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At least 1,261 records · Page 70Linked to original sources
PubMed2006

Intervertebral disc biomechanical analysis using the finite element modeling based on medical images.

In this paper, a 3D geometric model of the intervertebral and lumbar disks has been presented, which integrated the spine CT and MRI data-based anatomical structure. Based on the geometric model, a 3D finite element model of an L1-L2 segment was created. Loads, which simulate the pressure from above were applied to the FEM, while a boundary condition describing the relative L1-L2 displacement is imposed on the FEM to account for 3D physiological states. The simulation calculation illustrates the stress and strain distribution and deformation of the spine. The method has two characteristics compared to previous studies: first, the finite element model of the lumbar are based on the data directly derived from medical images such as CTs and MRIs. Second, the result of analysis will be more accurate than using the data of geometric parameters. The FEM provides a promising tool in clinical diagnosis and for optimizing individual therapy in the intervertebral disc herniation.

Biomechanical Phenomena↗
PubMed2005

Executive dysfunction in early stages of Huntington's disease is associated with striatal and insular atrophy: a neuropsychological and voxel-based morphometric study.

BACKGROUND: Huntington's disease (HD) is characterized by a progressive multisystem neuronal atrophy in the brain. Apart from motor signs, cognitive symptoms, particularly executive dysfunctions, are proposed to be recognizable in early stages of disease. The aim of the present study was to clarify if cognitive dysfunction in early stages of HD is correlated with loco-regional structural changes in 3D-MRI. METHODS: Twenty-five patients with genetically confirmed HD in early clinical stages were included in the study and underwent neuropsychological testing, i.e., the executive tasks Tower of Hanoi (ToH), Stroop Colour Word Interference Test (STROOP), and modified Wisconsin Card Sorting Test (mWCST). High-resolution volume-rendering MRI scans (MP-RAGE) were acquired on a 1.5 T scanner in all patients and were analyzed by statistical parametric mapping and voxel-based morphometry (VBM) in comparison to an age-matched control group. RESULTS: Group analysis of HD patients demonstrated robust regional decreases of gray matter volumes (p<0.05, corrected for multiple comparisons) in the caudate and the putamen bilaterally with a global maximum at Talairach coordinates 11/4/11 (Z-score=7.06). Executive dysfunction was significantly correlated with the areas of highest significant differences out of VBM results which were located bilaterally in the caudate (ToH: r=0.647, p<0.001; STROOP: r=0.503, p<0.01; mWCST: r=0.452, p<0.05). Moreover, subgroup analyses revealed marked insular atrophy (Talairach coordinates 43/-3/1; Z-score=5.64) in HD patients who performed worse in the single executive tasks. CONCLUSION: Two aspects were most remarkable in this correlational study: (i) striatal atrophy in HD patients in early stages plays an important role not only in impaired motor control but also in executive dysfunction, and (ii) extrastriatal cortical areas, i.e., the insular lobe, seem to be involved in executive dysfunction as assessed by neuropsychological tests requiring for planning and problem solving, stimulus response selectivity and concept formation.

Adult↗
PubMed2006

Detection of prodromal Alzheimer's disease via pattern classification of magnetic resonance imaging.

We report evidence that computer-based high-dimensional pattern classification of magnetic resonance imaging (MRI) detects patterns of brain structure characterizing mild cognitive impairment (MCI), often a prodromal phase of Alzheimer's disease (AD). Ninety percent diagnostic accuracy was achieved, using cross-validation, for 30 participants in the Baltimore Longitudinal Study of Aging. Retrospective evaluation of serial scans obtained during prior years revealed gradual increases in structural abnormality for the MCI group, often before clinical symptoms, but slower increase for individuals remaining cognitively normal. Detecting complex patterns of brain abnormality in very early stages of cognitive impairment has pivotal importance for the detection and management of AD.

Aged↗
PubMed2005

Sex differences in N-acetylaspartate correlates of general intelligence: an 1H-MRS study of normal human brain.

