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At least 631 records · Page 35Linked to original sources
PubMed1997

Medial temporal structures relate to memory impairment in Alzheimer's disease: an MRI volumetric study.

OBJECTIVES: Memory impairment is not only the earliest clinical symptom but a central and prominent feature throughout the course of Alzheimer's disease. Alzheimer related pathological alterations in the medial temporal structures may account for the memory impairments in patients with Alzheimer's disease. The aim of this study was to elucidate the role of the medial temporal structures in memory impairment caused by Alzheimer's disease. METHODS: Using high resolution MRI and a semiautomated image analysis technique, volumes of the medial temporal structures (amygdaloid complex, hippocampal formation, subiculum, and parahippocampal gyrus) were measured, and correlations between atrophy of each structure and memory dysfunction in patients with Alzheimer's disease were examined. RESULTS: Patients with Alzheimer's disease showed poor performance on verbal and non-verbal memory tests, and MRI volumetry showed a significant volume reduction of the medial temporal lobe structures. Volumes of the amygdaloid complex and of the subiculum correlated with memory performance. Stepwise regression analyses disclosed that the volume of the right amygdaloid complex specifically predicted visual memory function and to some extent verbal memory function, and that the volume of the left subiculum specifically predicted verbal memory function. Atrophy of the hippocampus did not predict severity of memory impairment. CONCLUSIONS: The presence of perihippocampal damage involving the amygdala proper, its surrounding cortex, and the subiculum further increased the severity of memory impairment attributable to hippocampal damage in Alzheimer's disease.

Adult↗
PubMed2004

[The visual pathways, from anatomical MRI to physiological with (f)MRI and tractography with diffusion tensor MRI (DTMRI)].

Advances in MRI technology have led to a better knowledge of visual pathways (1984-2004), with a new descriptive anatomy and functional model. The authors first describe the technical development of MRI over the last thirty years, then describe and illustrate the new descriptive anatomy. Cephalic MRI reveals brain structures that were previously invisible, on different encephalic planes, in the optic pathways, horizontally from the cornea to the calcarin fissure (neuro-ocular plane (NOP), oblique trans-hemispheric neuro-ocular (OTNOP) and neuro-opto-tractal planes (NOTP)), in their orthogonal orientation upon the oculomotor pathways: head and axonal optic nerve pack (visual deutoneurons in their meninges), optic tracts, lateral geniculate bodies, optic radiations and the calcarian fissure. Comparative anatomy with the rhesus macaque is mentioned. Functional neuroanatomy (physiology) benefits from cine-MRI for ocular motricity (OD MRI), growth by the observation of myelinization in children, blood and CSF circulation by MR angiography, local blood volumes by perfusion imaging, neuronal quantification with inflammation or myelin regeneration by spectroscopy (MRS), brain mapping by functional MR ((f)MRI) measuring local CBF enhancement by paradigmatic stimulations. The recent functional imaging method, tractography (or diffusion tensor MRI (DTMRI)), using diffusion MRI techniques, natural vector calculations with diffusion tensor and software power for morphological and statistical directional results, represents the direction of projection, association and commissural white matter tracts. Normal examples are shown and some common clinical consequences are discussed.

Adult↗
PubMed2003

Neuropsychological deficits in a child with a left penetrating brain injury.

This case study reports neuropsychological and structural magnetic resonance (MRI) studies of a 10-year-old girl with a left hemisphere lesion, caused by an underwater fishing harpoon penetrating her head when she was 6 years old. The patient showed a marked deficit in the acquisition of reading, writing and arithmetic, as well as an attentional deficit. Magnetic resonance images revealed left cortical lesions in the orbital region and the gyrus angularis, as well as in the caudate and putamen nuclei and longitudinal inferior fascicle. Neuropsychological assessment showed frontal and parietal lobe dysfunctions consistent with the lesional data. The structural data explain the neuropsychological impairment and suggest that, although the left lesion was early and relatively small, plasticity was incomplete.

Child↗
PubMed2001

Correlations between clinical and historical variables, and cerebral structural variables in people with mild intellectual disability and schizophrenia.

