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At least 415 records · Page 23Linked to original sources
PubMed1997

Putaminal petechial haemorrhage as the cause of chorea: a neuroimaging study.

OBJECTIVES: A hyperintense putamen on either CT or MRI as a finding associated with chorea has occasionally been described and is almost always associated with non-ketotic hyperglycaemia. The cause of the hyperintensity of the striatum in these images is still controversial. Some reports have found that calcification was responsible whereas others have advocated petechial haemorrhage as the cause. The purpose of this study was to determine whether hyperintense striata are caused by petechial haemorrhage or calcification, with the sequential imaging changes. SUBJECTS AND METHODS: Five patients presenting with an acute onset of either hemichorea or generalised chorea and showed either unilateral or bilateral hyperdense striatum on the initial CT were assessed. Neuroimaging studies including sequential CT and MRI examinations and detailed biochemical tests were performed. RESULTS: Three patients had pronounced hyperglycaemia and the other two patients had no biochemical abnormalities. In all patients, the first CT scans, performed within two weeks of the onset of chorea, showed a high density over the striatum contralateral to the chorea, which diminished or disappeared two months later. T1 weighted imaging disclosed hypersignal intensities over the striatum contralateral to the chorea on admission which diminished two months later. T2 weighted imaging at two months showed hyposignal intensity changes corresponding to the area with hypersignal changes on T1 weighted images, implying haemosiderin deposition. CONCLUSION: Based on the evolution of clinical manifestations and the findings of neuroimaging, putaminal petechial haemorrhage might be a new entity causing either hemichorea or generalised chorea.

Aged↗
PubMed1999

Relation between neuropsychological and neuroimaging findings in patients with late whiplash syndrome.

OBJECTIVES: The interpretation of long term cognitive impairment after whiplash injury is still a problem for many physicians. On the grounds of nuclear medicine findings previous research speculated that brain damage is responsible for cognitive problems of patients with whiplash. To test this hypothesis the relation between neuroimaging and neuropsychological findings was analysed. METHODS: Twenty one patients (11 women, 10 men, mean age 42.2 (SD 8.6) years) with the late whiplash syndrome (average interval of trauma 26.1 (SD 20.7) months) referred for diagnostic action to the Department of Neurology were investigated. Assessment included computer assisted assessment of working memory and divided attention, neuroimaging (by the means of [99mTc]-HMPAO-SPECT, [15O]-H2O-PET and [18F]-FDG-PET), testing of emotional functioning (depression and anxiety ratings), and pain intensity at the time of testing. RESULTS: On average, scoring on tests of cognitive functioning was very low. However, no significant correlations were found between regional perfusion or metabolism in any brain area and the scores of divided attention or working memory. By contrast, significant relations were found between indices of impaired emotional functioning (state anxiety) and divided attention. In addition, low scoring in divided attention was significantly correlated with pain intensity at the time of testing. CONCLUSIONS: The present data do not provide evidence of a significant relation between detectable morphological or functional brain damage and impaired cognitive performance in the late whiplash syndrome. Results indicate triggering of emotional and cognitive symptoms on the basis of initial injury of the cervical spine.

Adult↗
PubMed2003

Neuroimaging tools to rate regional atrophy, subcortical cerebrovascular disease, and regional cerebral blood flow and metabolism: consensus paper of the EADC.

Neuroimaging is a mainstay in the differential diagnosis of patients with cognitive impairment. The often equivocal clinical pictures, the prognostic uncertainty of the earliest stages of mild cognitive impairment, and the subtle brain changes mean that neuroimaging techniques are of potentially great incremental diagnostic value. A number of methods, ranging from very simple subjective visual ratings to highly sophisticated computerised tools, have been developed, which allow rating of structural and functional brain changes. The choice of the method is not obvious, and current guidelines provide no indications on which tools should be preferred. In this paper, we give indications for tools with demonstrated accuracy for detecting regional atrophy, cerebrovascular disease, and regional brain function, and discuss these according to increasing technological complexity, ranging from those with high feasibility that can be used at the patient's bedside to highly technological ones that require trained personnel and specific hardware and software.

Atrophy↗
PubMed1999

Computational neuroimaging of human visual cortex.

