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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., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Preservation of anatomic integrity and function of the cranial nerves during the removal of skull base tumors is one of the most challenging procedures in endoscopic endonasal surgery. It is possible to use intraoperative mapping and identification of the cranial nerves in order to facilitate their preservation.The purpose of this study was to evaluate the effectiveness of intraoperative trigger electromyography in prevention of iatrogenic damage to the cranial nerves., Methods: Twenty three patients with various skull base tumors (chordomas, neuromas, pituitary adenomas, meningiomas, cholesteatomas) underwent mapping and identification of cranial nerves during tumor removal using the endoscopic endonasal approach in Department of Neurooncology of Federal State Autonomous Institution "N.N. Burdenko National Medical Research Center of Neurosurgery" of the Ministry of Health of the Russian Federation from 2013 to 2018. During the surgical interventions, mapping and identification of the cranial nerves were carried out using electromyography in triggered mode. The effectiveness of the method was evaluated based on a comparison with a control group (41 patients)., Results: In the main group of patients, 44 nerves were examined during surgery using triggered electromyography. During the study, the III, V, VI, VII, and XII cranial nerves were identified intraoperatively. Postoperative cranial nerve deficiency was observed in 5 patients in the study group and in 13 patients in the control group. The average length of hospitalization was 9 days., Conclusion: We did not receive statistically significant data supporting the fact that intraoperative identification of cranial nerves using trigger electromyography reduces the incidence of postoperative complications in the form of cranial nerve deficits ( p  = 0.56), but the odds ratio (0.6) suggests a less frequent occurrence of complications in the study group.Based on our experience, the trigger electromyography methodology appears quite promising and requires further research., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (© The Author(s) 2018.)

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., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (© The Author(s) 2018.)

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., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: A thorough understanding of the central nervous system anatomy is a fundamental part of a neurosurgeon's training. Development of novel neurosurgical approaches and optimization of existing ones directly depend on the comprehensive study of topographic anatomy of the head and neck using cadaveric specimens. Staining the vessels of the arterial and venous systems of a cadaveric specimen aids a detailed study of the vascularization of anatomic structures of the brain. Here we describe an alternative expedited method for creating anatomic preparations of the human brain using colored silicone for vascular perfusion staining., Methods: A nonfixed, whole cadaver (with the head intact), without central nervous system pathology, no later than 48 hours after death, is used to prepare the human brain specimen through staining of arterial and venous vessels., Results: Our proposed method provides a fast and inexpensive approach to making anatomic preparations of the human brain with staining of the vascular system. The preparations thus obtained can be used for educational purposes, aiding the study of normal and topographic anatomy of the brain, as well as the development of new microsurgical and/or endoscopic approaches., Conclusions: In experienced hands, our proposed method allows the creation of anatomic preparations relatively fast, at low cost, and with excellent quality., (Copyright © 2018 Elsevier Inc. All rights reserved.)

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.

Objective: To conduct a comparative analysis of 2 groups of patients with skull base chordomas extending onto the craniovertebral junction, who underwent surgical treatment using extracranial approaches with and without craniocervical fusion., Methods: The study group included 29 patients with skull base chordomas, extending to the craniovertebral junction, who were operated on from 2000 to 2015. The patients underwent the following surgical treatment: posterior craniocervical fusion followed by tumor removal using transoral and combined transoral and transnasal approaches. The reference group included 21 patients with the same disease, who underwent tumor removal surgery using the transoral approach without craniocervical fusion., Results: In the study group, in 27.5% of all cases (8 patients), the tumors were removed radically; in 65.5% of all cases (19 patients), the tumors were removed subtotally; and in 7% of all cases (2 patients), the tumors were removed partially. In the reference group, the extent of surgical radicality was as follows: radical, 0%; subtotal, 19% (4 cases); partial, 81% (17 cases)., Conclusions: Use of the proposed surgical technique in clinical practice may help increase the radicality of tumor excisions, decrease the number of postoperative complications, accelerate the rehabilitation process, and increase the quality of life in patients with skull base tumors extending to the craniovertebral junction., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Introduction: Intraoperative identification of cranial nerves is crucial for safe surgery of skull base tumors. Currently, only a small number of published papers describe the technique of trigger electromyography (t-EMG) in endoscopic endonasal removal of such tumors., Objective: To assess the effectiveness of t-EMG in preventing intraoperative cranial nerve damage in endoscopic endonasal surgery of skull base tumors., Materials and Methods: Nine patients were operated on using the endoscopic endonasal approach within a 1-year period. The tumors included large skull base chordomas and trigeminal neurinomas localized in the cavernous sinus. During the surgical process, cranial nerve identification was carried out using monopolar and bipolar t-EMG methods. Assessment of cranial nerve functional activity was conducted both before and after tumor removal., Results: We mapped 17 nerves in 9 patients. Third, fifth, and sixth cranial nerves were identified intraoperatively. There were no cases of postoperative functional impairment of the mapped cranial nerves. In one case we were unable to get an intraoperative response from the fourth cranial nerve and observed its postoperative transient plegia (the function was normal before surgery)., Conclusion: t-EMG allows surgeons to control the safety of cranial nerves both during and after skull base tumor removal., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: An extended endoscopic endonasal approach is increasingly used in surgical treatment of space-occupying skull base lesions. The international literature reports only 20 cases of surgical treatment for fibrous dysplasia (PD) of the skull base using the endoscopic endonasal approach. We present our experience with the endoscopic endonasal approach in surgical treatment for giant fibrous dysplasia of the skull base, spreading to the right orbital cavity and nasopharynx., Clinical Case: A 26-year-old male patient presented with cranial pain, Vth nerve dysfunction on the right, right keratopathy. OD=0.2 (near acuity - 0.3), OS=1.0, OD - incomplete eyelid closure of 2 mm, conjunctival injection, mucous discharge, corneal opacity in the lower pole and paracentrally, OS - normal appearance. Severe right-sided exophthalmos (more than 15 mm), impaired nasal breathing on the right, nasal (hemorrhagic) discharge. Magnetic resonance imaging and spiral computed tomography scans revealed a bone density lesion located in the area of the orbit, nasal cavity, maxillary sinus on the right, and labyrinth of the ethmoid bone. The patient underwent endonasal endoscopic resection of the lesion., Results: The lesion was resected totally, which was confirmed by control SCT. Right-sided exophthalmos partially regressed (on the right: exophthalmos of 8 mm; protrusion: OD=23 mm, OS=15 mm; the eyeball was displaced downward and outward). The visual and oculomotor functions did not change. The neurological status remained at the preoperative level., Conclusion: Fibrous dysplasia of the skull base is an extremely rare disease. Modern techniques expand the indications for surgery of giant tumors of the skull base using minimally invasive approaches, in particular the endoscopic endonasal approach.

