Many diffusion tensor imaging (DTI) studies have reported an association between corticospinal tract (CST) injury and motor dysfunction. In this study, we investigated CST recovery in 29 pediatric patients with clinical hemiplegia using DTI. We measured the fractional anisotropy (FA), apparent diffusion coefficient (ADC), and asymmetric anisotropy (AA) of both CSTs. The patients were classified into three groups according to severity of CST disruption of the more affected hemisphere. DTI was followed up for 9.34 ± 2.07 months after initial evaluation. The FA value of the more affected CST showed a significant decrease compared to the opposite side at initial and follow up evaluation, respectively (p<0.05). The FA value of both CSTs showed a significant increase at follow up compared to the initial evaluation, while more changes were observed on the more affected side, compared with the less affected side (p<0.05). AA showed a significant decrease at follow up, and showed significant correlation with interval change of FA value of the more affected side, not with that of the less affected side (r=0.543, p<0.05). 19 patients showed change of CST integrity. In the current study, the results of DTI showed recovery of the CST and provided radiologic evidence for a scientific basis of brain plasticity in pediatric patients.

Accurate assessment of the cingulum is difficult, because it is a long neural tract that extends from the orbitofrontal cortex to the medial temporal lobe. We divided the cingulum into five parts and investigated changes caused by injury in these regions in patients with diffuse axonal injury (DAI) using diffusion tensor tractography (DTT). Twenty-one patients with DAI and 21 control subjects were recruited. The cingulum was divided into; the anterior, superior (the anterior and posterior portions), posterior, and inferior regions. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), and tract number were measured in each region. FA values and tract numbers in the patient group were lower in the anterior superior cingulum than in controls (p<0.05); whereas the ADC values in the patient group were higher in the anterior and posterior superior cingulum than in controls (p<0.05). In the superior cingulum, increases in the ADC values of the anterior portion (Δ8.1%) were higher than those of the posterior portion (Δ5.5%). We found that the superior cingulum was injured in patients with DAI, and that the anterior portion of the superior cingulum was more injured than the posterior portion. Consequently, the superior cingulum appears to be a vulnerable area and the anterior superior cingulum appears more vulnerable than the posterior superior cingulum in DAI.

A few studies have reported on the neural connectivity of some neural structures of the visual system in the human brain. However, little is known about the neural connectivity of the lateral geniculate body (LGB). In the current study, using diffusion tensor tractography (DTT), we attempted to investigate the neural connectivity of the LGB in normal subjects. A total of 52 healthy subjects were recruited for this study. A seed region of interest was placed on the LGB using the FMRIB Software Library which is a probabilistic tractography method based on a multi-fiber model. Connectivity was defined as the incidence of connection between the LGB and target brain areas at the threshold of 5, 25, and 50 streamlines. In addition, connectivity represented the percentage of connection in all hemispheres of 52 subjects. We found the following characteristics of connectivity of the LGB at the threshold of 5 streamline: (1) high connectivity to the corpus callosum (91.3%) and the contralateral temporal cortex (56.7%) via the corpus callosum, (2) high connectivity to the ipsilateral cerebral cortex: the temporal lobe (100%), primary visual cortex (95.2%), and visual association cortex (77.9%). The LGB appeared to have high connectivity to the corpus callosum and both temporal cortexes as well as the ipsilateral occipital cortex. We believe that the results of this study would be helpful in investigation of the neural network associated with the visual system and brain plasticity of the visual system after brain injury.

