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At least 1,009 records · Page 56Linked to original sources
PubMed2000

Spatial extent of neuronal metabolic dysfunction measured by proton MR spectroscopic imaging in patients with localization-related epilepsy.

PURPOSE: To assess the spatial extent of the decrease in the neuronal marker N-acetyl-aspartate (NAA) relative to creatine (Cr) in patients with localization-related epilepsy, and to assess clinical differences between patients with and without widespread NAA/Cr reduction. METHODS: We studied 51 patients with localization-related epilepsy. Patients were divided into three groups according to the EEG investigation: (a) temporal lobe epilepsy (TLE, n = 21), (b) extratemporal lobe epilepsy (extra-TLE, n = 20), and (c) multilobar epilepsy (patients with a wider epileptogenic zone, n = 10). We acquired proton magnetic resonance (MR) spectrocopic imaging (1H-MRSI) of temporal and frontocentroparietal regions in separate examinations for both patients and controls. NAA/Cr values 2 standard deviations below the mean of normal controls were considered abnormal. RESULTS: Twenty-three (45%) patients including 12 with TLE had normal MR imaging including volumetric studies of the hippocampus. Forty-nine (96%) patients had low NAA/Cr, indicating neuronal dysfunction in either temporal and/or extratemporal 1H-MRSIs; 38% of patients with TLE and 50% of patients with extra-TLE also had NAA/Cr reduction outside the clinical and EEG-defined primary epileptogenic area. The NAA/Cr reduction was more often widespread in the multilobar group [six (60%) of 10] than in temporal or extratemporal groups [five (31%) of 16]. Nonparametric tests of (a) seizure duration, (b) seizure frequency, and (c) lifetime estimated seizures showed no statistically significant difference (p > 0.05) for TLE and extra-TLE patients with or without NAA/Cr reduction outside the seizure focus. CONCLUSIONS: Of patients with localization-related epilepsy, 40-50% have neuronal metabolic dysfunction that extends beyond the epileptogenic zone defined by clinical-EEG and/or the structural abnormality defined by MRI.

Adolescent↗
PubMed2001

In vivo 1H magnetic resonance spectroscopic measurement of brain glycine levels in nonketotic hyperglycinemia.

Nonketotic hyperglycinemia (NKH) is an autosomal recessive disorder of glycine metabolism. Defective glycine cleavage causes elevated concentrations of glycine in plasma, urine, and cerebrospinal fluid. A longitudinal study using magnetic resonance imaging (MRI) and single-voxel 1H magnetic resonance spectroscopy (MRS) was performed on an infant with the typical clinical picture of NKH. He was examined twice during the course of treatment with sodium benzoate and dextromethorphan. At the age of 10 months, MRI showed normal brain structure, while MRS detected a prominent glycine peak in the brain. Repeat MRS at the age of 13 months showed a small increase in glycine peak and a prominent glutamate/glutamine peak not previously detected. The MRS measurements were consistent with the slight increase in blood glycine level and the elevation in glutamine level, indicating that 1HMRS can be a valuable tool in the diagnosis and monitoring of treatment effects in patients with NKH.

Aspartic Acid↗
PubMed2001

Continuous arterial spin labeling perfusion magnetic resonance imaging findings in postpartum vasculopathy.

Postpartum vasculopathy (PPV) is a rare heterogeneous nonatherosclerotic vasculopathy that occurs in the puerperium. It occurs spontaneously but may be triggered by vasoconstrictor substances. The angiographic findings vary and include narrowing of the intracranial arteries and vasospasm. The angiographic findings and the occurrence of ischemic infarcts suggest that cerebral blood flow (CBF) is impaired in PPV. The purpose of this study is to determine CBF in patients with PPV. The authors conducted a case study of 3 patients with clinical and laboratory criteria for PPV examined during a 2-year period. Clinical examination, computed tomography imaging, structural magnetic resonance imaging (MRI), cerebral angiography, and continuous arterial spin labeling perfusion (CASL-PI) MRI were performed in all patients. Mean global CBF was determined, and perfusion maps were visually inspected. The CBF values and perfusion maps were correlated with the clinical symptoms and the neuroimaging findings. Three women were studied (22, 34, and 36 years old). The median time of presentation was 4 days postpartum. One presented with intracranial hemorrhage and diffuse arterial narrowing, the other 2 with stroke-like lesions, encephalopathy, and segmental narrowing mainly in the posterior circulation. CASL-PI was performed within 1 week of symptom onset in all 3 patients. Global mean CBF values were 51.8, 39.3, and 41.8 cc/100 g/min. Although global CBF was mildly diminished, it was above ischemic levels. Visual inspection of the CASL-PI perfusion maps did not reveal areas of focal hypoperfusion or hyperperfusion. In this series of patients with PPV, CBF was close to normal. Although angiography often reveals diffuse arterial narrowing, the CBF values encountered in this study do not support a state of generalized or focal oligoemia. Vasomotor tone may change intermittently in patients with PPV.

