Woo Mok Byun

Motor outcome according to diffusion tensor tractography findings in the early stage of intracerebral hemorrhage

We tried to investigate the motor outcome according to diffusion tensor tractography (DTT) findings for the corticospinal tract (CST) in the early stage for hemiparetic patients with intracerebral hemorrhage (ICH). Forty patients with severe paralysis of the affected side were enrolled. DTT was obtained in the early stage of the stroke (7-30 days) and was classified into four groups: type A, the CST originating from primary motor cortex was preserved around the hematoma; type B, the CST was similar to type A except the fiber originated from the adjacent areas to the primary motor cortex; type C, the CST was interrupted at or around the hematoma; and type D, the CST did not reach the hematoma due to degeneration (Fig. 1). Six months after onset, motor function was measured and the statistical influence of the DTT type was tested. Initially, none of the motor function scales of the affected side differed among the four DTT types. Six months after the onset of ICH, motor functions of the same side were significantly different according to DTT type (p<0.05). All motor scales were highest in the DTT type A group, and were lowest in the DTT type D group (p<0.0003). The early DTT findings for CST may be used to predict the motor outcome of the affected extremities in hemiparetic patients with ICH.

The effect of transcranial direct current stimulation on the cortical activation by motor task in the human brain: An fMRI study

OBJECTIVESnWe attempted to evaluate whether cortical activation resulting from hand movements is changed by transcranial direct current stimulation (tDCS) applied on the primary motor cortex for the hand in the human brain, using functional MRI (fMRI).nnnMETHODSnFourteen normal subjects were recruited; subjects were randomly assigned to either the tDCS group (n=7) or the sham group (n=7). fMRI was performed with hand grasp-release movements at 1Hz before and after 20 min of intervention (the tDCS group: anodal tDCS, the sham group: sham stimulation).nnnRESULTSnThe activation of the tDCS underlying primary sensorimotor cortex (SM1) was significantly increased in the tDCS group (p<0.05). By contrast, the SM1 was significantly decreased in the sham group in terms of the voxel count and intensity (p<0.05). No subjects complained of any adverse symptoms or signs.nnnCONCLUSIONnWe demonstrated that anodal tDCS increased the cortical excitability of the underlying motor cortex in the human brain. It seems that tDCS is an effective modality to modulate brain function.

Comparison of TMS and DTT for predicting motor outcome in intracerebral hemorrhage

BACKGROUNDnTMS (transcranial magnetic stimulation) and DTT (diffusion tensor tractography) have different advantages in evaluating stroke patients. TMS has good clinical accessibility and economical benefit. On the contrary, DTT has a unique advantage to visualize neural tracts three-dimensionally although it requires an expensive and large MRI machine. Many studies have demonstrated that TMS and DTT have predictive values for motor outcome in stroke patients. However, there has been no study on the comparison of these two evaluation tools. In the current study, we compared the abilities of TMS and DTT to predict upper motor outcome in patients with ICH (intracerebral hemorrhage).nnnMETHODSnFifty-three consecutive patients with severe motor weakness were evaluated by TMS and DTT at the early stage (7-28 days) of ICH. Modified Brunnstrom classification (MBC) and the motricity index of upper extremity (UMI) were evaluated at onset and 6 months after onset.nnnRESULTSnPatients with the presence of a motor evoked potential (MEP) in TMS or a preserved corticospinal tract (CST) in DTT showed better motor outcomes than those without (p=0.000). TMS showed higher positive predictive value than DTT. In contrast, DTT showed higher negative predictive value than TMS.nnnCONCLUSIONSnTMS and DTT had different advantages in predicting motor outcome, and this result could be a reference to predict final neurological deficit at the early stage of ICH.

Cortical activation changes associated with motor recovery in patients with precentral knob infarct

We investigated the cortical activation changes associated with motor recovery in six hemiparetic patients with precentral knob infarct. fMRI at 1.5u2009T with finger movements at a fixed rate was performed twice in each patient, 1 and 6 months after stroke onset. From the images obtained, the LI (laterality index) for the primary sensorimotor cortex (SM1) was calculated to measure the degree of the cortical activity concentration in the contralateral hemisphere. Our results showed that a greater improvement in motor function scores was significantly correlated with a greater increment in LI induced by affected finger movements (pu2009<u20090.05). Motor recovery after precentral knob infarct was found to be positively related with the concentration of SM1 activity in the ipsilesional hemisphere. This finding may imply motor recovery through cortical reorganization after precentral knob infarct in the human brain.

