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At least 775 records · Page 43Linked to original sources
PubMed2006

[Pathophysiological aspects of brain structural disturbances in patients with Fabry disease: literature review].

Fabry Disease (FD) is a rare X-linked lysosomal storage disorder caused by deficiency of alpha-galactosidase A (alpha-GAL) enzyme activity. Neutral glycosphingolipides (esp. Gb3) accumulate in lysosomes of several tissues, particularly in vascular endothelium and smooth muscle cells. Cerebral manifestations that might be mainly due to progressive cerebrovascular dysfunction, are one major and often life-threatening burden of the disease. We reviewed the present literature concerning brain structural alterations in FD and discuss the possibly relevant underlying pathophysiological aspects of these disturbances. Cerebrovascular events (TIA, stroke) occur in FD at a rather early age. In female FD patients who were considered to be less affected "carriers" for a long time, the prevalence of cerebrovascular events seems to be at last as high as in male patients. In structural imaging white matter lesions (WML) can be found frequently even in young FD patients. In a recent study clinically equally affected men and women with FD showed a comparable severity of WML load. Different pathophysiological aspects of cerebral angiopathy and WML development are discussed against the background of current concepts (e. g. accumulation of Gb3 in vascular endothelium with consecutive cell proliferation and luminal stenosis, acceleration of focal intravasal pressure and disturbances of vascular auto-regulation). Pathological increase of pulvinar signal in T1-weighted MRI has also been described in FD. This finding was assumed to be caused by calcification as a consequence of disturbed local circulation. To enhance our knowledge about the relevant neurobiological processes the authors propose a more sensitive and early detection of brain structural changes in FD. New brain structural MRI methods such as diffusion-tensor imaging could provide a pattern of ultrastructural changes even in young patients without visible WML. This strategy could be as well useful for quantification of possible effects of the enzyme replacement therapy on brain structural alterations in FD. Based on recent data a systematic FD-screening by measuring Gb3 in urine of young patients with cryptogenic stroke should be discussed. Basically in such cases FD should be clinically considered.

Brain↗
PubMed1997

Specificity of volumetric magnetic resonance imaging in detecting hippocampal sclerosis.

BACKGROUND: Magnetic resonance imaging (MRI)-based volumetric measurements of the hippocampal formation are useful in detecting unilateral hippocampal sclerosis (HS) in patients with temporal lobe epilepsy. In this pathologic entity, volumetric MRI analysis shows the epileptogenic structure to be atrophic when compared with the normal, nonepileptogenic side. Some authors have suggested that the radiological features of atrophy of medial temporal lobe structures are common in patients with complex partial seizures, but also are seen frequently in other seizure types and can occur even in patients without epilepsy. OBJECTIVE: To determine if seizures originating in extrahippocampal sites cause gliosis, cell loss, and atrophy of medial temporal lobe structures (i.e., HS). METHODS: We studied 110 patients with chronic epilepsy using volumetric MRI measurements of the hippocampal formation. Seventeen patients had pathologically proven HS, 27 patients had seizures due to extratemporal structural lesions, 15 patients had seizures caused by extrahippocampal temporal lobe lesions, 29 patients had primary generalized epilepsy, and 22 patients had secondary generalized epilepsy. RESULTS: All 17 patients with HS showed significantly reduced absolute hippocampal formation volumes of greater than 2 SDs below the mean of the control groups. The preoperative hippocampal formation volume measurements correlated well with the severity of HS on pathological examination. Hippocampal volumes were within the normal range in all patients with primary generalized epilepsy, secondary generalized epilepsy, extratemporal structural lesions, and extrahippocampal temporal lobe lesions. CONCLUSIONS: Seizures originating at extrahippocampal sites do not cause gliosis, cell loss, or atrophy of medial temporal structures. Significant reduction in hippocampal volumes is a specific marker for HS.

Adolescent↗
PubMed2004

Hippocampal structural asymmetry in unsuccessful psychopaths.

