Diffusion tensor imaging findings of optic radiation in patients with putaminal hemorrhage.

OBJECTIVES: Little is known about optic radiation (OR) injury in intracerebral hemorrhage (ICH). We attempted to investigate OR injury in patients with ICH by diffusion tensor imaging (DTI). METHODS: Forty-three consecutive patients with putaminal hemorrhage and 40 normal healthy control subjects were recruited. DTI data were acquired at the beginning of rehabilitation (average 34 days after onset). DTI-Studio software was used to reconstruct the OR. Fractional anisotropies (FA) and fiber numbers of the ORs were measured. FA values and fiber numbers of affected ORs were described as abnormal when they were more than 2.5 SD lower than those of normal controls. RESULTS: Thirty (70%) of the 43 patients showed an OR abnormality in the affected hemisphere. In 13 (30%) patients, the affected OR was disrupted or nonreconstructable. On the other hand, of the 20 patients with preserved OR integrity, 14 (33%) had a low FA value and 3 (7%) a low FA and fiber number. The other 13 (30%) of the 43 patients had no abnormal OR findings. CONCLUSION: Seventy percent of patients showed any abnormality of OR in the affected hemisphere on DTI. This result suggests that patients with putaminal hemorrhage are at high risk of OR injury.

The effects of hydrocephalus on the periventricular white matter in intracerebral hemorrhage: a diffuser tensor imaging study.

OBJECTIVES: Many diffusion tensor imaging (DTI) studies have described the effects of hydrocephalus on periventricular white matter in patients with normal pressure hydrocephalus. However, little is known about hydrocephalus following stroke. We investigated the effect of hydrocephalus on periventricular white matter in patients with hydrocephalus after an intracerebral hemorrhage (ICH) using DTI. METHODS: Fourteen patients with ICH and hydrocephalus, and 17 age- and sex-matched normal control subjects were recruited. DTI parameters were estimated in six regions of interest (ROIs) in periventricular white matter: the anterior corona radiata, the posterior corona radiata, the genu of the corpus callosum, the splenium of corpus callosum, the anterior limb of the internal capsule, and the posterior limb of the internal capsule. RESULTS: Mean fractional anisotropy of the anterior corona radiata in patients was significantly higher than in controls (p < 0.05), but apparent diffusion coefficient (ADC) was not different in the two groups (p > 0.05). No significant differences between fractional anisotropies and ADCs were observed in the other five ROIs (p > 0.05). CONCLUSIONS: The anterior corona radiata was found to be more compressed by hydrocephalus than the other five regions of periventricular white matter examined in patients with hydrocephalus following ICH. It is believed that the results of the present study will be useful for the diagnosis and management of hydrocephalus following stroke.

Neural tract injuries by brain herniations after head trauma.

OBJECTIVES: : Little is known about the usefulness and findings of brain herniation on diffusion tensor tractography (DTT). Using DTT, we demonstrated neural tract injuries in 2 patients who showed subfalcine and trasntentorial herniations after subdural hematoma resulting from motor vehicle accident. DESIGN: : Two patients and 6 age- and sex-matched, healthy volunteers were recruited for this study. SETTING: : An inpatient rehabilitation unit. MAIN OUTCOME MEASURES: : Diffusion tensor tractography for the patients was performed 5 weeks after onset. RESULTS: : Diffusion tensor tractography of patient 1 showed complete injury of both cingulums at or around the rostrum of the corpus callosum, the fornix at the anterior and posterior body, and both corticospinal tracts at the pons. In addition, partial injury of both somatosensory tracts at the midbrain was also observed. Patient 2 showed complete injury of both cingulums above the body of the corpus callosum, the fornix at the anterior and posterior body, and right corticospinal tracts at the pons level and partial injury of the right somatosensory tract. We found that the fractional anisotropy values of all neural tracts, except fornix, in both patients and left somatosensory tract in patient 2 and voxel number for left somatosensory tract in patient 2 were decreased 2 SDs below that of normal controls. CONCLUSIONS: : We determined that DTT would be a good technique for use in the detection of underlying lesions in patients with brain herniation.

Neuronal loss in the medial cholinergic pathway from the nucleus basalis of Meynert in patients with traumatic axonal injury: a preliminary diffusion tensor imaging study.

