[Surgical treatment of brain tumors adjacent to corticospinal tract in children]. / Aktual'nye voprosy khirurgicheskogo lecheniya opukholei golovnogo mozga, prilegayushchikh k kortikospinal'nomu traktu u detei.

An urgent problem in modern neurosurgery is resection of brain tumors adjacent to corticospinal tract (CST) due to high risk of its damage and subsequent disability. The main methods for prevention of intraoperative damage to CST are preoperative MR tractography and intraoperative electrophysiological monitoring. Both methods are used in pediatric neurosurgery. We reviewed the PubMed database since 2000 using the following keywords: «tumors of the hemispheres in children¼, «corticospinal tract¼, «MR tractography¼, «intraoperative electrophysiological monitoring¼. We present available literature data on preoperative MR tractography and intraoperative electrophysiological monitoring in children with supratentorial tumors near CST. Algorithm of intraoperative electrophysiological monitoring is often missing or insufficiently described. MR tractography is usually presented in case reports. Researchers do not compare the effectiveness of MR tractography and intraoperative electrophysiological monitoring. In case of MR tractography, a limitation is impossible CST reconstruction in children 2-3 years old. This may be due to unformed pyramidal system in these children. CONCLUSION: Preoperative MR tractography and intraoperative electrophysiological monitoring are valid methods for assessment of CST. Optimal research parameters in children require careful study that will allow objective planning of each stage of preoperative management and increase resection quality for gliomas near CST in children without neurological deterioration.

[Surgical treatment of cervical neurovascular bundle tumors]. / Khirurgicheskoe lechenie bol'nykh s opukholyami sosudisto-nervnogo puchka shei.

OBJECTIVE: To determine the main principles of a patient-oriented individual approach to diagnosis and surgical treatment of cervical neurovascular bundle tumors considering the capabilities of neurosurgical hospital. MATERIAL AND METHODS: There were 92 patients with cervical soft tissue tumors affecting neurovascular bundle. Age of patients ranged from 9 to 81 years (mean 47). There were 65.1% women and 34.9% men. We found chemodectoma (47.4%), neurofibroma (15.8%), neurinoma (13.2%), papillary thyroid cancer (5.3%), salivary gland heterotopia (5.3%), salivary gland adenocarcinoma (5.3%), Hodgkin lymphoma (2.6%), hemangioendothelioma (2.6%) and cavernous lymphangioma (2.6%). Diagnostic algorithm included neurological examinations, Doppler ultrasound of supra-aortic arteries, transcranial ultrasound of cerebral vessels, MRI of cervical soft tissues, CT-AG, MR-AG, CT-perfusion, direct selective angiography. RESULTS: A total of 94 surgical interventions were performed. All surgeries were performed using surgical optics and neurophysiological monitoring of cranial nerves IX, X, XII. We chose resection technique depending on localization, histological features and blood supply of tumor. En-bloc resection was performed in 46 cases, removal of fragments - in 23 cases, intracapsular resection of tumor followed by resection of the capsule - in 26 cases. Total and subtotal resection was performed in 68 (72%) and 23 (24%) cases, respectively. Three (4%) patients underwent partial resection of infiltrative tumors for carotid artery decompression and histological analysis. In 76% of cases, baseline symptoms of disease regressed after surgery. Persistent moderate bulbar disorders were observed in 16 patients (17%). Ischemic complications with additional surgical interventions were observed in 2 cases. CONCLUSION: Patients with cervical soft tissue tumors require individual approach regarding choosing the optimal surgical treatment including possible preoperative embolization of tumor, en-bloc or intracapsular resection and carotid artery repair.

[Intraoperative visual evoked potential recording in occipital tumor surgery]. / Udalenie opukholei zatylochnoi doli s primeneniem intraoperatsionnoi registratsii korkovykh zritel'nykh vyzvannykh potentsialov.

