Magnetic Resonance Tractography Research Articles

Optimized uniform sampling and validation of fiber tracts from magnetic resonance tractography for in vivo architectural measurement of human forearm muscles.

In vivo muscle architectural parameters can be calculated from the fiber tracts using magnetic resonance (MR) tractography. However, the reconstructed tracts may be unevenly distributed within the muscle volume and there lacks commonly used metric to quantitatively evaluate the validity of the tracts. Our objective is to measure forearm muscle architecture by uniformly sampling fiber tracts from the candidate streamlines in MR tractography and validate the reconstructed fiber tracts qualitatively and quantitatively. We proposed farthest streamline sampling (FSS) to uniformly sample fiber tracts from the candidate streamlines. The method was evaluated on the MR data acquired from 12 healthy subjects for 17 forearm muscles and was compared with two conventional methods through uniform coverage performance. Anatomical correctness was verified by: 1. visually assessing fiber orientation, 2. checking whether architectural parameters were within physiological ranges and 3. classifying architectural types. The proposed FSS yielded optimal uniform coverage performance among the three methods (P<0.05). FSS reduced the sampling of long tracts (10% fiber length reduction, P<0.05), and the estimated architectural parameters were within the physiological ranges (P<0.05). The tractography visually matched cadaveric specimens. The architectural types of 16 muscles were correctly classified except for the palmaris longus, which exhibited a linear arrangement of fiber endpoints (R2 = 0.95±0.02, P<0.001). The proposed FSS method reconstructed uniformly distributed fiber tracts and the anatomical correctness of the reconstructed tracts was verified. The novel methods allow for accurate in vivo muscle architectural measurement, which was demonstrated through the characterization of architectural properties in human forearm muscles.

A Clinical Case of Corticospinal Tract Reorganization of Supplementary Motor Area in a Child After Acute Hypoxic Brain Injury

We present clinical observation of a 3-year-old child during recovery after acute hypoxic brain injury (freshwater drowning). Using diagnostic transcranial magnetic stimulation and magnetic resonance tractography with reconstruction of the corticospinal tract (CST) originated from the primary motor cortex and supplementary motor area (SMA), we determined that hypoxic brain injury induced activation of CST from the SMA. The period of reorganization was associated with the development of epileptiform patterns, that confirms the transient hyperexcitability of cortical neurons. Our findings indicate no recovery of motor function after acute hypoxic brain injury when CST originated only from SMA.

Прогнозування ризику розвитку розладів аутистичного спектра в дітей з епілептичними енцефалопатіями

Predicting the risk of developing autism spectrum disorders (ASD) in children with epileptic encephalopathies (EE) is an important task, which makes it possible to identify the most significant risk factors and develop ways of their modification. Purpose - to develop a model for predicting the risk of developing ASD in young children with EE. Materials and methods. 75 children aged 0-3 years with the onset of epileptic seizures in the first year of life, clinical manifestations of EE were examined. The most informative clinical, neurophysiological, and neuroimaging indicators for predicting the risk of clinical manifestations of ASD were determined: age of onset of epileptic seizures, index of spike-wave activity during NREM sleep, frequency and amplitude of alpha rhythm, frequency and amplitude of epileptiform activity, fractional anisotropy and mean diffusion coefficient in the Broca’s center, fractional anisotropy in the Wernicke center and knee of the corpus callosum. The multiple linear regression method was used to predict the risk of developing ASD symptoms. Results. A model for predicting the risk of developing clinical manifestations of ASD in children with EE has been developed. It was established that the risk of developing clinical manifestations of ASD increases with a decrease in the age of onset of epileptic seizures, decrease in the frequency and amplitude of the alpha rhythm according to electroencephalography (EEG) data, increase of the index of spike-wave activity, frequency and amplitude of epileptiform activity, increase in the index of fractional anisotropy in the anterior part of the arcuate tract, decrease in the average diffusion coefficient in the area of the Broca’s center, fractional anisotropy in the Wernicke center and the knee of the corpus callosum according to magnetic resonance tractography. Conclusions. A regression model for predicting the risk of clinical manifestations of ASD in children with EE was developed with an average error of approximation of 13.2% and a coefficient of determination of 0.74, which is recommended for use in clinical practice in order to form groups of children at high risk of ASD. Such children require further dynamic monitoring and early intervention by specialists of a multidisciplinary team for timely identification and correction of ASD symptoms The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the author.