The increased prevalence of schizophrenia in the population with mildly intellectual disability (ID) remains unexplained. The present study explores several possibilities by examining historical/clinical findings in relation to structural neuroimaging findings in three groups: (1) comorbid mild ID and schizophrenia; (2) schizophrenia alone; and (3) mild ID alone. Information about clinical and historical variables was obtained from 101 subjects (39 with comorbidity, 34 with schizophrenia and 28 with mild ID), out of whom 68 (23, 25 and 20, respectively) had had a cerebral magnetic resonance imaging (MRI) scan. Although a number of significant correlations exist between clinical variables and structural MRI abnormalities in all three groups, no clearly predictive inter- or between-group differences emerged. More striking was the finding that showed small amygdalo-hippocampal size to be associated with a history of central nervous system injury, especially meningitis. These findings provide support for the view that cognitive impairment and comorbid psychosis can result from a common cause, such as meningitis or obstetric complications, possibly interacting with other factors, such as family history.

Adolescent↗
PubMed1998

Herpes zoster oticus: correlations between clinical and MRI findings.

Many gadolinium-enhanced magnetic resonance imaging (MRI) studies focusing on the anatomy and pathology of the 7th cranial nerve have already been published. However, only scattered cases of herpes zoster oticus (HZO) have been described and only the MRI appearance of the soft temporal bone structures has been reported. Enhanced MRI was performed in 4 patients with HZO observed at the Department of Otorhinolaryngology of the University of Pisa. A good correlation was found between the clinical data and MRI findings in both the acute and chronic stages of the disease. The 2 cases with complete facial palsy presented prominent and diffuse enhancement of the 7th and 8th cranial nerves on postcontrast MRI, while the patient with grade III facial palsy showed more limited nerve enhancement. The patient with grade II facial palsy presented no MRI abnormalities. In our series, enhancement limited to the geniculate ganglion and to the labyrinthine segment of the facial nerve indicates a good prognosis while a widespread enhancement correlates with a poor prognosis. In conclusion, MRI with contrast may be useful during the acute stage of HZO because it can confirm the diagnosis and can provide prognostic information on the facial function.

Adult↗
PubMed2004

Characterizing function-structure relationships in the human visual system with functional MRI and diffusion tensor imaging.

A key objective in neuroscience is to improve our understanding of the relationship between brain function and structure. We investigated this in the posterior visual pathways of healthy volunteers by applying functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) with tractography. The optic radiations were segmented using the Probabilistic Index of Connectivity (PICo) tractography algorithm and extracted at several thresholds of connection confidence. The mean fractional anisotropy (FA) of the estimated tracts was found to correlate significantly with fMRI measures of visual cortex activity (induced by a photic stimulation paradigm). The results support the hypothesis that the visual cortical fMRI response is constrained by the external anatomical connections of the subserving optic radiations.

Adult↗
PubMed2006

3D source localization of interictal spikes in epilepsy patients with MRI lesions.

The present study aims to accurately localize epileptogenic regions which are responsible for epileptic activities in epilepsy patients by means of a new subspace source localization approach, i.e. first principle vectors (FINE), using scalp EEG recordings. Computer simulations were first performed to assess source localization accuracy of FINE in the clinical electrode set-up. The source localization results from FINE were compared with the results from a classic subspace source localization approach, i.e. MUSIC, and their differences were tested statistically using the paired t-test. Other factors influencing the source localization accuracy were assessed statistically by ANOVA. The interictal epileptiform spike data from three adult epilepsy patients with medically intractable partial epilepsy and well-defined symptomatic MRI lesions were then studied using both FINE and MUSIC. The comparison between the electrical sources estimated by the subspace source localization approaches and MRI lesions was made through the coregistration between the EEG recordings and MRI scans. The accuracy of estimations made by FINE and MUSIC was also evaluated and compared by R(2) statistic, which was used to indicate the goodness-of-fit of the estimated sources to the scalp EEG recordings. The three-concentric-spheres head volume conductor model was built for each patient with three spheres of different radii which takes the individual head size and skull thickness into consideration. The results from computer simulations indicate that the improvement of source spatial resolvability and localization accuracy of FINE as compared with MUSIC is significant when simulated sources are closely spaced, deep, or signal-to-noise ratio is low in a clinical electrode set-up. The interictal electrical generators estimated by FINE and MUSIC are in concordance with the patients' structural abnormality, i.e. MRI lesions, in all three patients. The higher R(2) values achieved by FINE than MUSIC indicate that FINE provides a more satisfactory fitting of the scalp potential measurements than MUSIC in all patients. The present results suggest that FINE provides a useful brain source imaging technique, from clinical EEG recordings, for identifying and localizing epileptogenic regions in epilepsy patients with focal partial seizures. The present study may lead to the establishment of a high-resolution source localization technique from scalp-recorded EEGs for aiding presurgical planning in epilepsy patients.