BACKGROUND: Structural and functional hippocampal abnormalities have been previously reported in institutionalized psychopathic and aggressive populations. This study assessed whether prior findings of a right greater than left (R > L) functional asymmetry in caught violent offenders generalize to the structural domain in unsuccessful, caught psychopaths. METHODS: Left and right hippocampal volumes were assessed using structural magnetic resonance imaging (MRI) in 23 control subjects, 16 unsuccessful psychopaths, and 12 successful (uncaught) community psychopaths and transformed into standardized space. RESULTS: Unsuccessful psychopaths showed an exaggerated structural hippocampal asymmetry (R > L) relative both to successful psychopaths and control subjects (p <.007) that was localized to the anterior region. This effect could not be explained by environmental and diagnostic confounds and constitutes the first brain imaging analysis of successful and unsuccessful psychopaths. CONCLUSIONS: Atypical anterior hippocampal asymmetries in unsuccessful psychopaths may reflect an underlying neurodevelopmental abnormality that disrupts hippocampal-prefrontal circuitry, resulting in affect dysregulation, poor contextual fear conditioning, and insensitivity to cues predicting capture.

Adult↗
PubMed2006

Application of magnetic resonance imaging movie to assess articulatory movement.

OBJECTIVE: To introduce the technique of magnetic resonance imaging (MRI) movie and to propose its feasibility for investigating articulatory movement. SUBJECTS: Five healthy adult females participated in the study. METHODS: Dynamic changes in oropharyngeal structures were assessed with MRI movie during the articulation of a bilabial consonant. RESULTS: Movements of the velum and tongue at a time resolution of 30 ms were complex at the tip of the tongue and the anterior part of the velum. These movements that were seen with a time resolution of 30 ms could not be interpolated or in any way derived from the results obtained with a time resolution of 120 ms. CONCLUSION: The results suggest that MRI movie may be useful in the evaluation of articulation. It is important to reduce the time resolution to 30 ms to obtain images of articulators.

Adult↗
PubMed1993

The role of nuclear magnetic resonance imaging in psychiatric research.

Magnetic resonance imaging (MRI) has become an important tool in the investigation of cerebral abnormalities associated with psychiatric illnesses. There are a number of benefits of investigating psychiatric illness with MRI, which is superior to computed tomography scanning. MRI has been used to study neurologic deficits seen in schizophrenia, affective disorders, dementia, and more recently, anxiety disorders. Magnetic resonance spectroscopy offers a new investigational technique that adds functional information to the structural changes seen with standard MRI scanning. This review highlights the current data in living human subjects that demonstrate structural changes in psychiatric disorders using MRI, including recent studies of the anxiety disorders.

Aged↗
PubMed2007

Unified structural equation modeling approach for the analysis of multisubject, multivariate functional MRI data.

The ultimate goal of brain connectivity studies is to propose, test, modify, and compare certain directional brain pathways. Path analysis or structural equation modeling (SEM) is an ideal statistical method for such studies. In this work, we propose a two-stage unified SEM plus GLM (General Linear Model) approach for the analysis of multisubject, multivariate functional magnetic resonance imaging (fMRI) time series data with subject-level covariates. In Stage 1, we analyze the fMRI multivariate time series for each subject individually via a unified SEM model by combining longitudinal pathways represented by a multivariate autoregressive (MAR) model, and contemporaneous pathways represented by a conventional SEM. In Stage 2, the resulting subject-level path coefficients are merged with subject-level covariates such as gender, age, IQ, etc., to examine the impact of these covariates on effective connectivity via a GLM. Our approach is exemplified via the analysis of an fMRI visual attention experiment. Furthermore, the significant path network from the unified SEM analysis is compared to that from a conventional SEM analysis without incorporating the longitudinal information as well as that from a Dynamic Causal Modeling (DCM) approach.

Attention↗
PubMed1998

The structural and functional mechanisms of motor recovery: complementary use of diffusion tensor and functional magnetic resonance imaging in a traumatic injury of the internal capsule.