Features of changes in fractional anisotropy of different brain parts during the progression of Parkinson's disease

BACKGROUND: Parkinson's disease is a neurodegenerative disease, in second place in terms of incidence in the world after Alzheimer's disease. It is currently believed that the presymptomatic stages of Parkinson's disease are mainly associated with degeneration of the subcortical and vegetetive nervous systems, and lesions of the cerebral cortex appear on later stages of the disease, however, it is of interest to study in more detail the involvement of the pathways of the brain in the pathological process in depending the disease progression.&#x0D; OBJECTIVE: to study features of damage to the brain pathways during the progression of Parkinson's disease by magnetic resonance tractography.&#x0D; MATERIAL AND METHODS: 88 patients with Parkinson's disease were examined (stage II disease — 42 people, stage III — 46 people according to the Hoehn and Yahr scale). The control group consisted of 35 people who did not differ in gender. All patients included in the study underwent a neurological examination, as well as magnetic resonance imaging of the brain with diffusion tensor imaging.&#x0D; RESULTS: We found that with increasing stage of Parkinson's disease, there was a significant increase in fractional anisotropy in the hippocampus, insular cortex, and inferior and superior temporal sulcus cortex in patients with Parkinson's disease; we also noted a significant decrease in putamen fractional anisotropy.&#x0D; CONCLUSION: the tractography study of the brain pathways during disease progression is a promising method that allows us to clarify in the pathogenesis of Parkinson's disease, including the role of extra-nigral pathology in the development of some non-motor disorders.

Microsurgical and fiber tract anatomy of the interthalamic adhesion.

The authors of this study aimed to define the microanatomy of the interthalamic adhesion (ITA) using microfiber dissection, magnetic resonance (MR) tractography, and histological analysis. Sagittal, coronal, and axial MR images from 160 healthy individuals 2-82 years of age were examined. The relationships between age range and ITA morphology as well as between gender and ITA morphology were evaluated statistically. Among these 160 individuals, 100 who had undergone MR tractography were examined. In this group, the presence of fiber tracts in the ITA and the relationship with ITA morphological types were examined. Thirty formalin-fixed human cadaveric brains were also examined endoscopically, and 6 hemispheres were dissected from the medial to lateral and superior to inferior directions under the microscope. Sections taken from one of the brains with an ITA type 2 with both thalami were examined histologically. Anti-neurofilament antibody was used in the histological examination. Four morphological types of ITA were observed. Type 1 had an adhesion/adherent appearance, type 2 had a bridge/commissure appearance, type 3 showed no adhesion, and type 4 had a double bridge. Tractographic examination revealed that 28% had no fiber tract transition in the ITA, 21% had a significant transition, and 51% had an indistinct transition. Statistically, the presence of the ITA was significantly higher in the pediatric (age) and female (gender) groups. In specimens with ITAs of a bridge/commissure appearance (type 2), fiber tracts showed clear transitions between thalami. In type 1 (adherent/adhesive appearance), fiber tracts were observed within the ITA, but a reciprocal transition was unclear. Dissection showed that these fiber tracts in the ITA reach the nucleus accumbens, caudate nucleus, and frontoorbital region anteriorly and the lateral habenula and posterior commissure posteriorly. Some fibers also joined the ansa peduncularis. In histological studies, axonal fibers moving in the ITA were observed with anti-neurofilament antibody staining. This is the first study to demonstrate fiber tracts of the ITA through fiber dissection and transillumination techniques as well as radiological and histological study. Statistical data were obtained by comparing the morphological group with age and gender groups. The anatomy of this structure, which has been neglected for many years, was reexamined. This study showed that the ITA has fibers connecting different parts of the brain, in contrast to previous studies suggesting that it was a simple massa.

Survey Assessment of Utility in Preoperative Magnetic Resonance (MR) Tractography Surgical Planning

Although tractography-guided surgery is used by many surgeons, there is controversy in the published literature as it relates to its clinical utility. Here we adopted a survey-based approach with the goal of attaining a broader view of how tractography influence preoperative planning in a sampling of practicing neurosurgeons. Three cases were prepared where the presence of a tumor distorted the optic radiation (case 1), arcuate fasciculus (case 2), and corticospinal tract (case 3). This survey was administered at the Medtronic Cranial Consortium attended by 20 practicing neurosurgeons. To avoid commercial bias, we used both the Brainlab and Medtronic platform to compute tractography. Each participant is asked to vote on a surgical trajectory before and after seeing the tractography images, as well as whether tractography added value in validating their surgical approach. In the 3 cases surveyed, 16%-44% of the surgeons changed the surgical corridor selected after seeing the tractography images. The most common finding associated with a change in surgical corridor involved intersection of the surgical corridor with visualized tracts. Consistently, >80% of the surgeons surveyed felt that tractography added value in their surgical planning. The clinical utility of tractography in preoperative planning varies as a function of surgeon and the tumor anatomy, with >80% of the participating surgeons believing that tractography added value in preoperative surgical planning.

