Corpus Callosum White Matter Tracts Research Articles

Fiber Tractography and Diffusion Tensor Imaging in Children with Agenesis and Dysgenesis of Corpus Callosum: A Clinico-Radiological Correlation

Background Corpus callosum is the largest commissure in human brain. It consists of tightly packed white matter tracts connecting the two cerebral hemispheres. In this study we aimed to evaluate role of fiber tractography (FT), and diffusion tensor imaging (DTI) in pediatric patients with corpus callosum anomalies and correlate findings with clinical presentation. Materials and Methods This prospective study included 115 children with clinical presentations and CT findings suggested corpus callosum anomalies. Their ages ranged between 2 and 12 year-old. They referred from Pediatric Neurology unit to Radiology Department in Minia University hospital for children, Minia (Egypt) from April 2018 till December 2018. They underwent MRI fiber tractography and diffusion tensor imaging after approval of ethical committee of our institution and informed consent form patients’ parents. Results Our study included 42 (36.5 %) males and 73 (63.5 %) females. They were reviewed for corpus callosum anomalies according to Hanna classification, the commonest was hypoplasia without dysplasia 37/115 (32 %). Using DTI and FT, corpus callosum fiber defects were classified into fronto-rostral, caudal and whole body defect. Significant statistical correlation was found between ADHD, autism and loss of fronto-rostral fibers. Epilepsy and developmental delay were correlated to whole body defect and caudal fiber tract defects. Conclusion Based on the results, Fiber tractography and diffusion tensor imaging are newly developed promising techniques. They proved high accuracy in localization of exact affected corpus callosum white matter tract. They help to predict prognosis of patients that could not be explained by morphological changes seen in conventional MRI.

MRS and DTI evidence of progressive posterior cingulate cortex and corpus callosum injury in the hyper-acute phase after Traumatic Brain Injury

ABSTRACTThe posterior cingulate cortex (PCC) and corpus callosum (CC) are susceptible to trauma, but injury often evades detection. PCC Metabolic disruption may predict CC white matter tract injury and the secondary cascade responsible for progression. While the time frame for the secondary cascade remains unclear in humans, the first 24 h (hyper-acute phase) are crucial for life-saving interventions.Objectives: To test whether Magnetic Resonance Imaging (MRI) markers are detectable in the hyper-acute phase and progress after traumatic brain injury (TBI) and whether alterations in these parameters reflect injury severity.Methods: Spectroscopic and diffusion-weighted MRI data were collected in 18 patients with TBI (within 24 h and repeated 7–15 days following injury) and 18 healthy controls (scanned once).Results: Within 24 h of TBI N-acetylaspartate was reduced (F = 11.43, p = 0.002) and choline increased (F = 10.67, p = 0.003), the latter driven by moderate-severe injury (F = 5.54, p = 0.03). Alterations in fractional anisotropy (FA) and axial diffusivity (AD) progressed between the two time-points in the splenium of the CC (p = 0.029 and p = 0.013). Gradual reductions in FA correlated with progressive increases in choline (p = 0.029).Conclusions: Metabolic disruption and structural injury can be detected within hours of trauma. Metabolic and diffusion parameters allow identification of severity and provide evidence of injury progression.

Extracellular signal‐regulated kinase 1/2 signaling promotes oligodendrocyte myelination in vitro