Adult↗
PubMed1993

Outcome of resective surgery for intractable partial epilepsy guided by subdural electrode arrays.

The aim of this paper was to evaluate the outcome and the factors predictive for a good prognosis of resective surgery for intractable partial epilepsy guided by subdural electrode arrays (SEA's) and operative electrocorticography. Sixty-four patients, aged 8-52 years, were evaluated with chronic SEAs in order to record interictal and ictal activity and delineate speech and motor areas by functionally mapping. Resection were individualized to each patient's SEA recorded electrocorticogram and operative electrocorticogram and functional mapping results (tailored resection). The follow-up time was a minimum of one year. Good seizure outcome was defined as seizure free from complex partial and secondary generalized seizures. After one year 70% of the patients with a temporal ictal focus was seizure free compared to 55% of the patients with an extra-temporal focus. Complete resection of interictal or ictal fields as mapped with SEAs, gave better prognosis than partial resection. Patients with no postresection spikes had a better prognosis than patients with residual postresection spikes evaluated with operative electrocorticography. Sex, age, duration of epilepsy prior to surgery, extent of temporal lobe resection and structural abnormalities determined by MRI were not associated with a favorable seizure outcome after surgery. We conclude that complete resection of the interictal and ictal field mapped with SEA's and absence of postresection spikes on operative electrocorticography are associated with an excellent seizure outcome.

Adolescent↗
PubMed2005

The corpus callosum in first episode schizophrenia: a diffusion tensor imaging study.

BACKGROUND: Neuropathological and imaging studies suggest that corpus callosum abnormalities (CC) are present in schizophrenia, but it remains to be determined whether these abnormalities are present at illness onset. Diffusion tensor imaging (DTI), which is more sensitive than conventional magnetic resonance imaging (MRI) in detecting subtle structural changes in the organisation and integrity of white matter tracts, is an ideal tool to investigate this question. OBJECTIVE: To determine whether CC abnormalities are present at illness onset in schizophrenia. METHODS: Twenty patients (14 men, six women) with first episode schizophrenia and 29 controls (11 men, 18 women) were studied. Both high resolution volumetric T1-weighted images and DTI were acquired. Regions of interest (ROI) were placed in the splenium and genu of the CC and fractional anisotropy (FA) and diffusivity (D) measured. RESULTS: No differences in FA or D were detected in these regions between patients and controls. In women, irrespective of group membership, FA was significantly lower and there was a trend for D to be higher than in men, indicating less barriers to diffusion in females. CONCLUSION: The negative findings of this study suggest that in the early stages of schizophrenia there is no disruption to the integrity of the CC and raise the possibility that the neuropathological abnormalities may appear later and be progressive, at least in some patients.

Adolescent↗
PubMed2003

Brain lesions in the course of generalised tetanus.

A 47-year-old woman developed left hemiparesis primarily affecting the lower limbs during the course of severe generalised tetanus. MRI on the 82nd hospital day revealed cortical and subcortical lesions predominantly in the right frontal and parietal lobes in addition to marked brain atrophy. Three months later, the enhancing lesions were still present on follow up MRI. We postulate that structures above brainstem may be involved in severe generalised tetanus.

Atrophy↗
PubMed1988

Evaluation of brain imaging techniques in mental illness.

