Endoscopic Anatomy of the Skull Base.

Presently, endoscopic skull base surgery has undergone significant advancements since its inception over two decades ago. Nevertheless, it is imperative to underscore that the fundamental basis of all surgical procedures lies in the meticulous understanding of anatomy, with particular emphasis on the ventral anatomy. This facet has recently garnered increased attention.Following the advancements in endoscopic skull base surgery techniques, this chapter will concentrate on the pertinent anatomical considerations that serve as key foundations for successful procedures. These considerations are categorized into two planes: the sagittal plane and the coronal plane.The sagittal plane is further subdivided into five distinct approaches, namely,(1) the transcribriform approach, (2) the transplanum approach, (3) the transsellar approach, (4) the transclival approach, and (5) the transodontoid approach.On the other hand, the coronal plane is delineated into seven specific zones to facilitate comprehension and potential applications: (1) the petrous apex approach, (2) the intrapetrous approach, (3) the suprapetrous approach, (4) the cavernous sinus approach, (5) the infratemporal approach, (6) the medial condyle approach, and (7) the jugular foramen approach.By organizing the anatomical aspects in this systematic manner, the information provided becomes more accessible, fostering a comprehensive understanding of the subject matter for potential future application.

Customized ventral bony and dural opening in the transplanum/transtuberculum and transclival variants of extended endoscopic endonasal approach to suprasellar craniopharyngiomas: an approach-based stepwise cadaveric dissection and clinical applicability.

BACKGROUND: Optimal initial exposure through an extended endoscopic endonasal approach (EEA) for suprasellar craniopharyngiomas ensures safe and unrestricted surgical access while avoiding overexposure, which may prolong the procedure and increase neurovascular adverse events. METHOD: Here, the authors outline the surgical nuances of a customized bony and dural opening through the transplanum/transtuberculum and transclival variants of the extended EEA to suprasellar craniopharyngiomas based on the tumor-pituitary stalk relationship. A stepwise cadaveric dissection and intraoperative photographs relevant to the approaches are also provided. CONCLUSION: Safe maximal resection of suprasellar craniopharyngiomas through extended EEAs can be feasibly and safely achieved by implementing of tailored ventral exposure.

How I do it: the endoscopic endonasal transclival approach for clipping of the ruptured vertebral artery aneurysm.

BACKGROUND: Vertebral artery aneurysms account for less than 5% of all cerebral aneurysms. They have a high risk of rupture and are associated with threatening clinical outcomes compared with anterior circulation aneurysms. METHOD: The endoscopic endonasal transclival approach (EETA) was used. During the temporary clipping, the neck of the aneurysm was dissected, and a permanent clip was applied. The repair of the skull base defect was carried out with the nasoseptal mucoperiosteal flap on the vascular pedicle. CONCLUSION: The EETA is a feasible alternative for the clipping of the medially located ruptured vertebral artery aneurysm. EETA can be recommended for centers with a large volume of cerebrovascular and endoscopic neurosurgical procedures.

The feasibility of three port endonasal, transorbital, and sublabial approach to the petroclival region: neurosurgical audit and multiportal anatomic quantitative investigation.

PURPOSE: The petroclival region represents the "Achille's heel" for the neurosurgeons. Many ventral endoscopic routes to this region, mainly performed as isolated, have been described. The aim of the present study is to verify the feasibility of a modular, combined, multiportal approach to the petroclival region to overcome the limits of a single approach, in terms of exposure and working areas, brain retraction and manipulation of neurovascular structures. METHODS: Four cadaver heads (8 sides) underwent endoscopic endonasal transclival, transorbital superior eyelid and contralateral sublabial transmaxillary-Caldwell-Luc approaches, to the petroclival region. CT scans were obtained before and after each approach to rigorously separate the contribution of each osteotomy and subsequentially to build a comprehensive 3D model of the progressively enlarged working area after each step. RESULTS: The addition of the contralateral transmaxillary and transorbital corridors to the extended endoscopic endonasal transclival in a combined multiportal approach provides complementary paramedian trajectories to overcome the natural barrier represented by the parasellar and paraclival segments of the internal carotid artery, resulting in significantly greater area of exposure than a pure endonasal midline route (8,77 cm2 and 11,14 cm2 vs 4,68 cm2 and 5,83cm2, extradural and intradural, respectively). CONCLUSION: The use of different endoscopic "head-on" trajectories can be combined in a wider multiportal extended approach to improve the ventral route to the most inaccessible petroclival regions. Finally, by combining these approaches and reiterating the importance of multiportal strategy, we quantitatively demonstrate the possibility to reach "far away" paramedian petroclival targets while preserving the neurovascular structures.