Currently, visual field defects are considered as an inevitable consequence of occipital lobe surgery. However, recent advances in neuroimaging techniques, such as diffusion tensor tractography allowing better visualization of optic radiation and its relationship with occipital lobe tumors, as well as intraoperative monitoring of cortical visual evoked potentials (cVEPs) can contribute to correct planning of surgery and minimizing the risk of visual field defects after surgery. OBJECTIVE: To evaluate the effectiveness of intraoperative monitoring of cVEP in patients with occipital lobe tumors. MATERIAL AND METHODS: Ten patients with occipital lobe tumors have undergone surgery with neurophysiological monitoring since 2020. Mean age of patients was 57 years. There were 6 women and 4 men. In 7 patients, neoplasms were located in the right hemisphere, in 3 patients - in the left hemisphere. According to preoperative automatic perimetry data, 7 patients had various visual field defects, and other ones had intact visual fields. All patients underwent pre- and postoperative MRI for visualization of optic radiation, its relationship with tumor and control of resection quality. Intraoperative monitoring of cVEPs was performed in all patients. RESULTS: Biopsy verified glioblastoma in 5 cases, metastasis of adenocarcinoma - 2 cases, diffuse glioma - 1 case, ganglioglioma - 1 case, CNS lymphoma - 1 case. Postoperative MRI confirmed total or subtotal resection of tumor in all cases. Enlargement of visual fields occurred in 3 patients after surgery. Two ones had deterioration and/or new homonymous defect. No changes of visual fields was observed in other cases. Analysis of visual field defects after surgery found no correlation with functional state of visual tract according to fractional anisotropy before and after surgery. CONCLUSION: MR tractography of optic radiation and intraoperative monitoring of cVEP allow choosing the safest approach for resection of occipital tumor and minimizing the risk of damage to visual cortex and optic radiation fibers. In most cases, postoperative visual functions do not worsen after intraoperative mapping of visual cortex and determining the safest trajectory for resection of occipital lobe tumors. Moreover, improvement is observed in some cases.

[Early results of intraoperative neurophysiological monitoring in surgical treatment of hemifacial spasm]. / Analiz blizhaishikh rezul'tatov intraoperatsionnogo neirofiziologicheskogo monitoringa pri khirurgicheskom lechenii gemifatsial'nogo spazma.

BACKGROUND: Neurophysiological monitoring in surgery for hemifacial spasm has been used since the 1990s, when Moller et al. demonstrated the effectiveness of intraoperative assessment of lateral spread response (LSR) regarding postoperative outcomes. Currently, there are conflicting data on effectiveness and feasibility of this technique. Widespread hemifacial spasm determines the relevance of neurophysiological monitoring in surgical treatment of these patients. OBJECTIVE: To evaluate the effectiveness of various methods of intraoperative neurophysiological monitoring in surgical treatment of hemifacial spasm regarding early postoperative outcomes. MATERIAL AND METHODS: The study group included 43 patients (8 men and 35 women) aged 26-68 years. We assessed severity of hemifacial spasm using the SMC Grading Scale. All patients underwent vascular decompression of the facial nerve under neurophysiological control: monitoring of transcranial motor evoked potentials from facial muscles (m. orbicularis oculi, m. orbicularis oris, m. mentalis) and recording unilateral LSR. The control group included 23 patients (4 men and 19 women) aged 29-83 years. In this group, facial nerve decompression was performed without neurophysiological control. The effect of neurophysiological monitoring on postoperative outcomes (in-hospital period and 3 postoperative months) after vascular decompression of the facial nerve was assessed using the SMC Grading Scale. We considered severity and incidence of spasms. RESULTS: Thirty-one (72%) patients in the main group had no spasms of mimic muscles at discharge. In the control group, there were no spasms in 15 patients (65%). At the same time, there were fewer Grade I patients in the control group (12%) compared to the main group (26%). Moreover, 27 (66%) and 12 (52%) patients were free from episodes of hemifacial spasm in both groups, respectively. Patients with hemifacial spasm grade I-II comprised 29% in the main group and 34% in the control group. The number of relapses within three months increased in the control group (13%). CONCLUSION: Intraoperative monitoring of transcranial motor evoked potentials from the facial muscles and LSR during vascular decompression of the facial nerve increases the efficiency of surgery for hemifacial spasm in early postoperative period. Less number of relapses and lower intensity of hemifacial spasm necessitate neurophysiological monitoring in neurosurgical treatment of these patients.

[Surgical treatment of hemispheric and subcortical gliomas adjacent to corticospinal tract in children using MR tractography and intraoperative electrophysiological monitoring]. / Opyt khirurgicheskogo lecheniya gliom bol'shikh polusharii i podkorkovykh struktur golovnogo mozga, prilegayushchikh k kortikospinal'nomu traktu, u detei s ispol'zovaniem MR-traktografii i intraoperatsionnogo elektrofiziologicheskogo monitoringa.