Brain imaging is increasingly applied in psychiatry, both for clinical evaluation and as a research tool. Computerized tomography (CT) and magnetic resonance imaging (MRI) have documented that structural brain abnormalities occur in some types of psychiatric patients, particularly those who suffer from schizophrenia. Dynamic imaging techniques such as single-photon emission computed tomography (SPECT) and positron emission tomography (PET) have documented decreased temporoparietal activity in Alzheimer's disease, hypofrontality in schizophrenia, and a variety of abnormalities in affective and anxiety disorders. These techniques promise to teach us a great deal about the underlying neural mechanisms in mental illness.

Brain↗
PubMed2001

Lateralization of minicolumns in human planum temporale is absent in nonhuman primate cortex.

Gross analyses of large brain areas, as in MRI studies of macroanatomical structures, average subtle alterations in small regions, inadvertently missing significant anomalies. We developed a computerized imaging program to microscopically examine minicolumns and used it to study Nissl-stained slides of normal human, chimpanzee, and rhesus monkey brains in a region of the planum temporale. With this method, we measured the width of cell columns, the peripheral neuropil space, the spacing density of neurons within columns, and the Gray Level index per minicolumn. Only human brain tissue revealed robust asymmetry in two aspects of minicolumn morphology: wider columns and more neuropil space on the left side. This asymmetry was absent in chimpanzee and rhesus monkey brains.

Algorithms↗
PubMed1990

1H magnetic resonance imaging study of bovine ocular tissue.

The present study used magnetic resonance imaging (MRI) to study bovine eyes using proton magnetic resonance at a 7-tesla field. The MRI images provide detailed structural information on various sections of the ocular tissues. Detailed images of the lens show several well-defined areas of water content. Relative rankings of various structures of the eye are obtained based on T1, T2 and spin density.

Animals↗
PubMed1994

Diagnosis and treatment of patients with "frontal lobe" syndromes.

Nine case descriptions illustrate the three major prefrontal syndromes seen in clinical practice: disorganized type, disinhibited type, and apathetic type. A mixture of symptoms from each subtype is usually seen, but dysfunction in one prefrontal system often dominates. A careful history and examination are essential for accurate diagnosis. A complete history can rarely be elicited from the patient alone. Structural brain imaging, especially MRI, and neuropsychological testing are key to the diagnostic workup. EEG, video-EEG, and functional brain imaging can be valuable in the evaluation of possible partial complex seizures of frontal lobe origin and other atypical frontal lobe disorders. Effective treatment requires educating the patient and the family about the illness and modulating environmental factors that influence the patient's behavior. Judicious use of psychoactive medication may be helpful, but adverse effects are common.

Adult↗
PubMed2001

Magnetoencephalography and magnetic source imaging in children.

Magnetoencephalography is a technique that detects the magnetic fields associated with the intracellular current flow within neurons, unlike electroencephalography, which measures extracellular volume currents. Superconducting quantum interference devices are used to amplify these very small magnetic field signals. Magnetic source imaging is the combination of functional data derived from magnetoencephalographic recordings coregistered with structural magnetic resonance imaging (MRI). The utility of magnetic source imaging lies in the combination of the submillisecond temporal resolution of magnetoencephalography with the precise anatomic images provided by magnetic resonance imaging. As such, magnetic source imaging is a useful tool for noninvasive localization of the epileptogenic zone in children who are candidates for epilepsy surgery. Similarly, using magnetoencephalographic recordings with evoked and event-related potentials, magnetic source imaging holds great promise as a noninvasive method for precise localization of somatosensory, motor, language, visual, and auditory cortex. Finally, magnetic source imaging is proving a valuable research tool in the investigation of epilepsy, head trauma, brain plasticity, and disorders of language, memory, cognition, and executive function in children.

Cerebral Cortex↗
PubMed2005

Risk factors for progression of brain atrophy in aging: six-year follow-up of normal subjects.