Techniques and challenges of the expanded endoscopic endonasal access to the ventrolateral skull base during the "far-medial" and "extreme medial" approaches.

BACKGROUND: Expanding the ventrolateral skull base corridor from the midline of lower clivus to the petroclival fissure is a challenging endonasal surgical task. Resection of lytic lesions like chondrosarcoma can cause cranial nerve morbidities and injury of ICA, necessitating accurate knowledge of correlative endoscopic anatomy with stereotactic landmarks. METHODS: We describe an extended endoscopic endonasal approach (EEA) for a right petroclival chondrosarcoma with the demonstration of ipsilateral surgical landmarks with contralateral normal correlates, using a stepwise comparative image-guided cadaveric dissection study. CONCLUSION: EEA for lytic lesions like chondrosarcomas needs to address brain shift and displacement of ICA, posing a chance for cranial nerve morbidities and ICA injury. Meticulous utilization of intraoperative stereotactic landmarks can help avoid and mitigate surgical complications.

[Extended endoscopic endonasal posterior (transclival) approach to tumors of the clival region and ventral posterior cranial fossa. Part 3. Analysis of surgical treatment outcomes in 127 patients]. / Éndoskopicheskii éndonazal'nyi zadnii rasshirennyi (transklival'nyi) dostup k opukholiam oblasti skata cherepa i ventral'nykh otdelov zadnei cherepnoi iamki. Chast' 3. Analiz rezul'tatov khirurgicheskogo lecheniia 127 patsientov.

Until recently, tumors of the clival region and ventral posterior cranial fossa were considered hard-to-reach and often inoperable via standard transcranial approaches. The introduction of minimally invasive methods combined with the endoscopic technique into neurosurgical practice has enabled removal of hard-to-reach tumors, including midline tumors of the ventral posterior cranial fossa. OBJECTIVE: To improve and introduce the extended endoscopic endonasal posterior (transclival) approach into clinical practice and to analyze the results of its application in surgical treatment of midline skull base tumors extending into the ventral posterior cranial fossa. MATERIAL AND METHODS: During the period from 2008 to the present, we have operated 127 patients with various skull base tumors located in the clival region and ventral posterior cranial fossa (60 males and 67 females); the patients' age was 3 to 74 years. The distribution of tumors by histology was as follows: 96 (75.6%) chordomas, 9 (7.1%) pituitary adenomas, 8 (6.3%) meningiomas, 3 (2.33%) cholesteatomas, 2 (1.6%) craniopharyngiomas, 3 (2.33%) fibrotic dysplasia, and 6 (4.7%) other tumors (giant cell tumor, glioma of the neurohypophysis, osteoma, plasmacytoma, carcinoid tumors, chondroma). The tumor size was as follows: 36 (28.35%) giant (more than 60 mm) tumors, 71 (55.9%) large (35-59 mm) tumors, 19 (14.96%) medium (21-35 mm) tumors, and 1 (0.79%) small (less than 20 mm) tumor. Intraoperative monitoring of the cranial nerves was performed (20 cranial nerves were identified) in 10 cases. RESULTS: The extent of chordoma resection was as follows: total removal - 63 (65.62%) cases, subtotal removal - 23 (23.96%) cases, and partial removal - 10 (10.42%) cases. Pituitary adenomas were resected totally in 6 cases, subtotally in 1 case, and partially in 2 cases. Meningioma was removed subtotally in 4 cases, partially in 3 cases, and less than 50% in 1 case. Other tumors (cholesteatoma, craniopharyngioma, fibrous dysplasia, giant cell tumor, glioma of the neurohypophysis, osteoma, plasmacytoma, carcinoid tumors, chondroma) were removed totally in 7 cases and subtotally in 7 cases. Postoperative cerebrospinal fluid leakage occurred in 9 (7.2%) cases, and meningitis developed in 12 (9.4%) cases. Oculomotor disorders occurred in 17 (13.4%) patients; in 10 of these patients, the disorders regressed within 4 to 38 days after surgery; in 7 patients the oculomotor disorders did not regress. A lethal outcome occurred in 2 (1.57%) cases. CONCLUSION: The extended endoscopic endonasal posterior (transclival) approach, being minimally invasive, enables removal of various midline skull base tumors with/without involvement of the clivus with high radicalness, low risk of postoperative complications, and low lethality. Until recently, these tumors were considered almost inoperable.

