Simultaneous functional magnetic resonance imaging in the rat spinal cord and brain

Functional magnetic resonance imaging (fMRI) method was developed to investigate the pattern and temporal relationship in neuronal pathways of brain and spinal cord. Signal intensity changes correlating with stimulation patterns were observed simultaneously in the rat spinal cord and brain using fMRI at 9.4 T. Electrical stimulation of the forepaw was used to elicit activity. A quadrature volume RF coil covering both brain and the cervical spinal cord was used. Sets of fast spin echo (FSE) images were acquire simultaneously for both brain and spinal cord fMRI. Experiments were repeated in single animal and across animals. Activities within the dorsal horn of the spinal cord and within the somatosensory cortex were observed consistently within each animal as well as across animals.     

Functional magnetic resonance imaging in rodents: Methodology and application to spinal cord injury

Functional MRI (fMRI) on spinal cord-injured rodents at 4 and 8 weeks post injury (PI) is described. The paradigm for fMRI, based on electrical stimulation of rat paws, was automated using an in-house designed microprocessor-based controller that was interfaced to a stimulator. The MR images were spatially normalized to the Paxinos and Watson atlas using publicly available digital images of the cryosections. In normal uninjured animals, the activation was confined to the contralateral somatosensory cortex. In contrast, in injured animals, extensive activation, which included structures such as ipsilateral cortex, thalamus, hippocampus, and the caudate putamen, was observed at 4 and 8 weeks PI. Quantitative cluster analysis was carried out to calculate the volumes and centers of activation in individual brain structures. Based on this analysis, significant increase in activation between 4 and 8 weeks was observed only in the ipsilateral caudate putamen and thalamus. These studies suggest extensive and ongoing brain reorganization in spinal cord-injured animals.     

Cortical reorganization in NT3-treated experimental spinal cord injury: Functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) studies were performed for visualizing ongoing brain plasticity in Neurotrophin-3 (NT3)-treated experimental spinal cord injury (SCI). In response to the electrical stimulation of the forepaw, the NT3-treated animals showed extensive activation of brain structures that included contralateral cortex, thalamus, caudate putamen, hippocampus, and periaqueductal gray. Quantitative analysis of the fMRI data indicated significant changes both in the volume and center of activations in NT3-treated animals relative to saline-treated controls. A strong activation in both ipsi- and contralateral periaqueductal gray and thalamus was observed in NT3-treated animals. These studies indicate ongoing brain reorganization in the SCI animals. The fMRI results also suggest that NT3 may influence nociceptive pathways.     

Proton magnetic resonance spectroscopic imaging studies in patients with newly diagnosed partial epilepsy

PURPOSE: To assess whether the N-acetyl aspartate (NAA) to creatine ratio (NAA/Cr) is abnormally low at the onset of epilepsy and whether successful treatment of seizures with antiepileptic drugs is sufficient for normalization of NAA/Cr. PATIENTS AND METHODS: Proton magnetic resonance spectroscopic imaging (1H-MRSI) was used to measure NAA/Cr in temporal lobes of eight patients with newly diagnosed epilepsy before or soon after starting medication. Six patients had follow-up 1H-MRSI examinations 7 months later. Clinical pattern of the seizures and the EEG findings suggested partial seizures in all and TLE in five patients. None of the patients had lesional epilepsy according to magnetic resonance imaging. RESULTS: Initial 1H-MRSI of the temporal lobes showed significantly low NAA/Cr values in five of eight patients. Five of six patients who had follow-up 1H-MRSI were seizure-free after using medication; the remaining patient did not take medication and continued to experience occasional auras. Wilcoxon rank sign comparison of NAA/Cr on initial 1H-MRSI examination and follow-up 1H-MRSIs showed no significant difference (Z = 135, p = 0.893, 2-tailed) for five seizure-free patients. CONCLUSIONS: Neuronal dysfunction is present at an early stage of the epileptic process. NAA/Cr recovery in seizure-free patients controlled with antiepileptic drugs is less evident, compared with successful surgical treatment. Thus, absence of seizures is not necessarily coupled with NAA/Cr improvement and observed variable response warrants further investigation.     