OBJECTIVES: To determine the rate of brain atrophy in neurologically asymptomatic elderly and to investigate the impact of baseline variables including conventional cerebrovascular risk factors, APOE epsilon4, and white matter hyperintensity (WMH) on its progression. METHODS: We assessed the brain parenchymal fraction at baseline and subsequent annual brain volume changes over 6 years for 201 participants (F/M = 96/105; 59.8 +/- 5.9 years) in the Austrian Stroke Prevention Study from 1.5-T MRI scans using SIENA (structural image evaluation using normalization of atrophy)/SIENAX (an adaptation of SIENA for cross-sectional measurement)(www.fmrib.ox.ac.uk/fsl). Hypertension, cardiac disease, diabetes mellitus, smoking, and regular alcohol intake were present in 64 (31.8%), 60 (29.9%), 5 (2.5%), 70 (39.3%), and 40 (20.7%) subjects, respectively. Plasma levels of fasting glucose (93.7 +/- 18.6 mg/dL), glycated hemoglobin A (HbA1c; 5.6 +/- 0.7%), total cholesterol (228.3 +/- 40.3 mg/dL), and triglycerides (127.0 +/- 75.2 mg/dL) were determined. WMH was rated as absent (n = 56), punctate (n = 120), early confluent (n = 14), and confluent (n = 11). RESULTS: The baseline brain parenchymal fraction of the entire cohort was 0.80 +/- 0.02 with a mean annual brain volume change of -0.40 +/- 0.29%. Univariate analysis demonstrated a higher rate of brain atrophy in older subjects (p = 0.0001), in those with higher HbA1c (p = 0.0001), higher body mass index (p = 0.02), high alcohol intake (p = 0.04), severe WMH (p = 0.03), and in APOE epsilon4 carriers (p = 0.07). Multivariate analysis suggested that baseline brain parenchymal fraction, HbA1c, and WMH score explain a major proportion of variance in the rates of brain atrophy in the cohort (corrected R2 = 0.27; p = 0.0001). CONCLUSIONS: Neurologically asymptomatic elderly experience continuing brain volume loss, which appears to accelerate with age. Glycated hemoglobin A (HbA1c) was identified as a risk factor for a greater rate of brain atrophy. Clustering of factors associated with the so-called metabolic syndrome in subjects with high HbA1c suggests a link between this syndrome and late-life brain tissue loss.

Age Distribution↗
PubMed1997

Brainstem CMV encephalitis in AIDS: clinical case and MRI features.

We describe the clinical case and MRI findings of a patient with acquired immune deficiency syndrome and pathologically confirmed cytomegalovirus encephalitis. Prevalent brainstem and cerebellar signs together with almost exclusive involvement as seen on MRI of posterior fossa structures at the onset of the symptoms were the main features of our case.

Acquired Immunodeficiency Syndrome↗
PubMed2005

Simulation study of magnetic resonance imaging-guided cortically constrained diffuse optical tomography of human brain function.

Diffuse optical imaging can measure brain activity noninvasively in humans through the scalp and skull by measuring the light intensity modulation arising from localized-activity-induced absorption changes within the cortex. Spatial resolution and localization accuracy are currently limited by measurement geometry to approximately 3 cm in the plane parallel to the scalp. Depth resolution is a more significant challenge owing to the limited angle tomography permitted by reflectance-only measurements. We combine previously established concepts for improving image quality and demonstrate, through simulation studies, their application for improving the image quality of adult human brain function. We show in a three-dimensional human head model that localization accuracy is significantly improved by the addition of measurements that provide overlapping samples of brain tissue. However, the reconstructed absorption contrast is significantly underestimated because its depth is underestimated. We show that the absorption contrast amplitude accuracy can be significantly improved by providing a cortical spatial constraint in the image reconstruction to obtain a better depth localization. The cortical constraint makes physiological sense since the brain-activity-induced absorption changes are occurring in the cortex and not in the scalp, skull, and cerebral spinal fluid. This spatial constraint is provided by segmentation of coregistered structural magnetic resonance imaging (MRI). However, the absorption contrast deep within the cortex is reconstructed superficially, resulting in an underestimation of the absorption contrast. The synthesis of techniques described here indicates that multimodality imaging of brain function with diffuse optical imaging and MRI has the potential to provide more quantitative estimates of the total and deoxyhemoglobin response to brain activation, which is currently not provided by either method independently. However, issues of depth resolution within the cortex remain to be resolved.

Algorithms↗
PubMed1985

Magnetic resonance imaging of the superior pericardial recesses.