OBJECTIVES: Recovery from focal motor pathway lesions may be associated with a functional reorganisation of cortical motor areas. Previous studies of the relation between structural brain damage and the functional consequences have employed MRI and CT, which provide limited structural information. The recent development of diffusion tensor imaging (DTI) now provides quantitative measures of fibre tract integrity and orientation. The objective was to use DTI and functional MRI (fMRI) to determine the mechanisms underlying the excellent recovery found after a penetrating injury to the right capsular region. METHODS: DTI and fMRI were performed on the patient described; DTI was performed on five normal controls. RESULTS: The injury resulted in a left hemiplegia which resolved fully over several weeks. When studied 18 months later there was no pyramidal weakness, a mild hemidystonia, and sensory disturbance. fMRI activation maps showed contralateral primary and supplementary motor cortex activation during tapping of each hand; smaller ipsilateral primary motor areas were activated by the recovered hand only. DTI disclosed preserved structural integrity and orientation in the posterior capsular limb by contrast with the disrupted structure in the anterior limb on the injured side. CONCLUSIONS: The findings suggest that the main recovery mechanism was a preservation of the integrity and orientation of pyramidal tract fibres. The fMRI studies do not suggest substantial reorganisation of the motor cortex, although ipsilateral pathways may have contributed to the recovery. The initial deficit was probably due to reversible local factors including oedema and mass effect; permanent damage to fibre tracts in the anterior capsular limb may account for the persistent sensory deficit. This study shows for the first time the potential value of combining fMRI and DTI together to investigate mechanisms of recovery and persistent deficit in an individual patient.

Adult↗
PubMed2002

High-resolution magnetic resonance imaging of human cochlea.

OBJECTIVES: High-resolution MRI (MRI) of human inner ear structures provides several advantages over other imaging modalities. High-resolution visualization of inner ear ultrastructure in a noninvasive manner may provide important information about inner ear disease that is not obtainable in other ways. The study was performed to demonstrate the capabilities of MRI at high resolution on the human cochlea, vestibular structures, and facial nerve. Comparative analyses of MRI anatomy with that seen on histological dissection were made. The aim of the study was to define the anatomy of human cadaveric cochlea using a 9.4-Tesla magnetic resonance scanner, currently the most powerful magnetic resonance magnet available. STUDY DESIGN: Experimental pilot study of cadaveric human cochleae. METHODS: Serial scanning using a 9.4-Tesla magnetic resonance imager on normal preserved and fresh cadaveric inner ears was performed in different planes. RESULTS: The images revealed detailed anatomy of the modiolus, utricle, saccule, semicircular canals, and facial nerve. Specifically, identifiable structures within the cochlea included the osseous spiral lamina, Reissner's membrane, membranous spiral lamina, spiral ligament, and others. CONCLUSIONS: Data established through the acquisition of images from cadaver cochlea, facial nerve, and vestibular complex provide a foundation for developing steps for testing temporal bones and, eventually, patients with Meniere's disease and other inner ear disease. The present ongoing project will provide information on baseline images of the inner ear using high-resolution MRI.

Cochlea↗
PubMedDate not supplied

Computer-assisted imaging of the fetus with magnetic resonance imaging.

The purpose of this paper is to review the use of magnetic resonance imaging (MRI) of the fetus and to propose future techniques and applications. Institutional review board approved MR images of the fetus were acquired in 66 patients with sonographically suspected fetal abnormalities. Axial, coronal, and sagittal short TR, short TE images were obtained. In addition, 12 studies were performed with rapid scans requiring 700-1200 ms using either GRASS or Spoiled GRASS techniques. Sequential studies demonstrating fetal motion were also performed. Three studies with 3D IR prepped GRASS were performed. These allowed for orthogonal and non-orthogonal reformatted views and 3D display. Normal fetal structures were shown with MRI, including brain, heart, liver, stomach, intestines, and bladder. Gross fetal anomalies could generally be demonstrated with MRI. MRI may give additional information to that of sonography in fetal anomalies, particularly those involving the central nervous system, and in the detection of fat, blood, and meconium. MRI of the fetus can demonstrate normal and abnormal structures. Newer techniques with faster imaging will allow for greater possibility of computer assisted manipulation of data.

Fetus↗
PubMed2003

[Clinical and magnetic resonance imaging findings in patients with surgically treated mesial temporal sclerosis].