Action Potentials↗
PubMed2006

Amplification strategies in MR imaging: activation and accumulation of sensing contrast agents (SCAs).

We review new strategies for the development of Gd3+-based T1-relaxation agents and paramagnetic chemical exchange saturation transfer (PARACEST) "sensing" contrast agents (SCAs) designed specifically to detect small molecules or enzymatic activity in living systems. The first class of agents exhibits molecular "sensing" properties as a result of water coordination sphere effects, cleavage, or synthesis of reactive precursor compounds that recombine with macromolecules with the resultant formation of immobilized or rotationally constrained paramagnetic cations. This effect results in changes of water proton relaxation times. The second class (PARACEST) comprises a family of lanthanide-based paramagnetic compounds suitable for CEST imaging. The need for both types of MR agents is justified by efforts to utilize magnetic resonance imaging (MRI) to visualize fine structures in living tissue, and to increase the molecular specificity of MRI.

Contrast Media↗
PubMed2000

Temporal lobe epilepsy: when are invasive recordings needed?

Temporal lobe epilepsy (TLE) is the most common type of medically intractable partial epilepsy amenable to surgery. In the majority of cases, the underlying pathology in temporal lobe epilepsy is mesial temporal sclerosis (MTS). Whereas historically invasive recordings were required for most epilepsy surgeries, indications have dramatically changed since the introduction of high-resolution MRI, which uncovers structural lesions in a high percentage of cases. No invasive recordings are required to perform a temporal lobectomy in patients with intractable epilepsy who have structural imaging suggesting unilateral MTS and concordant interictal and ictal surface EEG recordings, functional imaging, and clinical findings. Invasive testing is needed if there is evidence of bitemporal MTS on structural imaging and/or electrophysiologically, and additional information from functional imaging, neuropsychology, and the intracarotid amobarbital (Wada) test also does not help to lateralize the epileptogenic zone. Depth electrodes can be particularly helpful in this setting. However, no surgery is indicated, even without invasive recordings, if bitemporal-independent seizures are recorded by surface EEG and all additional testing is inconclusive. Other etiologies of TLE such as a tumor, vascular malformation, encephalomalacia, or congenital developmental abnormality account for about 30% of all patients who undergo epilepsy surgery. Epilepsy surgery is indicated after limited electrophysiologic investigations if neuroimaging and electrophysiology converge. However, approaches for resection in lesional temporal lobe epilepsy vary among centers. Completeness of resection is crucial and invasive recordings may be needed to guide the resection by mapping eloquent cortex and/or to determine the extent of the non-MRI-visible epileptogenic area. Specific approaches for the different pathologies are discussed because there is evidence that the relationship between the lesions visible on MRI and the epileptogenic zone varies among lesions of different pathologies, and therefore variable surgical strategies must be applied.

Adolescent↗
PubMedDate not supplied

"Magnetic resonance imaging negative positron emission tomography positive" temporal lobe epilepsy: FDG-PET pattern differs from mesial temporal lobe epilepsy.

