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PubMedDate not supplied

[Neuroimaging and cerebral palsy].

INTRODUCTION: A high percentage of subjects with cerebral palsy (CP) present brain injuries, which are revealed by neuroimaging techniques. On the whole the pattern of brain damage is heterogeneous. DEVELOPMENT: We review the studies that have described the brain damage in CP using structural and functional neuroimaging techniques. Brain damage is considered according to the type of CP and taking the gestational age into account. CONCLUSIONS: According to structural neuroimaging studies carried out in spastic diplegia, the brain pattern differs with the gestational age. In early subjects with spastic diplegia it is the periventricular white matter that is mainly affected. In spastic quadriplegia, cortico subcortical lesions and hypoplasia of the corpus callosum are also observed. Unilateral lesions predominate in the case of hemiplegia. Hemiplegic subjects may also present damage to the white matter, cortico subcortical lesions and congenital brain malformations. In these subjects, some of the injury patterns observed seem to be related with the clinical features they display. Dyskinetic CP is characterised by the absence of lesions and alteration of the basal ganglia and the thalamus. Very few studies have been conducted that take the different types of CP into account in comparing the findings of structural and functional neuroimaging.

Cerebral Palsy↗

PubMed2002

Epilepsy in children with congenital hemiplegia: correlation between clinical, EEG and neuroimaging findings.

OBJECTIVES: the aim of this retrospective, multicentre study was to investigate the relationship between epilepsy, clinical, electroencephalographic (EEG) and neuroimaging findings in children with congenital hemiplegia (CH). PATIENTS AND METHODS: two hundred and three children with CH were assessed by history, neurological and developmental examination. Electroencephalogram (EEG) and CT/MRI brain imaging were performed in 150 of them (81/150 had an MRI and 69/150 had a CT scan). Patients were re-evaluated every six months for, at least, a two-year follow-up period (range 2-14 yrs). RESULTS: the EEG was abnormal in 76% of patients; epileptic seizures developed in 38.9% of them. The frequency of epilepsy paralleled the degree of EEG abnormality, approaching 85% in patients with severe EEG abnormalities and was also closely related to the extent of neuroimaging findings (up to 79% in patients with cerebral malformations). The prevalence of epilepsy in 12/62 patients (19.4%) with mild hemiplegia was significantly lower as compared to 67/141 (47.5%) of patients with moderate or severe hemiplegia. 36.7% of the children had their first seizure between the 1st and the 5th year of life, and 26.5% during the first year of life. CONCLUSIONS: epileptic seizures developed in more than one third of patients with CH, although EEG abnormalities were evident in the majority of them. The prevalence of epilepsy is closely related to the severity of hemiparesis, the extent of neuroimaging findings and the degree of EEG abnormalities. The absence of EEG abnormalities and/or normal (or minor) neuroimaging findings was negatively related to the occurrence of epilepsy.

Child↗

PubMed2003

In vivo neuroimaging correlates of the efficacy of paroxetine in the treatment of mood and anxiety disorders.

The advent of neuroimaging technology has brought with it a deeper understanding of brain function and structure in health and psychiatric illness. This article overviews pertinent findings from neuroimaging studies in mood and anxiety disorders. Paroxetine is a particularly well-studied psychopharmacologic agent in this regard. The findings of neuroimaging studies of paroxetine will be placed into perspective for a better understanding of the interaction of this selective serotonin reuptake inhibitor (SSRI) with the serotonergic and noradrenergic systems in the brain that mediate clinical efficacy. When considered in the context of a burgeoning literature on neuroimaging research of the pathophysiology of mood and anxiety disorders, the findings of paroxetine studies suggest a neurobiological explanation for the mechanisms whereby chronic administration of paroxetine affects neural systems involved in the pathophysiology of major depression and several anxiety disorders such as obsessive-compulsive disorder, posttraumatic stress disorder, and social anxiety disorder.

Antidepressive Agents, Second-Generation↗

PubMed2001

Neuropsychological testing defines the neurobehavioral significance of neuroimaging-identified abnormalities.

Three cases are presented in patients all of whom sustained focal left frontal traumatic injury to the brain. Although each case was selected because of a neuroimaging-identified frontal lesion, the point is made that the behavioral significance of such lesions is defined by the neuropsychological examination process, and not the specific size, location, or type of lesion. While neuroimaging information is critical to the comprehensive evaluation of the neurologic patient, neuroimaging findings alone have only limited predictive ability with regard to neurobehavioral syndromes. The key role of information from neuropsychological test data, combined with neuroimaging findings to fully evaluate the neurologic patient, is made.

