradural Total Petrous Apex Resection With Trigeminal Translocation for Improved Exposure of the Posterior Cavernous Sinus and Petroclival Region

We have analyzed a strategy for improved exposure of the posterior cavernous sinus and petroclival region through an extradural subtemporal approach to be utilized in the removal of neoplastic processes with involvement of the apical petrous bone and posterior cavernous sinus. This surgical approach includes the following elements for improved exposure of the posterior cavernous sinus through the middle fossa corridor: (1) maximal extradural exposure and mobilization of the trigeminal nerve complex, allowing its elevation and anterior displacement, (2) complete extradural removal of the anterior petrous pyramid from the porus acousticus to the petrous apex under direct vision, (3) total exposure of the abducens nerve from the posterior fossa to its point of cross over the intracavernous carotid artery, and (4) wide extradural exposure of the cavernous carotid artery in the foramen lacerum region. This strategy can be combined with other related approaches; specifically, frontotemporal or posterior transpetrosal exposures for extensive lesions.

Microsurgical dissection and morphometric analysis were performed in 20 fixed cadaver specimens for the purposes of validating the method for clinical application and determining the key elements to maximization of exposure. The trigeminal complex could be anteromedially retracted 4.8 mm ± 1.3 (range = 3 to 6 mm) without skeletonization of V₂ and V₃. Liberating these two divisions from their bony canals to their first peripheral branch (10.4 mm ± 2.5 and 5.4 mm ± 1.1, respectively) resulted in increased mobilization an average of 9.1 mm ± 1.7 (7 to 14 mm). Further mobilization is achieved by dividing the attachment between the trigeminal connective tissue sheath and the fibrous carotid ring at the foramen lacerum. An average of 13.0 mm ± 3.1 (7 to 20 mm) of the posterior intracavernous carotid artery was exposed. Detailed microanatomic observations and a comprehensive morphometric analysis of the relevant anatomic relationships were made.

     

Modified infratemporal fossa approach via lateral transantral maxillotomy: a microsurgical model

BACKGROUND: Lateral approaches have traditionally been used to gain access to lesions of the infratemporal fossa (ITF). However, dysfunction of the facial nerve secondary to its translocation, conductive hearing loss, and dental malocclusion because of mandibular head resection or dislocation are significant limitations associated with some of these approaches. Although facial nerve translocation and extended maxillotomy approaches avoid some of these drawbacks, they are invasive and require extensive osteotomies and facial incisions. To avoid these potential complications and maintain an extranasal/extraoral exposure, we studied the use of a lateral and posterior extension of an anterior transmaxillary approach to the cavernous sinus. METHODS: The study was performed on 12 cadaver specimens and two dry skulls. An initial nasolabial fold incision, followed by an en bloc osteotomy of the anterior and lateral maxilla provides a window into the medial ITF. After osteotomy of the pterygoid plate and the posterior maxillary wall, the floor of the middle fossa is exposed to reveal the mandibular and maxillary divisions of the trigeminal nerve exiting their respective foramina. The floor of the middle fossa is then drilled postero-medial to the foramen ovale to gain access to the course of the C3-C4 portion of the petrous carotid artery and the eustachian tube. The upper two-thirds of the clivus and the pituitary gland are accessed after drilling of the floor of the sella turcica and form the posterior limit of this exposure. RESULTS: The technique offers a trajectory to the medial ITF and skull base that does not necessitate palatal splitting or opening of the nasopharynx. The anterior route avoids temporomandibular joint disruption, and spares the lacrimal apparatus and all branches of the facial nerve. In addition, the reflected pterygoid muscle can be used as a vascularized flap for closure of the skull base defect. CONCLUSION: The approach may be an alternative less invasive approach to the ITF and may be suitable for ITF lesions that have minimal lateral or intracranial extension.     

Surgical approaches to the cavernous sinus: a microsurgical study

The surgical approaches to the cavernous sinus were examined in 50 adult cadaveric cavernous sinuses using magnification of X3 to X40. The following approaches were examined: 1) the superior intradural approach directed through a frontotemporal craniotomy and the roof of the cavernous sinus; 2) the superior intradural approach combined with an extradural approach for removing the anterior clinoid process and unroofing the optic canal and orbit; 3) the superomedial approach directed through a supraorbital craniotomy and subfrontal exposure to the wall of the sinus adjacent to the pituitary gland; 4) the lateral intradural approach directed below the temporal lobe to the lateral wall of the sinus; 5) the lateral extradural approach for exposure of the internal carotid artery in the floor of the middle cranial fossa proximal to the sinus; 6) the combined lateral and inferolateral approach, in which the infratemporal fossa was opened and the full course of the petrous carotid artery and the lateral wall of the sinus were exposed and; 7) the inferomedial approach, in which the medial wall of the sinus was exposed by the transnasal-transsphenoidal route. It was clear that a single approach was not capable of providing access to all parts of the sinus. The intracavernous structures best exposed by each route are reviewed. The osseous relationships in the region were examined in dry skulls. Anatomic variants important in exposing the cavernous sinus are reviewed.     

