[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.

[MR-guided non-invasive typing of brain gliomas using machine learning]. / Pervye rezul'taty neinvazivnogo tipirovaniya gliom golovnogo mozga po dannym magnitno-rezonansnoi tomografii s pomoshch'yu mashinnogo obucheniya.

Gliomas are the most common neuroepithelial brain tumors. The modern classification of tumors of central nervous system and treatment approaches are based on tissue and molecular features of a particular neoplasm. Today, histological and molecular genetic typing of tumors can only be carried out through invasive procedures. In this regard, non-invasive preoperative diagnosis in neurooncology is appreclated. One of the perspective areas is artificial intelligence applied for neuroimaging to identify significant patterns associated with histological and molecular profiles of tumors and not obvlous for a specialist. OBJECTIVE: To evaluate diagnostic accuracy of deep learning methods for glioma typing according to the 2007 WHO classification based on preoperative magnetic resonance imaging (MRI) data. MATERIAL AND METHODS: The study included MR scans of patients with glial tumors undergoing neurosurgical treatment at the Burdenko National Medical Research Center for Neurosurgery. All patients underwent preoperative contrast-enhanced MRI. 2D and 3D MR scans were used for learning of artificial neural networks with two architectures (Resnest200e and DenseNet, respectively) in classifying tumors into 4 categories (WHO grades I-IV). Learning was provided on 80% of random examinations. Classification quality metrics were evaluated in other 20% of examinations (validation and test samples). RESULTS: Analysis included 707 contrast-enhanced T1 welghted images. 3D classification based on DenseNet model showed the best result in predicting WHO tumor grade (accuracy 83%, AUC 0.95). Other authors reported similar results for other methods. CONCLUSION: The first results of our study confirmed the fundamental possibility of grading axial contrast-enhanced T1 images according to the 2007 WHO classes using deep learning models.

[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.

[Comparison of resting state and task-based functional MRI in preoperative mapping in patients with brain gliomas]. / Sravnenie funktsional'noi magnitno-rezonansnoi tomografii v sostoyanii pokoya i stimul-zavisimoi funktsional'noi magnitno-rezonansnoi tomografii v predoperatsionnom kartirovanii u patsientov s gliomami golovnogo mozga.

OBJECTIVE: To analyze and compare the results of cerebral cortex mapping with task-based (tb-fMRI) and resting-state functional MRI in patients with glioma of eloquent cortical areas. MATERIAL AND METHODS: There were 55 patients (24 men and 31 women aged 24 - 74 years, median 39) with glial tumors. In 26 patients, the tumor was located in motor areas. Twenty-nine patients had lesions of Broca and Wernicke's areas. All patients underwent preoperative tb-fMRI and rs-fMRI. Then, resection of tumor was carried out in all cases. RESULTS: Comparison of fMRI and rs-fMRI activation maps was assessed by calculating the Dice coefficient for inclusive speech and motor cortex masks and exclusive masks without brainstem, cerebellum, subcortical nuclei. Inclusive Dice coefficient for motor cortex ranged from 0.11 to 0.50, for speech cortex - from 0.006 to 0.240 (p<0.05). In case of exclusive masks, this value ranged from 0.15 to 0.55 for motor cortex and from 0.004 to 0.205 for speech cortex (p<0.05). CONCLUSION: When comparing the results of cortical mapping in patients with glial tumors, the use of hemispheric exclusive and inclusive masks did not significantly increase activation maps matching. Probably, low degree of correspondence was associated with different genesis of activations, as well as with high variability of speech cortex.

[Periventricular changes following hydrocephalus: quantitative MR-based assessment of tissue characteristics]. / Periventrikulyarnye izmeneniya pri gidrotsefalii: kolichestvennaya otsenka tkanevykh kharakteristik metodom magnitno-rezonansnoi tomografii.