OBJECTIVE: The recent development of diffusion tensor imaging (DTI) allows visualization and estimation of the medial cholinergic pathway (MCP), which originates from the nucleus basalis of Meynert and provides cortical cholinergic innervation to the cerebral cortex. We investigated the injury to the MCP in patients with traumatic axonal injury (TAI), using DTI. DESIGN: Retrospective survey. PARTICIPANTS: Fourteen patients with chronic TAI and 14 age- and sex-matched normal control subjects. MAIN OUTCOME MEASURES: Using the Functional Magnetic Resonance Imaging of the Brain (FMRIB) Software Library (FMRIB analysis group, Oxford University, United Kingdom), diffusion tensor images were acquired by using a sensitivity-encoding head coil at 1.5 T DTIs. Fractional anisotropy (FA), mean diffusivity (MD), and tract volume of the MCP were measured. RESULTS: The FA value and tract volume were significantly decreased in the group with TAI compared with those of the control group (P < .05); in contrast, there was no difference in the MD value between the 2 groups (P > .05). CONCLUSIONS: Changes in DTI parameters of the TAI group appear to be due to neuronal loss of the MCP. We believe that DTI would be useful for the evaluation of the MCP in patients with TAI.

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.

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.

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.

Corticospinal tract location in internal capsule of human brain: diffusion tensor tractography and functional MRI study.

We attempted to elucidate the corticospinal tract location at the posterior limb of the internal capsule in the human brain. Ten healthy volunteers were recruited. Probabilistic mapping was performed using the functional MRI activation resulting from a hand motor task as region of interest 1 and the corticospinal tract area of the anterior pons as region of interest 2. The average location of the highest density point of the corticospinal tract was mid-posterior portion with the standard from the most medial point to the most posterior point of the lenticular nucleus. In conclusion, we demonstrated that the corticospinal tract for the hand descended through the posterior portion of the posterior limb at the mid-thalamic level.

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.

Motor recovery via the peri-infarct area in patients with corona radiata infarct.

OBJECTIVES: Diffusion tensor image tracography (DTT) could be useful for exploration of the state of the corticospinal tract at the subcortical white matter level. We investigated the neural pathway associated with motor recovery in the patients with corona radiata infarct (CR) using DTT. DESIGN: Three hemiparetic patients who showed severe weakness of the affected upper extremity at stroke onset, were recruited. DTT was performed twice (subacute and chronic stage) using 1.5-T system. Three-dimensional reconstructions of the fiber tracts were obtained with FA <0.2, angle >45 degrees as termination criteria. RESULTS: In all patients, the motor function of the affected upper extremity has recovered to be functional state at second DTT scanning. The motor tracts of the affected hemisphere were observed to pass along the posterior portion of the CR infarct on both the first and second DTT. CONCLUSIONS: It seems that the motor function of the affected upper extremity of the patients recovered via the posterior portion of infarct. This finding may reflect functional reorganization of the motor pathway following damage to the corticospinal tract.

Degeneration speed of corticospinal tract in patients with cerebral infarct.

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 degrees . 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.

Recovery of a partially damaged corticospinal tract in a patient with intracerebral hemorrhage: a diffusion tensor image study.

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.

Peri-infarct reorganization of motor function in patients with pontine infarct.

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 degrees 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.

Diffusion anisotrophy in the early stages of stroke can predict motor outcome.

PURPOSE: This study examined whether the degree of impairment of diffusion anisotrophy in the early stages of a stroke can predict the motor function outcome. METHODS: Thirty-one hemiplegic stroke patients were enrolled to this study. Diffusion anisotropy was measured by determining fractional anisotropy (FA) in the two ROIs (region of interests) at corona radiata (CR) and in the posterior limb of internal capsule (IC) during the early stages of stoke (average 7.9 days after stroke onset) and compared with motor outcome of the affected hand 3 months after stroke onset. RESULTS: Both ROIs (CR or IC) and lesion types (hemorrhage or infarction) did not have significant effect on the SBFA (symmetry of bilateral FA) and dMRC (medical research council score improvement), either. Patients with greater initial MRC score had significantly greater SBFA and dMRC. The regression equation between the dMRC (Y axis) and the SBFA (X axis) was semi-linear and significant (P < 0.05); for CR group, Y = 3.296 - 0.1192X + 0.0015X2; for IC group, Y = 2.342 - 0.0533X +0.0007(2). The regression lines had 'threshold points' where a minute SBFA change would make a steep increase in dMRC. CONCLUSION: The degree of impairment in diffusion anisotropy during the early stages of stroke appears to have the potential to predict motor outcome.

[Two cases of metronidazole-induced encephalopathy].

Metronidazole is a 5-nitroimidazole compound known as an antimicrobial agent widely used for the treatment of protozoal infection, anaerobic infection, Helicobacter pylori infection and hepatic encephalopathy. It may produce a number of neurologic side effects including peripheral neuropathy, seizure, encephalopathy, ataxic gait and dysarthritic speech. There have been ten or more reports of metronidazole-induced encephalopathy in the literatures including a few reports of brain imaging changes by magnetic resonance images (MRI). However, none of the case of metronidazole-induced encephalopathy in patients with hepatic encephalopathy has been reported yet. Recently, we experienced two cases of metronidazole-induced encephalopathy in patients with liver cirrhosis caused by chronic hepatitis B, which were diagnosed by brain MRI and MR spectroscopy. In this report, we present 2 cases of metronidazole-induced encephalopathy with MR imaging and MR spectroscopic changes including follow-up imaging performed after the discontinuation of the metronidazole with a review of the literatures.