Researchers have long attempted to determine brain correlates of intelligence using available neuroimaging technology including CT, MRI, PET, and fMRI. Although structural and functional imaging techniques are well suited to assess gross cortical regions associated with intelligence, the integrity and functioning of underlying white matter networks critical to coordinated cortical integration remain comparatively understudied. A relatively recent neuroimaging advance is magnetic resonance spectroscopy (MRS) which allows for interrogation of biochemical substrates of brain structure and function in vivo. In this study, we examined twenty-seven normal control subjects (17 male, 10 female) to determine whether N-acetylaspartate (NAA), a metabolite found primarily within neurons, is related to intelligence as assessed by the Wechsler Adult Intelligence Scale-III. Of the three white matter regions studied (i.e., left frontal, right frontal, left occipito-parietal), we found that a model including only left occipito-parietal white matter predicted intellectual performance [F(1,25) = 8.65, P = .007; r2 = .26], providing regional specificity to our previous findings of NAA-IQ relationships. Moreover, we found that a complex combination of left frontal and left occipito-parietal NAA strongly predicted performance in women, but not men [F(2,7) = 21.84, P < .001; adjusted r2 = .82]. Our results highlight a biochemical substrate of normal intellectual performance, mediated by sex, within white matter association fibers linking posterior to frontal brain regions.

Adolescent↗
PubMed2002

Reduced hippocampal volume and total white matter volume in posttraumatic stress disorder.

BACKGROUND: Reduced hippocampal volumes in posttraumatic stress disorder (PTSD) patients are thought to reflect specific changes of this structure. Previous magnetic resonance imaging (MRI) studies have not consistently examined indices of overall brain atrophy, therefore it cannot be completely ruled out that hippocampal changes are explained by whole-brain atrophy. The purpose of this study was to assess hippocampal and whole-brain volume in civilian PTSD. METHODS: Twelve subjects with PTSD and 10 control subjects underwent brain MRI. Hippocampal volumes were visually quantified using a computerized volumetric program. Whole-brain volumes were obtained with automated k-means-based segmentation. RESULTS: No differences were found in intracranial volumes (ICV). Subjects with PTSD had higher cerebrospinal fluid (CSF)/ICV ratios and lower white matter/ICV ratios, consistent with generalized white matter (WM) atrophy. The effect of age on CSF/ICV was more pronounced in the PTSD group. Subjects with PTSD had smaller absolute and normalized bilateral hippocampal volumes. These differences persisted after adjusting for lifetime weeks of alcohol intoxication. Posttraumatic stress disorder and depression scores correlated negatively with left hippocampal volume, but PTSD scores were a better predictor of hippocampal volumes. CONCLUSIONS: Our results replicate previous findings of reduced hippocampal volume in PTSD but also suggest independent, generalized, white matter atrophy.

Adult↗
PubMed1997

Serum neuron-specific enolase levels do not increase after electroconvulsive therapy.

BACKGROUND: Cognitive disorders occurring after electroconvulsive therapy (ECT) are regarded as an expression of brain damage, despite computed tomography (CT) and magnetic resonance imaging (MRI) showing no signs of structural brain damage. Serum neuron-specific enolase (NSE) is a sensitive marker of neuronal damage (i.e., after stroke or cardiac arrest). The objective of this study was to investigate whether ECT leads to a rise in the serum NSE level as an expression of neuronal damage. METHODS: We investigated seven patients (four women, three men; mean age 6212 years) with major depressive disorder, who were treated with ECT for the first time. ECT was administered every 2 days, three times a week under standard conditions (anaesthesia: thiopental, succinylcholine, 100% oxygen, unilateral ECT, seizure duration more than 20 s). Blood samples were drawn at the following times. For the first ECT: 15 and 1 min before ECT, and 1, 5, 10, 15, 20, 25, 30, 45, 60, 75, 90, 105, 120 min, and 8, 12, 24 h after ECT. For all subsequent ECT: 1 min before and 4 h after every ECT. Serum NSE was measured by means of enzyme immunoassay (Cobas Core NSE, EIA, Hoffmann-La Roche). RESULTS: On average, each patient underwent ECT 10 times (range 5-20). In the first ECT there was no difference in serum NSE levels before and at all times following ECT. A comparison of serum NSE levels before and after each subsequent bout of ECT revealed no differences. Moreover, comparing the baseline serum NSE levels (before the first ECT) with the values after final ECT showed no differences either. CONCLUSION: ECT did not increase serum NSE values, indicating that electroconvulsive therapy does not cause neuronal damage.