Characterization and Classification of Spatial White Matter Tract Alteration Patterns in Glioma Patients Using Magnetic Resonance Tractography: A Systematic Review and Meta-Analysis.

Magnetic resonance (MR) tractography can be used to study the spatial relations between gliomas and white matter (WM) tracts. Various spatial patterns of WM tract alterations have been described in the literature. We reviewed classification systems of these patterns, and investigated whether low-grade gliomas (LGGs) and high-grade gliomas (HGGs) demonstrate distinct spatial WM tract alteration patterns. We conducted a systematic review and meta-analysis to summarize the evidence regarding MR tractography studies that investigated spatial WM tract alteration patterns in glioma patients. Eleven studies were included. Overall, four spatial WM tract alteration patterns were reported in the current literature: displacement, infiltration, disruption/destruction and edematous. There was a considerable heterogeneity in the operational definitions of these terms. In a subset of studies, sufficient homogeneity in the classification systems was found to analyze pooled results for the displacement and infiltration patterns. Our meta-analyses suggested that LGGs displaced WM tracts significantly more often than HGGs (n = 259 patients, RR: 1.79, 95% CI [1.14, 2.79], I2 = 51%). No significant differences between LGGs and HGGs were found for WM tract infiltration (n = 196 patients, RR: 1.19, 95% CI [0.95, 1.50], I2 = 4%). The low number of included studies and their considerable methodological heterogeneity emphasize the need for a more uniform classification system to study spatial WM tract alteration patterns using MR tractography. This review provides a first step towards such a classification system, by showing that the current literature is inconclusive and that the ability of fractional anisotropy (FA) to define spatial WM tract alteration patterns should be critically evaluated. We found variations in spatial WM tract alteration patterns between LGGs and HGGs, when specifically examining displacement and infiltration in a subset of the included studies.

Microstructural Brain Pathology in Paranoid Schizophrenia (According to Magnetic Resonance Tractography)

Background: inconsistency of the obtained results of research on the pathology of microstructural connectivity in schizophrenia on the basis of tractography, absence of clinical application of special MRI techniques justify the need to continue scientific search in this direction. Objective: to identify the features of microstructural pathology of the brain in paranoid schizophrenia. Patients and methods: 25 patients diagnosed with paranoid schizophrenia (F20.0) were included in the main group, 30 healthy subjects without neurological and somatic diseases made up the control group. Instrumental studies were carried out on a Philips Ingenia magnetic resonance tomograph (magnetic field strength 1.5 T) using a DTI pulse sequence. Subsequent processing was carried out using “DSI Studio” (software for the analysis of tractor data). Results and discussion: the resulting microstructural brain changes demonstrated differences in the microstructural connectivity of the brain in patients with paranoid schizophrenia compared to the control group. Significant connections were revealed (at the given parameters for constructing connectivity matrices) between the hippocampus and the cingulate gyrus, the hippocampus and thalamus, thalamus and structures of the striopallidar system, and the absence of significant connections between the amygdala in the main group compared to the control group. The results of graph theoretical analysis of neural network indicators of the brain demonstrated higher values of indicators of “clustering” and the “small world” coefficient, characteristic path length, transitivity, density, and lower values of the global efficiency indicator of the main group compared to the control group. Conclusion: the obtained results demonstrate microstructural semiotics of neural network changes of brain in paranoid schizophrenia. Changes in the connectivity of the hippocampus, thalamus, and amygdala appear to be important tractographic semiotic features of the microstructural pathology of the brain in paranoid schizophrenia. The study is one of the stages of the search for a method of objectification and detection of disruption of brain neuroplasticity processes in the endogenous pathology of the schizophrenic spectrum.

