[Transoral approach in surgery for chordomas extending into craniovertebral junction: a systematic review of the literature]. / Transoral'nyi dostup v khirurgii khordom, rasprostranyayushchikhsya v oblast' kraniovertebral'nogo perekhoda: sistematicheskii obzor literatury.

To date, treatment of chordomas involves maximal tumor resection followed by proton therapy. Various approaches are used depending on location of tumor (transcranial and through natural anatomical openings (nose, mouth), as well as their combinations). Although transoral approach has been introduced into neurosurgical practice for a long time, it is routinely used in patients with chordoma only in certain hospitals in the world. OBJECTIVE: To analyze postoperative outcomes in patients with chordomas of skull base and craniovertebral joint after transoral surgery. MATERIAL AND METHODS: We analyzed literature data devoted to patients with chordomas of skull base and craniovertebral joint after transoral surgery or another approach combined with transoral access. Among 111 primary articles, we selected 38 manuscripts including description of 109 patients with skull base chordoma who underwent transoral surgery or combination of approaches including transoral one. RESULTS: Gross total resection was achieved in 45.9% (n=50) of cases including 1 patient after en bloc resection. Subtotal resection was carried out in 28.4% of cases, partial - in 24.8%, biopsy - in 0.9% of cases. The complication rate in this group was 30%. The most common events were swelling of the tongue (10%) and diastasis of posterior pharyngeal wall sutures (8.2%) that required redo surgery. CSF leakage and meningitis were rare (1.8% and 3.6%, respectively). CONCLUSION: Transoral access allows for gross total resection of midline tumors with low incidence of severe complications. Combination of transoral and transcranial approaches is advisable to increase extent of resection.

[Endoscopic transnasal resection of clival meningiomas]. / Rezul'taty endoskopicheskogo transnazal'nogo udaleniya meningiom oblasti skata.

BACKGROUND: Surgical treatment of ventral and ventrolateral meningiomas of posterior cranial fossa is difficult in modern neurosurgery. This is due to peculiarities of approach to these areas and concentration of critical structures (cranial nerves and great vessels). Currently, endoscopic transnasal approach to these meningiomas allows partial, and in some cases, total resection. However, this technique is not widespread. OBJECTIVE: To analyze the world literature data on postoperative outcomes in patients with clival and petroclival meningiomas after endoscopic transnasal resection. MATERIAL AND METHODS: We analyzed 22 articles representing treatment of 61 patients with clival and petroclival meningiomas. RESULTS: Total or near-total resection was achieved in 22.9% of cases, subtotal resection - 40.9%, partial resection - 26.2% (data were not provided in other cases). Even partial and subtotal resection leads to significant regression of symptoms. CONCLUSION: Endoscopic transnasal surgery is a full-fledged alternative to transcranial approaches in surgical treatment of clival meningiomas. It is also an additional option for patients with petroclival meningiomas after ineffective transcranial approaches. Transnasal tumor shrinkage and devascularization lead to brainstem decompression, regression of hydrocephalus and baseline clinical symptoms.

[Predictors of postoperative remission of acromegaly. (Experience of the Burdenko Neurosurgical Center)]. / Prediktory posleoperatsionnoi remissii akromegalii. (Opyt FGAU «NMITs neirokhirurgii im. akad. N.N. Burdenko¼).

BACKGROUND: Treatment of acromegaly is still an unresolved problem. Overall postoperative remission rate ranges from 34 to 85%. These values are better for microadenomas (75-90%) and worse for macroadenomas (45-70%). Identification of predictors of acromegaly remission after surgical treatment is an urgent objective to improve the quality of medical care for these patients. OBJECTIVE: To analyze postoperative freedom from acromegaly and predictors of remission. MATERIAL AND METHODS: A retrospective single-center study included 227 patients with acromegaly who underwent resection of pituitary adenoma between August 2018 and August 2021. RESULTS: Remission (normalization of serum IGF-1) was achieved in 65 (55%) patients. Growth hormone and IGF-1 index decreased after surgery in all patients. Mean preoperative serum growth hormone was 12.45 [6.88, 29.85] ng/ml, early postoperative concentration - 1.54 [0.80, 3.38] ng/ml, in delayed period - 1.15 [0.57, 3.80] ng/ml. Mean IGF-1 index was 2.18 [1.69, 2.71], 1.47 [0.99, 1.90] and 0.99 [0.74, 1.43], respectively. CONCLUSION: Significant predictors of acromegaly remission after neurosurgical treatment were age, preoperative level of growth hormone, tumor size and location, growth hormone and IGF-1 index in early postoperative period and residual tumor after surgery. Multivariate analysis revealed a significant association of acromegaly remission with small tumor size, low postoperative level of growth hormone and no residual tumor within 3-6 month after surgery.