Aged↗
PubMed2002

Revision strategies for lumbar pseudarthrosis.

Revision surgery for pseudarthrosis remains costly and complicated. Local and systemic factors should be corrected or improved before further surgery is performed. Careful evaluation is mandatory, and patients' expectations should be addressed fully by the surgeon before undertaking any surgical procedure. The single most important factor in achieving a successful clinical outcome in revision spine surgery is patient selection. Pseudarthrosis is still one of the most difficult conditions to assess as a source of symptoms, and not surprisingly the outcome from repair of pseudarthrosis is the most difficult to predict. In evaluation of a solid fusion, the preliminary test includes plain radiographs that include flexion and extension films. More definitive evaluation of pseudarthrosis usually requires CT with two-dimensional and possibly three-dimensional reconstruction. Adjacent levels and the status of neural structures may be evaluated via MRI scanning, discography, and myelography. After determining the presence of pseudarthrosis and ascertaining through clinical examination and evaluation the level of symptomatic pseudarthrosis, operative intervention may be considered once conservative management has failed. Posterior procedures for revision of a failed lumbar fusion have not yielded reliably successful results; however, this approach does have a significant role in the appropriately selected candidate. A combined anteroposterior approach may be more effective in restoring sagittal balance and enhancing fusion rates. The use of posterior instrumentation in light of an anterior pseudarthrosis or anterior support in light of a posterior pseudarthrosis is a viable option for treatment in these circumstances. Several osteoinductive growth factors, referred to as bone morphogenetic proteins, have been shown to induce transformation of undifferentiated mesenchymal cells into chondroblasts and osteoblasts, which results in the formation of de novo bone. Numerous animal studies have demonstrated the superiority of bone morphogenetic proteins over autogenous bone grafts in various orthopedic settings. Bone morphogenetic protein (by itself or in conjunction with autogenous bone) has been shown repeatedly to produce a better quality of spine fusion in a decreased interval of time when compared with the use of autogenous bone alone. These materials, however, remain investigational and currently are not widely used. Prevention of pseudarthrosis is the most successful treatment, although this is not always possible. Appropriate patient selection, surgical techniques, and the use of biologic implants and gene therapy in the near future will make spinal fusion a more predictable procedure to perform. Undoubtedly there is great difficulty in performing satisfactory and statistically verifiable conclusions from the available published studies. Better prospective outcomes studies are needed to improve our knowledge regarding overall patient satisfaction, function, residual pain, and health impact of the treatment of lumbar spine pseudarthrosis.

Humans↗
PubMed2003

Blunted prolactin response to D-fenfluramine in post-stroke major depression.

BACKGROUND: This study investigated whether patients suffering from post-stroke depressive disorder had a similar disturbance in central serotonergic function to that described in non-brain injured depressed patients. METHODS: Twenty-three depressed patients (nine major, 14 minor) and 38 non-depressed patients were examined 4-8 weeks post-stroke with a structured interview, rating scales and MRI brain scans. Patients were administered 30 mg D-fenfluramine orally and plasma prolactin and D-fenfluramine concentrations were measured for 6 h post-dose. RESULTS: The prolactin response was significantly blunted in major depression compared to minor depression and non-depressed patients as measured by both delta prolactin and area under the prolactin versus time curve. There was no significant relationship between prolactin response and lesion lateralization or any of the measured clinical characteristics. LIMITATIONS: The major limitation of the study is the relatively small number in each depressive group. CONCLUSIONS: Patients suffering from major depression in the post-stroke period have a blunted prolactin response to D-fenfluramine. This indicates a serotonergic abnormality consistent with that found in major depression where neurological disease is not present.