The system of intensive neurophysiological rehabilitation in the complex rehabilitation of children with autism spectrum disorders: application experience and evaluation of effectiveness

SYSTEM OF INTENSIVE NEUROPHYSIOLOGY REHABILITATION IN THE COMPLEX REHABILITATION OF CHILDREN WITH AUTISTIC SPECTRUM DISORDERS: APPLICATION EXPERIENCE AND EVALUATION OF EFFICIENCY Yurii G. Antipkin, Liudmyla G. Kyrylova, Oleksandr O. Miroshnikov State University «Academician O. M. Lukyanova Institute of Pediatrics, Obstetrics and Gynecology of the National Academy of Medical Sciences of Ukraine», Platona Maiborody Str., 8, Kyiv 04050, Ukraine Introduction. Today, autistic spectrum disorders (ASD) remain one of the most important and complex problems of modern neuropediatrics and rehabilitation, due to their increasing prevalence in all countries of the world, the complexity of early diagnosis, and the ambiguity of treatment strategies. In separate studies, the positive impact of the system of intensive neurophysiological rehabilitation (INR) according to the method of prof. V.I. Kozyavkin on motor and coordination functions of children with autism spectrum disorders was proved. The aim of the work is to determine the effectiveness of the system of intensive neurophysiological rehabilitation in children with ASD, as well as to study its influence on the dynamics of language, social and communicative functions in this group of children. Materials and methods. We observed 55 children with ASD aged 2-6 years (average age 3.80 ± 1.22 years), among them 32 boys and 23 girls. All children had an established diagnosis of ASD, according to the DSM-V criteria and the results of the M-CHAT questionnaire. A comprehensive examination of the state of the children's nervous system was carried out using a generally accepted neurological examination, video-EEG monitoring, brain MRI and MR-tractography. Results. In most children of the main group, after the end of the treatment course, improvement in all subscales of APEC was noted. On all four scales, the children of the main group managed to achieve higher positive results of treatment compared to the control group. However, compared to the indicators of children in the control group, statistically significant differences were found only on scales I (language, communicative functions) and IV (physical functions, behavior). In the children of the main group, there was a decrease in hyperactivity, improvement in self-control, a decrease in the level of aggression and self-aggression, normalization of muscle tone, improvement in gross and fine motor skills, gait, balance, and posture correction. Conclusions. The results of our study show that among 55 children with ASD who received treatment using the system of intensive neurophysiological rehabilitation, the majority of patients showed improvement in language, cognitive, and social functions, increased range of motion, and improvement in gross and fine motor skills. Thus, the results of the conducted study showed a positive impact of the INR on the physical, communicative and cognitive functions of children with ASD. Keywords: system of intensive neurophysiological rehabilitation, V. I. Kozyavkin's method, autistic spectrum disorders, magnetic resonance tractography, rehabilitation.

Magnetic Resonance Tractography and Intraoperative Direct Electrical Stimulation in Eloquent Area Glioma Surgery for 102 Cases: A Tertiary Care Center Experience From Northwest India.

Surgery of eloquent area gliomas is challenging and requires monitoring of the nearby white fiber tracts. In the present study, we analyzed 102 patients with eloquent region gliomas and discussed the concept of intraoperative dynamic white fiber tract navigation and monitoring. A total of 102 patients with an eloquent area glioma (52 insular, 29 motor area, 21 temporoparietal) were evaluated. The position of the white fiber tracts (corticospinal tract [or motor fiber; CST], inferior fronto-occipital fasciculus [ventral language fiber; IFOF], superior longitudinal fasciculus [SLF], and arcuate fasciculus [dorsal language fiber; AF) was recorded. Awake mapping of the cortical and subcortical eloquent structures was performed for all 102 patients. The suction stimulator was coregistered and used as a dynamic stimulator navigator. Of the 102 patients, 60 were men and 42 were women, with an average age of 39.8 years. Most of the white fiber tracts were normal (CST, 31.3%; IFOF, 39.2%; SLF/AF, 40.19%) or displaced (CST, 59.8%; IFOF, 47.05%; AF/SLF, 44.11%). A few were disrupted (CST, 8.8%; IFOF, 13.7%; SLF/AF, 15.7%). The extent of tumor resection was 82.8%, 86.5%, and 94% for those with insular glioma, motor area glioma, and temporoparietal glioma, respectively. Of the 102 patients, 18 had developed transient speech and language disturbances with improvement, and 14 had developed motor deficits, of whom, all except for 2, had shown gradual improvement. When the dynamic suction stimulator navigator was used, the extent of resection was 96.5%, without any added deficits. The use of intraoperative neuronavigation and neurophysiological assessment can help achieve maximal tumor resection of eloquent area gliomas. Use of the integrated suction stimulator navigator provided dynamic navigation and mapping of the peritumoral eloquent fibers.