Trans-zygomatic middle cranial fossa approach to access lesions around the cavernous sinus and anterior parahippocampus: a minimally invasive skull base approach

Purpose  Exposure of the cavernous sinus or anterior parahippocampus often involves a wide exposure of the temporal lobe and mobilization of the temporalis muscle associated with temporal lobe retraction. The authors present a cadaveric study to illustrate the feasibility, advantages and landmarks necessary to perform a trans-zygomatic middle fossa approach to lesions around the cavernous sinus and anterior parahippocampus. Methods  The authors performed bilateral trans-zygomatic middle fossae exposures to reach the cavernous sinus and parahippocampus in five cadavers (10 sides). We assessed the morbidity associated with this procedure and compared the indications, advantages, and disadvantages of this method versus more extensive skull base approaches. A vertical linear incision along the middle portion of the zygomatic arch was extended one finger breadth inferior to the inferior edge of the zygomatic arch. Careful dissection inferior to the arch allowed preservation of facial nerve branches. A zygomatic osteotomy was followed via a linear incision through the temporalis muscle and exposure of the middle cranial fossa floor. Results  A craniotomy along the inferolateral temporal bone and middle fossa floor allowed extradural dissection along the middle fossa floor and exposure of the cavernous sinus including all three divisions of the trigeminal nerve. Intradural inspection demonstrated adequate exposure of the parahippocampus. Exposure of the latter required minimal or no retraction of the temporal lobe. Conclusions  The trans-zygomatic middle fossa approach is a simplified skull base exposure using a linear incision, which may avoid the invasivity of more extensive skull base approaches while providing an adequate corridor for resection of cavernous sinus and parahippocampus lesions. The advantages of this approach include its efficiency, ease, minimalism, preservation of the temporalis muscle, and minimal retraction of the temporal lobe.     

Anatomical study of the pterygopalatine fossa using an endoscopic endonasal approach: spatial relations and distances between surgical landmarks

OBJECT: The pterygopalatine fossa is an area that lies deep within the skull base. The recent extensive use of the endoscopic endonasal approach has provided neurosurgeons with a method to reach various areas of the skull base through a less invasive approach than traditional transcranial or transfacial approaches. This study aims to provide neurosurgeons with new data concerning direct endoscopic measurements and precise anatomical topography features of the pterygopalatine fossa. METHODS: An anatomical dissection of six fixed cadaver heads (12 pterygopalatine fossae) was performed to analyze spatial relationships and distances between the most important neurovascular structures in this region, and to estimate the size of the endoscopic surgical field for operations in this area. The endoscopic endonasal approach offers direct access to the pterygopalatine fossa through its anteromedial walls. CONCLUSIONS: Using an endoscopic endonasal approach makes it possible to identify all of the anatomical landmarks of the pterygopalatine fossa and almost all of the contiguous skull base areas.     

Surgical results of an endoscopic endonasal approach for clival chordomas

Background

The surgical approaches for clival chordomas remain controversial, although the extent of resection is one of the most important factors for long survival rates. Recently an endoscopic endonasal approach in good collaboration with otolaryngologists has attracted major attention as a surgical approach for clival chordomas. We describe our experience with the endoscopic endonasal approach and provide a review of the literature.

Methods

Between 2008 and 2011, six operations were performed via the endoscopic endonasal approach for clivus chordomas. The mean tumor size was 35 mm in diameter. The tumor location was mainly from the upper to middle clivus. The tumor extended into the cavernous sinus in five cases and intradurally in three cases. A binostril approach was performed in four cases, while a one nostril approach was performed in two cases.

Results

Gross total removal was achieved in three cases. The analysis of cases with incomplete resection suggested that residual tumors were observed epidurally and subdurally. The residual on the epidura was observed from the posterior clinoid to the posterior compartment of the cavernous sinus. On the other hand, the residual on the subdural was observed behind the upper part of the pituitary gland. There was no postoperative cerebrospinal fluid (CSF) leakage using vascularized nasoseptal flaps in any of the cases.

Conclusions

The endoscopic endonasal transclival approach allows an appropriate extent of resection with acceptable complication rates in comparison with other approaches. In our series, the accomplishment of gross total removal was associated with the relationship between the tumors and surrounding structures, such as the pituitary gland and the cavernous portion of the intracranial carotid artery (ICA).