Aged↗
PubMed1999

Fat suppression magnetic resonance imaging of the triangular fibrocartilage complex. Comparison with spin echo, gradient echo pulse sequences and histology.

Magnetic resonance imaging (MRI) of the triangular fibrocartilage complex (TFCC) of the wrist was performed in ten healthy volunteers using spin echo T1-weighted (SE-T1), fast spin echo T2-weighted (FSE-T2), gradient echo T2-weighted (GRE-T2) and fat suppression spin echo T1-weighted (FS-T1) images. The images were obtained in the coronal plane and were compared to the corresponding histological coronal sections obtained from five fresh frozen cadavers. In our analysis, the FS-T1 pulse sequence visualized the details of the TFCC best, followed by the GRE-T2 images. Delineation of the TFCC on the SE-T1 and the FSE-T2 was poor. The coronal morphology of the TFCC represented on the fat suppression image was almost identical to the corresponding histological sections. We conclude that the fat suppression MRI clearly shows the complex structure of the TFCC and is useful for the morphological evaluation of the TFCC.

Adult↗
PubMed2000

Sex effects on rate of change of P300 latency with age.

OBJECTIVE: Recent MRI evidence suggests that neuroanatomic structures may change more rapidly with age in males compared with females. Sex differences for P300 latency were tested to determine whether similar results might appear for P300 latency, a neurophysiological measure sensitive to age and neurodegenerative processes. METHODS: Auditory event related potentials (ERPs) were recorded using an auditory 'oddball' to elicit the N200 and P300 components. Forty-two male and 42 female healthy normal subjects (age range 15-85 years) were entered in this study. Both linear and curvilinear correlations of N200 and P300 latency/amplitude with age were tested. RESULTS: The slope of P300 latency on age for males was steeper than for females at Pz in subjects who were 30 years of age and older. N200 and P300 latencies were inversely correlated with age in young adult males (<30 years old). CONCLUSIONS: Males may experience more rapid change of P300 latency, but not amplitude, than females in middle to old age. Further research is required to determine whether those change reflects neural pathophysiology, or is mediated by such factors as neuroanatomic differences, body temperature, or mild auditory deficits.

Adolescent↗
PubMed2004

Three dimensional virtual reality model of the normal female pelvic floor.

The anatomy of the pelvic floor is complex and difficult to visualize from conventional two-dimensional anatomy pictures. The goal of this project was to establish the methods necessary to develop a static three-dimensional virtual reality model of the normal female pelvic floor from high-resolution magnetic resonance imaging (MRI) scans. An asymptomatic nulliparous 23-year-old female with no urinary incontinence symptoms underwent a high-resolution pelvic floor MRI scan. Selected pelvic floor structures were manually segmented: bladder, urethra, vagina, uterus, cervix, levator ani, obturator externus, obturator internus, and pubic bone. With high-resolution scans, accurate segmentation of the structures was possible. The completed models were displayed on an ImmersaDesk Virtual Reality system and three clinicians verified their accuracy. Stereovision glasses were used to enhance the model while a receiver tracked head position. Three-dimensional virtual reality models of the female pelvic floor can enhance our understanding of anatomy and physiology of this complex part of the body. They can be used as tools for both research and teaching, facilitating improved treatment of pelvic floor pathologies.

Adult↗
PubMed2003

A critical discussion of the role of neuroimaging in mild cognitive impairment.