Functional magnetic resonance imaging is a new neuroimaging method for probing the intact, alert, human brain. With this tool, brain activity that has been hidden can now be measured. Recent advances in measuring and understanding human neural responses underlying motion, color, and pattern perception are reviewed. In individual human brain, we can now identify the positions of several retinotopically organized visual areas; measure retinotopic organization within these areas; identify the location of a motion-sensitive region in individual brains; measure responses associated with contrast, color, and motion; and measure effects of attentional modulation on visually evoked responses. By framing experiments and analyses as questions about visual computation, these neuroimaging measurements can be coupled closely with those from other basic vision-science methods.

Animals↗
PubMed2002

Beyond phrenology: what can neuroimaging tell us about distributed circuitry?

Unsupervised models of how the brain identifies and categorizes the causes of its sensory input can be divided into two classes: those that minimize the mutual information (i.e., redundancy) among evoked responses and those that minimize the prediction error. Although these models have the same goal, the way that goal is attained, and the functional architectures required, are fundamentally different. This review describes the differences, in the functional anatomy of sensory cortical hierarchies, implied by the two models. We then consider how neuroimaging can be used to disambiguate between them. The key distinction reduces to whether backward connections are employed by the brain to generate a prediction of sensory inputs. To ascertain whether backward influences are evident empirically requires a characterization of functional integration among brain systems. This review summarizes the approaches to measuring functional integration in terms of effective connectivity and proceeds to address the question posed by the theoretical considerations. In short, it will be shown that the conjoint manipulation of bottom-up and top-down inputs to an area can be used to test for interactions between them, in elaborating cortical responses. The conclusion, from these sorts of neuroimaging studies, points to the prevalence of top-down influences and the plausibility of generative models of sensory brain function.

Animals↗
PubMed2005

Models of brain function in neuroimaging.

Inferences about brain function, using neuroimaging data, rest on models of how the data were caused. These models can be quite diverse, ranging from conceptual models of functional anatomy to nonlinear mathematical models of hemodynamics. However, they all have to be internally consistent because they model the same thing. This consistency encompasses many levels of description and places constraints on the statistical models, adopted for data analysis, and the experimental designs they embody. The aim of this review is to introduce the key models used in imaging neuroscience and how they relate to each other. We start with anatomical models of functional brain architectures, which motivate some of the fundaments of neuroimaging. We then turn to basic statistical models (e.g., the general linear model) used for making classical and Bayesian inferences about where neuronal responses are expressed. By incorporating biophysical constraints, these basic models can be finessed and, in a dynamic setting, rendered causal. This allows us to infer how interactions among brain regions are mediated.

Biophysical Phenomena↗
PubMedDate not supplied

Neuroimaging in pediatric leukemia and lymphoma: differential diagnosis.

Recent advances in therapy for pediatric hematologic neoplasms have greatly improved the prognosis but have resulted in an increased incidence of associated complications and toxic effects. The main neuroimaging features in pediatric patients with leukemia or lymphoma treated with chemotherapy or radiation therapy were retrospectively reviewed. To simplify the approach and facilitate differential diagnosis, the neuroimaging features have been classified into three main categories: central nervous system manifestations of primary disease, side effects of therapeutic procedures (radiation therapy, chemotherapy, bone marrow transplantation), and complications due to immunosuppression, particularly infections. Manifestations of primary disease include cerebrovascular complications (hemorrhage, cerebral infarction) and central nervous system involvement (infiltration of the meninges, parenchyma, bone marrow, orbit, and spine). Effects of radiation therapy include white matter disease, mineralizing microangiopathy, parenchymal brain volume loss, radiation-induced cryptic vascular malformations, and second neoplasms. Effects of chemotherapy and bone marrow transplantation include hemorrhage, dural venous thrombosis, white matter disease, reversible posterior leukoencephalopathy syndrome, and anterior lumbosacral radiculopathy. Both the underlying malignancy and antineoplastic therapy can cause immunosuppression. Fungi are the most frequent causal microorganisms in immunosuppressed patients with infection. Familiarity with the imaging findings is essential for proper diagnosis of neurologic symptoms in pediatric patients with oncohematologic disease.

Adolescent↗
PubMedDate not supplied

Neuroimaging studies of brain activation for language, with an emphasis on functional magnetic resonance imaging: a review.

Neuroimaging studies have greatly enhanced the potential to understand brain-behavior relationships in complex behaviors such as language. The method of functional magnetic resonance imaging (fMRI) is one of the newest tools for neuroimaging, and it will in all likelihood contribute substantially to new knowledge about brain activation for language processing. This review summarizes basic information about fMRI, including principles of operation, experimental pitfalls and examples of application to language.

Brain↗
PubMed2001

Pathology and neuroimaging in pediatric temporal lobectomy for intractable epilepsy.