Multiple extracellular factors have been implicated in orchestrating myelination of the CNS; however, less is known about the intracellular signaling cascades that regulate this process. We have previously shown that brain-derived neurotrophic factor (BDNF) promotes oligodendrocyte myelination. Here, we screened for the activation of candidate signaling pathways in in vitro myelination assays and found that extracellular signal-regulated kinase (Erk) signaling positively correlated with basal levels of oligodendrocyte myelination as well as BDNF-induced myelination in vitro. By selectively manipulating Erk1/2 activation in oligodendrocytes in vitro, we found that constitutive activation of Erk1/2 significantly increased myelination, mimicking the promyelinating effect of BDNF, and also caused myelination to occur earlier. Conversely, selective inhibition of Erk1/2 in oligodendrocytes significantly reduced the basal level of myelination and blocked the promyelinating effect of BDNF. Analysis of myelinating spinal cord and corpus callosum white matter tracts revealed that the majority of mature oligodendrocytes are co-labeled with phospho-Erk1/2, whereas phospho-Erk1/2 was rarely observed in oligodendrocyte progenitor cells. Finally, the total level of phospho-Erk1/2 correlated with myelin formation during the early postnatal period. Collectively, these data identify that Erk1/2 signaling within oligodendrocytes exerts an important and direct effect to promote myelination.

Secondary Corpus Callosum Abnormalities Associated with Antiepileptic Drugs in Temporal Lobe Epilepsy

Epilepsy is more than a grey-matter disorder affecting large white matter connections of the brain with seizure generation and propagation. The mechanism for such changes remains unclear. The purpose of this study was to investigate the microstructural changes in the corpus callosum in temporal lobe epilepsy (TLE) patients and whether these abnormalities are related to antiepileptic drug (AED) therapy. Ten TLE patients receiving AED therapy, ten TLE patients with no therapy and ten controls were included in the study. The regions of interest in the corpus callosum were outlined to each Witelson region (WR). Fractional anisotrophy (FA), apparent diffusion coefficient (ADC), three main diffusivity values (λ1, λ2, λ3) and tractography were acquired from each WR. DTI indices of these tracts and each WR were compared between the three subject groups and correlates examined with clinical variables that included duration of epilepsy, gender, AED type and AED therapy exposure. In TLE subjects with receiving AED therapy significantly (p<0.05) decreased FA and increased ADC values of corpus callosum were obtained when compared to the other groups. There was no significant relationship between AED type and DTI indices. Analysis of eigen values in the splenium of corpus callosum (WR7) showed λ1 values were significantly decreased in relation to AED medication duration (p<0.05). FA values of rostrum and corpus showed a reduction with duration of epilepsy. TLE is associated with abnormal integrity of corpus callosum white matter tracts. AED therapy may cause additional damage on secondary degeneration and medication time effects especially on the splenium of corpus callosum.

Reduced interhemispheric connectivity in schizophrenia-tractography based segmentation of the corpus callosum

Background A reduction in interhemispheric connectivity is thought to contribute to the etiology of schizophrenia. Diffusion Tensor Imaging (DTI) measures the diffusion of water and can be used to describe the integrity of the corpus callosum white matter tracts, thereby providing information concerning possible interhemispheric connectivity abnormalities. Previous DTI studies in schizophrenia are inconsistent in reporting decreased Fractional Anisotropy (FA), a measure of anisotropic diffusion, within different portions of the corpus callosum. Moreover, none of these studies has investigated corpus callosum systematically, using anatomical subdivisions. Methods DTI and structural MRI scans were obtained from 32 chronic schizophrenic subjects and 42 controls. Corpus callosum cross sectional area and its probabilistic subdivisions were determined automatically from structural MRI scans using a model based deformable contour segmentation. These subdivisions employ a previously generated probabilistic subdivision atlas, based on fiber tractography and anatomical lobe subdivision. The structural scan was then co-registered with the DTI scan and the anatomical corpus callosum subdivisions were propagated to the associated FA map. Results Results revealed decreased FA within parts of the corpus interconnecting frontal regions in schizophrenia compared with controls, but no significant changes for callosal fibers interconnecting parietal and temporo-occipital brain regions. In addition, integrity of the anterior corpus was statistically significantly correlated with negative as well as positive symptoms, while posterior measures correlated with positive symptoms only. Conclusions This study provides quantitative evidence for a reduction of interhemispheric brain connectivity in schizophrenia, involving corpus callosum, and further points to frontal connections as possibly disrupted in schizophrenia.