OBJECTIVE: In this paper, the current neuroimaging literature is reviewed with regard to characteristic findings in mild cognitive impairment (MCI). Particular attention is drawn to the possible value of neuroimaging modalities in the prediction and early diagnosis of Alzheimer's disease (AD). METHODS: First, the potential contribution of neuroimaging to an early, preclinical diagnosis of degenerative disorders is discussed at the background of our knowledge about the pathogenesis of AD. Second, relevant neuroimaging studies focusing on MCI are explored and summarized. Neuroimaging studies were found through Medline search and by systematically checking through the bibliographies of relevant articles. RESULTS: Structural volumetric magnetic resonance imaging (MRI) and positron emission tomography (PET)/single photon emission tomography (SPECT) are currently the most commonly used neuroimaging modalities in studies focusing on MCI. There were considerable variations in demographical and clinical characteristics across studies. However, significant hippocampal and entorhinal cortex volume reductions were consistently found in subjects with MCI as compared with cognitively unimpaired controls. While hippocampal and entorhinal cortex atrophy in subjects with MCI are also well-established risk factors for the development of AD, these measures cannot be regarded as being of high predictive value in an individual case. Evidence for other typical neuroimaging changes in MCI is still scarce. In PET and SPECT studies, reduced blood flow and/or glucose metabolism in temporoparietal association areas, posterior cingulate and hippocampus were associated with a higher risk of progressive cognitive decline in MCI. In quantitative electroencephalogram (QEEG), low beta, high theta, low alpha and slowed mean frequency were associated with development of dementia. CONCLUSIONS: Existing studies suggest that neuroimaging measures have the potential to become valuable tools in the early diagnosis of AD. To establish their value in routine use, larger studies, preferably with long prospective follow-up are needed.

Alzheimer Disease↗
PubMed2002

Clinical and genetic heterogeneity in familial temporal lobe epilepsy.

PURPOSE: Familial forms of temporal lobe epilepsy have been described recently. A locus on ch 10q has been linked to partial epilepsy with auditory symptoms. We investigated the proportion of families segregating temporal lobe epilepsy (TLE) linked to ch 10q and sought to establish genotype-phenotype correlations. METHODS: We studied 15 unrelated families segregating TLE. A total of 153 individuals, including 79 patients, were analyzed in this study. Family members were genotyped for four polymorphic dinucleotide repeat markers: D10S185, D10S574, D10S577, and D10S192, which flank the 15-cM candidate interval on ch 10q. Two-point lod scores were calculated for each family separately. RESULTS: Fourteen of our families had ictal semiology of mesial temporal onset of seizures and magnetic resonance imaging (MRI) abnormalities in the mesial structures; only one family, with seven affected individuals, reported auditory symptoms and had normal MRIs. Pedigree analysis showed an autosomal dominant transmission with 0.75 penetrance. Only two families had informative lod scores. A large family, with 22 affected individuals segregating mesial TLE, had negative lod scores for all four markers genotyped. The lod scores were significantly negative (less than -2.00) up to 0.05 for D10S185, 0.10 for D10S574, 0.25 for D10S577, and 0.15 for D10S192. The single family with auditory symptoms had positive lod scores for all markers genotyped, with a Z max of 1.52 at 0.0 for D10S574. CONCLUSIONS: We identified two different clinical groups of families segregating TLE. Most families identified in this study had mesial TLE. Only one single family segregating lateral TLE was found. We significantly excluded linkage between familial mesial TLE and the locus on ch 10q. In addition, we showed evidence for linkage between one family with lateral TLE and markers on ch 10q. This is strong evidence for clinical and genetic heterogeneity among familial forms of TLE.

Chromosome Segregation↗
PubMed2006

Neural mechanisms of genetic risk for impulsivity and violence in humans.

Neurobiological factors contributing to violence in humans remain poorly understood. One approach to this question is examining allelic variation in the X-linked monoamine oxidase A (MAOA) gene, previously associated with impulsive aggression in animals and humans. Here, we have studied the impact of a common functional polymorphism in MAOA on brain structure and function assessed with MRI in a large sample of healthy human volunteers. We show that the low expression variant, associated with increased risk of violent behavior, predicted pronounced limbic volume reductions and hyperresponsive amygdala during emotional arousal, with diminished reactivity of regulatory prefrontal regions, compared with the high expression allele. In men, the low expression allele is also associated with changes in orbitofrontal volume, amygdala and hippocampus hyperreactivity during aversive recall, and impaired cingulate activation during cognitive inhibition. Our data identify differences in limbic circuitry for emotion regulation and cognitive control that may be involved in the association of MAOA with impulsive aggression, suggest neural systems-level effects of X-inactivation in human brain, and point toward potential targets for a biological approach toward violence.