Surgical treatment of gliomas in motor zone under control of neurophysiological monitoring

Background. Primary tumors of central nervous system account for about 2 % of all human tumors. Generally, the tumor removal is a necessary treatment step. The main goal of the intracerebral tumors surgical treatment is the formation removal in the most radical physiologically possible way, because this directly affects the patients’ life length and its quality.Aim. To assess the results of surgical treatment of motor zone tumors and identify predictors of development of irreversible motor disorders.Materials and methods. A retrospective analysis of results of surgical treatment from 105 patients with tumors that affect corticospinal tract and primary motor cortex of the brain or localized in close proximity to those areas (up to 10 mm). All patients were treated in the neurosurgical department of N.I. Pirogov National Medical and Surgical Center, Ministry of Health of Russia (Moscow) in the period from 2014 to 2020. There were 48 (46 %) men, 57 (54 %) women aged from 22 to 79 (mean age 47.6 ± 14.5) years. Tumors volume before surgery ranged from 5.16 to 283.3 (mean volume 80.9 ± 55.1) cm3. The tumors’ size and their relationship with the surrounding structures were assessed by pre‑surgery magnetic resonance imaging and magnetic resonance tractography. For the intraoperative assessment of motor zone state dynamics, the transcranial electrical stimulation (n = 105, 100 %) and direct transcortical stimulation (with the eight‑contact electrode stripe) (n = 68, 64.8 %) of the primary motor cortex were used. To assess the proximity of the motor zones, a straight cortical and subcortical bi‑ or monopolar electrical stimulation was used (n = 105, 100 %).Results. Sixty‑seven tumors (63.8 %) were removed completely, close to total removal was in 22 (20.9 %) tumors, 11 (10.5 %) tumors removal was subtotal and 5 (4.8 %) tumors were removed partially. Tumor volume after surgery ranged from 0 to 84.4 (mean volume – 3.54 ± 5.01) cm3, Development of novel motor deficiency or increase in pre‑surgery motor deficiency was observed in 46 (43.8 %) patients 24 hours after surgery and in 32 (30.5 %) of them 7 days after the treatment. However, during course of conservative therapy, the majority of patients showed regress of motor deficit and it remained only in 12 (11.4 %) patients on examination that was performed 6 months after surgery. Assessment of factors affecting development of persistent motor deficiency revealed its statistically significant association with intraoperative response decrease according to transcranial stimulation (p &lt; 0.001) and transcortical stimulation (p &lt; 0.001) data. There were no significant changes in the functional status of patients during postoperative period depending on strength of the direct stimulation when the resection was stopped (р = 0.9) or depending on radicality of tumor removal (p = 0.393).Conclusion.Removal of tumors of motor cortex and corticospinal tract using the multimodal neurophysiological mapping allows to achieve maximal resection of the tumor tissue with good functional outcomes. All of the above leads to significant improvement of patients’ life quality and allows further chemoradiotherapy.Combined use of 4 methods of the neurophysiological mapping (transcranial, transcortical, direct cortical ang sub‑cortical stimulation) helps to minim ize the disadvantages of each of the methods and achieve radicality of the motor zone tumor removal with maintai ning their functional status.Motor deficiency in patients increases after removal of motor zone tumors and then gradually restores to the original level or is improved 6 months after surgery.A predictor of development of persistent motor deficiency is decrease in amplitude of motor evoked potentials by 50 % or more from baseline (according to transcranial and transcortical neurophysiological stimulation data).When the motor evoked potentials in response to 1 mA direct monopolar neurostimulation are preserved then resection of the tumor is not a predictor of irreversible motor disorders during postoperative period.

Mapping of cortical speech zones and arcuate tract in patients with gliomas of temporal lobe of left hemisphere (analysis of a series of 27 observations)

