CC BY
55
Section 7. Medical science
Aminov Khabibulla, Tashkent Institute for Postgraduate Medical Education, Medical Radiology department.
Tashkent, Uzbekistan. E-mail: westferry1@rambler.ru
Assessing the functional architecture of the brain with diffusion mri in paediatric patients
Abstract: The paper presents the results of the evaluation with MRI diffusion in the diagnosis of structural brain damage in children with symptomatic epilepsy in the background of developmental abnormalities of the brain and comparison of changes detected with routine MRI parameters. We studied parameters of MR diffusion weighted imaging in symptomatic epilepsy paediatric patients and determined the quantitative standards of numerical values of diffusion of white matter in children with symptomatic epilepsy in brain anomalies. The regions with abnormal white matter FA and ADC values not only matched to limbic circle zones, but also to areas of intra- and interhemispheric connections uniting the frontal, temporal, parietal and occipital lobes of the brain. Determining the damaged zones of white matter of brain in symptomatic epilepsy, regardless of etiology, is important to predict the prognosis of the disease and the likely possibility of cognitive impairment in children.
Keywords: Epilepsy, Fractional anisotropy, anisotropy, Average diffusion capacity, white matter, mean diffusion, statistical parametric mapping.
Introduction
According to the recent literature, malformations of the brain are detected in approximately 30% ofcases in a population of children with epileptic seizures [1, 51-61]. These children have a wide range of embryo fetal lesions of the central nervous system (CNS), which plays key role in the pathogenesis of early childhood epilepsy [2, 1-15]. The introduction ofMRI in clinical practice has greatly expanded the identification of various structural changes in brain tissue underlying the formation of the epileptic focus, which usually leads to the subsequent development of epilepsy. Congenital disorders of brain has a major part in epilepsy origin, which manifest themselves in early periods of childhood [3, 250-264]. Diffusion imaging is an MRI method that produces in vivo magnetic resonance images of biological tissues sensitized with the local characteristics of molecular diffusion, generally water [4, 5-20]. An increased number of neuronal cell bodies in the white matter (as in mi-crodysgenesis) could disrupt the white matter tracts and cause a reduction in anisotropy. Anisotropy is usually highest in the major white matter tracts and lower in the tissue close to the cortex where fibres are crossing or fanning out [6, 206-215]. Several studies have shown reduced diffusivity during partial status epilepticus correlated with the cortical areas involved [7, 676-685]. The most important parameter of DWI MRI, characterized by the integration of the white matter is fractional anisotropy (FA), Average diffusion capacity (ADC) is also used as indicator to evaluate the results of diffusion tensor MRI.
The aim of this study was to determine the quantitative standards of numerical values of diffusion of white matter in children with symptomatic epilepsy in brain anomalies.
Materials and methods
MRI studies were conducted among 54 children with symptomatic epilepsy to developmental abnormalities of the
brain. Age grading ranged from 1 year to 14 years, mean age 5,9 ± 0,56 years. The debut of epileptic seizures observed from birth to 8 years old, the average age of debut 2,3 ± 0,59 years. The disease duration averaged 4,4 ± 0,96 years. The patients were examined and treated in the neurological department of the clinic of the Tashkent Pediatric Medical Institute and diagnostic center LLC "MDS-Service" for the period from 2012 to 2014. All children (54 children) was conducted routine MRI, of whom 26 held MR-diffusion (main group). The control group consisted of 20 healthy children with no clinical manifestations of epilepsy and no signs of epileptic activity on the EEG. (Total number of children studied were 74).
Conventional MRI scanning protocol. MRI studies were performed on a GE tomography with a magnetic field of 1.5 T using a head radio frequency coil consisting of18 elements. The study protocol included a standardized program of MRI of the brain, as well as aiming neuroimaging the me-diobasal temporal lobe with thin sections with the possibility of post processing and imaging in different planes. Among the special programs used fast spin-echo T2-weighted, perpendicular to the longitudinal axis of the hippocampus slice thickness of 2 mm, and 3D T1 SP6R — pulse sequences with the reform and obtaining images mediobasal temporal lobe perpendicular and parallel to the longitudinal axis of the hippocampus.