Alleles↗
PubMed1998

Quantitative evidence for neuroanatomic and neuropsychological markers in dementia of the Alzheimer's type.

Meta-analytic methods were used to determine the sensitivity of neuropsychological, structural, and physiological measures to temporal-hippocampal system function in dementia of the Alzheimer's type. Effect sizes are reported for the California Verbal Learning Test, the Wechsler Memory Scale-Revised, structural (i.e., magnetic resonance imaging [MRI]), and functional (i.e., positron emission tomography [PET], single photon emission computed tomography [SPECT]) neuroimaging methods. Overall, effect sizes from MRI studies are larger than those obtained from SPECT and PET, respectively, but not as large as those obtained from the neuropsychological measures. On the basis of this finding, the neuropsychological and gross pathologic similarities between Alzheimer's disease, other dementing conditions, and mixed dementias, warrants the coupling of neuropsychological evaluation for its sensitivity with neuroimaging visualization for its specificity in improving diagnostic and differential accuracy.

Aged↗
PubMed2002

Seizures in paediatric Chiari type I malformation: the role of single-photon emission computed tomography.

UNLABELLED: Chiari type I malformation is one of the posterior fossa maldevelopments with which different clinical manifestations have been associated. Seizures have only recently been associated with Chiari type I malformation. This study reports on 4 children with epilepsy (2M, 2F; age range 8-15 y) diagnosed with Chiari type I malformation by brain magnetic resonance imaging (MRI), in whom no cortical structural involvement was observed. In these patients an interictal ethylcysteinate-dimer-single-photon emission computed tomographic (ECD-SPECT) study was performed to define more precisely the relationship between Chiari type I malformation and seizures. In these patients the hypoperfusion area correlated with electroencephalographic (EEG) focal abnormalities. These hypoperfusions may represent the functional aspect of a cerebral microdysgenesis; seizures and EEG epileptic anomalies may also be linked to the complex network connection between cortices and cerebellar hemispheres. A cerebellar hypoperfusion was also detected in two of the four examined patients, indicating a functional or structural involvement. CONCLUSION: Interictal SPECT scans are helpful for the clarification of seizures in patients with Chiari type I malformation.

Adolescent↗
PubMed1989

Acid and alkaline phosphatase activity in bone following intense magnetic field irradiation of short duration.

Consideration of the biological effects of electromagnetic radiation is particularly important with regard to bone metabolism. Magnetic fields have been applied to the treatment of bone fractures, and similar fields are employed in the visualization of skeletal structures through magnetic resonance imaging (MRI). The present investigation addressed the effect of MRI-intensity (1 Tesla) magnetic fields on enzymatic indices of bone metabolism. Mice were exposed to intense static (direct current) magnetic fields for 30 min on each of 10 successive days. After this exposure regimen the primary spongiosum of the humerus was assayed for acid and alkaline phosphatase activity. No significant difference was detected in tissue levels of either enzyme in bones from control (n = 10), sham-exposed (n = 10), and magnetic field-exposed (n = 10) mice. These results suggested that the effects of magnetic field irradiation do not appear to involve modification of the activities of regulatory enzymes in bone.

Acid Phosphatase↗
PubMed2006

Visual recognition and visually guided action after early bilateral lesion of occipital cortex: a behavioral study of a 4.6-year-old girl.

We report the case of a 4.6-year-old girl born pre-term with early bilateral occipital damage. It was revealed that the child had non-severely impaired basic visual abilities and ocular motility, a selective perceptual deficit of figure-ground segregation, impaired visual recognition and abnormal navigating through space. Even if the child's visual functioning was not optimal, this was the expression of adaptive anatomic and functional brain modifications that occurred following the early lesion. Anatomic brain structure was studied with anatomic MRI and Diffusor Tensor Imaging (DTI)-MRI. This behavioral study may provide an important contribution to understanding the impact of an early lesion of the visual system on the development of visual functions and on the immature brain's potential for reorganisation related to when the damage occurred.

Attention↗