OBJECTIVES: Firstly, to study the pathology at surgery in children undergoing temporal lobectomy for intractable partial epilepsy. Secondly, to compare neuroimaging techniques (CT, MRI) in the preoperative detection of pathology. Lastly, to examine the surgical outcome in children. METHODS: Forty-two pediatric patients undergoing temporal lobectomy for intractable epilepsy at the Comprehensive Epilepsy Program at the University of Alberta Hospital between the years 1988-1998 were studied. Patients had extensive preoperative investigations including CT and MRI. The pathology at surgery was reviewed and compared to preoperative neuroimaging. Charts were reviewed to determine surgical outcome. RESULTS: Brain tumors were the most common pathology, found in 13/42 patients. Mesial temporal sclerosis (MTS) was found in 8 patients and dual pathology in an additional 5. Focal cortical dysplasia (FCD) was seen in 4 patients, 1 patient had a porencephalic cyst and 4 patients had tubers of tuberous sclerosis. Seven patients had no specific pathology detected. MRI was clearly more sensitive than CT in the detection of pathology. MRI was abnormal in 27/42 cases (64%), while CT scan was found to be abnormal in only 12/39 (31%). Surgical outcome was excellent, with 34/42 patients (80%) having an Engel class I outcome. One patient had significant improvement with an Engel class II outcome, 3 (7%) had little improvement (Engel class III) and 4 (10%) were unchanged (Engel class IV). Three patients (7%) had surgical complications. CONCLUSIONS: A wide variety of developmental pathology is seen following temporal lobectomy for intractable epilepsy of childhood. Brain tumors, FCD and MTS are common. MRI is superior to CT in the detection of pathology, which may be subtle in children. Surgical outcome is excellent, with most children being seizure free and few complications being seen.

Adolescent↗
PubMed1999

Neuroimaging in the diagnosis of frontotemporal dementia.

The role of neuroimaging for the diagnosis of frontotemporal dementia (FTD) remains controversial. The modern history of imaging in the study of FTD is outlined. Also, the findings on MRI and SPECT in 15 consecutive FTD patients is noted. Both MRI and SPECT detected focal frontal involvement in nearly every single case (MRI 14/15 and SPECT 15/15). Also, the majority of patients showed asymmetry on MRI (8/15) and SPECT (12/15). This study confirms that neuroimaging is sensitive to the frontotemporal degeneration associated with FTD. Additionally, it suggests that this is often asymmetric in the relative involvement of these brain regions.

Dementia↗
PubMed2002

Evaluating geometric accuracy of multi-platform stereotactic neuroimaging in radiosurgery.

We used a spherical phantom to evaluate geometric accuracy in multi-platform stereotactic neuroimaging for radiosurgery. The phantom consisted of two plastic 16-cm-diameter hemispheres in which an exchangeable 8-cm plastic functional cube was incorporated. The functional cube contained cylinder and point targets. The targets were filled with a mixed aqueous solution of 2-mM copper sulfate and 300-mg/ml iodinated contrast medium and were visible on both MR and X-ray images. Two MR scanners and a biplane X-ray angio-suite were used to scan the phantom stereotactically in two sessions of the experiment. The angio-suite was equipped with digital subtraction and distortion-correction software. The resulting stereotactic images were transferred to a dose-planning computer for length measurement and coordinate determination of the targets. The mean errors of the measured cylinder length on distortion non-corrected X-ray stereotactic images were 0.24 +/- 0.14 and 0.73 +/- 0.10 mm, respectively, in the experiments; on distortion-corrected images 0.22 +/- 0.10 and 0.35 +/- 0.39 mm. They were 0.50 +/- 0.24, 0.25 +/- 0.19 and 0.49 +/- 0.34, 0.23 +/- 0.25 mm, respectively, of the two MR scanners. The mean errors of coordinate determination of point targets between the stereotactic MR and the distortion-corrected X-ray images were 0.70 +/- 0.18, 0.52 +/- 0.22 and 0.76 +/- 0.25, 0.40 +/- 0.10 mm, respectively, in the experiments. We found that the overall geometric errors of target delineation between stereotactic MR and X-ray images were in the submillimeter range. The current study validates the multi-platform and multi-facility stereotactic neuroimaging practice and ensures imaging accuracy in radiosurgery.

Angiography↗
PubMed2003

Long-term citicoline (cytidine diphosphate choline) use in patients with vascular dementia: neuroimaging and neuropsychological outcomes.