DWIscanningprotocol. Scans were performed on a 1.5 T GE Ovation. Single-shot CSF-suppressed diffusion-weighted echoplanar imaging (EPI) was used [TR/TE/TI (repetition time/echo time/inversion time) 5000/78/1788 ms], acquisition matrix 96 x96, reconstruction matrix 128 x128, FOV (field of view) 24 cm, slice thickness 5 mm covering the whole brain. Diffusion scanning time was 19 min. Total scanning time including diffusion, localizer and high-resolution EPI
Assessing the functional architecture of the brain with diffusion mri in paediatric patients
anatomical scan was 25 min. Images were transferred to a separate workstation for post-processing.
Results of the study
Neurological symptoms in 46.3% of the children (25 children) was characterized by central paresis, at 92.6% (50 children) were observed varying degrees of severity delayed mental and motor development. In our study, cortical dysplasia characterized by licencephaly (agyria) pachygyry, micropolygiry, shizencephaly and transmantil dysplasia. In this group of children were observed combined multifo-cal and generalized violations in electroencephalographic (EEG) studies. Based on the analysis of MRI data in children with licencephaly observed: complete diffuse agyria,
Таблица 1. - Findings of FA and MD in children
with the presence of fragmentary agyria individual convolutions in the frontal and temporal regions of the brain, sometimes medial or basal surface of the frontal lobes. Just diagnostic importance is straightforward nature of the border between gray and white matter of the brain, white matter hypoplasia, ventriculomegaly, and the expansion of the central sulcus Sylvian. We have studied the values of FA and MD in healthy children. Firstly we established individual normal values, then compared these findings to epilepsy patients and we have established a significant decrease in quantitative values of FA in frontal, temporal, parietal, and occipital region of the brain.
Below compared with the control group (Table. 1).
with symptomatic epilepsy and brain anomalies
Etiology of symptomatic epilepsy Frontal lobe white matter Temporal lobe Parietal lobe Occipital lobe Corpus callo-sum Internal capsule
Healthy children (n=20)FA 0,50±0,004 0,51±0,004 0,50±0,004 0,51±0,004 0,52±0,004 0,52±0,004
Brain anomalies (n=26)FA 0,38±0,02* 0,36±0,002 0,37±0,03* 0,50±0,004 0,54±0,02* 0,56±0,004
Healthy children (n=20) MD 1,2±0,03 1,3±0,03 1,25±0,04 1,35±0,04 1,06±0,04 1,02±0,03
Brain anomalies (n=26) MD 1,5±0,06* 1,55±0,06 1,6±0,06* 1,65±0,06 1,36±0,05* 1,11±0,05
Note: * — the accuracy of the data compared with the norm (* — P <0.01) Source: Author.
To evaluate the results ofMR diffusion used as indicator of the average diffusion capacity (ADC), which increase in value is due to a defect or loss of neurogenesis of cells with a consequent increase in the extracellular space. When analyzing the correlation between the indicators of the FA and MD in
children of main group the strong negative relationship in all areas were revealed, which is result of neurogenesis deficit, which in turn can be a predictor of symptomatic epilepsy with anomalies of the brain.
Fig. 1. Patient 1: bilateral frontoparietal gyral abnormalities with thickened cortex. (A) Normalized axial anisotropy maps at the same slice localization for the averaged 30 control subjects. (B) The patient. Note that the difference in the signal-to-noise ratio between the two maps is due to averaging of the 30 control subjects. (C) Regions of significantly decreased anisotropy identified with SPM are superimposed (blue) on the patient's normalized anisotropy map. (D) The equivalent slice of the patient's T1-weighted image. The regions of decreased anisotropy not only coincide with the localization of the gyral abnormalities with thickened cortex, but are also found in the normal-appearing occipital lobes. Note that right on the images is the patient's right.
Analyzing the data of MR diffusion in children with symp- dren with symptomatic epilepsy on a background of develop-
tomatic epilepsy on the background abnormalities of brain development we have identified low levels of FA in frontal and parietal lobes (0,38 ± 0,02 and 0,37 ± 0,02, respectively; P <0.01) as compared with the normal values. Indicators of MD in chil-
mental abnormalities of the brain underwent the following changes: the frontal lobe figures were 1,50 ± 0,06 (p <0.01) for the rear — 1,59 ± 0,06 (P <0.01). There was a significant deviation of MD from normal values, 22.11% for the frontal