Difficult total resection of supratentorial gliomas adjacent to the corticospinal tract (CST) is due to the high risk of its injury and disability of patients. The main methods for preventing intraoperative CST damage are preoperative MR tractography and intraoperative electrophysiological monitoring. The problem of total resection of gliomas adjacent to the CST with preservation of high functional status is difficult due to immaturity and plasticity of brain structures in children. Moreover, the advantages of MR tractography combined with intraoperative monitoring have not been described. The authors present surgical treatment of supratentorial gliomas adjacent to the CST at different anatomical levels. Patients underwent preoperative and postoperative MR tractography and intraoperative electrophysiological monitoring. MR tractography provided preoperative data on CST lesion. Intraoperative monitoring made it possible to identify and preserve CST in the depth of surgical wound. MR tractography and intraoperative electrophysiological monitoring increase resection quality in patients with hemispheric and subcortical gliomas without postoperative functional deterioration.

Prediction of Postoperative Speech Dysfunctions in Neurosurgery Based on Cortico-Cortical Evoked Potentials and Machine Learning Technology.

Intraoperative recording of cortico-cortical evoked potentials (CCEPs) enables studying effective connections between various functional areas of the cerebral cortex. The fundamental possibility of postoperative speech dysfunction prediction in neurosurgery based on CCEP signal variations could serve as a basis to develop the criteria for the physiological permissibility of intracerebral tumors removal for maximum preservation of the patients' quality of life. The aim of the study was to test the possibility of predicting postoperative speech disorders in patients with glial brain tumors by using the CCEP data recorded intraoperatively before the stage of tumor resection. Materials and Methods: CCEP data were reported for 26 patients. To predict the deterioration of speech functions in the postoperative period, we used four options for presenting CCEP data and several machine learning models: a random forest of decision trees, logistic regression, and support vector machine method with different types of kernels: linear, radial, and polynomial. Twenty variants of models were trained: each in 300 experiments with resampling. A total of 6000 tests were performed in the study. Results: The prediction quality metrics for each model trained in 300 tests with resampling were averaged to eliminate the influence of "successful" and "unsuccessful" data grouping. The best result with F1-score = 0.638 was obtained by the support vector machine with a polynomial kernel. In most tests, a high sensitivity score was observed, and in the best model, it reached a value of 0.993; the specificity of the best model was 0.370. Conclusion: This pilot study demonstrated the possibility of predicting speech dysfunctions based on CCEP data taken before the main stage of glial tumors resection; the data were processed using traditional machine learning methods. The best model with high sensitivity turned out to be insufficiently specific. Further studies will be aimed at assessing the changes in CCEP during the operation and their relationship with the development of postoperative speech deficit.

[Machine learning for resting state fMRI-based preoperative mapping: comparison with task-based fMRI and direct cortical stimulation]. / Primenenie mashinnogo obucheniya dlya predoperatsionnogo kartirovaniya po dannym funktsional'noi magnitno-rezonansnoi tomografii pokoya: sravnenie so stimul-zavisimoi funktsional'noi magnitno-rezonansnoi tomografiei i pryamoi elektricheskoi stimulyatsiei kory.

OBJECTIVE: To develop a system for preoperative prediction of individual activations of motor and speech areas in patients with brain gliomas using resting state fMRI (rsfMRI), task-based fMRI (tb-fMRI), direct cortical stimulation and machine learning methods. MATERIAL AND METHODS: Thirty-three patients with gliomas (19 females and 14 males aged 19 - 540) underwent DCS-assisted resection of tumor (19 ones with lesion of motor zones and 14 patients with lesions of speech areas). Awake craniotomy was performed in 14 cases. Preoperative mapping was performed according to special MRI protocol (T1, tb-fMRI, rs-fMRI).Machine learning system was built on open source data from The Human Connectome Project. MR data of 200 healthy subjects from this database were used for system pre-training. Further, this system was trained on the data of our patients with gliomas. RESULTS: In DCS, we obtained 332 stimulations including 173 with positive response. According to comparison of functional activations between rs-fMRI and tb-fMRI, there were more positive DCS responses predicted by rs-fMRI (132 vs 112). Non-response stimulation sites (negative) prevailed in tb-fMRI activations (69 vs 44). CONCLUSION: The developed method with machine learning based on resting state fMRI showed greater sensitivity compared to classical task-based fMRI after verification with DCS: 0.72 versus 0.66 (p<0.05) for identifying the speech zones and 0.79 versus 0.62 (p<0.05) for motor areas.

[Higher efficacy of botulinum toxin therapy for hemifacial spasm recurrence after vascular decompression. Case report and literature review]. / Uvelichenie effektivnosti botulinoterapii pri vozvrate simptomov gemifatsial'nogo spazma posle vaskulyarnoi dekompressii. Klinicheskii sluchai i obzor literatury.