Malformations of the spinal cord in 53 patients with spina bifida studied by magnetic resonance imaging

The incidence of associated malformations of the hindbrain and spinal cord in patients with spina bifida was investigated by a clinical and magnetic resonance study. The incidence of these malformations in combination with spina bifida was 49/53 (92.5%). Fiftytree children born with spina bifida aperta (40 patients) or spina bifida occulta (13 patients) formed the study group. The incidence of the various malformations were: Chiari malformations, type I, 10/53 (19%), and type II, 20/53 (38%); syringomyelia, 13/53 (24.5%); hydromyelia 4/53 (7.5%); tethered cord malformation, 35/53 (66%); diastematomyelia 2/53 (4%). Thirty-seven of the 49 patients with associated malformations had no clinical signs at the time of our study. The results point to the fact that in the pediatric age group, associated spinal defects often remain asymptomatic.     

Examination of spinal cord tissue architecture with magnetic resonance diffusion tensor imaging

Magnetic resonance diffusion tensor imaging yields images with detailed information about tissue water diffusion. Diffusion-weighted imaging of the human spinal cord requires dedicated magnetic resonance pulse sequences that minimize the effects of subject motion, distortions, and artifacts from lipids and CSF flow. These problems are accentuated by the anatomic properties of the spinal cord (i.e., a small crosssectional dimension and a location deep inside the body). The diffusion tensor (a simplified model for complex diffusion in structured tissues) can be estimated for each image pixel by measuring diffusion along a minimum of six independent directions. It can then be used to derive mean diffusivity, diffusion anisotropy, and the dominant orientation of the diffusion process. The observation that diffusion along nerve fibers is much higher than across fibers, allows a noninvasive reconstruction of the spinal cord nerve fiber architecture. This includes not only the primary cranio-caudad running connections, but also secondary, transverse running collateral fibers. With fiber tracking, the pixel-based diffusion information can be integrated to obtain a three-dimensional view of axonal fiber connectivity between the spinal cord and different brain regions. The development and myelination during infancy and early childhood is reflected in a gradual decrease of mean diffusivity and increase in anisotropy. There are several diseases that lead to either local or general changes in spinal cord water diffusion. For therapy research, such changes can be studied noninvasively and repeatedly in animal models.     

Diagnosis of spinal cord ependymoma and astrocytic tumours with magnetic resonance imaging

Ependymoma and astrocytic tumours, both originating from the glial tissue, constitute the majority of intramedullary spinal cord tumours. The purpose of this study is to evaluate the diagnostic ability of magnetic resonance imaging (MRI) in these two types of intramedullary spinal cord tumours. MRI findings of 17 ependymomas and 11 astrocytic tumours of the spinal cord were reviewed. Precontrast T₁-weighted images revealed abnormal enlargement of the spinal cord in all cases. Peritumoural cyst formation was noted in 14 ependymomas (82%) and four astrocytic tumours (36%). Evidence of haemorrhage was identified in five (29%) ependymomas and one (9%) astrocytic tumour. Gadolinium-MRI (Gd-MRI) revealed marked enhancement in 11 ependymomas (65%), while six ependymomas showed irregular, partial or no enhancement. Five of these six ependymomas had evidence of prior haemorrhage. Eight astrocytic tumours (73%) were enhanced on Gd-MRI and the pattern of enhancement was more irregular or partial than that of ependymomas. Two pilocytic astrocytomas showed marked ring-like enhancement. In conclusion, detection of haemorrhage and Gd-MRI will help to differentiate these two types of tumours. Further study will be needed to elucidate the relationship between the histological subtypes of the tumours and MRI findings.     

