Mi Young Lee

Somatotopic arrangement of the corticospinal tract at the medullary pyramid in the human brain.

Objectives: Somatotopic arrangements of the corticospinal tract (CST) in the human brain have been generally elucidated; however, very little is known about the somatotopy at the medullary pyramid (MP). Using diffusion tensor tractography (DTT), we investigated the somatotopic arrangement of the CST at the MP in the normal human brain. Methods: We recruited 30 healthy volunteers for this study. Diffusion tensor images were scanned using 1.5 T and the CSTs for hand and leg were obtained using FMRIB software. Normalized DTT was reconstructed using the Montreal Neurological Institute echo-planar imaging template supplied with the SPM software. Results: The hand somatotopy of the CST was located at the medial portion of the MP; in contrast, the leg somatotopy occupied the lateral portion of the MP. Conclusions: We found that the somatotopies for hand and leg were arranged in the mediolateral direction at the MP in the human brain.

Aging of the cingulum in the human brain: Preliminary study of a diffusion tensor imaging study

The cingulum, a major structure of the limbic system, is closely associated with memory function. In the current study, we investigated aging of the cingulum according to the location of the cingulum in each part of the cingulum after dividing the cingulum into five parts in normal subjects, using DTT parameters (fractional anisotropy (FA) and fiber number (FN)). Ninety healthy subjects (males: 44, females: 46, mean age: 49.0 years; range: 20-78 years) were enrolled in this study. Subjects were categorized according to six groups by age intervals of 10 years; each age group consisted of 15 subjects. The cingulum was divided into five parts (anterior, anterior superior, posterior superior cingulum, posterior, and inferior cingulum). The FA and FN of each part were measured. The FA value indicates the degree of directionality and integrity of white matter microstructures such as axons, myelin, and microtubules, and the FN reflects the total number of fibers in a neural tract. Age-related decline in the FA value may indicate demyelination, and a decline in the number of myelinated fibers of a neural tract can also lead to a decline of the FN. Significant differences in the FA value of the anterior cingulum and anterior superior cingulum, and the FN of the inferior cingulum were observed between age groups (AVOVA, p<0.05). A significant decrease was observed in the FA values of the anterior and anterior superior cingulum of the 60s and 70s age groups compared with those of the 20s and 30s age groups, and in the FN of the inferior cingulum of the 60s and 70s age groups compared with that of the 20s age group (LSD post hoc test, p<0.05). Aging of the cingulum began at both ends of the cingulum in the 20s or 30s, and progressed steadily at a near continuous rate over the lifespan and a significant degenerative aging effect at both ends of the cingulum occurred into the 60s, compared with the 20s or 30s.

Termination differences in the primary sensorimotor cortex between the medial lemniscus and spinothalamic pathways in the human brain

The medial lemniscus (ML) and its thalamocortical pathway is responsible for proprioception, in contrast, the spinothalamic tract (ST) and its thalamocortical pathway is the neural tract for pain and body temperature. Therefore, the ML pathway plays a crucial role in skillful movements and may be more linked to motor function than the ST pathway. We investigated the differences in the distribution of the primary motor cortex (M1) and the primary somatosensory cortex (S1) between the ML and ST pathways. Adults (mean age: 40.4 years, range: 21-61 years) were recruited for this study. The seed masks for the ML and ST pathways were given on the color map of the medulla according to the known anatomy and waypoint masks were placed on the ventro-postero-lateral nucleus of the thalamus. The volume of ML pathway did not show any difference between the M1 (10.94) and S1 (13.02) (p>0.05). By contrast, the mean voxel number of the ST pathway in the M1 (18.25) and S1 (27.38) showed significant difference between the M1 and S1 (p<0.05). As for relative voxel number percentage of the M1 compared to the S1, the ML pathway (84%) was significantly higher than ST pathway (67%) (p<0.05). We found that more neural fibers of the ML pathway were terminated in the M1 relative to the S1 compared to the SLP, and this may be linked to the inherent execution of movements of the M1.

Comparison of cortical activation patterns by somatosensory stimulation on the palm and dorsum of the hand.

