Min Cheol Chang

Primary motor cortex activation by transcranial direct current stimulation in the human brain.

Transcranial direct current stimulation (tDCS) can modulate motor cortex excitability in the human brain. We attempted to demonstrate the cortical stimulation effect of tDCS on the primary motor cortex (M1) using functional MRI (fMRI). An fMRI study was performed for 11 right-handed healthy subjects at 1.5 T. Anodal tDCS was applied to the scalp over the central knob of the M1 in the left hemisphere. A constant current with an intensity of 1.0 mA was applied. The total fMRI paradigm consisted of three sessions with a 5-min resting period between each session. Each session consisted of five successive phases (resting-tDCS-tDCS-tDCS-tDCS), and each of the phases was performed for 21s. Our findings revealed that no cortical activation was detected in any of the stimulation phases except the fourth tDCS phase. In the result of group analysis for the fourth tDCS phase, the average map indicated that the central knob of the left primary motor cortex was activated. In addition, there were activations on the left supplementary motor cortex and the right posterior parietal cortex. We demonstrated that tDCS has a direct stimulation effect on the underlying cortex. It seems that tDCS is a useful modality for stimulating a target cortical region.

Corticoreticular pathway in the human brain: diffusion tensor tractography study.

The corticoreticular pathway (CRP) is involved in postural control and locomotor function. No study has been conducted for identification of the CRP in the human brain. In the current study, we attempted to identify the CRP in the human brain, using diffusion tensor tractography (DTT). We recruited 24 healthy volunteers for this study. Diffusion tensor images were scanned using 1.5-T. For reconstruction of the CRP, a seed region of interest (ROI) was placed on the reticular formation of the medulla. The first target ROI was placed on the midbrain tegmentum and the second target ROI was placed on the premotor cortex (Brodmann area 6). Values of fractional anisotropy, mean diffusivity, and tract volume of the CRP were measured. The CRP, which originated from the premotor cortex, descended through the corona radiata and the posterior limb of the internal capsule anterior to the corticospinal tract. In the midbrain and pons, it passed through the tegmentum and terminated at the pontomedullary reticular formation. No differences in terms of fractional anisotropy, mean diffusivity, and tract volume were observed between hemispheres (P>0.05). We identified the CRP in the human brain using DTT. These methods and results would be helpful to both clinicians and researchers in the neuroscience field.

The relation between fornix injury and memory impairment in patients with diffuse axonal injury: A diffusion tensor imaging study

Little is known about the relation between fornix injury and memory impairment in diffuse axonal injury (DAI). In the current study, we attempted to investigate fornix injury in patients with memory impairment following DAI, using diffusion tensor imaging (DTI). Nine patients with DAI and nine age-and sex-matched control subjects were recruited. The DTIs were acquired using a sensitivity-encoding head coil on a 1.5 T. Five regions of interest (ROI) were drawn manually on a color fractional anisotropy (FA) map: two ROIs for each column, one ROI for the body, and two ROIs for each crus. The FA and apparent diffusion coefficient (ADC) were measured in each of the ROIs. Cognitive function was evaluated using the Memory Assessment Scale, Wechsler Intelligence Scale, and Mini-Mental State Exam. In the DAI group, the FA value in the fornix body was significantly decreased compared with that of the control group. In contrast, we did not find significant differences in the column and crus of the fornix. Among all of the cognitive function scales, only the Memory Assessment Scale scores were significantly correlated with the FA values of the fornix body in the DAI group. We found that memory impairment in patients with DAI is closely related to neuronal injury of the fornix body among the three fornix regions that we assessed. DTI could be useful in the evaluation of patients with memory impairment following DAI.

The clinical characteristics of motor function in chronic hemiparetic stroke patients with complete corticospinal tract injury.

Clarification of the clinical characteristics of motor function in stroke patients with complete corticospinal tract (CST) injury would be of importance in stroke rehabilitation. However, this topic has not been clearly elucidated. We conducted an investigation of the clinical characteristics of motor function in chronic hemiparetic stroke patients with complete CST injury, as confirmed by transcranial magnetic stimulation and diffusion tensor imaging. Forty-one consecutive chronic hemiparetic stroke patients who showed an absence of motor evoked potential in muscles of the upper and lower extremities upon transcranial magnetic stimulation and in whom the integrity of the CST discontinued around stroke lesion on diffusion tensor imaging tractography were recruited. Mean Medical Research Council scores for distal musculature were lower than those for proximal musculature (P< 0.001). Mean Medical Research Council scores for upper extremity muscles were lower than those for lower extremity muscles (P< 0.001). The mean Motricity Index score for muscles of the upper extremities was lower than that for muscles of the lower extremities (P< 0.001). None of the patients had a functional hand; in contrast, 56% of patients were able to walk independently. We found that motor weaknesses of distal joint musculature and upper extremities were more severe than those of proximal joint musculature and lower extremities following complete injury of the CST in stroke, respectively. As a result, despite the absence of a functional hand in all patients, more than half were able to walk independently.