首发精神分裂症患者的功能磁共振初步研究

目的 利用血氧水平依赖性(blood oxygenation level-dependent,BOLD)功能磁共振成像(functional magnetic resonance imaging,fMRI)技术探讨首发精神分裂症患者治疗前后认知功能激发图像的特点。方法 13例首发精神分裂症患者入组,用利培酮或氯丙嗪治疗后9例患者复查fMRI。以词语流畅性作业(verbal fluency task,VF)作为任务,采用Block设计,用梯度回波-平面回波成像(GRE-EPI)序列采集数据,经工作站处理后获功能图像。结果 (1)VF激活受试者的额叶(前额叶)、顶叶及颞叶皮层;(2)复查的9例受试者中,7例激活增强,2例激活减弱;(3)治疗后激活增强的7例受试者的双侧额上、中、下回激活有增加趋势,而双侧颞上、中、下回激活有减少趋势(P>0.05);但左额叶背外侧面治疗后的激活明显强于治疗前(P=0.032)。结论 BOLD-fMRI可用于研究人脑的高级认知功能。首发精神分裂症患者治疗前后脑功能图像有明显变化,提示认知缺陷症状是可以治疗的。     

Lumbosacral spinal cord infarction. Data from magnetic resonance imaging

A 77-year old woman and a 61-year old man with lumbosacral spinal cord ischaemic lesions and paraplegia presented with dissociated or partial forms of the lumbar enlargement artery (Adamkiewicz's artery) syndrom. Magnetic resonance imaging (MRI) was performed in both patient with an 0.15 Tesla resistive magnet. A hypersignal on T2-weighted images was present in both cases, which corresponded to the infarction affecting the lumbosacral part of the cord. MRI provided accurate delineation of the lesions and clinicoradiological correlations in both patients. The hypersignal occupied the lumbar cord in case 1 and the conus medullaris in case 2. The clinical signs and location of the lesions seemed to be determined by the different patterns of lumbosacral arterial supply. Since such images could be confused with tumoral images, surgical exploration was carried out in both patients; it failed to demonstrate any tumour or cyst and only showed a pale cord. Surgical cord biopsy in case 2 demonstrated ischaemic tissue. We conclude that ischaemia of the spinal cord can be demonstrated by MRI, but owing to the low specificity of this imaging method aedema cannot be distinguished from necrosis, gliosis or demyelination.     

Post-traumatic spinal cord cysts evaluated by magnetic resonance imaging.

In order to determine a more accurate prevalence of post-traumatic spinal cord cysts (PTSCC) in spinal cord injured (SCI) patients, we retrospectively reviewed magnetic resonance scans from symptomatic imaging and asymptomatic SCI patients. We found the incidence of PTSCC to be 51% in our patient population. The only symptom that correlated to the presence of a cyst was spasticity. The cyst develops at the site of injury and appears to be a common sequela of SCI. We believe that conservative treatment is indicated in most patients with a PTSCC.     

A case of adrenomyeloneuropathy with marked spinal cord atrophy on magnetic resonance imaging

A 29-year-old man complained of increasing paraplegia and sphincter disturbances. On admission, he was 23 years old. He had moderate pigmentation of the skin, and his neurological examinations revealed spastic paraplegia, hyperreflexia of both legs with Babinski's signs, a pinprick sensation deficit below the L-1 level, loss of vibration sense in the lower extremities and horizontal nystagmus on lateral gaze. Endocrinological examinations revealed adrenocortical insufficiency. CSF, EEG, EMG, brain-CT and myelography did not show any abnormalities, but metrizamide CT myelography at the low thoracic spinal cord revealed decreased cord diameter. Nerve conduction velocities showed impairment in the tibial and peroneal motor fibers. Auditory brain-stem response revealed elongated III-V interval. A cystometrogram disclosed a reflex neurogenic bladder. In the analysis of the fatty acid component of plasma sphingomyelin, the C26/C22, C25/C22, C24/C22 ratios were found to be increased, and the diagnosis of adrenomyeloneuropathy (AMN) was confirmed. The patient's mother was also found to be asymptomatic carrier of AMN on the basis of long chain fatty acid plasma levels. The MRI performed in his age of 29 years, showed marked spinal atrophy from low cervical to low thoracic regions and mild cerebellar atrophy. This findings seems to correspond with chronic progressive demyelination of spinal white matter such as pyramidal tract and fasciculus gracilis.     