[Endoscopic transnasal resection of clival meningiomas]. / Endoskopicheskoe transnazal'noe udalenie meningiom skata.

Treatment of clival meningiomas is still one of the unresolved issues in modern neurosurgery. There are several treatment strategies. These ones include various combinations of follow-up, surgical CSF drainage, tumor resection and radiotherapy. OBJECTIVE: To assess postoperative outcomes in patients with clival meningiomas. MATERIAL AND METHODS: We analyzed 18 patients with large or giant clival meningiomas. RESULTS: We assessed extent of resection using the scale by G. Frank and E. Pasquini (2002): total resection - 95-100%, subtotal - 80-95%, partial - 50-80%, extended biopsy - <50% of tumor. Total resection was achieved in 1 patient (5.5%), subtotal - 5 (27.8%), partial - 12 (66.7%). At the same time, brainstem decompression and regression of hydrocephalus were observed in all cases. Fourteen patients were followed-up. Median follow-up was 8.5 months. Seventeen patients underwent radiotherapy due to predominant partial and subtotal resection. Total focal dose ranged from 50 to 57 Gy in standard fractionation mode. None patient had residual tumor enlargement throughout the follow-up period. There were no lethal outcomes. CONCLUSION: Endoscopic transnasal access to clival meningiomas in appropriate anatomical features of tumor and surrounding structures is a full-fledged alternative to transcranial treatment in these patients. This approach provides total resection and brainstem decompression. These facts increase life expectancy without deterioration of the quality of life.

[Minimally invasive surgery for invaginated CII odontoid process]. / Miniinvazivnaya khirurgiya invaginirovannogo zubovidnogo otrostka CII pozvonka.

Odontoidectomy is indicated for anterior compression of the brainstem by invaginated odontoid process. This procedure can currently be performed via transoral microsurgical and transnasal endoscopic access. OBJECTIVE: To analyze the results of endoscopic transnasal odontoidectomy. MATERIAL AND METHODS: We assessed treatment outcomes in 10 patients with anterior compression of the brainstem by invaginated odontoid process. All patients underwent endoscopic transnasal odontoidectomy. RESULTS: Brainstem decompression was achieved in all cases. CONCLUSION: Currently, endoscopic transnasal approach is gradually replacing the transoral one in some patients requiring anterior odontoidectomy. Analysis of literature data reflects the development of this technique taking into account various features of surgical treatment including optimization of dimensions of surgical field, attempts to perform C1-sparing surgeries and analysis of sufficient size of trepanation. Nasopalatine and nasoclival lines are used to select optimal access. Nevertheless, the choice of access depends on equipment of the hospital and surgical experience in most cases.

[Awake percutaneous tracheostomy in neurosurgical patients: clinical cases and literature review]. / Punktsionno-dilatatsionnaya trakheostomiya u patsientov s neirokhirurgicheskoi patologiei, vypolnennaya na fone samostoyatel'nogo dykhaniya cherez estestvennye dykhatel'nye puti: klinicheskie nablyudeniya i obzor literatury.

Transoral or combined transnasal-transoral approach is sometimes used for tumor resection in patients with skull base and vertebral neoplasms. In such cases, percutaneous tracheostomy before surgical intervention is advisable. Tracheostomy facilitates surgical access, eliminates intraoperative risk of endotracheal tube kinking and provides airway protection from aspiration in early postoperative period in case of bulbar disorders, hypopharynx and tongue edema. The authors present two patients with massive proliferation of pathological tissue in nasopharynx and oropharynx that excluded tracheal intubation before tracheostomy. These patients underwent awake percutaneous tracheostomy.