Hemifacial spasm (HFS) is an involuntary synchronous tonic and/or clonic contraction of mimic muscles following ipsilateral facial nerve dysfunction. The last one is a result of neurovascular conflict between the facial nerve and vessel. Currently, vascular decompression is a pathogenetic treatment modality for primary HFS. Various authors describe postoperative recurrence of HFS, and botulinum toxin therapy remains the only option for these patients. We aimed to describe the efficacy of botulinum toxin therapy in patients with HFS recurrence after surgical vascular decompression. The article presents a female patient with a long-term history of HFS and botulinum toxin therapy (with different formulations). Efficacy of therapy gradually decreased (progressive reduction of intervals between injections). MRI revealed a close relationship between posterior inferior cerebellar artery and roots of acoustic-facial nerves near the brainstem. The patient underwent vascular decompression of the left facial nerve root under intraoperative monitoring with positive postoperative outcome. However, HFS symptoms recurred in 3 days after surgery. Botulinum toxin type A (BTA) injections were resumed with significant positive effect that can be explained by reduction of one of the factors involved into HFS. Thus, patients with HFS recurrence after vascular decompression may benefit from BTA therapy.

[Broca's area intraoperative mapping with cortico-cortical evoked potentials]. / Intraoperatsionnoe kartirovanie rechevoi zony Broka metodom registratsii kortiko-kortikal'nykh vyzvannykh potentsialov.

OBJECTIVE: Mapping of effective speech connections between the frontal and temporal lobes with cortico-cortical evoked potentials. MATERIAL AND METHODS: There were 3 patients with brain tumors in the left frontoparietal region. The neoplasms were localized in the dominant hemisphere near cortical speech centers and pathways. Cortico-cortical evoked potentials were intraoperatively recorded in response to bipolar stimulation with a direct current delivered through the subdural electrodes (single rectangular biphasic impulses with duration of 300 µs and frequency of 1 Hz). Stimulation intensity was gradually increased from 2 mA within 3-4 mA. Registration was carried out by averaging ECoG (30-50 stimuli in each session) in the 300-ms epoch after stimulus. Direct cortical stimulation was used to validate the results of cortico-cortical speech mapping with cortico-cortical evoked potentials. RESULTS: In our cases, we obtained cortico-cortical evoked potentials from inferior frontal gyrus after stimulation of superior temporal gyrus. In one case, this effective relationship was unidirectional, in the other two patients reciprocal. Mean latency of N1 peak was 65 ms (range 49.6-90 ms), mean amplitude 71 µV (range 50-100 µV). Cortico-cortical mapping data were confirmed by detection of Broca's area in 2 out of 3 cases out during direct cortical stimulation with maximum amplitude of N1 wave. «Awake craniotomy¼ protocol was applied. In one case, Broca's area was not detected during direct stimulation. No postoperative speech impairment was noted. CONCLUSION: Initial results of cortical mapping with cortico-cortical evoked potentials in a small sample confirmed its practical significance for analysis of cortical projections of effective speech communications between the frontal and temporal lobes. Further study of this method in large samples is required.

[Occipital gliomas. Case report and literature review]. / Intraoperatsionnaya registratsiya korkovykh zritel'nykh vyzvannykh potentsialov pri udalenii gliomy zatylochnoi doli. Klinicheskoe nablyudenie i obzor literatury.

The authors report intraoperative mapping with cortical visual evoked potentials during occipital tumor resection. This approach was valuable to reduce the risk of visual cortex and visual pathways damage and, accordingly, the likelihood of postoperative visual impairment. The peculiarity of this case is registration of clear cortical visual evoked potentials in various positions before and after tumor resection. Intraoperative monitoring was valuable to avoid damage to visual cortex and visual pathways during tumor resection. There was no postoperative visual deterioration. Moreover, we observed partial recovery of visual fields after resection of occipital malignant tumor.

[Comparative analysis of mono- and bipolar pyramidal tract mapping in patients with supratentorial tumors adjacent to motor areas: comparison of data at 64 stimulation points]. / Sravnitel'nyi analiz potochechnogo mono- i bipolyarnogo kartirovaniya piramidnogo trakta u patsientov s supratentorial'nymi opukholyami, prilezhashchimi k motornym zonam golovnogo mozga: sravnenie dannykh v 64 tochkakh stimulyatsii.