Journal Article↗

PubMedDate not supplied

[Cognition and neural networks, a new perspective based on functional neuroimaging].

AIM: We went through a critical review of the current status of neuroimaging studies of cognition. Thus, we argue why the use of a neuronal network perspective could led us to a better understanding of cognition than a localizationism perspective. METHOD: The question about how cognitive functions are organized in the brain, comes from the very early lesions studies. Electrocortical stimulation and the intracorotid amytal procedure collaborate together with lesions studies to increase the knowledge about the organization of cognitive functions in the brain. Functional neuroimaging could help to this issue answering the following questions: where, when and how the activity is produced in the brain. Many of the functional neuroimaging studies have addressed the question of where the activity is located, but very few has been concentrated into describe the spatio temporal profiles of brain activity, and then how the neural networks which support cognition are organized. Taking into account just one of this perspectives (where or when) we could achieve a reductionism view of the problem. CONCLUSIONS: Executive function, memory or language are more distributed than located in just one area, even the different subprocesses that are included in each of this functions are supported by a network rather than a particular area. We analyze the current available functional neuroimaging techniques under this view and its possibilities to describe the neural networks which support cognition.

Brain↗

PubMed2004

The role of neuroimaging in the investigation of patients with single seizures, febrile seizures, or refractory partial seizures.

Seizures are a symptom of an underlying brain disorder. The accurate identification of the nature of the disease generating the seizures facilitates treatment and can prevent further brain damage. The understanding of the physiopathology underlying the seizures has been greatly enhanced by the possibility to examine these patients with advanced forms of neuroimaging. Among different forms of investigation, neuroimaging techniques play a major role in diagnosis and decision-making in the care of patients with epilepsy. We review the contributions of current methods of imaging in the investigation of patients with single seizures, febrile seizures or refractory seizures, assessing the practical aspects, benefits, and operational costs of various neuroimaging techniques. The focus is on MRI, which is the imaging modality of choice for outpatient investigation. We also assessed the benefits from CT scans, which remain the first option for emergency seizure assessment. The aim was to evaluate how the structural, functional and metabolic information provided by modern techniques of neuroimaging decreases the need for additional investigation and speeds the management of these epileptic disorders. This makes it possible to accurately define the location and the nature of the epileptogenic lesions related to seizures.

Brain↗

PubMed1996

Functional neuroimaging of hallucinations in schizophrenia: toward an integration of bottom-up and top-down approaches.

Hallucinations in schizophrenia represent an important clinical problem, an interesting neuropsychological enigma, and a significant challenge for neuroscientific research. Functional neuroimaging techniques allow the in vivo, systems-level study of brain dysfunction underlying this debilitating symptom. Clinical and scientific vantage points that can inform the design and interpretation of functional neuroimaging studies of schizophrenic hallucinations are outlined. These include considerations of the phenomenology of hallucinations, the relationship of hallucinations to other symptoms of schizophrenia, and the neuropsychological functions that are thought to be disrupted in hallucinations. They also include the anatomical and chemical brain systems in which abnormalities are implicated in schizophrenia, the neurologic conditions in which hallucinations may occur, the neurochemical contexts that are associated with hallucinations, and the methodologic details of the functional neuroimaging techniques employed. Bottom-up and top-down functional neuroimaging strategies for the investigation of schizophrenic hallucinations with positron emission tomography (PET), single photon emission computed tomography (SPECT) and functional magnetic resonance imaging (fMRI) are reviewed. Bottom-up approaches start with or measure the biology associated with hallucinations. Top-down approaches start from the specific neuropsychological dysfunctions thought to be associated with hallucinations. The distributed brain regions, systems and functions implicated in schizophrenic hallucination formation are then discussed in the context of an integration of bottom-up and top-down approaches. Focus is placed upon abnormalities in the functions of, and interactions among, auditory-linguistic association cortices, caudal and rostral limbic/paralimbic systems, prefrontal cortices, ventral striatum and (non-specific projection and associative) thalamic nuclei, as well as upon the glutamatergic, GABAergic and ventral tegmental dopaminergic modulation of these systems.

Brain Mapping↗

PubMed2000

Systematic review of clinical prediction rules for neuroimaging in the evaluation of dementia.