Introduction. Craniotomy in conscious patients is a possible tool for optimizing of tumor resection degree (Extent of Resection) while maintaining the quality of life. Traditionally, the main focus during these operations is on the cortical speech areas. At the same time, there is a shortage of studies on mapping of long associative tracts during the removal of gliomas of dominant speech hemisphere.Aim. To analyze the data of intraoperative mapping and the postoperative state of speech function in patients with temporal lobe gliomas of left hemisphere (including those involving arcuate bundle) operated by the use of method of craniotomy in consciousness.Materials and methods. Gliomas of temporal lobe of left hemisphere were removed in 27 patients aged 14 to 67 years (median age 43 years). In 10 patients, the tumor was localized in middle parts of temporal lobe (at the level of middle and upper temporal gyri), in 9 patients – in posterior parts of temporal lobe and exited into the supramarginal zone, in 8 it spread partially from temporal lobe to insular area. Gliomas of high degree of malignancy were detected in 21 patients, 6 had tumors of low degree of malignancy. Surgical intervention was performed with intraoperative “awakening”. All patients underwent cortical electrophysiological stimulation in order to control localization of cortical speech zones, subcortical stimulation was performed in 21 cases to identify terminals of arcuate bundle. Speech disorders before and after surgery (on day 4–6) were evaluated by neuropsychologist using the method proposed by A. R. Luria, an automated test with the naming of pictures was additionally used intraoperatively. The average current strength of direct electrical stimulation was 3 (1.9–6.5) mA. In 12 cases, magnetic resonance (MR) tractography with construction of arcuate tract was performed before and after the surgery.Results. Cortical temporal speech zones during intraoperative electrical stimulation were detected in 20 (74 %) of 27 patients. In 10 patients, the arcuate tract was mapped in form of appearance of mixed speech disorders in the depth of surgical wound. In 23 (85.2 %) of 27 patients in early postoperative period, an increase in speech disorders was noted of which 13 people had disorders of temporal type only and 10 people (surgery on deep posterior parts of temporal lobe) had a combination of temporal and frontal types of speech disorders (conduction aphasia). Postoperative MR‑tractography (performed in 12 patients) revealed direct intraoperative tract lesion in 5 cases and ischemia of the tract area passage in 2 cases. These 7 patients had combined speech disorders after surgery. Gross sensory aphasia after surgery was manifested in 4 patients, in 2 of them ischemia was revealed according to postoperative magnetic resonance imaging, and 2 more had hemorrhagic impregnation in the removed tumor bed.Conclusion. When removing tumors of temporal lobe in “awakening” conditions it is necessary to map speech zones not only in the cortical, but also in the subcortical area with terminals of arcuate bundle. Mapping of speech zones in these different localizations makes it possible to identify fundamentally different speech disorders.

Diffusion tensor imaging – Magnetic resonance tractography in stroke patients to predict clinical outcome

Diffusion tensor imaging – Magnetic resonance tractography in stroke patients to predict clinical outcome

Organization and current understanding of speech function of the brain: literature review

Introduction. History of study of speech function of the brain has started in the middle of the 19th century. First studies discovered cortical representations of speech in the brain, proposed different theories of speech function structure. Technological breakthroughs of the 20th century allowed to study not only cortical representations of speech function but also complex connections of the white matter important for practical work of neurosurgeons. Deeper studies of speech led to revisions of the old theories, proposals of new theories. Current study methods showed complexity of speech organization, multifunctionality of speech tracts.Aim. To analyze and systemize historical and current scientific data on organization of speech function of the brain, as well as methods of preoperative evaluation and intraoperative techniques of identification of speech zones in the cerebral cortex.Materials and methods. As a results of data search in the PubMed database, 77 articles published between 1954 and 2020 were selected.Results. Studies of characteristics of speech function are widely represented in current scientific literature, and their number grows every year. Some researchers study individual speech aspects: cortical representation, individual speech tracts. Others deal with general consequences of speech impediments after tumor resection, strokes, traumas. The authors cross-linked and systemized numerous data from different sources of information.Conclusion. Speech function of the brain is one of the most complexly organized aspects of the higher nervous function, and it is being actively researched worldwide. Implementation of such revolutionary examination techniques as intraoperative mapping of the cerebral cortex, magnetic resonance tractography provided a plethora of new information on morphofunctional characteristics of speech function. Further studies of speech function of the brain and systematization of the obtained data are necessary for deeper understanding of the details of speech organs' functionality. Advances in this direction will help surgeons avoid unwanted neurological deficit in communication ability, one of the most important abilities, and improve patients' quality of life.