BACKGROUND: Cytidine diphosphate choline (citicoline) has been previously shown to have efficacy in reducing the functional impairments associated with acute stroke. Citicoline is thought to have neuroprotective benefits and has been used for the treatment of chronic cerebrovascular disorders, though its effectiveness has not been fully tested. This randomized, double-blind clinical trial was conducted to determine whether daily citicoline treatment improves neurocognitive and neuroimaging outcome over 12 months among patients diagnosed with vascular dementia (VaD). METHODS: 30 patients diagnosed with VaD, based upon NINDS-AIREN and DSM-IV criteria, were randomized and treated with either 500 mg of citicoline or placebo twice per day. Patients were assessed at baseline, and at 6, and 12 months on a battery of neurocognitive tests. Neuroimaging measures of total brain volume and subcortical/periventricular hyperintensity (SH) volume on magnetic resonance imaging (MRI) were collected at baseline and the 12-month follow-up. RESULTS: The citicoline and placebo treatment groups did not differ in their neuropsychological performance at baseline and the 12-month follow-up. Significant declines in neuropsychological performance were noted, as well as significantly increased SH and reduced total brain volumes on MRI for both groups at the 12-month follow-up. CONCLUSIONS: The efficacy of long-term citicoline treatment for cognitive impairment and neuropathological decline in those patients already meeting criteria for VaD does not appear to be substantiated by the current study.

Aged↗
PubMed2004

Neuroimaging as a diagnostic tool in dementia with Lewy bodies.

Due to similar presenting symptoms, many physicians find it difficult to distinguish cases of dementia with Lewy bodies (DLB) from Alzheimer's disease or Parkinson's disease with dementia. The pathologic diagnosis of DLB has improved because of the discovery of probes for alpha-synuclein, a protein found in Lewy bodies. However, pathologic diagnosis can be employed postmortem only, and therefore diagnostic techniques that can be employed to guide patient management are still needed. Consensus criteria have been developed for establishing a clinical diagnosis of DLB, but they lack sensitivity. Therefore, a review of the recent literature was conducted to establish whether neuroimaging studies are useful diagnostic tools to help differentiate these syndromes. At least six types of tests can be used to image the brain of patients with dementia. Structural studies (x-ray, magnetic resonance imaging and computerized tomography) can disclose the presence of stroke sequelae and other lesions, whereas functional studies (magnetic resonance spectroscopy, positron emission tomography and single-photon emission computed tomography) can disclose metabolic and blood flow alterations that may be characteristic for different types of dementia. Although more formal studies are needed to confirm that these imaging techniques are reliable diagnostic tools for DLB and permit the establishment of guidelines for their use, neuroimaging techniques currently are being employed in practice to differentiate dementia types as a guide to treatment.

Acetylcholinesterase↗
PubMed2005

Neuroimaging and cardiac correlates of cognitive function among patients with cardiac disease.

In the present study, we examined the relationships between whole brain volume (WBV), subcortical hyperintensities (SH), indices of cardiac disease and cognitive function in nondemented cardiac patients with evidence of mild cerebrovascular disease. A total of 27 individuals with evidence of cardiac disease underwent neuropsychological examination, neuroimaging, and cardiac assessment. Cognition was assessed with the Dementia Rating Scale-2 (DRS). WBV and SH were quantified using a semi-automated thresholding program based on MRI. Correlational analyses revealed that WBV predicted performance on the overall DRS score, the attention subscale and the initiation/perseveration scale. SH were significantly associated with performance on the attention subscale, and the initiation/perseveration subscale. Regression analyses revealed that SH accounted for most of the variance in the initiation/perseveration scale, whereas WBV accounted for most of the variance in the attention scale. The only cardiac structural or functional variable related to the neurological indices was aortic diameter, which was strongly related to both neuroimaging variables, as well as performances on the DRS attention and initiation/perseveration subscales. Our results highlight the importance of overall brain parenchyma in determining cognitive status among patients at risk for cognitive decline and suggest that select indices of structural cardiac morphology may be related to the early phases of cerebrovascular disease and cognitive status.

Aged↗
PubMed2006

Use of advanced neuroimaging techniques in the evaluation of pediatric traumatic brain injury.