OBJECTIVE: To compare monopolar and bipolar mapping in point-by-point fashion by using of threshold amperage, frequency of positive motor responses and the number of muscles involved in response. MATERIAL AND METHODS: A prospective non-randomized study included 14 patients with supratentorial tumors who underwent surgery in 2018-2019. All neoplasms were localized within 2 cm from the motor cortex and pyramidal tract. Age of patients ranged from 25 to 74 years. There were 9 women and 5 men. Eight patients had malignant glioma (grade III - 4, grade IV - 4), 6 patients - meningioma. Motor functions were assessed in all patients before and after surgery (1, 7 days and 3 months later) by using of a 5-point scale. In addition to routine neurophysiological monitoring, comparative mono- and bipolar mapping of the pyramidal tract within the bed of excised tumor was carried out at the end of surgery. The points of motor responses were marked. Comparative analysis of mono- and bipolar stimulation at identical points included threshold amperage, frequency of positive motor responses and the number of muscles involved in response (leg, forearm, hand, facial muscles). Brain MRI was performed in early postoperative period for assessment of resection quality. RESULTS: There were 64 points of motor responses in 14 patients. The number of these points ranged from 2 to 8 per a patient (mean 5 points). Motor responses were recorded in 57 points during monopolar and bipolar stimulation, in other 7 points - only during monopolar stimulation. Amperage of monopolar stimulation was 3-15 mA, bipolar stimulation - 2.5-25 mA. Threshold amperage (7.37 mA for monopolar stimulation and 8.88 mA for bipolar stimulation; p=0.12), frequency of positive motor responses and the number of muscles involved in response (p=0.1 and p=0.73) were similar. Seven (50%) patients had neurological deterioration in early postoperative period (4 patients with glial tumors and 3 patients with meningiomas). At the same time, only 2 patients (14.3%) had persistent neurological deficit (both patients with infiltrative meningioma). According to postoperative MRI in T1+C mode, resection volume was 100% in 1 patient with contrast-enhanced glioma and 94% in another one. According to FLAIR MRI data, resection volume exceeded 70% in 2 patients with non-enhancing glioma and less than 70% in 2 patients. Meningioma resection volume was estimated according to postoperative T1+C MRI data and made up over 90% in 4 patients. CONCLUSION: Monopolar stimulation is a reliable method of pyramidal tract identification in supratentorial brain tumor surgery.

[Treatment of sciatic posttraumatic neuropathy with chronic neuromodulation and endoscopic technics]. / Lechenie posttravmaticheskoi nevropatii sedalishchnogo nerva s ispol'zovaniem khronicheskoi neirostimulyatsii i endoskopicheskoi tekhniki.

OBJECTIVE: Sciatic nerve injury in the deep gluteal space is a major clinical problem due to microsurgical manipulations in this region are limited in scope. We offer new endoscopic approach to the sciatic nerve in the deep gluteal space which allows to perform microsurgical manipulations, neurophysiological mapping and electrode installation for the chronic nerve stimulation. MATERIAL AND METHOD: 3 patients with sciatic neuropathy have been operated. Before the operation they suffered from neuropathic pain in the the posterior thigh and calf, reaching 7-8 points on the visual analog scale (VAS). Paresis of triceps surae and biceps femur also was occurred. We performed endoscopic approach to the deep gluteal space through a small incision under the gluteal fold. Microsurgical external and internal decompression of sciatic nerve was performed under the endoscopic control. Next, intra-trunk nerve mapping was performed to visualize sensory fibers. Cylindrical electrodes for chronic neurostimulation were directly placed on the sensory fibers of sciatic nerve. RESULTS: Pain relief was obtained in all cases after activating the simulator, the patient noted a 50% reduction in pain. Muscle straight restoration was observed in all cases 2-3 months later. The clinical effect was stable in the follow up (6 months). CONCLUSION: This technique, combining minimal invasiveness and intraoperative neurophysiological control, makes it possible to optimally position the electrode, both to achieve positive analgesic effect and for potential restoration of nerve function.

[Resting-state fMRI in preoperative non-invasive mapping in patients with left hemisphere glioma]. / Funktsional'naya magnitno-rezonansnaya tomografiya sostoyaniya pokoya v predoperatsionnom neinvazivnom kartirovanii u patsientov s gliomami levogo polushariya golovnogo mozga.