PURPOSE: Mesial temporal sclerosis (MTS) is one of the leading causes of medically intractable complex partial seizures. Magnetic resonance imaging (MRI) and clinical findings in seventeen patients who had surgery for medically intractable mesial temporal lobe epilepsy (MTLE) are presented in this report. MATERIALS AND METHODS: 17 patients (9 females and 8 males) aged 19-35 years with clinically and electrophysiologically proven MTLE have been included in the study. Age at seizure onset was six months to 17 years, frequency of seizures 4-20 times/month, and duration of medical treatment 10-28 years with no response. MRI and volumetry of the mesial temporal structures were performed in all patients. RESULTS: On preoperative MRI and volumetry, pathologic signal, loss of internal structures and atrophy were present in the right hippocampus in twelve cases and left hippocampus in five. The hippocampal head and body were involved in ten cases and all three parts in seven. The Wada test was performed in three cases showing that memory and speech functions were controlled by the noninvolved side. All patients underwent surgery. The histopathological examination result was MTS in all cases. In the postoperative follow up period of one to 24 months, 12 patients were assessed as class I and II, and seven as III according to the Engel Classification. CONCLUSION: MRI and volumetry are among the most important tools in the preoperative diagnosis of MTS. All patients have benefited from surgery, verifying the preoperative clinical and MR imaging diagnosis. Interpretation of MR findings is important in determining surgical candidates and success of surgery in MTS, which is a major cause of medically intractable temporal epilepsy.

Adult↗
PubMed2006

Simultaneous MRI and PET imaging of a rat brain.

Multi-modality imaging is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET fused with anatomical structure images created by MRI will allow the correlation of form with function. Our group is developing a system to acquire MRI and PET images contemporaneously. The prototype device consists of two opposed detector heads, operating in coincidence mode. Each MRI-PET detector module consists of an array of LSO detector elements coupled through a long fibre optic light guide to a single Hamamatsu flat panel position-sensitive photomultiplier tube (PSPMT). The use of light guides allows the PSPMTs to be positioned outside the bore of a 3T MRI scanner where the magnetic field is relatively small. To test the device, simultaneous MRI and PET images of the brain of a male Sprague Dawley rat injected with FDG were successfully obtained. The images revealed no noticeable artefacts in either image set. Future work includes the construction of a full ring PET scanner, improved light guides and construction of a specialized MRI coil to permit higher quality MRI imaging.

Algorithms↗
PubMed1999

MR imaging of the chest: mediastinum and chest wall.

This review presents the options and limitations of MRI in non-vascular diseases of the mediastinum and the chest wall. In numerous thoracic pathologies, MRI is a useful supplement to spiral CT. This imaging procedure also allows a contrast-media-free differentiation of solid tumors and vascular lesions (e. g., aortic aneurysms). The advantages of MRI over CT are particularly useful when multiplanar tumor imaging is required prior to surgery to establish the exact spatial relationship between tumor and the other mediastinal structures. Primary indications for MRI in diseases of the mediastinum and chest wall are therefore: (a) tumors of the posterior mediastinum for determining their position in relation to the neural foramina and the spinal canal; (b) chest wall tumors; (c) preoperative multiplanar imaging of primary mediastinal tumors; and (d) contraindications against CT exams with iodine contrast media.

Contrast Media↗
PubMed2004

Cerebral atrophy in Parkinson's disease with and without dementia: a comparison with Alzheimer's disease, dementia with Lewy bodies and controls.

Parkinson's disease is a common neurodegenerative disorder primarily characterized by rigidity, tremor and bradykinesia. Cognitive impairment and neuropsychiatric symptoms are frequent in Parkinson's disease, with a 70% cumulative incidence of dementia. The aim of this cross-sectional study was to establish the pattern of cerebral atrophy on MRI in Parkinson's disease patients with dementia. We used voxel-based morphometry (VBM) to provide an unbiased means of investigating brain volume loss. Whole brain structural T1-weighted MRI scans from Parkinson's disease patients with dementia (PDD, n = 26), Parkinson's disease patients without dementia (n = 31), Alzheimer's disease patients (n = 28), patients with dementia with Lewy bodies (DLB, n = 17) and control subjects (n = 36) were acquired. Images were analysed using SPM99 and the optimized method of VBM. Reduced grey matter volume in PDD patients compared with controls was observed bilaterally in the temporal lobe, including the hippocampus and parahippocampal gyrus, and in the occipital lobe, the right frontal lobe and the left parietal lobe, as well as some subcortical regions. Parkinson's disease patients without dementia showed reduced grey matter volume in the frontal lobe compared with control subjects. There was significant grey matter atrophy bilaterally in the occipital lobe of PDD patients compared with Parkinson's disease patients. In addition, significant temporal lobe atrophy, including the hippocampus and parahippocampal gyrus was detected in Alzheimer's disease relative to PDD. No significant volumetric differences were observed in PDD compared with DLB. Thus, Parkinson's disease involves grey matter loss in frontal areas. In PDD, this extends to temporal, occipital and subcortical areas, with occipital atrophy in PDD being the only difference between the two groups. This provides important information about the pattern of cerebral atrophy in Parkinson's disease and PDD.