[Extended endoscopic endonasal posterior (transclival) approach to tumors of the clival region and ventral posterior cranial fossa. Part 1. Topographic and anatomical features of the clivus and adjacent structures]. / Éndoskopicheskii éndonazal'nyi zadnii rasshirennyi (transklival'nyi) dostup k opukholiam oblasti skata i ventral'nykh otdelov zadnei cherepnoi iamki. Chast' 1. Topografo-anatomicheskie osobennosti skata i pogranichnykh s nim obrazovanii.

OBJECTIVE: to describe the main topographic and anatomical features of the clival region and its adjacent structures for improvement and optimization of the extended endoscopic endonasal posterior (transclival) approach for resection of tumors of the clival region and ventral posterior cranial fossa. MATERIAL AND METHODS: We performed a craniometric study of 125 human skulls and a topographic anatomical study of heads of 25 cadavers, the arterial and venous bed of which was stained with colored silicone (the staining technique was developed by the authors) to visualize bed features and individual variability. Currently, we have clinical material from more than 120 surgical patients with various skull base tumors of the clival region and ventral posterior cranial fossa (chordomas, pituitary adenomas, meningiomas, cholesteatomas, etc.) who were operated on using the endoscopic transclival approach. RESULTS: We present the main anatomical landmarks and parameters of some anatomical structures that are required for performing the endoscopic endonasal posterior approach. The anatomical landmarks, such as the intradural openings of the abducens and glossopharyngeal nerves, may be used to arbitrarily divide the clival region into the superior, middle, and inferior thirds. The anatomical landmarks important for the surgeon, which are detected during a topographic anatomical study of the skull base, facilitate identification of the boundaries between the different clival portions and the C1 segments of the internal carotid arteries. The superior, middle, and inferior transclival approaches provide an access to the ventral surface of the upper, middle, and lower neurovascular complexes in the posterior cranial fossa. CONCLUSION: The endoscopic transclival approach may be used to access midline tumors of the posterior cranial fossa. The approach is an alternative to transcranial approaches in surgical treatment of clival region lesions. This approach provides results comparable (and sometimes better) to those of the transcranial and transfacial approaches.

[Extended endoscopic endonasal posterior (transclival) approach to tumors of the clival region and ventral posterior cranial fossa. Part 2. Topographic and anatomical aspects and surgical technique]. / Éndoskopicheskii éndonazal'nyi zadnii rasshirennyi (transklival'nyi) dostup k opukholiam oblasti skata cherepa i ventral'nykh otdelov zadnei cherepnoi iamki. Chast' 2. Topografo-anatomicheskie aspekty i operativnaia tekhnika.

PURPOSE: to present the main topographic and anatomical features of the clivus and adjacent structures for improving and optimizing the extended endoscopic transnasal posterior (transclival) approach in removal of clival and ventral posterior cranial fossa lesions. MATERIAL AND METHODS: We performed a topographic and anatomical study of 25 cadaver heads, the vascular bed of which was filled with colored silicone using the original technique for visualizing the bed features and individual variability. RESULTS: We present the main anatomical landmarks necessary for performing the extended endoscopic endonasal posterior approach. Superior, medial, and inferior transclival approaches provide access to the anterior surface of the upper, middle, and lower neurovascular complexes of the posterior cranial fossa. CONCLUSION: The endoscopic transclival approach can be used to reach ventral posterior cranial fossa lesions. The endoscopic transnasal transclival approach is an alternative to transcranial approaches to clival lesions.

Full endoscopic endonasal transclival approach: meningioma attached to the ventral surface of the brainstem.

BACKGROUND: Intracranial meningiomas without dural attachment (MWODA) are rare entities. We present the first case published, to the best of our knowledge, regarding a MWODA attached to the ventral surface of the brainstem. This location makes the patient subsidiary to treatment through an expanded endonasal transclival approach. CLINICAL PRESENTATION: A 16-year-old female with suspected diagnosis of recurrence of a clear cell meningioma (CCM) at a distance from the initial lesion, located on the premedullary cistern. The patient underwent a pure endoscopic low transclival approach. The attachment to the ventral surface of the brainstem was confirmed intraoperatively. Postoperative MRI confirmed gross total resection and treatment was complemented with adjuvant fractionated stereotactic radiotherapy. No complications related to the procedure were observed. CONCLUSION: MWODA may appear attached to the ventral brainstem. The expanded endonasal approach to the clivus provides a critical anatomical advantage in the treatment of medial lesions, even ventral meningiomas, to the lower cranial nerves. Reconstruction principles must be strictly respected to reduce complications.

