Yoon Woo Cho

Transcallosal fibers from corticospinal tract in patients with cerebral infarct

Diffusion tensor image tractography (DTT) can visualize white matter tracts and provide a powerful vehicle with which to investigate the neural pathway at the subcortical level. We attempted to demonstrate the clinical significance of transcallosal fibers (TCF) originating from the corticospinal tract in patients with corona radiata infarct located below the corpus callosum, using diffusion tensor image tractography (DTT). Forty patients with corona radiata infarct located below the corpus callosum and 26 control subjects were enrolled in this study. We classified the DTT findings as follows: no transcallosal fiber from the CST (type A), transcallosal fiber ended in the corpus callosum or connected to the cortex of the opposite hemisphere (type B), and transcallosal fiber that descended toward the lesion after passing through the corpus callosum (type C). Type C indicated that the presence of transcallosal fibers starting from the CST of the unaffected hemisphere was significantly more prevalent in the patients, and these patients showed the poorest motor function. It seems that transcallosal fibers originated from the CST of the unaffected hemisphere, and fibers descending toward the lesion in patients with corona radiata infarct may act to compensate for motor deficits.

Cortical reorganization of sensori-motor function in a patient with cortical infarct

PURPOSE We describe a patient with cortical infarct, whose sensori-motor function for the hand seemed to be reorganized into the lateral area, as demonstrated by functional MRI (fMRI). METHODS A 59-year-old male patient presented with severe sensori-motor dysfunction of the left hand, which first occurred at the onset of an infarct in the right primary sensori-motor cortex (SM1) centered on the precentral knob. The sensori-motor function of the affected hand recovered to a normal state at 6 months from onset. fMRI was performed using the blood oxygen level-dependent technique at 1.5T with a standard head coil (at 6 months from onset). The active and passive movements were performed at the metacarpophalangeal joint using a specially equipped apparatus, and touch stimulation was applied on the dorsum of the hand using a rubber brush. RESULTS The contralateral SM1 centered on the precentral knob was found to be activated during the active movements, passive movements, and touch of the unaffected (right) hand movements. By contrast, the lateral area of the infarcted SM1 of the right hemisphere was activated during the three kinds of stimulation of the affected hand. CONCLUSIONS We conclude that the sensori-motor function of the affected hand seemed to have been reorganized into the lateral area of the infarcted SM1.

The Relation Between Injury of the Spinothalamocortical Tract and Central Pain in Chronic Patients With Mild Traumatic Brain Injury.

Objectives:Little is known about the pathogenetic etiology of central pain in patients with traumatic brain injury (TBI). We investigated the relation between injury of the spinothalamocortical tract (STT) and chronic central pain in patients with mild TBI. Design:Retrospective survey. Participants:We recruited 40 consecutive chronic patients with mild TBI and 21 normal control subjects: 8 patients were excluded by the inclusion criteria and the remaining 32 patients were finally recruited. The patients were classified according to 2 groups based on the presence of central pain: the pain group (22 patients) and the nonpain group (10 patients). Methods:Diffusion tensor tractography for the STT was performed using the Functional Magnetic Resonance Imaging of the Brain Software Library. Values of fractional anisotropy (FA), mean diffusivity (MD), and tract volume of each STT were measured. Results:Lower FA value and tract volume were observed in the pain group than in the nonpain group and the control group (P < .05). By contrast, higher MD value was observed in the pain group than in the nonpain group and the control group (P < .05). However, no significant differences in all diffusion tensor imaging parameters were observed between the nonpain group and the control group (P > .05). Conclusions:Decreased FA and tract volume and increased MD of the STTs in the pain group appeared to indicate injury of the STT. As a result, we found that injury of the STT is related to the occurrence of central pain in patients with mild TBI. We believe that injury of the STT is a pathogenetic etiology of central pain following mild TBI.

Limb apraxia in a patient with cerebral infarct: Diffusion tensor tractography study

We report on a patient with ideomotor apraxia (IMA) and limb-kinetic apraxia (LKA) following cerebral infarct, which demonstrated neural tract injuries by diffusion tensor tractography (DTT). A 67-year-old male was diagnosed as cerebral infarct in the left frontal cortex (anterior portion of the precentral gyrus and prefrontal cortex) and centrum semiovale. The patient presented with severe paralysis of the right upper extremity and mild weakness of the right lower extremity at onset. At the time of DTT scanning (5 months after onset), the patient was able to move all joint muscles of the right upper extremity against gravity, except for the finger extensors, which he could extend partially against gravity. The patient showed intact ideational plan for motor performance; however, his movements were slow, clumsy, and mutilated when executing grasp-release movements of his affected hand. The patients score on the ideomotor apraxia test was 20 (cut-off score < 32). DTTs for premotor cortex fibers, supplementary motor area fibers, and superior longitudinal fasciculus of the left hemisphere showed partial injuries, compared with those of the right side, and these injuries appeared to be responsible for IMA and LKA in this patient.

