Abstract: Purpose: We investigated the motor recovery mechanism of a stroke patient using functional MRI (fMRI) and diffusion tensor image tractography (DTT). Methods: A 60 year-old woman with right corona radiata infarct presented with complete paralysis of the left upper extremity. The motor function of the affected upper extremity recovered slowly for 6 months to a point of nearly normal function. The motor function of the patient was evaluated by fMRI and DTT at 6 months from the onset. FMRI was performed at 1.5 T with timed hand grasp-release movements. DTT was performed using 1.5 T with a synergy-L Sensitivity Encoding…head coil. Three dimensional reconstructions of the fiber tracts were obtained with FA < 0.3, angle > 45° as termination criteria. Results: The contralateral primary sensorimotor cortex (SM1) was activated during both affected (left) and unaffected hand movements. DTT showed that the tracts originated from either SM1; the tracts then descended along the known pathway of the corticospinal tract, with the exception that the tract of the affected (right) hemisphere descended along the posterior portion of the infarcted corona radiata. Conclusions: It seems that the motor function of the affected upper extremity was reorganized to the posterior portion of the infarcted corona radiata. This finding may reflect functional reorganization of the motor pathway following corticospinal tract damage. This appears to be one motor recovery mechanism of subcortical infarct.
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Abstract: Purpose: We hypothesized that diffusion tensor imaging (DTI) could be useful for exploring corticospinal tract (CST) regeneration if longitudinal changes of diffusion anisotropy can be detected. In this study, we explored the recovery of a CST partially damaged by intracerebral hematoma in a patient by DTI. Methods: A 61-year-old female patient and six age-matched control subjects were evaluated. The patient presented with complete paralysis of the left extremities, which occurred at the onset of a spontaneous intracerebral hemorrhage (ICH) in the right corona radiata and internal capsule. Over the five-month period following onset, motor function of the affected extremities slowly…recovered to the normal range. Two longitudinal DTIs were acquired from the patient (at 3 weeks and 5 months from onset) and one DTI from the control subjects. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were measured using a region of interest (ROI) method. Results: On the 3-week DTI, FA values of ROIs in the ICH regions in the affected hemisphere were significantly lower, and ADC values of ROIs in the same areas were significantly higher than those of the control subjects (p<0.002). However, both mean FA and ADC values of the affected hemisphere in the 5-month DTI showed no significant differences versus those of the control.
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Abstract: Objectives: Combined functional MRI (fMRI) and diffusion tensor tractography (DTT) imaging provides a powerful vehicle for the investigation of motor recovery mechanisms. Using this combined method, we investigated the motor recovery mechanism in patients with pontine infarct. Design: We evaluated six healthy control subjects and two patients with pontine infarct at 6 months from onset. fMRI was performed at 1.5 T with timed hand grasp-release movements. For DTT, we used each of the 32 noncollinear diffusion-sensitizing gradients. Three-dimensional reconstructions of the fiber tracts were obtained with FA <0.3, angle >45° as termination criteria. Results: fMRI data revealed activation only in…the contralateral primary sensorimotor cortex during movement of either hand. DTI findings from controls and the unaffected hemisphere of the patients showed that the corticospinal tract descended through the known corticospinal tract pathway. However, the tracts of the affected hemisphere in the patients were observed to pass along peri-infarct areas (patient 1: lateral, patient 2: posterior) in the pons. Conclusions: It seems that the peri-infarct areas compensate for corticospinal tract damage at the pons; this may be one mechanism of motor recovery for patients with pontine infarct.
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Keywords: Functional MRI, diffusion tensor image, stroke, motor recovery, hemiplegia
Abstract: Objectives: Diffusion tensor image tractography (DTT) could be useful for exploring the state of the corticospinal tract (CST) at the level of the subcortical white matter. The purpose of this study was to demonstrate the speed of degeneration of the CST in patients with cerebral infarct, using DTT. Design: Two patients with middle cerebral artery territory infarct were recruited for this study. DTT was performed 5 times with an interval of 7 days, starting at 2 days after onset, using a 1.5-T system with a synergy-L Sensitivity Encoding head coil. The termination criteria used were fractional anisotrophy < 0.3, 0.2,…0.1, respectively, and an angle change > 45°. Results: Detection of CST degeneration began at the 9 day DTT in both patients. The most rapid CST degeneration was noted for 7 days at 16 days from onset. We did not detect any tract in the affected hemisphere of both patients at the 23-day DTT. Conclusions: We demonstrated that CST degeneration begins before 9 days from onset and progresses rapidly in patients with middle cerebral artery territory infarct. It seems that the CST degeneration began earlier than expected.
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Abstract: Objectives: Diffusion tensor imaging (DTI) with fiber tractography (FT) could be useful for exploration of the state of the corticospinal tract (CST) at the subcortical white matter level. The purpose of this study was to demonstrate focal lesions of the CST in patients with diffuse axonal injury (DAI), using DTI with FT. Design: Two patients with DAI and six normal control subjects were recruited to this study. DTI was performed using 1.5-T with a synergy-L Sensitivity Encoding (SENSE) head coil. Fractional anisotropy (FA) and apparent diffusion coefficients (ADC) were measured using a region of interest (ROI) method. FTs were obtained…with FA <0.3 and an angle change >45° as termination criteria. Results: On the DTI with FT, the focal lesions, which could not observed using routine brain MRI, were detected in the left brainstem of patient 1 and in the right pons and the left and right medulla of patient 2. The patients showed significantly decreased FA values in the focal lesions compared to normal controls. Conclusions: DTI with FT demonstrated focal lesions at the brainstem that had not been revealed by conventional brain MRI; these focal lesions explained the weaknesses of the patients. We conclude that DTI with FT may be a useful modality for use in investigating the status of CST in patients with DAI.
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