Transclival endoscopic approach for prepontine cistern neurocysticercosis causing trigeminal neuralgia: illustrative case.

BACKGROUND: Neurocysticercosis (NCC) is a public health problem in most of the world. Approximately 50 million people worldwide experience this disease, and it remains one of the most important causes of neurological morbidity. Extraparenchymal NCC (basal cisterns) is associated with high rates of morbidity and mortality. Currently, minimally invasive approaches, including the endoscopic endonasal approach, are used with good functional results. OBSERVATIONS: A 25-year-old patient presented with headache and pain in the left hemiface. Magnetic resonance imaging (MRI) showed cystic lesions in the prepontine basal cisterns compressing and displacing the left trigeminal nerve. The cysticercal lesions were excised using a transclival endoscopic approach. There were no complications during surgery, and pathology confirmed the diagnosis of NCC. The pain subsided after surgery. No residual cysts were observed on control MRI. LESSONS: Minimally invasive approaches can be used to treat tumor and infectious problems of the skull base, as in this case, with good functional results. https://thejns.org/doi/10.3171/CASE24223.

Long-Term Outcomes after Multimodal Treatment for Clival Chordoma: Efficacy of the Endonasal Transclival Approach with Early Adjuvant Radiation Therapy.

This study investigates the long-term outcomes of clival chordoma patients treated with the endonasal transclival approach (ETCA) and early adjuvant radiation therapy. A retrospective review of 17 patients (2002-2013) showed a 10-year progression-free survival (PFS) rate of 67.4%, with the ETCA group showing fewer progressions and cranial neuropathies than those treated with combined approaches. The ETCA, a minimally invasive technique, provided a similar extent of resection compared to conventional skull-base approaches and enabled safe delivery of high-dose adjuvant radiotherapy. The findings suggest that ETCA is an effective treatment for centrally located clival chordomas.

Endoscopic Extended Transclival Approach for Lower Clival Meningioma.

We present a case of lower clival meningioma treated with the endoscopic transnasal extended transclival approach.1,2 A 52-year-old woman with a large clival meningioma had undergone transcondylar approach3 and posterolateral approach4 in the previous hospital and presented with mild swallowing difficulty and hypoglossal nerve palsy in the right side. The tumor compressed the medulla oblongata, involving the lower cranial nerves bilaterally and facial nerve on the right side. The patient underwent the endoscopic transnasal extended transclival approach (Video 1). The anterior aspect and the floor of the sphenoid sinus were drilled off, and the sella, bilateral carotid prominences, and clivus were revealed. The clival bone and jugular tubercles were then removed. The dura mater on the clivus was widely exposed and coagulated to manage the arterial blood supply for the tumor. The dura was incised in a rectangular shape, and the successful mass reduction was achieved except for the tumor components strongly adherent to the lower cranial nerves on the right side. For skull base reconstruction, fascia lata was placed in and on the dural defect with multilayer fashion and the pharyngeal flap was rectified. The balloon catheter was inserted and inflated to compress the fascia and pharyngeal flap, and lumber drainage with the pressure-control valve system was performed for 72 hours.5 After surgery, her symptoms gradually improved. The residual tumor was treated with Gamma Knife surgery. The tumor was successfully controlled for 3 years, and the patient didn't show any neurologic symptom at the last follow-up.

Basilar Artery Injury During Endonasal Surgery: Stepwise to Control Bleeding.