[Endoscopic transnasal approach in surgical treatment of petrous temporal bone cholesteatoma extending towards the clivus. Three clinical observations and literature review]. / Endoskopicheskii transnazal'nyi dostup v khirurgicheskom lechenii kholesteatom piramidy visochnoi kosti, rasprostranyayushchikhsya v oblast' skata. Tri klinicheskikh nablyudeniya i obzor literatury.

Petrous temporal bone Cholesteatoma is widely described in the literature and accounts for up to 9% of all neoplasms of this localization. These cholesteatomas rarely spread towards the clivus. Isolated clival cholesteatomas are described only as single cases. There is currently no consensus on the choice of surgical approach for resection of similar neoplasms. OBJECTIVE: To demonstrate the possibilities of endoscopic transnasal approach in surgery for clival and petrous cholesteatoma. MATERIAL AND METHODS: This article presents 3 clinical cases: 2 patients with apical cholesteatoma of petrous part of temporal bone extending to the clivus and 1 patient with massive petrous temporal bone cholesteatoma extending towards the clivus according to the classification of Sanna M. All patients underwent endoscopic transnasal surgery. RESULTS AND CONCLUSION: In our opinion, endoscopic transnasal approach is optimal for resection of similar neoplasms. Total and subtotal resection was performed in 2 and 1 case, respectively. However, there are certain limitations of this approach in accessing the most lateral parts of the neoplasm. Nevertheless, endoscopic transnasal approach ensures resection of petrous temporal bone cholesteatoma extending to the clivus without the risk of damage to acoustic-facial cranial nerves. It is especially significant in patients without their baseline dysfunction.

[Anatomy of anterior craniovertebral junction in endoscopic transnasal approach]. / Anatomiya perednikh otdelov kraniovertebral'nogo sochleneniya pri endoskopicheskom transnazal'nom dostupe.

Modern achievements in endoscopic technologies ensure extending the indications for endoscopic transnasal approach in skull base surgery. Knowledge on topographic anatomy of craniovertebral junction is a prerequisite for surgical interventions in this area. Transnasal endoscopic surgery of craniovertebral junction is a relatively new field. Therefore, this manuscript and similar anatomical studies are extremely important for neurosurgeons.

Cell therapy assisted autotransplantation of olfactory tract into the optic nerve: A potential treatment for optic neuropathy.

Optic neuropathy is an invaliding pathology with diverse clinical manifestation and varying causes. Current understanding of etiopathological aspects of optical neuropathy does not provide an effective treatment protocol. In this article we discuss existing treatment methods, and their effectiveness, evaluated depending on disease etiology. The olfactory tract is a source of olfactory ensheating cells, whose unique properties can have treatment potential in correction of nerve degeneration. Transplantation of an olfactory tract graft into the damaged optic nerve is a technically achievable intervention, though anatomical limitations exist in the proposed surgical access. Optic nerve defects can also be potentially treated with axon growth stimulating therapy (Zymosan and CTP-cAMP). Optic neuropathy can be potentially cured by autotransplantation of a portion of the olfactory tract. Neuroanatomical and histomorphological aspects of olfactory tract autotransplantation into the damaged optic nerve are provided. Feasibility, technical and anatomical features, potential setbacks and limitations are discussed. Anatomical limitations exist, but with current neurosurgical technology can be overcome. Regenerative potential of olfactory tract glial cells plays an important role in nerve restoration and can play a crucial role in further understanding of nerve degeneration treatment.

[Neurosarcoidosis of the anterior visual pathway (a case report and literature review)]. / Neirosarkoidoz perednego zritel'nogo puti (klinicheskie nabliudeniia i obzor literatury).