The clinical application of the arcuate fasciculus for stroke patients with aphasia: A diffusion tensor tractography study

Little is known about the clinical usefulness of diffusion tensor tractography (DTT) for the arcuate fasciculus (AF) in stroke patients with aphasia. Using DTT, we attempted to investigate the clinical usefulness of the AF in patients with aphasia. Five stroke patients and 7 age- and sex-matched normal subjects were recruited for this study. We recruited stroke patients with language dysfunction who had lesions in the left corona radiata and basal ganglia level. DTT for the AF was reconstructed using DTI-studio software. Korean-Western Aphasia Battery (K-WAB) was used for measurement of language function. Patient 1, who showed mild dysarthria, revealed a normal left AF in terms of integrity and DTT parameters. In patient 2, with conduction aphasia, the left AF showed partial injury; however, the integrity of the left AF was spared. Patients 3 and 4, who had no brain lesions at Brocas area on conventional brain MRI, showed disruptions of the left AF over the stroke lesions after originating from Wernickes area and they presented with Brocas aphasia. Patient 5 revealed global aphasia on K-WAB and the left AF was not reconstructed due to severe injury and Wallerian degeneration. We found that DTT for the AF could provide useful information on the presence or severity of injury of the AF, which could not be detected on conventional brain MRI in stoke patients. In addition, it could be helpful in classification of the aphasia type of stroke patients.

Diffusion tensor imaging demonstrated radiologic differences between diplegic and quadriplegic cerebral palsy.

Little information is available on the use of imaging for the classification of cerebral palsy patients. The present study examined the radiological differences between quadriplegic cerebral palsy patients (QCP), diplegic cerebral palsy patients (DCP) and normal control subjects (NC) by performing diffusion tensor imaging (DTI) of the corticospinal tract (CST) of upper and lower extremities. Twenty-three cerebral palsy patients (11 QCP, 12 DCP) and 12 NC were enrolled. DTI were scanned using a 1.5 T and the CST images were analyzed using FMRIB software. We measured the fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of the CST. Compared to DCP and NC, QCP had decreased mean FA and increased mean ADC values of the CSTs of upper and lower extremities. The mean FA values of the lower extremities in DCP were significantly decreased, compared to NC; however this was not observed for the mean FA value of the upper extremities. The DTI results of the CST in QCP and DCP significantly corresponded with their typical clinical manifestation. DTI may thus be a very powerful modality to assess the state of CST in cerebral palsy patients.

Cingulum injury in patients with diffuse axonal injury: A diffusion tensor imaging study

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.

Neural injury of uncinate fasciculus in patients with diffuse axonal injury

The recent development of diffusion tensor imaging (DTI) allows visualization and estimation of the uncinate fasciculus (UF). We investigated injuries of the UF in patients with diffuse axonal injury (DAI) who showed no specific lesions except for DAI lesions on conventional brain MRI. Twenty-one chronic patients with DAI, and 21 age- and sex-matched normal control subjects were recruited for this study. Diffusion tensor images were acquired using a sensitivity-encoding head coil at 1.5 T and the UF was reconstructed using DTI-Studio software. Fractional anisotropy (FA), apparent diffusion coefficient (ADC) value, and fiber number of the UF were measured. In the DAI group, the FA values and fiber numbers were significantly decreased compared to those of the control group (P< 0.05). The FA value and fiber number decreased 8.4% and 26.5% in the DAI group compared to those of the control group. By contrast, the ADC value did not show any difference between the DAI and control groups (P> 0.05). Changes in the DTI parameters of the DAI group appeared to indicate neural injury of the UF. We believe that DTI can be a useful evaluation tool for detecting hidden neural injuries of UF in patients with DAI.

Callosal Disconnection Syndrome after Corpus Callosum Infarct: A Diffusion Tensor Tractography Study

We report a patient who presented with callosal disconnection syndrome (CDS) and fiber disconnection on diffusion tensor tractography (DTT) after an infarct of the corpus callosum (CC). A 72-year-old woman presented with manifestations of CDS, including frontal alien hand syndrome (AHS), left agraphia, right hemiparesis, right somatosensory deficit, left neglect, and impaired visual recognition. DTT was performed for the evaluation of CC fibers, followed by comparison with DTT findings of normal subjects. DTT of the normal subject revealed bilateral extension of CC fibers to the frontal, parietal, and occipitotemporal cortices. By contrast, CC fibers of the patient revealed extensive disruption, with the exception of CC fibers passing through the anterior genu and the posterior splenium. The extensive disruption of CC fibers appears to explain the patients various CDS symptoms. In brief, DTT could be useful for detection of CC lesions in patients with CDS.

Prediction of motor outcome based on diffusion tensor tractography findings in thalamic hemorrhage

Abstract Objectives: Little is known about the usefulness of diffusion tensor tractography (DTT) findings of the corticospinal tract (CST) in terms of predicting motor outcome after thalamic hemorrhage. We investigated the predictive value of DTT for motor outcome in patients with thalamic hemorrhage. Methods: Twenty-one patients were recruited; DTTs were obtained within 7–30 d of thalamic hemorrhage. We determined fractional anisotropies (FAs), tract numbers, and tract lengths of CSTs and calculated affected CST versus unaffected CST ratios for each value. In addition, patients were classified into two groups; a DTT type A group, in which the CST was preserved around the hematoma, and a DTT type B group, in which the CST was interrupted. Six months after thalamic hemorrhage, motor functions of affected sides were evaluated using upper Motricity Index (MI), lower MI, total MI, the modified Brunnstrom classification (MBC) and functional ambulation category (FAC). Results: DTT parameters of CSTs, that is, FA ratios, tract number ratios and tract length ratios of affected/unaffected CSTs were found to be positively correlated with 6-month upper MIs, lower MIs, total MIs, MBCs and FACs. In addition, all motor function scores at 6 months after onset were higher in the DTT type A group than in the DTT type B group. Conclusions: Early DTT evaluation of CSTs appears to be useful for predicting motor outcomes of affected extremities at chronic stage in patients with thalamic hemorrhage.