Objective perimetry using functional magnetic resonance imaging in patients with visual field loss

In ophthalmic clinics, subjective perimetry is a standard examination method. However, for certain patients, objective perimetry is useful since it avoids the need for subjective judgments. The purpose of the present study is to demonstrate the feasibility of objective perimetry using functional magnetic resonance imaging (fMRI). fMRI was performed in 8 patients with visual field defects caused by cerebral lesions. The composite stimulus was either the combination of an expanding ring and a clockwise rotating wedge, or a contracting ring and a counter-clockwise rotating wedge. The largest radius was a 10° visual angle with magnifying glasses. The cycle period for the ring and wedge components differed, enabling us to distinguish the two targets within a single time series. Data were analyzed using custom software that interprets the two stimuli and estimates visual field maps. Regions of interest (ROIs) were set covering the entirety of the occipital lobes, and the most effective visual field location for each voxel was calculated from these two response components. The visual field maps obtained with fMRI were compared with the 10-2 Humphrey visual field (HVF) program. While some divergences were observed, in most subjects the visual field defects on fMRI agreed with those on HVF. Cross-correlation coefficients between grayscale values of visual field maps obtained with fMRI and decibel values obtained with HVF were significant (P < 0.05) in all subjects. fMRI in conjunction with our method is feasible for objectively and efficiently measuring the visual field of patients with visual field loss.     

Tethered spinal cord and lipoma. Contribution of magnetic resonance imaging

A 12 year-old boy was investigated for progressive deformity of the left foot developing over 2 years. The foot was hollow with equinus varus and claw toes. Signs of a lesion of left L5 and S1 roots were present and spina bifida at L5 was noted on X-rays. Magnetic resonance imaging (MRI) showed a tethered spinal cord associated with a lipoma at the level of the S1 vertebra. Modes of presentation and physiopathology of disorders related to tethered cords are reviewed and the diagnostic value of MRI is emphasized.     

Extensive spinal cord involvement in magnetic resonance imaging evaluation on schistosomal myelitis

The diagnosis of schistosomal myelitis (SM) is frequently presumptive because no findings from any complementary examination are pathognomonic for this disease. The present report describes some abnormalities seen on magnetic resonance imaging (MRI) evaluation of a series of SM patients and discusses their etiopathogenesis. Methods: This study evaluated SM patients at the time of their diagnosis. These patients routinely underwent MRI on all segments of the spinal cord. Results: Thirteen patients were evaluated. The MRI was abnormal in 12 (92.3%) of them. In 11 patients (84.61%), the damage reached two or more spinal segments. Conclusions: MRI was an important diagnostic aid in this sample, because of the high rate of abnormalities detected. The tissue damage observed on MRI was extensive in the majority of the patients.     

Serial cranial and spinal cord magnetic resonance imaging in multiple sclerosis.