Little is known about the neural connectivity of the fornix in the human brain. In the current study, using diffusion tensor imaging, we attempted to investigate the neural connectivity of the posterior body of the fornix in the normal human brain. A total of 43 healthy subjects were recruited for this study. DTIs were acquired using a sensitivity-encoding head coil at 1.5T. For connectivity of the posterior body of the fornix, a seed region of interest was used on the posterior body of the fornix. Connectivity was defined as the incidence of connection between the posterior body of the fornix and any neural structure of the brain at the threshold of 5, 25, and 50 streamline. At the threshold of 5, 25, and 50, the posterior body of the fornix showed connectivity to the precentral gyrus (37%, 19%, and 15%), the postcentral gyrus (25%, 11.5%, and 7%), the posterior parietal cortex (16.5%, 5%, and 5%), the brainstem (12%, 4.5%, and 3.5%), the crus of the fornix (34%, 10.5%, and 7%), the contralateral splenium of the corpus callosum (12.5%, 5%, and 0%), and the ipsilateral splenium of the CC (69.8%%, 33.7%, and 23.3%), respectively. Findings of this study showed that the posterior body of the fornix had connectivity with the cerebral cortex, the brainstem, the fornical crus, and the contralateral splenium through the splenium of the corpus callosum in normal subjects. We believe that the results of this study would be helpful in investigation of the neural network related to memory and recovery mechanisms following fornical injury in the human brain.

Research on the neural connectivity of the intralaminar thalamic nuclei (ILN) has been limited. Since the introduction of diffusion tensor imaging (DTI), many probabilistic DTI studies have reported on neural connectivity of neural structures in normal subjects. However, no study on the neural connectivity of the ILN has been reported so far. In this study, using probabilistic DTI, we investigated the neural connectivity of the ILN in normal subjects. A total of 40 healthy subjects were recruited for this study. A seed region of interest was placed on the ILN of the thalamus using the FMRIB Software Library. Connectivity was defined as the incidence of connection between the ILN and target brain areas. We found high connectivity between the ILN and arousal-related areas (prefrontal cortex 100%, reticular formation 100%, pedunculopontine nucleus 97.5%, basal forebrain 95%, and hypothalamus 92.5% at threshold 5), attention related area (prefrontal cortex 100% at threshold 5), and sensori-motor function related areas (primary motor cortex 100%, globus pallidus 100%, putamen 98.8%, premotor cortex 96.3%, primary somatosensory cortex 95.0%, caudate nucleus 92.5%, and posterior parietal cortex 90.0% at threshold 5). Findings of this study showed that ILN has high connectivity with brain areas related to arousal, attention, and sensorimotor function. This result indicates a close association of ILN with these functions in the human brain.

The parieto-insular vestibular cortex (PIVC) is a core region of vestibular input into regions of the cortex. The vestibular nuclei have reciprocal connections with the PIVC. However, little is known about injury of the core vestibular pathway to the PIVC in patients with dorsolateral medullary infarctions. In this study, using diffusion tensor tractography (DTT), we investigated injury of the neural connections between the vestibular nuclei and the PIVC in patients with typical central vestibular disorder.

Precise evaluation of the ascending reticular activating system (ARAS) is important for diagnosis, prediction of prognosis, and management of patients with disorders of impaired consciousness. In the current study, we attempted to reconstruct the direct neural pathway between the brainstem reticular formation (RF) and the cerebral cortex in normal subjects, using diffusion tensor imaging (DTI). Forty-one healthy subjects were recruited for this study. DTIs were performed using a sensitivity-encoding head coil at 1.5Tesla with FMRIB Software Library. For connectivity of the brainstem RF, we used two regions of interest (ROIs) for the brainstem RF (seed ROI) and the thalamus and hypothalamus (exclusion ROI). Connectivity was defined as the incidence of connection between the brainstem RF and target brain regions at the threshold of 5 and 50 streamlines. Regarding the thresholds of 5 and 50, the brainstem RF showed high connectivity to the lateral prefrontal cortex (lPFC, 67.1% and 20.7%) and ventromedial prefrontal cortex (vmPFC, 50.0% and 18.3%), respectively. In contrast, the brainstem RF showed low connectivity to the primary motor cortex (31.7% and 3.7%), premotor cortex (24.4% and 3.7%), primary somatosensory cortex (23.2% and 2.4%), orbitofrontal cortex (17.1% and 7.3%), and posterior parietal cortex (12.2% and 0%), respectively. The brainstem RF was mainly connected to the prefrontal cortex, particularly lPFC and vmPFC. We believe that the methodology and results of this study would be useful to clinicians involved in the care of patients with impaired consciousness and researchers in studies of the ARAS.

We investigated differences in recovery course of motor weakness according to the state of the corticospinal tract (CST) in putaminal hemorrhage, using diffusion tensor tractography (DTT).