Abstract Objectives: Little is known about differences of cortical activation according to body location. We attempted to compare brain activation patterns by somatosensory stimulation on the palm and dorsum of the hand, using functional magnetic resonance imaging (fMRI). Method: We recruited 15 healthy right-handed volunteers for this study. fMRI was performed during touch stimulation using a rubber brush on an area of the same size on the palm or dorsum of the hand. Regions of interest (ROIs) were drawn at the primary sensory–motor cortex (SM1), posterior parietal cortex, and secondary somatosensory cortex. Results: Group analysis of fMRI data indicated that touch stimulation on the palm resulted in production of more activated voxels in the contralateral SM1 and posterior parietal cortex than on the dorsum of the hand. The most activated ROI was found to be the contralateral SM1 by stimulation of the palm or dorsum, and the number of activated voxels (5875) of SM1 by palm stimulation was more than 2 times that (2282) of dorsum stimulation. The peak activated value in the SM1 by palm stimulation (16.43) was also higher than that of the dorsum (5.52). Conclusion: We found that stimulation of the palm resulted in more cortical activation in the contralateral SM1 than stimulation of the dorsum. Our results suggested that the palm of the hand might have larger somatotopy of somatosensory representation for touch in the cerebral cortex than the dorsum of the hand. Our results would be useful as a rehabilitation strategy when more or less somatosensory stimulation of the hand is necessary.

Analysis for Sit-to-Stand Performance According to the Angle of Knee Flexion in Individuals with Hemiparesis

[Purpose] Sit-to-stand (STS) is one of the important functional tasks people perform throughout the day. This study investigated whether varying angles of knee flexion affect STS patterns in individuals with hemiparesis by using a foot plantar pressure measurement system. [Methods] Fifteen stroke patients with hemiparesis participated for this study. They performed sit-to-stand with three angles of knee flexion (70°, 90°, and 110°). We measured the trajectory of the center of pressure, peak plantar pressure, and symmetry index using a Mat-scan system (Tekscan, South Boston, MA, USA). [Results] As a result, we found that there were significant differences among the three angle conditions (trajectory of center of pressure, peak plantar pressure on the affected side, and symmetry index). However, there was no significant difference in peak pressure according to the knee flexion on the unaffected side. [Conclusion] In the current study, we found that stroke patients with hemiparesis had a compensated STS pattern according to knee flexion angles. This indicates that the peak value of plantar pressure increased and that the trajectory of the center of pressure widened as the angle of knee flexion increased. We also suggest that hemiparesis patients should be more concerned about proper knee angle for symmetrical STS pattern.

Differences of the frontal activation patterns by finger and toe movements: A functional MRI study

It is well-known that physical exercise can affect cognition and the frontal lobe is an important structure involved in motor function and cognition. Furthermore, many functional neuroimaging studies have demonstrated that cortical activation patterns of hand and leg movements differ. However, no study has been undertaken to identify differences between the frontal activation patterns generated by hand and leg movements. In the present study, the frontal activation patterns associated with finger and toe movements, as visualized by functional MRI, were investigated and compared. Twelve healthy volunteers were recruited. Functional MRI was performed using a 1.5 T Philips Gyroscan Intera. Flexion-extension movements of fingers or toes were performed in one extremity. Regions of interest (ROIs) were set at the primary sensory-motor cortex (SM1: Brodmann area [BA] 1, 2, 3, 4), the premotor area (PMA: BA 6), and the prefrontal cortex (PFC: BA 8, 9, 10, 11, 46). In SM1, finger movements (10,809) induced more activation than toe movements (5349). On the other hand, in the PMA and PFC, toe movements (PMA: 4201, PFC: 921) induced more activation than finger movements (PMA: 2887, PFC: 912) respectively. In the analysis of relative voxel counts in the PMA and PFC versus the SM1, toe movements generated more activation in the PMA and PFC than finger movements. The PMA and PFC were more activated by toe than finger movements, although the SM1 was more activated by finger movements.

Difference of neural connectivity for motor function in chronic hemiparetic stroke patients with intracerebral hemorrhage.