Twenty-nine mildly disabled patients with multiple sclerosis underwent serial clinical and magnetic resonance imaging (MRI) evaluations (pre- and postgadolinium cranial and spinal cord MRI) on at least 3 occasions at 13-week intervals and during periods of suspected relapse. Using clinical judgment of the presence of recent active disease as the gold standard, combined MRI studies confirmed the clinical impression of active disease in 93% of follow-up visits (sensitivity) and the absence of active MS in 63% of follow-up visits (specificity). None of the cranial and spinal MRI-detected abnormalities disappeared. Gadolinium administration particularly increased the yield of spinal MRI. Cranial MRI alone detected 80% of the MRI-active visits. Clinical and MRI concordance was significantly better for the presence of recent disease activity than for the anatomical localization of the presumed site of activity. MRI evidence of apparent ongoing disease activity was seen more frequently in patients believed to have active multiple sclerosis in the preceding year (13 of 21) than in patients who had been in clinical remission for at least the 2 preceding years (2 of 8). Although clinical evidence of new disease activity was much less common in patients with active, chronic-progressive disease (1 of 8) than in patients with active, relapsing disease (9 of 13), the proportion of patients with either infrequent relapses, frequent relapses, or slow chronic-progressive disease in the preceding year in whom MRI activity developed and the pattern of this new MRI activity was similar between these types of active patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Feasibility of 3.0 T diffusion-weighted nuclear magnetic resonance imaging in the evaluation of functional recovery of rats with complete spinal cord injury

Diffusion tensor imaging is a sensitive way to reflect axonal necrosis and degeneration, glial cell regeneration and demyelination following spinal cord injury, and to display microstructure changes in the spinal cord in vivo. Diffusion tensor imaging technology is a sensitive method to diagnose spinal cord injury; fiber tractography visualizes the white matter fibers, and directly displays the structural integrity and resultant damage of the fiber bundle. At present, diffusion tensor imaging is restricted to brain examinations, and is rarely applied in the evaluation of spinal cord injury. This study aimed to explore the fractional anisotropy and apparent diffusion coefficient of diffusion tensor magnetic resonance imaging and the feasibility of diffusion tensor tractography in the evaluation of complete spinal cord injury in rats. The results showed that the average combined scores were obviously decreased after spinal cord transection in rats, and then began to increase over time. The fractional anisotropy scores after spinal cord transection in rats were significantly lower than those in normal rats(P 0.05); the apparent diffusion coefficient was significantly increased compared with the normal group(P 0.05). Following spinal cord transection, fractional anisotropy scores were negatively correlated with apparent diffusion coefficient values(r = –0.856, P 0.01), and positively correlated with the average combined scores(r = 0.943, P 0.01), while apparent diffusion coefficient values had a negative correlation with the average combined scores(r = –0.949, P 0.01). Experimental findings suggest that, as a non-invasive examination, diffusion tensor magnetic resonance imaging can provide qualitative and quantitative information about spinal cord injury. The fractional anisotropy score and apparent diffusion coefficient have a good correlation with the average combined scores, which reflect functional recovery after spinal cord injury.     

Use of longitudinal magnetic resonance imaging in preclinical models of spinal cord injury

<正>Spinal cord injury (SCI) is a distressing event with grave socio/economic consequences to our society. Pathophysiological response following SCI involves blood-spinal cord barrier breakdown, neuroinflammation and formation of a glial scar that altogether govern the feasibility of spontaneous axonal     

Endogenous recovery of injured spinal cord: longitudinal in vivo magnetic resonance imaging

Pathological changes were followed longitudinally with in vivo magnetic resonance imaging (MRI) and behavioral studies in experimental spinal cord injury (SCI). MRI-observed pathology was correlated with histology. On MRI, the cavitated regions of the injured cord were gradually filled with viable tissue between two and 8 weeks postinjury, and a concomitant improvement was observed in the neurobehavioral scores. By weeks 3-6, on MRI, the gray matter (GM) returned in the segments caudal, but not rostral, to the injury site. The corresponding histological sections revealed motor neurons as well as other nuclei in the gray matter immediately caudal to the epicenter, but not at the site of injury, suggesting neuronal recovery in perilesioned areas. The neuronal and neurological recovery appeared to occur about the same time as neovasculature that was reported on the contrast-enhanced MRI, suggesting a role for angiogenesis in recovery from SCI. The role of angiogenesis in neuronal recovery is further supported by the immunohistochemical observation of greater bromodeoxyuridine uptake by blood vessels near the lesion site compared with uninjured cords.