Aged↗
PubMed2006

Are "structural abnormalities" on magnetic resonance imaging a contraindication to the successful conservative treatment of chronic nonspecific low back pain?

STUDY DESIGN: Prospective study. OBJECTIVE: To examine the association between structural abnormalities recorded on magnetic resonance imaging (MRI) and outcome after evidence-based conservative treatment in patients with chronic nonspecific low back pain (LBP). SUMMARY OF BACKGROUND DATA: In most guidelines for the management of LBP, MRI is not recommended unless the diagnostic triage suggests serious spinal pathology or nerve root involvement for which surgical treatment is foreseen. This is because many structural changes seen on MRI appear to be as common in asymptomatic individuals as in people with LBP and are, therefore, considered of little value in either explaining the cause of pain or deciding the subsequent course of management. However, to our knowledge, no studies have assessed whether the presence of such MRI abnormalities influences the outcome of the conservative treatment that patients with chronic nonspecific LBP typically receive. METHODS: T2-weighted, 4-mm spin-echo MRI sequences of the lumbar spine were obtained from 53 patients with chronic nonspecific LBP before a 3-month program of exercise therapy. Disc degeneration, disc bulging, high intensity zones, and endplate/bone marrow changes were assessed for each lumbar segment. Back pain (average and worst) and disability (Roland Morris score) were assessed before and after therapy, and 12 months later, and the improvements were examined in relation to the presence or absence of baseline MRI "abnormalities." RESULTS: Eighty-nine percent of patients had severe disc degeneration (grade 4 or 5), 74% had disc bulging, 60% had high intensity zones, and 62% had endplate/bone marrow changes in at least 1 lumbar segment. Only 11% patients had none of these changes at any level. The MRI abnormalities showed only minimal association with baseline symptoms. In multivariate regression analyses, in which age, gender, and baseline symptoms were controlled for, only 1 significant association between the MRI variables and outcome was observed: the presence of a high intensity zone in any vertebral segment was associated with lower average pain at the 12-month follow-up (standardized beta -0.376, P = 0.006, 16.5% variance accounted for). CONCLUSION: In the patient group examined, the presence of common "structural abnormalities" on MRI had no significant negative influence on the outcome after therapy.

Adult↗
PubMed1994

Phantom studies simulating the impact of trabecular structure on marrow relaxation time, T2'.

Phantom studies were conducted to investigate the impact of trabecular structure on the T2' signal measured by MRI. For a separation of density from structural effects, several phantoms were built. They consisted of parallel polyethylene strings arranged in a variety of different patterns to simulate a) a constant uniform trabecular distribution with increasing trabecular thickness and b) different structures with identical overall trabecular density. An asymmetric spin echo sequence was used to determine the apparent relaxation time T2'. Changes in T2' are induced by susceptibility differences between the polyethylene strings simulating trabeculae and Gd-DTPA doped saline simulating bone marrow. The results showed an increasing T2' decay rate with a) decreasing spacing while the string density was constant and b) with increasing string density while the string arrangement was constant. The results demonstrate that the T2' signal is affected not only by density but also by spatial distribution. However, the results also indicate that a separation of the two effects is not possible from a T2' measurement alone, but that e.g., a matching CT slice that would provide purely density information is additionally needed. Theoretical simulations confirmed these results.