BACKGROUND: Intraoperative injury during endoscopic endonasal surgery of the carotid artery has been previously described in the literature. However, the accidental damage of the basilar artery in such scenario is not defined. OBJECTIVE: To define the protocol of action for massive bleeding from an artery in the posterior fossa. METHODS: The reported patient was diagnosed with a partially calcified clival chordoma featured by a huge intradural component. An endoscopic endonasal transpterygoid transclival approach was selected for the treatment of this tumor. During the surgical procedure, the basilar artery injury was injured, causing intense bleeding. We present and discuss the surgical maneuvers that could save a patient's life after this dramatic complication. RESULTS: Different techniques were performed in order to control the massive bleeding, including injection of hemotastic matrix with thrombin (Floseal©), bipolar coagulation, and vessel reconstruction by means of a vascular clip. Finally, an autologous muscle graft reinforced with an overlying fibrin sealant patch (Tachosil©) was chosen and was an effective technique. Afterwards, the patient was treated with a flow diverter device to occlude an iatrogenic pseudoaneurysm. A monoplegia of the right upper limb was the only remarkable sequel 6 mo after surgery. CONCLUSION: The muscle graft together with the coordinated action with interventional neuroradiology for the reconstruction of the vessel are possibly the best options to try to preserve the neurological function. In such a scenario, the assumption of potential ischemic events prevails over the intraoperative death of the patient.

Anatomical location of the vertebrobasilar junction: computed tomography morphometrics for planning endoscopic transsphenoidal transclival approaches.

BACKGROUND: The aim of this study was to determine the anatomical localisation and morphometry of vertebrobasilar junction (VBJ) by computed tomography (CT) images which may be helpful in planning the correct procedure before surgery such as endoscopic transsphenoidal transclival approach to the retroclival space. MATERIALS AND METHODS: Vertebrobasilar junction level was determined on axial, coronal reformat and sagittal reformat images. Clivus length, the distances of the VBJ to the upper and lower end of the clivus and to the bottom of the sphenoid sinus were measured. In addition, the position and distance of the VBJ relative to the midline were measured. The vertebral artery dominance was determined and the position of VBJ relative to the midline was evaluated. RESULTS: When compared by gender, 1, a, b and c values were significantly longer in males than in females (p < 0.05). The location of the bottom of the sphenoid sinus was higher than the VBJ level in 263 (98.1%) cases, equal to the VBJ level in 1 (0.4%) case, and lower than the VBJ level in 4 (1.5%) cases. There was no statistically significant difference between the distances to the midline when the VBJs with right and left localisation were compared (p > 0.05). A statistically significant relationship was found between vertebral artery predominance and localisation of VBJ relative to the midline (p < 0.001). CONCLUSIONS: Careful perusal of CT images and the described VBJ morphometrics can help in accurate procedure planning to avoid basilar artery injury.

Endoscopic Endonasal Approach to Foramen Magnum Meningioma: Two-Dimensional Surgical Video.

Even for the most experienced neurosurgeons, foramen magnum meningiomas represent a surgical challenge owing to their delicate position surrounded by the brainstem, lower cranial nerves, and vertebral arteries. The treatment goal is gross total resection, but choosing the most appropriate approach is crucial. Basically, 3 surgical approaches are commonly used: posterolateral approach (far-lateral), anterolateral approach (extreme-lateral), and posterior midline approach. However, over the years, skull base surgery has evolved from standard open craniotomies to the use of microscopes and, more recently, to the development of endoscopic techniques. The endoscopic endonasal approach (EEA) permits a direct extradural route without brain retraction and shorter postoperative recovery. In contrast to the oral route, the soft palate and retropharyngeal soft tissues are preserved, allowing patients to resume a regular diet on the first postoperative day. Despite the advantages, the EEA is yet not widely used for treating foramen magnum meningiomas, even in cases where EEA use is possible. The EEA is feasible especially in cases with no vascular encasements and with a limited inferior extension allowing minimal manipulation of lower cranial nerves. Care must be taken with tumors with a more lateral and caudal extension (below the tip of the odontoid process), when a far lateral approach may be the best approach. In this surgical Video 1, we present the surgical details with a stepwise narrative of the EEA for ventrolateral foramen magnum meningiomas through an illustrative case of a 48-year-old woman. Institutional informed consent was obtained for surgery and publication of this video.

The Eustachian Tube as a Landmark for Early Identification of the Abducens Nerve During Endonasal Transclival Approaches.