Maximum resection and preservation of neurological function are main principles in surgery of brain tumors, especially glial neoplasms with diffuse growth. Therefore, exact localizing of eloquent brain areas is an important component in surgical planning ensuring optimal resection with minimal postoperative neurological deficit. Functional MRI is used to localize eloquent brain areas adjacent to the tumor. This paper is an initial stage in analysis of resting-state fMRI in assessment of functional changes of neuronal activity caused by brain gliomas of different localization. We report two patients with glial tumors localized within the precentral gyrus of the left hemisphere and near speech area. Considering data of task-based and resting-state fMRI, as well as direct cortical stimulation, we propose a methodology for assessing the overlap of activations obtained by these methods.

[Intraoperative mapping of long association fibers in surgery of gliomas of the speech-dominant frontal lobe]. / Intraoperatsionnoe kartirovanie dlinnykh assotsiativnykh traktov v khirurgii gliom dominantnoi po rechi lobnoi doli.

Surgery of intracerebral tumors involving long association fibers is a challenge. In this study, we analyze the results of intraoperative mapping of the superior longitudinal, arcuate, and frontal aslant tracts in surgery of brain gliomas. PURPOSE: The study purpose was to compare the results of intraoperative mapping and the postoperative speech function in patients with gliomas of the premotor area of the speech-dominant frontal lobe, which involved the superior longitudinal, arcuate, and frontal aslant tracts, who were operated on using awake craniotomy. MATERIAL AND METHODS: Twelve patients with left frontal lobe gliomas were operated on: 11 patients were right-handed, and one patient was a left-hander retrained at an early age. Histological types of tumors were represented by Grade II diffuse astrocytomas (6 patients), Grade III anaplastic astrocytomas (1 patient), Grade IV glioblastoma (1 patient), Grade II oligodendroglioma (1 patient), and Grade III anaplastic oligodendrogliomas (3 patients). The mean age of patients was 45 (29-67) years; there were 6 males and 6 females. All patients underwent preoperative and postoperative MRI with reconstruction of the long association fibers and determination of the topographic anatomical relationships between the fibers and the tumor. Surgery was performed using the asleep-awake-asleep protocol with intraoperative awakening of patients. All patients underwent cortical and subcortical electrophysiological stimulation to control the localization of eloquent structures and to clarify the safe limits of resection. For intraoperative speech monitoring, a computerized naming test was used with naming of nouns or verbs, and automatic speech was evaluated (counting from 1 to 10, enumeration of months and days of the week), which was complemented by a talk with the patient. Speech disorders before, during, and after surgery were evaluated by a neuropsychologist. The mean current strength during direct electrical stimulation was 3 (1.9-6.5) mA. RESULTS: The association fibers were intraoperatively identified in all patients (SLF/AF in 11 patients; FAT in one patient). In 4 patients, the cortical motor speech area was intraoperatively mapped; in three cases, tumor resection was accompanied by speech disturbances outside the stimulation. During direct electrical stimulation, speech disturbances developed in 7 of 12 cases. All patients underwent control MRI within the first 48-72 h: total resection (more than 90% of the tumor) was performed in 7 cases; subtotal resection was achieved in two patients; partial resection was performed in two cases. According to postoperative MR tractography, the resected tumor bed was adjacent to the SLF/AF complex in 7 cases, located near the SLF/AF complex in three cases, and adjacent to the FAT in two cases. Postoperatively, 11 out of 12 patients had worsening of neurological symptoms in the form of various speech disturbances. In one patient, speech disturbances developed 2 days after surgery, which was associated with an increase in edema. On examination 3 months after surgery, severe speech disturbances remained in 1 patient. CONCLUSION: Resection of frontal lobe tumors in the speech-dominant hemisphere using early postoperative awakening is associated with a high rate of complex speech disorders due to injury to the SLF/AF complex and FAT. In these cases, intraoperative speech mapping with allowance for the course of long association fibers is an essential procedure. Preoperative tractography in combination with intraoperative speech mapping enables identification of association fibers of the SLF/AF complex and FAT, which may help to avoid severe conduction aphasia with poor speech recovery after tumor resection.

[Evaluation of vascular reactivity to overcome limitations of neurovascular uncoupling in BOLD fMRI of malignant brain tumors]. / Otsenka vazoreaktivnosti dlia preodoleniia ogranichenii neirovaskuliarnogo razobshcheniia BOLD fMRT pri zlokachestvennykh opukholiakh golovnogo mozga.