Magnetic resonance tractography of the brachial plexus: step-by-step

BackgroundMagnetic resonance (MR) tractography of the brachial plexus (BP) is challenging due to different factors such as motion artifacts, pulsation artifacts, signal-to-noise ratio, spatial resolution; eddy currents induced geometric distortions, sequence parameters and choice of used coils. Notably challenging is the separation of the peripheral nerve bundles and skeletal muscles as both structures have similar fractional anisotropy values. We proposed an algorithm for robust visualization and assessment of BP root bundles using the segmentation of the spinal cord (SSC, C4-T1) as seed points for the initial starting area for the fibre tracking algorithm.MethodsTwenty-seven healthy volunteers and four patients with root avulsions underwent magnetic resonance imaging (MRI) examinations on a 3T MR scanner with optimized measurement protocols for diffusion-weighted images and coronal T2 weighted 3D short-term inversion recovery sampling perfection with application optimized contrast using varying flip angle evaluation sequences used for BP fibre reconstruction and MR neurography (MRN). The fibre bundles reconstruction was optimized in terms of eliminating the skeletal muscle fibres contamination using the SSC and the tracking threshold of the normalized quantitative anisotropy (NQA) on reconstruction of the BP. In our study, the NQA parameter has been used for fiber tracking instead of fractional anisotropy (FA). The diffusion data were processed in individual C4-T1 root bundles using the generalized q-sampling imaging (GQI) algorithm. Calculated diffusion parameters were statistically analysed using the two-sample t-test. The MRN was performed in MedINRIA and post-processed using the maximum intensity projection (MIP) method to demonstrate BP root bundles in multiple planes.ResultsIn control subjects, no significant effect of laterality in diffusion parameters was found (P>0.05) in the BP. In the central part of the BP, a significant difference between control subjects and patients at P=0.02 was found in the NQA values. Other diffusion parameters were not significantly different.ConclusionsUsing NQA instead of FA in the proposed algorithm allowed for a better separation of muscle and root nerve bundles. The presented algorithm yields a high quality reconstruction of the BP bundles that may be helpful both in research and clinical practice.

ДИФЕРЕНЦІАЛЬНА ДІАГНОСТИКА ЦЕРЕБРАЛЬНИХ СУДИННИХ ВАД І ОБ’ЄМНИХ НОВОУТВОРЕНЬ ФУНКЦІОНАЛЬНО ВАЖЛИВИХ ДІЛЯНОК МОЗКУ: КРИТЕРІЇ ВИБОРУ НЕЙРОХІРУРГІЧНОЇ ТАКТИКИ

Introduction. We believe, that in the planning of the surgical removal of cerebral vascular malformations (CVM) of eloquent brain areas, a question of whether they include the functionally sustainable brain tissue remains relevant. The question of whether the surgical procedure is safe is paramount. Aim. To assess the value of magnetic resonance (MR) tractography in deciding on the tactics of surgical treatment of CVM through comparison with morphological studies. Study methods. A review of the literature concerning the surgical treatment of cavernous malformations (CM) and arteriovenous malformations (AVM) localized in eloquent brain areas (EBA). Four patients with CVM of EBA were selected based on the availability of MR tractography data and histologic specimens. The method of optical microscopy was used to study microslides stained with the classic (hematoxylin-eosin) and specialized methods (Masson’s and Hart’s methods). Results. Patients’ MR-tractography data showed the presence of conductive paths in the tissues of CM and AVM and the reduced fractional anisotropy in the regions of interest, which indicates their involvement. During optical microscopy of specimens of CVMs, we found brain tissues between pathological vessels. To our opinion, this explains the visualization of conducting paths in CVMs during MR tractography. Conclusions. When planning surgeries in case of CVMs, attention should be paid to the results of conductive path visualization. According to MR tractography and morphological data, in some cases, there is brain parenchyma in the structure of CMs and AVMs, which may require additional attention in deciding on the radical resection of CVMs of EBAs.

Magnetic resonance tractogtaphy: possibilities and limitations, modern approach to data processing