PURPOSE: Some patients with temporal lobe epilepsy (TLE) lack evidence of hippocampal sclerosis (HS) on MRI (HS-ve). We hypothesized that this group would have a different pattern of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG)-positron emission tomography (PET) hypometabolism than typical mesial TLE/HS patients with evidence of hippocampal atrophy on magnetic resonance imaging (MRI) (HS+ve), with a lateral temporal neocortical rather than mesial focus. PROCEDURES: Thirty consecutive HS-ve patients and 30 age- and sex-matched HS+ve patients with well-lateralized EEG were identified. FDG-PET was performed on 28 HS-ve patients and 24 HS+ve patients. Both groups were compared using statistical parametric mapping (SPM), directly and with FDG-PET from 20 healthy controls. RESULTS: Both groups showed lateralized temporal hypometabolism compared to controls. In HS+ve, this was antero-infero-mesial (T = 17.13); in HS-ve the main clustering was inferolateral (T = 17.63). When directly compared, HS+ve had greater hypometabolism inmesial temporal/hippocampal regions (T = 4.86); HS-ve had greater inferolateral temporal hypometabolism (T = 4.18). CONCLUSIONS: These data support the hypothesis that focal hypometabolism involves primarily lateal neocortical rather than mesial temporal structures in 'MRI-negative PET-positive TLE.'

Adult↗
PubMed2005

Whiplash-associated disorders impairment rating: neck disability index score according to severity of MRI findings of ligaments and membranes in the upper cervical spine.

The aim of this study was to explore whether reported pain and functional disability in whiplash-associated disorders (WAD) patients is associated with lesions to specific soft tissue structures in the upper cervical spine, as assessed by MRI. Pre-selected structures for MRI assessment included the alar ligaments, the transverse ligament, the tectorial and the posterior atlanto-occipital membranes. The questionnaire employed was a modification of the Oswestry Low Back Pain Index. It was comprised of ten single items related to pain and activity of daily living. Ninety-two whiplash patients and 30 control persons, randomly drawn, were included. WAD patients reported significantly more pain and functional disability than the controls, both for total score and each of the ten single items. In the WAD patients, MRI lesions to the alar ligaments showed the most consistent association to the reported pain and disability. Lesions to other structures often occurred in combination with lesions to the alar ligaments. Lesions to the transverse ligament and to the posterior atlanto-occipital membrane also appeared to be related to the NDI score, although the association was weaker than for the alar ligament. The disability score increased with increasing number of abnormal (grade 2-3) structures. These results indicate that symptoms and complaints among WAD patients can be linked with structural abnormalities in ligaments and membranes in the upper cervical spine, in particular the alar ligaments.

Activities of Daily Living↗
PubMed2005

Differentiation of perianal fistulas with digital subtraction magnetic resonance fistulography.

BACKGROUND: Pelvic magnetic resonance imaging (MRI) is accurate in identifying perianal fistulas. The exact visualization of fistulous tracts and concomitant abscesses determine the type of treatment. To improve the detection of perianal fistulas, we studied digital subtraction MR-fistulography for tissue differentiation based on signal intensity measurements. METHODS: This study included 75 patients with the clinical diagnosis of perianal fistula. All patients were analyzed by a thin-slice, high-resolution, fast low-angle shot 3-dimensional sequence in the axial plane before and after intravenous injection of gadobenate dimeglumine, followed by image subtraction. Operator-defined regions of interest were used to calculate signal intensities of the inflamed fibrous walls of fistulas, the common femoral artery, the internal and external sphincter muscles, and the gluteus muscle. The fistulas were classified according to Parks classification. RESULTS: Based on signal intensity measurements in 75 patients with perianal fistulas, diagnosed by digital subtraction MR-fistulography, a significant differentiation between fistulous tracts and anatomic structures was possible. MRI identified 116 perianal fistulas (34 intersphincteric, 33 transsphincteric, 10 suprasphincteric, and 39 extrasphincteric) and 35 abscesses. CONCLUSIONS: Digital subtraction MR-fistulography is a new, promising, noninvasive imaging technique for the detection of perianal fistulas and abscesses.

Adolescent↗
PubMed1993

The neuropathology of schizophrenia. A focus on the subcortex.