Advanced neuroimaging techniques are now used to expand our knowledge of traumatic brain injury, and increasingly, they are being applied to children. This review will examine four of these methods as they apply to children who present acutely after injury. (1) Susceptibility weighted imaging is a 3-dimensional high-resolution magnetic resonance imaging technique that is more sensitive than conventional imaging in detecting hemorrhagic lesions that are often associated with diffuse axonal injury. (2) Magnetic resonance spectroscopy acquires metabolite information reflecting neuronal integrity and function from multiple brain regions and provides sensitive, noninvasive assessment of neurochemical alterations that offers early prognostic information regarding the outcome. (3) Diffusion weighted imaging is based on differences in diffusion of water molecules within the brain and has been shown to be very sensitive in the early detection of ischemic injury. It is now being used to study the direct effects of traumatic injury as well as those due to secondary ischemia. (4) Diffusion tensor imaging is a form of diffusion weighted imaging and allows better evaluation of white matter fiber tracts by taking advantage of the intrinsic directionality (anisotropy) of water diffusion in human brain. It has been shown to be useful in identifying white matter abnormalities after diffuse axonal injury when conventional imaging appears normal. An important aspect of these advanced methods is that they demonstrate that 'normal-appearing' brain in many instances is not normal, i.e. there is evidence of significant undetected injury that may underlie a child's clinical status. Availability and integration of these advanced imaging methods will lead to better treatment and change the standard of care for use of neuroimaging to evaluate children with traumatic brain injury.

Body Water↗
PubMed2003

Functional neuroimaging studies of motor recovery after stroke in adults: a review.

BACKGROUND: The precise mechanisms of and biological basis for motor recovery after stroke in adults are still largely unknown. Reorganization of the motor system after stroke as assessed by functional neuroimaging is an intriguing but challenging new field of research. Provocative but equivocal findings have been reported to date. SUMMARY OF REVIEW: We present an overview of functional neuroimaging studies (positron emission tomography or functional MRI) of motor tasks in patients recovered or still recovering from motor deficit after stroke. After a brief account of the connectivity of motor systems and the imaging findings in normal subjects, the literature concerning stroke patients is reviewed and discussed, and a general model is proposed. CONCLUSIONS: Both cross-sectional and longitudinal studies have demonstrated that the damaged adult brain is able to reorganize to compensate for motor deficits. Rather than a complete substitution of function, the main mechanism underlying recovery of motor abilities involves enhanced activity in preexisting networks, including the disconnected motor cortex in subcortical stroke and the infarct rim after cortical stroke. Involvement of nonmotor and contralesional motor areas has been consistently reported, with the emerging notion that the greater the involvement of the ipsilesional motor network, the better is the recovery. This hypothesis is supported by the enhanced activity of the ipsilesional primary motor cortex induced by motor training and acute pharmacological interventions, in parallel with improved motor function. Further longitudinal studies assessing the relationships between such changes and actual recovery, as well as manipulating such changes by rehabilitation or pharmacological maneuvers, should provide further information on these fundamental questions. This review closes with some perspectives for future research.

Adult↗
PubMedDate not supplied

Contribution of functional neuroimaging to understanding neuropsychiatric side effects of interferon in hepatitis C.

Patients with hepatitis C who are treated with interferon may develop neuropsychiatric symptoms, including fatigue and depression. The authors discuss the potential use of functional neuroimaging in the identification and treatment of these patients. The authors provide an overview of functional neuroimaging studies of fatigue and depressive symptoms in various medical and psychiatric conditions and suggest future directions for research that may increase understanding of the specific neural substrates of neuropsychiatric side effects associated with hepatitis C and interferon treatment. This knowledge may help consultation-liaison psychiatrists identify patients at high risk for developing side effects related to hepatitis C and interferon, which would allow for implementation of validated strategies for prophylactic treatment of these patients.

Antineoplastic Agents↗
PubMed2001

Neuroimaging studies of antisocial behaviour.

OBJECTIVE: To review recent neuroimaging studies of antisocial behaviour, including criminality, psychopathy, sexual offending, aggression, and violence. METHOD: Using OVID software, Psycinfo and Medline were searched for studies undertaken in the last 15 years. A brief outline of each technology is followed by a survey of published reports from refereed journals. Where indicated, critical appraisal is offered. RESULTS: Converging evidence from multiple studies of structure and function indicates that abnormal prefrontal (and probably subcortical) circuitry are very likely involved in antisocial behaviour. CONCLUSIONS: Clinicians should be aware of emerging findings from biological studies of antisociality. Future neuroimaging and other biologically based work, especially when combined with psychosocial initiatives, should yield fruit in attempts to better understand, treat, and prevent such socially devastating and destructive behaviour.

Antisocial Personality Disorder↗