Purpose: systematization of the knowledge about diffusion tensor magnetic resonance tomography; analysis of literature related to current limitations of this method and possibilities of overcoming these limitations.Materials and methods. We have analyzed 74 publications (6 Проанализировано 74 публикации (6 Russian, 68 foreign), published in the time period from 1986 to 2021years. More, than half of these articles were published in the last ten years, 19 studies-in the time period from 2016 to 2021years.Results. In this article we represent the physical basis of diffusion weighted techniques of magnetic resonance tomography, principles of obtaining diffusion weighted images and diffusion tensor, cover the specific features of the probabilistic and deterministic approaches of the diffusion tensor MRI data processing, describe methods of evaluation of the diffusion characteristics of tissues in clinical practice. Article provides a thorough introduction to the reasons of existing limitations of diffusion tensor MRI and systematization the main developed approaches of overcoming these limitations, such as multi-tensor model, high angular resolution diffusion imaging, diffusion kurtosis visualization. The article consistently reviews the stages of data processing of diffusion tensor magnetic resonance tomography (preprocessing, processing and post processing). We also describe the special aspects of the main approaches to the quantitative data analysis of diffusion tensor magnetic resonance tomography (such as analysis of the region of interest, analysis of the total data amount, quantitative tractography).Conclusion. Magnetic resonance tractography is a unique technique for noninvasive in vivo visualization of brain white matter tracts and assessment of the structural integrity of their constituent axons. In the meantime this technique, which has found applications in numerous pathologies of central nervous system, has a number of significant limitations, and the main of them are the inability to adequately visualize the crossing fibers and the relatively low reproducibility of the results. Standardization of the data postprocessing algorithms, further upgrading of the magnetic resonance scanners and implementation of the alternative tractography methods have the potential of partially reducing of the current limitations.

GPU-accelerated connectome discovery at scale

Diffusion magnetic resonance imaging and tractography enable the estimation of anatomical connectivity in the human brain, in vivo. Yet, without ground-truth validation, different tractography algorithms can yield widely varying connectivity estimates. Although streamline pruning techniques mitigate this challenge, slow compute times preclude their use in big-data applications. We present ‘Regularized, Accelerated, Linear Fascicle Evaluation’ (ReAl-LiFE), a GPU-based implementation of a state-of-the-art streamline pruning algorithm (LiFE), which achieves >100× speedups over previous CPU-based implementations. Leveraging these speedups, we overcome key limitations with LiFE’s algorithm to generate sparser and more accurate connectomes. We showcase ReAl-LiFE’s ability to estimate connections with superlative test–retest reliability, while outperforming competing approaches. Moreover, we predicted inter-individual variations in multiple cognitive scores with ReAl-LiFE connectome features. We propose ReAl-LiFE as a timely tool, surpassing the state of the art, for accurate discovery of individualized brain connectomes at scale. Finally, our GPU-accelerated implementation of a popular non-negative least-squares optimization algorithm is widely applicable to many real-world problems.

Neurovisualization features of brain anatomy in children with spastic cerebral palsy revealed by magnetic resonance tractography

Aim. To perform quantitative evaluation of the degree of white matter tract abnormalities in children with spastic cerebral palsy by magnetic resonance tractography to determine severity of the disease, as well as to carry out a dynamic assessment of treatment effectiveness.Materials and methods. The study included 46 children (32 males, 14 females; average age 5.4 ± 1.1 years). The participants were divided into two groups. The experimental group consisted of 23 children with spastic cerebral palsy. The control group included 23 children without any neurological disorder. Examination of the brain was performed on the Siemens Essenza 1,5 Т system (Siemens, Germany) and included magnetic resonance tractography to reconstruct the major white matter tracts. The number of fibers, average fractional anisotropy value, apparent diffusion coefficient, and coefficient of myelination of major white matter tracts in the brain were calculated and analyzed.Results. We found a significant difference in the above-stated parameters between the groups. The experimental group showed a decrease in the absolute number of fibers at the central and posterior segments of the corpus callosum, corticospinal tracts, and left inferior longitudinal fasciculus. Besides, we detected a decrease in fractional anisotropy at 2–5 segments of the corpus callosum and right lateral corticospinal tract, an increase in the apparent diffusion coefficient at 2, 4, and 5 segments of the corpus callosum and left lateral corticospinal tract, and a decrease in the myelination coefficient in all the examined tracts, except for superior longitudinal fasciculus. We revealed a positive correlation between the intensity of the motor disturbance and the coefficient of myelination at the anterior corpus callosum and inferior longitudinal fasciculus.Conclusion. Magnetic resonance tractography is an informative technique for unbiased evaluation of white matter tract anatomy, as well the level and degree of motor tract damage. The most useful characteristics of white matter tract anatomy are the absolute number of fibers in the tract, fractional anisotropy, and coefficient of myelination. Some of them correlated with the intensity of motor disturbance, so they can be regarded as potential predictors of rehabilitation potential.

Microsurgical and White Matter Anatomy of the Hypothalamus: A Fiber Dissection Study Correlating With Magnetic Resonance Tractography.

Microsurgical and White Matter Anatomy of the Hypothalamus: A Fiber Dissection Study Correlating With Magnetic Resonance Tractography.