BACKGROUND: Expanded endonasal approaches have the potential to injure the abducens nerve (cranial nerve [CN] VI). The nerve's root entry zone (REZ) and cisternal segment (CS) are particularly prone to injury during the clivus resection and dural incision of transclival approaches. OBJECTIVE: To investigate the role of the eustachian tube (ET) as a surgical landmark for the REZ and CS of CN VI. METHODS: Transclival expanded endonasal approaches were performed bilaterally in 6 fresh-frozen cadaveric specimens (12 sides). Anatomic relationships between ET and CN VI were documented with neuronavigation. RESULTS: The mean vertical distance from the inferior brainstem point to the horizontal projection of CN VI REZ, CS midpoint, and interdural segment (ID) were 26.38 mm (95% confidence interval [CI] 17.36-35.4), 38.61 mm (95% CI 25.61-51.61), and 42.68 mm (95% CI 30.14-55.22), respectively. The relative vertical distance from the ET to the horizontal projections of the REZ, CS midpoint, and its ID were 6.43 mm (95% CI 3.25-9.61), 18.66 mm (95% CI 11.52-25.8), and 22.72 mm (95% CI 16.02-29.42), respectively. In the axial plane the angles between the ET and (1) the REZ and its midline horizontal projection point, (2) the midpoint and its midline horizontal projection point, and (3) ID and its midline horizontal projection point were 9.81 ± SD 5.20°, 18.50 ± SD 4.87°, and 24.71 ± SD 6.21°, respectively. CONCLUSION: The ET may serve as a constant landmark to reliably predict the position of the REZ and CS of CN VI.

Endoscopic Endonasal Transclival Approach to Tumors of the Clivus and Anterior Region of the Posterior Cranial Fossa (Results of Surgical Treatment of 136 Patients).

INTRODUCTION: With the introduction into the neurosurgical practice of minimally invasive methods using endoscopic techniques, it became possible to effectively remove hard-to-reach tumors, including central tumors of the anterior region of the posterior cranial fossa. OBJECTIVE: To analyze the results of surgical treatment of patients with various centrally located tumors of the base of the skull that extend into the anterior region of the posterior cranial fossa using the endoscopic endonasal transclival approach. METHODS: The personal surgical experience of the first author is 136 patients with various tumors (e.g., chordomas, meningiomas, pituitary adenomas, and fibrous dysplasia). RESULTS: Radicality of tumor removal was total 61.03%; subtotal 25%; partial 13.23%; and insufficient removal 0.74%. Postoperative cerebrospinal fluid leaks occurred in 9 cases (6.62%) and meningitis in 13 cases (9.56%). In 2 cases, surgical treatment had a lethal outcome (1.47%). CONCLUSIONS: The endoscopic endonasal transclival approach can be used to obtain access to centrally located skull base tumors. This approach allows for a radical and low-risk removal of various skull base tumors of central localization that, until recently, were considered to be almost inoperable.

Endoscopic Endonasal Transclival Approach to Tumors of the Clivus and Anterior Region of the Posterior Cranial Fossa: An Anatomic Study.

OBJECTIVE: To present the basic topographic and anatomic features of the clivus and adjacent structures with an objective of possible improvements and optimization of the extended endoscopic endonasal posterior (transclival) approach when removing tumors of the clivus and anterior regions of the posterior cranial fossa. MATERIALS AND METHODS: A craniometric study was conducted on 125 human skulls. A topographic anatomic study was conducted on 25 cadaver head specimens with arterial and venous beds stained with colored silicone, according to the method developed by us, to visualize its features and individual variability. RESULTS: The most important anatomic features of the external and internal regions of the clivus and the adjacent neural and vascular structures were analyzed. An accessible zone for the most effective transclival approach to the posterior cranial fossa is also specified. CONCLUSION: The endoscopic endonasal transclival approach can be used to obtain access to centrally located tumors of the posterior cranial fossa. It is an alternative to transcranial approaches in the surgical treatment of tumors of the clivus.

Endoscopic endonasal transclival removal of tumors of the clivus and anterior region of the posterior cranial fossa (results of surgical treatment of 140 patients).