Sarcoidosis is a multisystem granulomatous disorder of unknown nature. Patients often present with pulmonary, skin, eye, and orbital lesions. Involvement of the central nervous system (CNS) is accompanied by granulomatous leptomeningitis and damage to the basal brain structures with formation of granulomas near the cranial nerves, hypothalamus, pituitary gland, cavernous sinuses, optic chiasm, and intracranial optic nerves. The optic nerves can be affected independently of the other CNS regions, which may be the first manifestation of the disease. The article presents two clinical cases of sarcoidosis affecting the anterior visual pathway. Diagnosis of the disease was associated with certain difficulties. A biopsy revealed a sarcoidosis lesion.

[Anterior stabilization of the CI-CIII vertebrae after transoral removal of an aggressive aneurysmal bone cyst of the CII vertebra (a case report and literature review)]. / Peredniaia stabilizatsiia SI-SIII pozvonkov posle transoral'nogo udaleniia agressivnoi anevrizmaticheskoi kisty SII pozvonka (klinicheskoe nabliudenie i obzor literatury).

Treatment of patients with atlantoaxial instability caused by various diseases of the skull base and craniovertebral junction combined with ventral compression of the brainstem is a complex issue that is ambiguously resolved in different ways. We present a case of stepped treatment, the most important component of which was successful transoral removal of an aggressive aneurysmal bone cyst of the CII vertebra with anterior CI-CIII segment stabilization using an individual system, which was performed through the same approach. CLINICAL CASE: A 31-year-old male patient presented with destruction of the CII body and odontoid process affected by an aggressive aneurysmal bone cyst causing disintegration of the CII posterior wall and odontoid process, which clinically manifested by constricted motion and pain in the cervical spine. RESULTS: Three-step surgical treatment was performed. First, we performed a puncture biopsy of the CII body through the submandibular approach as well as posterior occipitospondylodesis with metal instrumentation from the occipital bone level to the CIV vertebra. Two months later, the patient underwent transoral removal of the CII body and odontoid process lesion and anterior CI-CIII segment stabilization using an individual cover metal system through the same approach. Two weeks after the second intervention, the occipitospondylodesis was transformed to a posterior CI-CIII stabilization system. Control CT 8 months after surgery showed the correct position of both stabilization systems. CONCLUSION: The use of individual instrumentation for anterior stabilization of the CI-CIII vertebrae in various diseases of the craniovertebral junction area is an effective and promising technique.

[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.

[A technique of manufacturing anatomical preparations of the human brain based on injecting vessels with colored silicone (a technical note)]. / Sposob izgotovleniia anatomicheskikh preparatov golovnogo mozga cheloveka s in''ektsiei sosudov tsvetnym silikonom (tekhnicheskoe opisanie).

OBJECTIVE: The objective was to produce anatomical preparations by injecting vessels with colored silicone to study the brain and skull base anatomy. MATERIAL AND METHODS: Fresh, undissected, and unfixed cadavers were used. The internal carotid arteries and internal jugular veins were identified on both sides of the neck. The vessels were washed with running water. Then, a complex solution consisting of white silicone rubber, silicone oil (solvent), and a coloring pigment (red and blue pigments) at a ratio of 1:(0.9-1.1):(0.04-0.06), respectively, was prepared. About 30-60 s before injecting the complex solution into the vessels, a catalyst-hardener was added to the solution at a ratio of 1:(0.05-0.07). The complex solution was first introduced into the internal carotid artery until the solution came out from the contralateral internal carotid artery; then, the solution was injected into the internal jugular vein until the solution emerged from the contralateral internal jugular vein. RESULTS: The technique enables quick and high-quality visualization of both large and very small vessels of the brain and skull base. CONCLUSION: The proposed simple and inexpensive technique of manufacturing anatomical preparations improves the quality of training and mastering of microsurgical skills in residents and practicing neurosurgeons.

Cranial nerve monitoring in endoscopic endonasal surgery of skull base tumors (observing of 23 cases).

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.

[Additive technologies in neurosurgery]. / Additivnye tekhnologii v neirokhirurgii.