Diffusion tensor tractography can predict hemiparesis in infants with high risk factors

Diffusion tensor tractography (DTT) is known to be useful in detecting white matter lesions. In the current study, we report on two hemiparetic patients with risk factors who showed abnormalities of the corticospinal tract (CST) on diffusion tensor tractography (DTT) prior to the manifestation of hemiparesis. Two hemiparetic patients with risk factors (preterm, low birth weight) and six age-matched normal control subjects were enrolled to this study. Diffusion tensor imaging (DTI) was performed at the age of 43 weeks (patient 1) and 33 weeks (patient 2) using 1.5-T with a Synergy-L Sensitivity Encoding (SENSE) head coil. We measured fractional anisotropy (FA), apparent diffusion coefficients (ADCs), and fiber counts of the CST. There were no definite asymmetric findings on physical examination and conventional brain MRI. By contrast, DTT showed a unilateral CST disruption at the periventricular white matter, low FA values, and low CST fiber counts compared with those of the unaffected CST and controls. These patients were diagnosed with hemiparetic cerebral palsy when we re-evaluated these patients at the age of 6 years (patient 1) and 3 years of age (patient 2), respectively. In these two patients, DTT revealed abnormalities of the CST prior to the manifestation of hemiparesis. Therefore, it seems that DTT would be a useful modality in detecting CST abnormalities in advance of clinical manifestation in infants with high risk factors.

Identification of the medial lemniscus in the human brain: Combined study of functional MRI and diffusion tensor tractography

The medial lemniscus (ML) plays a critical role in sensory function and skillful movement. Using combined functional MRI (fMRI) and diffusion tensor tractography (DTT), we attempted to identify the ML pathway and quantify the characteristics of the ML compared to the corticospinal tract (CST). Eleven young healthy subjects without any history of neurological disorder were recruited for this study. For tracking of the ML, a seed region of interest (ROI) was determined using the fMRI activation in the primary sensorimotor cortex (SM1) following proprioceptive input, and a target ROI was given in the ML area of the pons. We were able to locate the ML in 9 out of 11 subjects. All ML started from the ML area just posterior to the transpontine fiber in the pons, and ascended to the SM1 posterolaterally to the cerebral peduncle of the midbrain, the posterior limb of the internal capsule (PLIC), and the corona radiata along with the CST. The fractional anisotropy (FA) value of the ML was similar to that of the CST. We could identify the ML pathway in the human brain using the combined fMRI/DTT method. These results and technique will be helpful for research about the ML in the human brain.

Diffusion tensor magnetic resonance imaging of microstructural abnormalities in children with brain injury

We present two pediatric cases demonstrating that diffusion tensor imaging is more efficient at revealing microstructural abnormalities of the brain than conventional magnetic resonance imaging because it enables measurements of the directionality and integrity of white matter fiber tracts. One patient suffered from left hemiparesis, and the other had right hemiparesis. However, whereas conventional magnetic resonance imaging showed only the findings of traumatic contusional hemorrhages in the left temporal and parietal lobes of the first patient and focal encephalomalacia in the left anterior thalamus of the second patient, diffusion tensor imaging successfully disclosed microstructural abnormalities in the right cerebral peduncle of the midbrain of the first patient and in the posterior limb of the left internal capsule of the second. Theses two cases demonstrate that diffusion tensor imaging is more capable than magnetic resonance imaging at detecting the microstructural pathologic lesions that are responsible for clinical motor weakness, especially when conventional magnetic resonance imaging has failed to detect subtle structural abnormalities.

Ipsilateral motor pathway confirmed by diffusion tensor tractography in a patient with schizencephaly.

We evaluated the hand motor function of a right hemiparetic patient with schizencephaly using a combination of fMRI, transcranial magnetic stimulation, and diffusion tensor tractography (DTT). Only the unaffected (right) primary sensori-motor cortex was found to be activated during either affected (right) or unaffected hand movements. Evoked motor potentials with similar characteristics were obtained from both abductor pollicis brevis muscles simultaneously when stimulating the unaffected motor cortex. Moreover, a tract presumed to be a corticospinal tract was observed in the unaffected hemisphere by DTT, however, no tract was observed in the affected hemisphere. Our results indicate that the ipsilateral corticospinal tract extended from the unaffected (right) motor cortex to both hands. This finding may reflect functional reorganization of motor function in a patient with congenital brain disorder.

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.

Periventricular white matter injury by primary intraventricular hemorrhage: a diffusion tensor imaging study.

Objectives: Intraventricular hemorrhage (IVH) in adult stroke patients is known to be an independent risk factor for poor functional outcome. Using diffusion tensor imaging (DTI), we attempted to investigate the effect of IVH on the white matter. Methods: We recruited 10 consecutive patients with IVH and 18 age- and sex-matched control subjects. Using a 1.5-T Philips Gyroscan Intera system, DTI data was acquired at an average of 84 days (range: 38–149) after IVH onset. We measured fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values at the fornix, corpus callosum (CC), corona radiata (CR), and posterior limb of the internal capsule (PL). In addition, integrity and fiber number were measured for the fornix. Results: DTI revealed disruption of the fornix in all patients. FA values showed a decrease in the fornix, CC, and CR; in contrast, the ADC value showed an increase in the CC, without changes in the fornix or CR. Fiber number of the fornix also decreased. However, no change was observed in the PL. Conclusions: We found periventricular white matter (fornix, CC, and CR) injury following IVH. We think that this result would be helpful in the establishment of management strategies for patients with IVH.