BACKGROUND: Until recently, tumors of the clivus and the anterior region of the posterior cranial fossa were considered extremely difficult to access and often inoperable using standard transcranial approaches. With the introduction into the neurosurgical practice of minimally invasive methods utilizing endoscopic techniques, it became possible to effectively remove hard-to-reach tumors, including central tumors of the anterior region of the posterior cranial fossa. METHODS: From 2008 to the present time, the inpatient institution has operated on 140 patients with various tumors of the base of the skull, localized to the clivus and anterior region of the posterior cranial fossa (65 men and 75 women). The age of patients ranged from 3 to 74 years. Tumor distribution according to the histopathological features was as follows: chordomas, 103 (73.57%); meningiomas, 12 (8.57%); pituitary adenomas, 9 (6.43%); fibrous dysplasia, 4 (2.86%); cholesteatoma, 3 (2.14%); craniopharyngiomas, 2 (1.43%); plasmacytomas, 2 (1.43%); and other tumors (giant cell tumor, neurohypophyseal glioma, osteoma, carcinoid, chondroma), 5 (3.57%). The tumors had the following size distribution: giant (more than 60 mm), 35 (25%); large (35-59 mm), 83 (59.3%); medium (21-35 mm), 21 (15%); and small (less than 20 mm), 1 (0.7%). In 11 cases, intraoperative monitoring of the cranial nerves was performed (21 cranial nerves were identified). RESULTS: Upper, middle, and lower transclival approaches provide access to the anterior surface of the upper, middle, and lower neurovascular complexes of the posterior cranial fossa. The chordoma cases were distributed as follows according to extent of removal: total removal, 68 (66.02%); subtotal removal, 25 (24.27%); and partial removal, 10 (9.71%). The adenomas of the pituitary gland were removed totally in 6 cases, subtotally in 1 case and partially in 2 cases. The meningiomas were removed totally in 1 case, subtotally in 5 cases, and partially in 5 cases, with less than 50% of the tumor removed in 1 case. Other tumors (cholesteatoma, craniopharyngioma, fibrous dysplasia, giant cell tumor, glioma of the neurohypophysis, osteoma, plasmacytoma, carcinoid, and chondroma) were removed totally in 9 cases and subtotally in 7 cases. Postoperative CSF leaks occurred in 9 cases (6.43%) and meningitis in 13 cases (9.29%). Oculomotor disorders developed in 19 patients (13.57%), 12 of which regressed during the period from 4 to 38 days after surgery, and 7 of which were permanent. In 2 cases, surgical treatment had a lethal outcome (1.43%). CONCLUSION: The endoscopic endonasal transclival approach can be used to obtain access to the centrally located tumors of the posterior cranial fossa. It is an alternative to transcranial approaches in the surgical treatment of tumors of the clivus. The results of using this approach are comparable with the results of transcranial and transfacial approaches and, in some cases, surpass them in effectiveness. The extended endoscopic endonasal posterior (transclival) approach, considering its minimally invasive nature, allows fora radical and low-risk (in terms of postoperative complications and lethality) removal of various skull base tumors of central localization with the involvement and without the involvement of the clivus, which, until recently, were considered to be almost inoperable.

Assessment of the endoscopic endonasal approach to the basilar apex region for aneurysm clipping.

OBJECTIVEThe expanded endoscopic endonasal approach (EEA) has shown promising results in treatment of midline skull base lesions. Several case reports exist on the utilization of the EEA for treatment of aneurysms. However, a comparison of this approach with the classic transcranial orbitozygomatic approach to the basilar apex (BAX) region is missing.The present study summarizes the results of a series of cadaveric surgical simulations for assessment of the EEA to the BAX region for aneurysm clipping and its comparison with the transcranial orbitozygomatic approach as one of the most common approaches used to treat BAX aneurysms.METHODSFifteen cadaveric specimens underwent bilateral orbitozygomatic craniotomies as well as an EEA (first without a pituitary transposition [PT] and then with a PT) to expose the BAX. The following variables were measured, recorded, and compared between the orbitozygomatic approach and the EEA: 1) number of perforating arteries counted on bilateral posterior cerebral arteries (PCAs); 2) exposure and clipping lengths of the PCAs, superior cerebellar arteries (SCAs), and proximal basilar artery; and 3) surgical area of exposure in the BAX region.RESULTSExcept for the proximal basilar artery exposure and clipping, the orbitozygomatic approach provided statistically significantly greater values for vascular exposure and control in the BAX region (i.e., exposure and clipping of ipsilateral and contralateral SCAs and PCAs). The EEA with PT was significantly better in exposing and clipping bilateral PCAs compared to EEA without a PT, but not in terms of other measured variables. The surgical area of exposure and PCA perforator counts were not significantly different between the 3 approaches. The EEA provided better exposure and control if the BAX was located ≥ 4 mm inferior to the dorsum sellae.CONCLUSIONSFor BAX aneurysms located in the retrosellar area, PT is usually required to obtain improved exposure and control for the bilateral PCAs. However, the transcranial approach is generally superior to both endoscopic approaches for accessing the BAX region. Considering the superior exposure of the proximal basilar artery obtained with the EEA, it could be a viable option when surgical treatment is considered for a low-lying BAX or mid-basilar trunk aneurysms (≥ 4 mm inferior to dorsum sellae).