Difference of neural connectivity for motor function had been studied by observation of neural activity within gray matter and nucleus using functional neuroimaging techniques. Diffusion tensor imaging (DTI) by a probabilistic tracking is useful for exploration of structural connectivity in the brain. We attempted to investigate difference of neural connectivity for motor function of the affected hand in chronic hemiparetic patients with intracerebral hemorrhage (ICH). Forty-four patients with ICH and 31 normal control subjects were recruited. Diffusion tensor imaging was acquired using a sensitivity-encoding head coil at 1.5 T. Motor function was evaluated using the motricity index (MI) for hand and Modified Brunnstrom Classification (MBC). The presence or absence of a connection was confirmed between the precentral knob of the affected hemisphere and seven areas. Compared with healthy subjects, the patient group showed lower connectivity to the contralesional primary motor cortex, ipsilesional basal ganglia, ipsilesional thalamus, contralesional cerebellum, and ipsilesional medullary pyramid in the affected hemisphere (p<0.05). Connections to the ipsilesional basal ganglia, ipsilesional thalamus, and ipsilesional medullary pyramid showed positive correlation with MI and MBC (p<0.05). We found difference of neural connectivity for motor function between chronic hemiparetic patients with ICH and control subjects. Our results suggest that the motor function of the stroke patient is related to neural connectivity between the ipsilesional M1 and the ipsilesional medullary pyramid, ipsilesional basal ganglia, and ipsilesional thalamus.

Delayed gait recovery in a stroke patient.

We report on a stroke patient who showed delayed gait recovery between 8 and 11 months after the onset of intracerebral hemorrhage. This 32-year-old female patient underwent craniotomy and drainage for right intracerebral hemorrhage due to rupture of an arteriovenous malformation. Brain MR images revealed a large leukomalactic lesion in the right fronto-parietal cortex. Diffusion tensor tractography at 8 months after onset revealed that the right corticospinal tract was severely injured. At this time, the patient could not stand or walk despite undergoing rehabilitation from 2 months after onset. It was believed that severe spasticity of the left leg and right ankle was largely responsible, and thus, antispastic drugs, antispastic procedures (alcohol neurolysis of the motor branch of the tibial nerve and an intramuscular alcohol wash of both tibialis posterior muscles) and physical therapy were tried to control the spasticity. These measures relieved the severe spasticity, with the result that the patient was able to stand at 3 months. In addition, the improvements in sensorimotor function, visuospatial function, and cognition also seemed to contribute to gait recovery. As a result, she gained the ability to walk independently on even floor with a left ankle foot orthosis at 11 months after onset. This case illustrates that clinicians should attempt to find the cause of gait inability and to initiate intensive rehabilitation in stroke patients who cannot walk at 3–6 months after onset.

Clinical Characteristics and Brain Activation Patterns of Mirror Movements in Patients with Corona Radiata Infarct

Objective: Mirror movements (MMs) are a phenomenon of involuntary movements that accompany physically intended movements of the opposite side of the body. In the current study, we investigated the clinical characteristics and cortical activation patterns of MMs in patients with corona radiata (CR) infarct, using functional MRI. Subjects and Methods: We recruited 31 consecutive hemiparetic stroke patients with CR infarct. Functional MRI was performed to verify brain activation patterns during grasp-release movements of the affected hand, and MM of the unaffected hand was observed simultaneously. Results: The prevalence of MMs was 54.8% (17 out of 31 patients), and the intensity of MMs ranged from mild to moderate. The severity of MM in the unaffected hand is closely related to the poor motor function of the affected upper extremity and to activations of the unaffected motor cortex and both supplementary motor areas (SMAs) during the movement of the affected hand. In addition, the activations of unaffected motor cortex and both SMAs were closely related to poor motor function of the affected upper extremity. Conclusions: The results suggest that MMs, poor motor function, and the activations of ipsilateral motor cortex and both SMAs are closely interconnected in patients with CR infarct.

Prediction of motor outcome using remaining corticospinal tract in patients with pontine infarct: Diffusion tensor imaging study

Abstract The aim of this study was to investigate the relationship between the remaining corticospinal tract (CST) as determined by diffusion tensor imaging (DTI) and 6-month motor outcome in patients with pontine infarct. Ratios of fractional anisotropy (FA), fiber number (FN), and CST area were calculated, and the FN ratio and CST area ratio showed significant correlation with all 6-month motor outcome. Thus, the remaining CST in the pons measured using DTI at early stage of stroke could predict motor outcome in patients with pontine infarct.