Modern achievements of technical progress, in particular additive technologies (ATs) and three-dimensional printing, have been increasingly introduced in neurosurgical practice. The increasing complexity of surgical interventions requires thorough planning of surgery and a high level of training of young neurosurgeons. Creation of full-scale three-dimensional models for planning of surgery enables visualization of the anatomical region of interest. Additive technologies are especially extensively used in reconstructive surgery of skull defects. ATs enable fast and efficient solving of the following tasks: - generation of accurate models of the skull and an implant; - development and fabrication of individual molds for intraoperative formation of implants from polymeric two-component materials (e.g., PMMA); - fabrication of individual implants from titanium alloys or polyetheretherketone (PEEK) for further use in surgery.

[Application of intraoperative electromagnetic frameless navigation in transcranial and endoscopic neurosurgical interventions]. / Primenenie bezramnoi sistemy intraoperatsionnoi élektromagnitnoi navigatsii pri transkranial'nykh i éndoskopicheskikh neirokhirurgicheskikh vmeshatel'stvakh.

The paper summarizes the experience in using a system of electromagnetic intraoperative frameless navigation in various neurosurgical pathologies of the brain. The electromagnetic navigation technique was used for 102 operations in 98 patients, including 36 transnasal endoscopic interventions. There were no intraoprtative and postoperative complications associated with the use of the system. In the process of using the system, factors influencing the accuracy of navigation and requiring additional control by the surgeon were identified. PURPOSE: The study purpose was to evaluate the use of electromagnetic navigation in surgical treatment of patients with various brain lesions. MATERIAL AND METHODS: The system of electromagnetic navigation was used for 102 operations in 98 patients (42 males and 56 females, including 18 children; median age, 34.8 years (min, 2.2 years; max, 69 years)) in the period from December 2012 to December 2016. In 36 patients, the system was used for endoscopic interventions. In 19 patients, electromagnetic navigation was used in combination with neurophysiological monitoring. RESULTS: In our series of cases, the frameless electromagnetic navigation system was used in 66 transcranial operations. The mean error of navigation was 1.9±0.5 mm. In 5 cases, we used the data of preoperative functional MRI (fMRI) and tractography for navigation. At the same time, in all 7 operations with simultaneous direct stimulation of the cortex, there was interference and significant high-frequency noise, which distorted the electrophysiological data. A navigation error of more than 3 mm was associated with the use of neuroimaging data with an increment of more than 3 mm, image artifacts from the head locks, high rate of patient registration, inconsequence of touching points on the patient's head, and unsatisfactory fixation to the skin or subsequent displacement of a non-invasive localizer of the patient. In none of the cases, there was a significant effect of standard metal surgical tools (clamps, tweezers, aspirators) located near the patient's head on the navigation system. In two cases, the use of massive retractors located near the patient's localizer caused noise in the localizer and navigation errors of more than 10 mm due to significant distortions of the electromagnetic field. Thirty-six transnasal endoscopic interventions were performed using the electromagnetic frameless navigation system. The mean navigation error was 2.5±0.8 mm. CONCLUSION: In general, electromagnetic navigation is an accurate, safe, and effective technique that can be used in surgical treatment of patients with various brain lesions. The mean navigation error in our series of cases was 1.9±0.5 mm for transcranial surgery and 2.5±0.8 mm for endoscopic surgery. Electromagnetic navigation can be used for different, both transcranial and endoscopic, neurosurgical interventions. Electromagnetic navigation is most convenient for interventions that do not require fixation of the patient's head, in particular for CSF shunting procedures, drainage of various space-occupying lesions (cysts, hematomas, and abscesses), and optimization of the size and selection of options for craniotomy. In repeated interventions, disruption of the normal anatomical relationships and landmarks necessitates application of neuronavigation systems in almost mandatory manner. The use of electromagnetic navigation does not limit application of the entire range of necessary intraoperative neurophysiological examinations at appropriate surgical stages. Succession in application of neuronavigation should be used to get adequate test results.

[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.

[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.

[Endoscopic transnasal surgery for giant fibrous dysplasia of the skull base, spreading to the right orbital cavity and nasopharynx (a case report and literature review)]. / Endoskopicheskaya transnazal'naya khirurgiya gigantskoi fibroznoi displazii osnovaniya cherepa, rasprostranyayushcheisya v polost' pravoi orbity i nosoglotku (opisanie nablyudeniya i obzor literatury).

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.