Investigations into the neuropathology of schizophrenia have increasingly altered the perception of the illness. Early studies focused on finding consistent and discrete areas of cortical pathology in the brain material of schizophrenic patients. After nearly a half century of study, little evidence emerged from a great body of data suggesting any consistent, discrete neuropathologic finding associated with this illness. This lack of evidence led to obvious frustration on the part of researchers and movement within the psychiatric community towards significantly less brain-based theories of the genesis of schizophrenia. With the advent of new technologies such as enhanced structural imaging (CT, MRI), functional imaging (PET, SPECT), and better neuropathologic methods, the focus of schizophrenia research has again turned towards the brain. Ultimately, hypotheses regarding the cause of schizophrenia will be proved or disproved on neuropathologic evidence. Few, if any, modern schizophrenia researchers would make the argument that there is a single, consistent neuropathologic lesion that is responsible for the entire illness of schizophrenia. Current theories tend to interpret the wide variety of neuropathologic changes in this illness as evidence of disturbed nervous system maturation--either acquired or inherent--or perhaps as a response to damage with aberrant neuronal regeneration. Evidence for a neurodegenerative disorder has not proved to be compelling. Furthermore, these theories emphasize dysfunction of elements of distributed neuronal systems, including subcortical systems, not discrete "lesions." The danger with the theoretic approach of distributed systems is, as Steriade and McCarley noted so well, that the flexibility of this idea can "mean a retreat into vagueness so that hypotheses concerning the role of multiple interrelated structures in the genesis of a given behavioral state cannot be proved wrong." (p 23). Despite the risks, this approach to investigation promises to offer more than just information pertinent to schizophrenia research; it offers insights into the mechanisms of behavior as a product of integrated brain function.

Brain↗
PubMed2003

[Computed tomography and magnetic resonance tomography of the normal temporal bone].

The normal anatomy of the temporal bone and the inner ear will be described in detail on high resolution computed tomography (HRCT) and magnetic resonance images. The imaging technique of computer tomography--either single detector or multi detector CT--is normally obtained in an axial plane without the intravenous application of contrast material. The images are reconstructed in a high resolution bone window level setting. The coronal images are reconstructed either if used single detector or multi detector CT. Only in some cases a scan in the coronal plane is directly obtained using a single detector CT. MR imaging of temporal bone is usually performed in a head coil. Axial high resolution 3D-T2-weighted sequences either in fast spin echo technique or gradient echo technique--for example CISS-sequence--are obtained, then an axial high resolution T1-weighted sequence before and after the application of gadopentate dimiglumine is performed. HRCT excellently demonstrates the osseous structures of the temporal bone as well as of the inner ear, while MRI excellently depicts soft tissue structures especially those of the inner ear. Due to the susceptibility artifacts MRI is not very suitable for imaging the external auditory canal or the middle ear or the pneumatic system. In conclusion HRCT is so far excellent to delineate the osseous structures of the temporal bone and inner ear while MRI excellently depicts the soft tissue structures of the inner ear, the internal auditory canal and the cerebellopontine angle. Reissner's membrane, the cochlear duct, and the organ of Corti cannot be visualized even using high-resolution MRI. HRCT and MRI are therefore used as complementary methods for imaging the temporal bone.

Anatomy, Cross-Sectional↗
PubMed2001

On the heating of linear conductive structures as guide wires and catheters in interventional MRI.

The interest in performing vascular interventions under magnetic resonance (MR) guidance has initiated the evaluation of the potential hazard of long conductive wires and catheters. The objective of this work is to present a simple analytical approach to address this concern and to demonstrate the agreement with experimental results. The first hypothesis is that a long conductive structure couples with the electric field of the radio frequency (RF) transmit coil. The second hypothesis is that this coupling induces high voltages near the wire ends. These voltages can cause tissue heating due to induced currents. The experimental results show an increase in coupling when moving a guide wire toward the wall of an RF transmit coil, documented with a temperature increase of a saline solution in close proximity to the tip of the guide wire. The coupling of the wire not only presents a potential hazard to the patient, but also interferes with the visualization of the wire. A safe alternative would be the use of nonconducting guide wires. J. Magn. Reson. Imaging 2001;13:105-114.

Catheterization↗
PubMed2006

Vulnerability of the anterior commissure in moderate to severe pediatric traumatic brain injury.