Bone Marrow↗
PubMed2005

T(2) + measurement during acute cerebral ischemia by Carr-Purcell MRI at 4T.

Metabolic and structural changes occur in brain tissue within minutes of ischemia. The adiabatic multi-echo (Carr-Purcell) localization pulse sequence LASER has shown promise in detecting tissue contrast changes within the first hour of ischemia. The purpose of this initial study was to combine the LASER localization sequence with fast 3D echo-planar imaging (EPI) to quantify the regional apparent transverse relaxation (T(2) (dagger)) in a rabbit model of acute embolic ischemia at 4 Tesla. Carr-Purcell T(2) (dagger)-weighted images were acquired at 7 different echo-times and used to estimate T(2) (dagger) in both cortex and striatum. In ischemic tissue identified by 2,3,5-triphenyltetrazolium chloride (TTC) staining, the T(2) (dagger) increased by approximately 31% after 1 hour of ischemia and remained elevated until study completion at 4 h of ischemia. Lesion volume, defined as the number of pixels with T(2) (dagger) greater than 90 ms, increased by 40% between 1 and 4 h after induction of ischemia. Carr-Purcell LASER-EPI T(2) (dagger)-weighted images show promise in detecting early tissue changes in focal cerebral ischemia.

Acute Disease↗
PubMed1994

Near-microscopic magnetic resonance imaging of the brains of phenylalanine hydroxylase-deficient mice, normal littermates, and of normal BALB/c mice at 9.4 Tesla.

The near-microscopic resolution of the mouse brain, by magnetic resonance imaging (MRI) at 9.4 T, permits in situ examination of the entire brain and longitudinal studies of neural development. MRI can be utilized to reveal brain structure at a resolution of 100 microns in the X, Y, and Z planes of brain, to differentiate the gray from white (myelin-rich) matter, and to reveal the ventricular compartments. The present report describes the structure of normal BALB/c mouse brain as revealed by imaging at 9.4 T and by histological stains; the structure of normal brain is compared with that from a phenylalanine hydroxylase-deficient mouse mutant line (Pah(enu2)) and those from normal littermates. The brains of patients with phenylketonuria (PKU) were reported to have demyelination and other structural abnormalities revealed by magnetic resonance imaging (MRI). Therefore, high-resolution MRI was used to examine the brain of this mutant, an animal model for the study of human phenylketonuria. Our study revealed no evidence of demyelination or other abnormalities in the brains of Pah(enu2) mice. Histologically, the mutant and normal mouse brains appear similar. This is consistent with a recent study from our laboratory which demonstrated that the histology of the brain of an untreated male patient, who died with PKU at the age of 29, was similar to control brain with the exception of changes directly related to visual blindness and seizures experienced by the patient.

Adult↗
PubMed1999

ROC analysis of statistical methods used in functional MRI: individual subjects.

The complicated structure of fMRI signals and associated noise sources make it difficult to assess the validity of various steps involved in the statistical analysis of brain activation. Most methods used for fMRI analysis assume that observations are independent and that the noise can be treated as white gaussian noise. These assumptions are usually not true but it is difficult to assess how severely these assumptions are violated and what are their practical consequences. In this study a direct comparison is made between the power of various analytical methods used to detect activations, without reference to estimates of statistical significance. The statistics used in fMRI are treated as metrics designed to detect activations and are not interpreted probabilistically. The receiver operator characteristic (ROC) method is used to compare the efficacy of various steps in calculating an activation map in the study of a single subject based on optimizing the ratio of the number of detected activations to the number of false-positive findings. The main findings are as follows: Preprocessing. The removal of intensity drifts and high-pass filtering applied on the voxel time-course level is beneficial to the efficacy of analysis. Temporal normalization of the global image intensity, smoothing in the temporal domain, and low-pass filtering do not improve power of analysis. Choices of statistics. the cross-correlation coefficient and t-statistic, as well as nonparametric Mann-Whitney statistics, prove to be the most effective and are similar in performance, by our criterion. Task design. the proper design of task protocols is shown to be crucial. In an alternating block design the optimal block length is be approximately 18 s. Spatial clustering. an initial spatial smoothing of images is more efficient than cluster filtering of the statistical parametric activation maps.

Brain↗