The sensitivity of fMRI in identification of eloquent cortical centers in the case of large infiltrative growing tumors and pronounced peritumoral edema may be reduced or significantly limited in some cases. The main cause is an attenuated Blood-Oxygen-Level-Dependent response (BOLD) caused by pathological vascular reactivity and subsequent neurovascular uncoupling of fMRI. In our study, we attempted to overcome these limitations and increase the sensitivity of this technique in identification of eloquent cortical areas adjacent to brain tumors by using vasoreactivity features of a breath-holding test and including these data in the BOLD analysis. Local vasoreactivity using a breath-holding paradigm with the same block design of both motor and speech tests was determined in 5 healthy volunteers and 3 patients in the preoperative period (two patients with high grade gliomas and one patient with single metastasis). A coherence-based model was developed for analysis of BOLD fMRI, which took into account altered hemodynamics in peritumoral zones. Obtained coherence maps demonstrated clinically more significant activation zones that were not seen with standard methods of fMRI processing. Thus, neurovascular uncoupling that is known to affect the accuracy of the BOLD fMRI response adjacent to brain tumors may be partially overcome by including an independent measurement of vasoreactivity using a breath-holding test in the BOLD analysis.

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.

[Dynamics of functional MRI and speech function in patients after resection of frontal and temporal lobe tumors]. / Dinamika funktsional'noi MRT i rechevoi funktsii u bol'nykh posle udaleniia vnutrimozgovykh opukholei lobnoi i visochnoi dolei mozga.

RATIONALE: There are no studies on application of functional MRI (fMRI) for long-term monitoring of the condition of patients after resection of frontal and temporal lobe tumors. PURPOSE: The study purpose was to correlate, using fMRI, reorganization of the speech system and dynamics of speech disorders in patients with left hemisphere gliomas before surgery and in the early and late postoperative periods. MATERIAL AND METHODS: A total of 20 patients with left hemisphere gliomas were dynamically monitored using fMRI and comprehensive neuropsychological testing. The tumor was located in the frontal lobe in 12 patients and in the temporal lobe in 8 patients. Fifteen patients underwent primary surgery; 5 patients had repeated surgery. Sixteen patients had WHO Grade II and Grade III gliomas; the others had WHO Grade IV gliomas. Nineteen patients were examined preoperatively; 20 patients were examined at different times after surgery. Speech functions were assessed by a Luria's test; the dominant hand was determined using the Annette questionnaire; a family history of left-handedness was investigated. Functional MRI was performed on an HDtx 3.0 T scanner using BrainWavePA 2.0, Z software for fMRI data processing program for all calculations >7, p<0.001. RESULTS: In patients with extensive tumors and recurrent tumors, activation of right-sided homologues of the speech areas cold be detected even before surgery; but in most patients, the activation was detected 3 months or more after surgery. Therefore, reorganization of the speech system took time. Activation of right-sided homologues of the speech areas remained in all patients for up to a year. Simultaneous activation of right-sided homologues of both speech areas, the Broca's and Wernicke's areas, was detected more often in patients with frontal lobe tumors than in those with temporal lobe tumors. No additional activation foci in the left hemisphere were found at the thresholds used to process fMRI data. Recovery of the speech function, to a certain degree, occurred in all patients, but no clear correlation with fMRI data was found. CONCLUSION: Complex fMRI and neuropsychological studies in 20 patients after resection of frontal and temporal lobe tumors revealed individual features of speech system reorganization within one year follow-up. Probably, activation of right-sided homologues of the speech areas in the presence of left hemisphere tumors depends not only on the severity of speech disorder but also reflects individual involvement of the right hemisphere in enabling speech function. This is confirmed by right-sided activation, according to the fMRI data, in right-sided patients without aphasia and, conversely, the lack of activation of right-sided homologues of the speech areas in several patients with severe postoperative speech disorders during the entire follow-up period.

[Neurophysiological identification of the cranial nerves in endoscopic endonasal surgery of skull base tumors]. / Neirofiziologicheskaya identifikatsiya cherepnykh nervov v endoskopicheskoi endonazal'noi khirurgii opukholei osnovaniya cherepa.

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.

[Diffusion tensor imaging tractography and intraoperative neurophysiological monitoring in surgery of intracranial tumors located near the pyramidal tract].