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.

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.

Unlabelled: Surgical treatment of skull base tumors invading the craniovertebral junction is a complex medical problem due to a high rate of adverse postoperative outcomes in these patients., Aim: The study aim was to optimize surgical treatment in patients with skull base tumors invading the craniovertebral junction., Material and Methods: A comparative analysis of 2 groups of patients was performed. The study group included 28 patients with skull base and craniovertebral junction chordomas who underwent single-stage surgery, including posterior occipitospondylodesis and tumour resection using the transoral and combined transoral and transnasal approaches, in the period between 2000 and 2015. The control group included 21 patients with the same pathology who underwent microsurgery using the transoral approach without occipitospondylodesis in the period between 1990 and 2009., Results: Most of the patients in both groups were operated on at late disease stages when they presented with gross clinical signs. The use of single-stage occipitospondylodesis and transoral skull base tumor removal significantly (compared to the control group) extends indications for surgical treatment of skull base tumors, which were previously considered unresectable, and provides better results., Conclusion: New surgical techniques significantly increase the completeness of tumor resection, decrease the rate of postoperative complications, accelerate the rehabilitation process, and improve the patient's quality of life.

Introduction: Intraoperative identification of the cranial nerves is a useful technique in removal of skull base tumors through the endoscopic endonasal approach. Searching through the scientific literature found one pilot study on the use of triggered electromyography (t-EMG) for identification of the VIth nerve in endonasal endoscopic surgery of skull base tumors (D. San-Juan, et al, 2014)., Aim: The study objective was to prevent iatrogenic injuries to the cranial nerves without reducing the completeness of tumor tissue resection., Material and Methods: In 2014, 5 patients were operated on using the endoscopic endonasal approach. Surgeries were performed for large skull base chordomas (2 cases) and trigeminal nerve neurinomas located in the cavernous sinus (3). Intraoperatively, identification of the cranial nerves was performed by triggered electromyography using a bipolar electrode (except 1 case of chordoma where a monopolar electrode was used). Evaluation of the functional activity of the cranial nerves was carried out both preoperatively and postoperatively., Results: Tumor resection was total in 4 out of 5 cases and subtotal (chordoma) in 1 case. Intraoperatively, the IIIrd (2 patients), Vth (2), and VIth (4) cranial nerves were identified. No deterioration in the function of the intraoperatively identified nerves was observed in the postoperative period. In one case, no responses from the VIth nerve on the right (in the cavernous sinus region) were intraoperatively obtained, and deep paresis (up to plegia) of the nerve-innervated muscles developed in the postoperative period. The nerve function was not impaired before surgery., Conclusion: The t-EMG technique is promising and requires further research.

Objective: the study was aimed at assessment of the efficacy of percutaneous high frequency selective rhizotomy (PHFSR) after failure of conservative treatment of trigeminal neuralgia (TN) in multiple sclerosis (MS)., Material and Methods: A retrospective analysis of 28 patients with TN associated with MS who underwent percutaneous rhizotomy in the period from 2000 to 2014 was performed. All patients were definitely diagnosed with MS according to the McDonald criteria (version of 2001, 2005, and 2010). The patients were divided by age, gender, and the trigeminal nerve branches involved in the process. The patients' condition was evaluated at different times after surgery., Results: Good outcomes in the form of pain syndrome regression were achieved in 100% of the patients. A disease recurrence was observed in 6 (21%) patients during a follow-up period of 3 months to 14 years. Dysesthesia complications occurred in 4 (14%) patients. There were no deaths and severe complications. The percentage of minor complications was low., Conclusion: These data confirm that PHFSR is a safe, repeatable, and effective method of symptomatic neurosurgical treatment of TN associated with MS and may be recommended in the case of failure/intolerance of medication.

Aim: The objective of the study was to develop the tactics of surgical treatment of large and giant pituitary adenomas, spreading into the posterior cranial fossa., Material and Methods: Patients with large hormonally inactive pituitary adenoma, extending to the right cavernous sinus and posterior cranial fossa., Results: The endoscopic endonasal removal a large endo-supra-latero(D)-retrosellar pituitary tumor was conducted. Control MRI shows that the tumor was removed radically. Oculomotor disturbances were observed in the early postoperative period, which significantly regressed within 6 months. The article provides detailed analysis of the world literature on the issue under discussion. Illustrative pre-, intra-, and post-operative photographs, as well as histological preparations are shown., Conclusion: Modern minimally invasive techniques make it possible to remove large pituitary adenomas (and other tumors) of the posterior cranial fossa using endoscopic endonasal approach. Such operations must be carried out at highly specialized institutions by the surgeons who have extensive experience in endoscopic transnasal surgery of skull base tumors.