In relation to the adult brain, the immature brain might be more vulnerable to damage during and following traumatic brain injury, particularly in white-matter tracts. Given well-established evidence of corpus callosum atrophy, we hypothesized that anterior commissure volume (using quantitative magnetic resonance imaging [MRI]) in this structure would be decreased in children with moderate to severe traumatic brain injury relative to typically developing children. Second, given the purported role of the anterior commissure in interhemispheric axon conveyance between temporal lobes, we hypothesized that temporal lobe white matter, temporal lesion volume, and injury severity (Glasgow Coma Scale score) would be predictive of decreased anterior commissure cross-sectional volume in patients with traumatic brain injury. Finally, we wished to establish the relationship between the anterior commissure and the temporal stem, a major white-matter tract into the temporal lobes, using diffusion tensor imaging fiber-tracking maps for each patient. We also hypothesized that children with traumatic brain injury would exhibit decreased fractional anisotropy in relation to typically developing children in a fiber system including the anterior commissure and the temporal lobes. Decreased anterior commissure cross-sectional volume was observed in patients with traumatic brain injury, and, as predicted, anterior commissure and temporal white-matter volumes were positively related to each other and to higher Glasgow Coma Scale scores. Lesion volume was not independently predictive of anterior commissure volume in the overall model. Diffusion tensor imaging fractional anisotropy values differed between the groups for the temporal stem-anterior commissure system, with the traumatic brain injury group exhibiting decreased fractional anisotropy. The anterior commissure, like the corpus callosum, appears to be highly vulnerable to white-matter degenerative changes resulting from mechanisms such as the direct impact of trauma, progressive axonal injury as tissue in other brain regions atrophies, or myelin degeneration. This is the first systematic examination of anterior commissure atrophy following traumatic brain injury using in vivo quantitative MRI and diffusion tensor imaging fiber tracking in pediatric subjects.

Adolescent↗
PubMed2002

Structural magnetic resonance imaging in the practical assessment of dementia: beyond exclusion.

Neuroimaging is increasingly used to aid diagnosis in dementia. The traditional view that imaging is important solely as means of excluding treatable causes of dementia is maintained by many guidelines. These conditions however, account for a tiny proportion (<1%) of all causes of dementia. Over the past few years it has been recognised that a more accurate diagnosis and prognosis is important for patients and their families. The different pathological processes that produce cerebral dysfunction at a cellular level also produce macroscopic effects that can be detected in vivo with imaging. Clinically useful measures that distinguish between neurodegenerative disorders at an early stage are still awaited. The most likely future use of structural imaging will be the identification of patients at risk for Alzheimer's disease or with preclinical Alzheimer's disease. For magnetic resonance imaging (MRI) this will mean focusing on those areas that are affected earliest in the disease; ie, entorhinal cortex and hippocampus, using high resolution structural MRI or sophisticated brain mapping techniques. Imaging research is also likely to focus on measuring progression and detecting therapeutic effect. As such, MRI is already become an indispensable tool in clinical trials in dementia.

Brain↗
PubMed1986

Computerized tomography, magnetic resonance imaging, and positron emission tomography in the study of brain trauma. Preliminary observations.

Results of computerized tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), xenon-133 measurement of cerebral blood flow (CBF), and neuropsychological assessments are described in three head-injured patients. The patients were selected because they presented with intracranial hemorrhage diagnosed by CT. Two of the patients were studied acutely and again approximately 6 months later. In the acute stage, MRI was superior to CT in identifying the precise location and extent of intracranial hemorrhage and associated edema. Small subdural hematomas diagnosed on MRI were missed with CT scanning. The extent of apparent encephalomalacia in the chronic stages of injury was also better defined with MRI. Positron emission tomography showed disturbances of glucose metabolism that extended beyond the structural abnormalities demonstrated by MRI and CT; anterior temporal lobe dysfunction was particularly evident in all three patients. Regional CBF studies failed to detect a number of the abnormalities seen on MRI and CT, and even ignored the metabolic dysfunction evident on PET that should have been accompanied by changes in regional CBF. The neuropsychological studies localized frontal lesions, but did not reveal abnormalities attributable to the structural lesions and the reduced metabolism in the anterior temporal lobes.

Adult↗