OBJECTIVE: To study tissue characteristics of periventricular white matter in patients with open hydrocephalus using DWI MRI and their correlations with CSF flow parameters. MATERIAL AND METHODS: MRI was performed in 55 patients (35 women and 20 men) with open normal pressure hydrocephalus, as well as 16 patients with malignant occlusive hydrocephalus and interstitial edema (control group). We determined the correlations between severity of hydrocephalus, periventricular lesions and CSF flow parameters considering MR data. Dimensions of ventricular system were assessed using the Evans' index, periventricular changes - using visual four-level scale with calculation of apparent diffusion coefficient (ADC) and fractional anisotropy coefficient (FA). RESULTS: Among patients with open hydrocephalus, ACD range for periventricular white matter was 1.57±0.15·10-3 mm2/s in subgroup of patients without periventricular changes (n=29) and 1.62±0.11×10-3 mm2/s in patients with periventricular changes (n=26). In the control group, mean ADC was 1.76±0.18·10-3 mm2/s (p<0.05). In patients with open hydrocephalus, FA coefficient in the areas of periventricular changes was 0.70-0.80, in case of occlusive hydrocephalus - 0.68-0.82. There was a significant relationship between the Evans' index and CSF pulsation velocity amplitude, Evans' index and stroke volume, Evans' index and cerebral aqueduct cross-sectional area in patients with open hydrocephalus. Periventricular changes were pronounced in patients with open hydrocephalus and Evans' index > 0.4 (p<0.05). CONCLUSION: According to MR data, periventricular changes in patients with open hydrocephalus differ from true periventricular interstitial edema following occlusive hydrocephalus. Severity of periventricular changes in patients with open hydrocephalus depends on patient age and width of the ventricles, but does not correlate with CSF flow parameters. In our opinion, periventricular changes are associated with dysfunction of glymphatic system. Further research is required to study the functioning of glymphatic system and related processes.

3D pseudo-continuous arterial spin labeling-MRI (3D PCASL-MRI) in the differential diagnosis between glioblastomas and primary central nervous system lymphomas.

PURPOSE: The aim of the study was to compare the parameters of blood flow in glioblastomas and primary central nervous system lymphomas (PCNSLs), measured by pseudo-continuous arterial spin labeling MRI (3D PCASL), and to determine the informativeness of this method in the differential diagnosis between these lesions. METHODS: The study included MRI data of 139 patients with PCNSL (n = 21) and glioblastomas (n = 118), performed in the Burdenko Neurosurgical Center. No patients received chemotherapy, hormone therapy, or radiation therapy prior to MRI. On the 3D PCASL perfusion map, the absolute and normalized values of tumor blood flow were calculated in the glioblastoma and PCNSL groups (maxTBFmean and nTBF). RESULTS: MaxTBFmean and nTBF in the glioblastoma group were significantly higher than those in the PCNSL group: 168.9 ml/100 g/min versus 65.6 and 9.3 versus 3.7, respectively (p < 0.001). Arterial spin labeling perfusion had high sensitivity (86% for maxTBFmean, 95% for nTBF) and specificity (77% for maxTBFmean, 73% for nTBF) in the differential diagnosis between PCNSL and glioblastomas. Blood flow thresholds were 98.9 ml/100 g/min using absolute blood flow values and 6.1 using normalized values, AUC > 0.88. CONCLUSION: The inclusion of 3D PCASL in the standard MRI protocol can increase the specificity of the differential diagnosis between glioblastomas and PCNSL.

[Conduction aphasia in patients with glioma in the left hemisphere]. / Provodnikovaya afaziya u bol'nykh s gliomami levogo polushariya.

Background. According to Wernicke-Geschwind model, conduction aphasia following arcuate tract lesion was canonized as primary disorder of repetition in relatively intact speech. OBJECTIVE: Syndromic analysis of speech and writing disorders in patients with arcuate tract lesion using the method by A.R. Luria and their comparison with well-known types of aphasia. MATERIAL AND METHODS: Clinical and neuropsychological survey was performed in 14 patients with gliomas who underwent surgical treatment at the Burdenko Neurosurgical Center (10 gliomas of the frontal lobe and 4 tumors of the temporal lobe). All patients underwent MRI, HARDI MRI tractography and A.R. Luria's neuropsychological examination prior to surgery and after 5-6 postoperative days. Thirteen patients underwent awake craniotomy, 3 of them were examined one year after surgery. RESULTS: In all patients, the tumor was localized near arcuate tract and its infiltration was noted. No intraoperative damage to the tract was ever noted according to speech monitoring data. However, postoperative edema followed by infiltration and dislocation of the tract (in all patients), as well as local ischemia in 4 patients were observed. After resection of prefrontal and premotor gliomas, aphasia included frontal (perseveration) and temporal components (disorders of naming, auditory-speech memory). Unusual verbal paraphrases were noted. We also observed severe violation of writing (temporal type) even if spontaneous speech and repetition were preserved. In case of resection of deep posterior temporal gliomas, speech disorders included signs of frontal lobe lesion (perseveration) and writing disorders. Similar motor abnormalities were identified in writing. CONCLUSION: Arcuate tract lesion can result speech and writing disorders as signs of damage to certain cortical speech zones (frontal and temporal lobe). Violations of repetition were not predominant in any case. At the same time, interruption of connection between motor and auditory image of the word could be revealed in writing.

[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.

[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.