BACKGROUND: Practical application of methods for intravital examination of the brain pathways, such as preoperative diffusion tensor imaging (DTI) tractography and intraoperative neurophysiological monitoring, facilitates safer resection of intracranial tumors located near the pyramidal tracts (PTs). PURPOSE: The study purpose was to investigate the relationships between intracerebral tumors of different histological nature and the pyramidal tract based on preoperative DTI tractography and various methods of intraoperative neurophysiological monitoring for intraoperative identification of the pyramidal tract, depending on different variants of the topographo-anatomic relationships between the pyramidal fascicle and the tumor. MATERIAL AND METHODS: The study included 29 patients with supratentorial tumors of a different histological structure. Of these, 2 patients had grade I tumors, 8 patients had grade II tumors, 4 patients had grade III tumors, 11 patients grade IV tumors, and 4 patients had brain metastases. The patients underwent preoperative DTI tractography with PT reconstruction and evaluation of the topographo-anatomic relationships between the pyramidal tract and the tumor (tract: intact, infiltrated, displaced). Neurophysiological monitoring (direct electrical stimulation in 24 patients and transcranial motor evoked potentials in 26 patients) was used during surgery. The strength of stimulating current for direct stimulation was varied from 10 to 30 mA. Postoperatively, the motor function was evaluated by using a 5-score scale, and the data were compared to the preoperative data. RESULTS: According to preoperative DTI tractography in patients with grade I-II gliomas, the corticospinal tracts were infiltrated in 2 cases, displaced in 3 cases, and intact in 5 cases. In patients with grade III-IV gliomas and metastases, the tracts were infiltrated in 8 cases, displaced in 4 cases, and intact in 7 cases. Motor responses evoked by direct electrical stimulation were obtained in 5 out of 6 patients with the pyramidal tract displaced by the tumor and in 7 out of 8 patients with the tract infiltrated by the tumor. In the case of the intact tract, the PT to tumor distance and the stimulus strength play an important role: responses were obtained in 4 out of 10 patients. In the case of transcranial motor evoked potentials (TCMEPs), no dynamics of the potential amplitude was detected in 17 out of 26 patients during surgery; a reduced TCMEP amplitude was detected in 9 patients. CONCLUSION: 1. Patients with an infiltrated or displaced pyramidal tract had significantly more often hemiparesis before surgery and aggravation of hemiparesis after the surgery compared to patients with an intact tract. 2. In the case of direct electrical stimulation of the PT, motor responses (according to preoperative DTI tractography) were significantly more often observed for the pyramidal tract infiltrated and displaced by the tumor. 3. A reduction in the motor neurologic deficit in the postoperative period was significantly more often observed for application of a larger current strength during direct electrical stimulation. 4. Persistence of the TCMEP amplitude during surgery is a reliable predictor for no aggravation of the motor neurological deficit after surgery. Postoperative aggravation of hemiparesis was significantly more often observed when TC MEPs decreased during surgery.

[The structure of activation of the language zone in patients with intracerebral tumors according to fMRI with respect to tumor location and the functional asymmetry profile].

MATERIAL AND METHODS: A total of 50 patients were examined prior to surgical resection of intracranial tumors of the temporal and frontal lobes. Left-sided tumors were observed in 33 patients and right-sided tumors were observed in 17 patients. The functional asymmetry profile was determined using self-assessment, the Annet questionnaire, and the dichotic listening task. Twelve patients were left-handers or retrained left-handers and the remaining 38 patients were right-handers. FMRI examination was carried out on a 3.0 T SignaHDxt magnetic resonance tomograph (GE). The standard language block design paradigm was used in the study. We used the following tests: 1) recitation of months in reverse order; 2) generation of nouns according to the initial letters shown on the screen (K, M, L, N, P, C); 3) generation of verbs according to simple actions shown on the screen; 4) producing sentences using nouns shown on the screen; 5) listening to text through headphones. Data were processed using the standard BrainWave PA software (General Electric). Z-test was used in the range from 6 to 9. In all the studies, p<0.001. Statistical data processing included the nonparametric Spearman's test to determine the correlation between lateralization of the detected activation zone under speech load and tumor location (tumor is adjacent to the language zone, invades the language zone, or is located far from the language zone), as well as left- or right-handedness. RESULTS: Among 16 patients (right-handers and 2 left-handers) the activation of language zones was observed only on the left side; in one left-handed patient, Broca's area was detected only on the right side. In other patients (including right-handers with right-sided tumors), lateralization of language zones was different, including bilateral. Statistical processing revealed that bilateral activation of both Broca's and Wernicke's areas was more frequently observed in left-handers. Broca's area was more frequently detected on the left side in the presence of a distant tumor, while this trend did not apply for Wernicke's area. CONCLUSION: Localization of activation of Broca's area is more dependent on tumor location, while it depends on personal characteristics of an individual in the case of Wernicke's area.