The potential of magnetic resonance imaging (MRI) of the superior pericardial space was evaluated in a retrospective review of MR images of 46 subjects. The superior pericardial space and its two recesses had low signal intensity. The preaortic recess was demonstrated on 82% of nongated transverse scans. The retroaortic recess was demonstrated on 67% of nongated transverse scans. Generally, both recesses were shown with an even higher frequency on ECG-gated and ECG-permutation-gated scans. Knowledge of the location and typical appearance of these pericardial recesses should preclude mistaking them on MRI for a vascular structure, aortic dissection, or an atherosclerotic plaque or mural thrombus within the ascending aorta.

Adolescent↗
PubMed2003

Anatomic landmarks for locating parotid lesions in relation to the facial nerve: cross-sectional radiologic study.

OBJECTIVES: To determine the accuracy of using surrogate anatomic structures radiologically to predict the relation of parotid lesions to the intraparotid facial nerve. SETTING: Tertiary centre. DESIGN: Retrospective. PATIENTS AND METHODS: All patients with parotid masses over a 5-year period who undertook parotidectomy were considered. A radiologist and an otolaryngologist reviewed the images. Their decision regarding the location of the lesions using four surrogate structures was compared with intraoperative documentation. OUTCOME MEASURE: We determined the sensitivity and the specificity of using the external carotid artery, retromandibular vein, posterior belly of the digastric muscle, and tragal pointer. RESULTS: Thirty films were examined (24 magnetic resonance images [MRIs] and 6 computed tomographic [CT] scans). The sensitivity and the specificity of the retromandibular vein were 0.85 and 0.57, respectively, whereas for the external carotid artery, they were 0.94 and 0.3, respectively. It was too impractical to relate the other two structures to the lesions. CONCLUSIONS: The retromandibular vein is the most accurate surrogate structure to use on MRI or CT for predicting the location of a parotid lesion to the facial nerve. However, the substantial proportion of deep lesions misjudged limits the benefit of performing the imaging.

Facial Nerve↗
PubMed2026

Genetic Correlation Between Brain Imaging Phenotypes and Externalizing Behavior: A Large-Scale LDSC Analysis of UK Biobank IDPs.

Externalizing has been associated with differences in brain structure and function; however, it remains unclear whether these associations reflect shared common-variant genetic influences. Cross-trait linkage disequilibrium score regression was used to estimate genome-wide genetic correlations between externalizing genome-wide association study (GWAS) results and 3,935 brain imaging-derived phenotypes from the UK Biobank BIG40 resource. The imaging phenotypes covered structural magnetic resonance imaging (MRI), diffusion MRI, susceptibility-weighted imaging, resting-state functional MRI, and task-based functional MRI. Results were included in the primary analysis when the imaging phenotype had positive single-nucleotide polymorphism (SNP) heritability, a heritability Z statistic of at least 1.96, a mean GWAS chi-square statistic of at least 1.02, at least 200,000 regression SNPs, and a complete LDSC result without a fatal error. Technical imaging quality-control phenotypes were excluded from biological inference. Individual results were corrected using the Benjamini-Hochberg false discovery rate procedure. Aggregated Cauchy association tests (ACATs) were used to evaluate evidence across all imaging phenotypes and within predefined imaging categories. Statistical power, simultaneous confidence bounds, and alternative quality-control definitions were examined in sensitivity analyses. Of the 3,935 imaging phenotypes, 3,716 produced estimable genetic correlations, 2,980 met the primary LDSC quality-control criteria, and 2,967 were classified as biological imaging phenotypes. No individual phenotype survived false discovery rate correction. The smallest unadjusted P value was 0.0005, and the minimum adjusted q value was 0.486. The distribution of genetic correlations was centered near zero, with a median genetic correlation of 0.0014 and a median absolute genetic correlation of 0.0338. ACAT provided no evidence of an aggregate association across all biological imaging phenotypes (P = 0.302), and no predefined imaging category survived multiple-testing correction. The median minimum detectable genetic correlation at 80% power was 0.216. Bonferroni-adjusted simultaneous confidence intervals were fully contained within the interval [-0.30, 0.30] for 80.0% of phenotypes in the primary analysis and 88.0% under the stringent heritability quality-control definition. Broad and stringent sensitivity analyses produced the same overall conclusions. In this study, no statistically robust evidence of genome-wide genetic correlations between externalizing and individual UK Biobank brain imaging phenotypes was found. Nevertheless, small, localized, mixed-direction, or developmentally specific genetic effects remain possible.

Journal Article↗