Relation between cingulum injury and cognition in chronic patients with traumatic brain injury; diffusion tensor tractography study

OBJECTIVES Many diffusion tensor imaging (DTI) studies have reported an association between cingulum injury and cognition in patients with traumatic brain injury (TBI) using DTI parameters. In this study, we attempted to investigate the relation between cingulum injury and cognition in chronic patients with TBI, using the integrity of the cingulum as well as DTI parameters. METHOD Thirty five consecutive chronic patients with TBI were recruited. The intelligence quotient (IQ) of the Wechsler Intelligence Scale and Memory Assessment Scale (MAS) was used for assessment of cognition. The patients were classified into three groups, according to continuity to the lower portion of the genu of the corpus callosum: type A-both sides of the cingulum showed intact continuity, type B-either cingulum showed a discontinuation, and, type C-both cingulums showed discontinuation. We measured the fractional anisotropy (FA), apparent diffusion coefficient (ADC), and voxel number of both cingulums. RESULTS The IQ and MAS scores of type A and B were significantly higher than those of type C, respectively (p < 0.05), however, we did not observe a significant difference between type A and type B (p > 0.05). A positive correlation was observed between the FA value of the cingulum, and IQ and MAS, respectively (IQ r = 0.373, p < 0.05, MAS r = 0.357, p < 0.05), and between the voxel number and MAS (r = 0.500, p < 0.05). By contrast, we observed a negative correlation between the ADC value and IQ (r = -0.353, p < 0.05). CONCLUSION In terms of integrity to the basal forebrain and DTI parameters of the injured cingulum, DTI findings showed a close association with whole cognition and memory in chronic patients with TBI.

Cortical activation pattern of compensatory movement in stroke patients

OBJECTIVE Little is known about the cortical activation pattern of compensatory movement (CM) in stroke patients. We attempted to investigate the cortical activation pattern of compensatory movement in stroke patients, using functional MRI (fMRI). METHODS Eight hemiparetic stroke patients were recruited for this study. We measured the shoulder abduction angle when each subject was simulating eating in a sitting position, which was considered as the degree of CM. The fMRI was performed at 1.5T using an elbow motor task at a frequency of 0.5 Hz. RESULTS There was an inverse correlation between the shoulder abduction angle of the affected side and the LI (Laterality Index) (r=-0.745; p< 0.05). The shoulder abduction angle of the affected side was significantly related to the sum of activated voxels in all regions of interest (r=0.776; p< 0.05) and the activated voxels of the supplementary motor area (r=951; p< 0.05). However, we did not find any correlation between the shoulder abduction angle and the activated voxels of other brain areas. CONCLUSIONS We demonstrated that a greater shoulder abduction angle on the affected side requires more cortical activation. Therefore, CM appears to be related to the change of the cortical motor control toward greater recruitment of cortical neurons.

Motor function reorganization in a patient with a brainstem lesion: DTT, fMRI and TMS study.

OBJECTIVE We report on a hemiparetic patient who showed a new motor pathway posterior to the lesion in the midbrain and upper pons, demonstrated by three combined method of diffusion tensor tractography(DTT)/functional MRI(fMRI)/transcranial magnetic stimulation(TMS). METHODS A 21-year-old left hemiparetic male who suffered from tuberous meningitis at the age of 12 months after birth. The evaluations were performed at 20 years after onset. Brain MRI showed focal encephalomalatic lesions~due to infarcts in right anterior thalamus, midbrain and upper pons. DTT, fMRI and TMS were performed simultaneously. RESULTS The contralateral primary sensori-motor cortex was activated during either affected or unaffected hand movements. DTT showed that the motor tracts descended along the known pathway of the CST, with the exception of the motor tract of the affected hemisphere, which descended along the posterior portion to the lesion in the right midbrain and the pons, and then rejoined the CST in the mid-pons. The TMS results suggested that the motor tract of the affected hemisphere had the characteristics of a CST. CONCLUSION We believe that the motor function of the affected hand in this patient had been recovered through the pathway posterior to the lesion in the midbrain and upper pons.

Prognostic factors for motor outcome in patients with compressed corticospinal tract by intracerebral hematoma.

Little is known about prognostic factors associated with motor outcome when the corticospinal tract (CST) was compressed by hematoma. Using diffusion tensor tractography (DTT), we attempted to investigate prognostic factors for motor outcome in patients whose affected CST was compressed by hematoma. The study included 51 consecutive severe hemiparetic patients with a hematoma involving the corona radiata and basal ganglia. Integrities of the affected CSTs were preserved to the cerebral cortex and were found to be compressed by a hematoma on DTT. Patients were classified into four groups according to the region which the CST was originated from the precentral gyrus (type A), postcentral gyrus (type B), posterior parietal cortex (type C), and premotor cortex (type D). We measured the ratios of DTT parameters between affected/unaffected hemispheres.The motor function of the affected extremities at 6-month after onset was better with the following order: DTT type A, type B, type C, and type D patients. The 6-month motor function for DTT type A patients was higher than that of DTT type D patients (p=0.008). The fractional anisotropy ratio between the affected and unaffected CST was positively correlated with the 6-month motor function of the affected extremities (Pearsons correlation coefficient, p=0.025, r=0.313). We found that motor outcome differed according to the originated area of the affected CST and the degree of injury of the affected CST in patients whose affected CST was compressed by hematoma.