The predictive value of cortical activation by passive movement for motor recovery in stroke patients.

PURPOSE: Contralateral primary sensori-motor cortex (SM1) activation by passive movement was investigated by functional MRI (fMRI) at the early stage of stroke, to determine whether SM1 activation can be used to predict the degree of motor recovery of the hemiplegic hand. METHODS: We studied 17 stroke patients who showed complete paralysis of a hemiplegic hand at onset. The motor function of the hemiplegic hand was assessed on 4 separate occasions (at onset, at fMRI evaluation (performed < 4 weeks after onset), and 3 and 6 months after onset). Significant motor recovery was defined as recovery of the affected hand to the extent of it being able to prehend an object against gravity at least at 6 months after onset. RESULTS: The patients having an activated contralateral SM1 showed better motor recovery than those who did not. Only a fourth of the patients with an activated contralateral SM1 experienced a significant motor recovery, whereas none of the patients with an inactivated SM1 showed an improvement 6 months after onset, however, the incidence of significant motor recovery was not significantly difference between the two groups. CONCLUSION: It appears that contralateral SM1 activation by passive movement in the early stage of stroke has a low predictive value for the motor recovery of the hemiplegic hand, because the activation of the contralateral SM1 by passive movement appears to be mediated by somatosensory input to the cortex from the thalamus rather than from the motor pathway.

Bilateral primary sensori-motor cortex activation of post-stroke mirror movements: an fMRI study.

This fMRI study was undertaken to test whether the pathophysiological mechanism of mirror movements in hemiparetic stroke patients involves activation of the unaffected motor cortex. We studied 16 control subjects and 51 stroke patients. fMRI was performed at 1.5 T using a finger flexion-extension movement paradigm. The incidence of bilateral primary sensorimotor cortex activation was significantly increased during movements of the affected hand of stroke patients who showed mirror movements. Moreover, the incidence of bilateral primary sensorimotor cortex activation increased with the severity of mirror movements and primary sensorimotor cortex was activated bilaterally in all patients who showed sustained mirror movements. We conclude that the motor cortex activation on the non-stroke side is associated with mirror movements and is correlated with the severity of mirror movements. It seems that the pathophysiological mechanism of sustained mirror movements in stroke patients involves the unaffected motor cortex.

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 1.5 T 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 (p < 0.05). 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.

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.

Diffusion-weighted MR imaging of metastatic disease of the spine: assessment of response to therapy.

BACKGROUND AND PURPOSE: In cases of metastatic disease of the spine, monitoring the response to medical therapy with plain radiography, bone scanning, and conventional spin-echo sequence MR imaging is unsatisfactory because of the insensitivity or nonspecific findings of these imaging modalities. The purpose of this study was to investigate signal intensity changes of bone marrow after therapy by using diffusion-weighted MR imaging to monitor the response to medical therapy in cases of metastatic disease of the spine. METHODS: Twenty-four patients with metastatic disease of the spine were examined with MR imaging. Diffusion-weighted MR imaging and spin-echo MR imaging were performed in all patients before and after radiation therapy. Follow-up diffusion-weighted MR imaging and spin-echo MR imaging were performed for comparison purposes in nine cases at 1 month, in seven cases at 2 months, in seven cases at 3 months, and in three cases at 6 months after therapy. The diffusion-weighted MR imaging sequences were based on a steady-state free precession with a low b value (165 s/mm(2)) and a single shot stimulated echo-acquisition mode with a high b value (650 s/mm(2)). Apparent diffusion coefficient maps were obtained using two different b values incorporated in a diffusion-weighted single shot stimulated echo-acquisition mode sequence. Apparent diffusion coefficient maps were obtained in three cases. Signal intensity changes of the metastatic disease of the vertebral bone marrow before and after therapy on conventional spin-echo sequence and diffusion-weighted MR images were evaluated. RESULTS: As shown by diffusion-weighted MR imaging, metastatic disease of the vertebral bone marrow included in our study before therapy was hyperintense to normal vertebral bodies. In 23 patients with clinical improvement, metastatic disease of the spine after therapy was hypointense relative to normal vertebral bodies on the follow-up diffusion-weighted MR images. In one patient with hepatocellular carcinoma, the clinical symptoms did not improve and follow-up bone scanning performed 6 months after therapy showed increased uptake. Persistent hyperintense bone marrow after therapy was also noted on diffusion-weighted MR images. Decreased signal intensity of the metastatic disease of the spine on diffusion-weighted MR images was observed >1 month after therapy. CONCLUSION: Diffusion-weighted MR imaging shows that, with successful therapy, there is decreased signal intensity of metastatic disease of the vertebral bone marrow.