BACKGROUND: Clinical practice guidelines for dementia do not recommend routine neuroimaging but vary in their recommended clinical prediction rules to identify patients who should undergo neuroimaging for potentially reversible causes of dementia. METHODS: Using a MEDLINE search supplemented by other strategies, we identified studies from January 1, 1983, through December 31, 1998, that evaluated the diagnostic performance of a clinical prediction rule. We calculated the sensitivity and specificity of each rule, then evaluated their diagnostic performance in a hypothetical cohort of 1000 patients with dementia, varying the prevalence of potentially reversible dementia from 1% to 15%. RESULTS: We identified 7 studies that evaluated at least 1 of 6 different clinical prediction rules. Only one rule consistently had high sensitivity (>85%) across all studies; none consistently had high specificity (>85%). Six of the 7 studies included less than 15 cases of potentially reversible dementia; thus the sensitivity and specificity for each rule had relatively wide confidence intervals. At a 5% prevalence of potentially reversible dementia, all rules had low positive predictive value (<15%) in our hypothetical cohort. Depending on the rule, our analysis predicts 6 to 44 of the 50 patients with potentially reversible dementia (5% prevalence in cohort of 1000 patients) would not undergo imaging. CONCLUSIONS: There is considerable uncertainty in the evidence underlying clinical prediction rules to identify which patients with dementia should undergo neuroimaging. Application of these rules may miss patients with potentially reversible causes of dementia.

Aged↗

PubMed1997

The neuroimaging findings in Sotos syndrome.

We reviewed the neuroimaging studies of 40 patients with classic Sotos syndrome. The studies consisted of CT scans only in 4 patients and one or more MRI scans in 36 patients. The diagnosis of Sotos syndrome was made using well-established clinical criteria. The neuroimaging studies of each patient were evaluated subjectively by visual inspection and the chief findings were tabulated and grouped into five categories: 1) ventricular abnormalities, 2) extracerebral fluid spaces, 3) midline abnormalities, 4) migrational abnormalities, and 5) others. The most common abnormality of the cerebral ventricles was prominence of the trigone (90%), followed by prominence of the occipital horns (75%) and ventriculomegaly (63%). The supratentorial extracerebral fluid spaces were increased for age in 70% of the patients and the fluid spaces in the posterior fossa were increased in 70% also. A variety of midline abnormalities were noted but anomalies of the corpus callosum were almost universal. Gray matter heterotopias occurred in only 3 (8%) of 36 patients. Periventricular leukomalacia, presumably the result of prenatal or perinatal difficulties and unrelated to the basic condition, was the most common of the miscellaneous other abnormalities noted. The neuroimaging findings of Sotos syndrome are distinct enough to allow differentiation of this syndrome from other mental retardation syndromes with macrocephaly.

Abnormalities, Multiple↗

PubMed1997

Multiple brain atlas database and atlas-based neuroimaging system.

For the purpose of developing multiple, complementary, fully labeled electronic brain atlases and an atlas-based neuroimaging system for analysis, quantification, and real-time manipulation of cerebral structures in two and three dimensions, we have digitized, enhanced, segmented, and labeled the following print brain atlases: Co-Planar Stereotaxic Atlas of the Human Brain by Talairach and Tournoux, Atlas for Stereotaxy of the Human Brain by Schaltenbrand and Wahren, Referentially Oriented Cerebral MRI Anatomy by Talairach and Tournoux, and Atlas of the Cerebral Sulci by Ono, Kubik, and Abernathey. Three-dimensional extensions of these atlases have been developed as well. All two- and three-dimensional atlases are mutually preregistered and may be interactively registered with an actual patient's data. An atlas-based neuroimaging system has been developed that provides support for reformatting, registration, visualization, navigation, image processing, and quantification of clinical data. The anatomical index contains about 1,000 structures and over 400 sulcal patterns. Several new applications of the brain atlas database also have been developed, supported by various technologies such as virtual reality, the Internet, and electronic publishing. Fusion of information from multiple atlases assists the user in comprehensively understanding brain structures and identifying and quantifying anatomical regions in clinical data. The multiple brain atlas database and atlas-based neuroimaging system have substantial potential impact in stereotactic neurosurgery and radiotherapy by assisting in visualization and real-time manipulation in three dimensions of anatomical structures, in quantitative neuroradiology by allowing interactive analysis of clinical data, in three-dimensional neuroeducation, and in brain function studies.

Anatomy, Artistic↗

PubMed1999

B-SPID: an object-relational database architecture to store, retrieve, and manipulate neuroimaging data.

We propose a hardware and software architecture to respond to crucial problems in the neuroimaging field: storage, retrieval, and processing of large datasets. The B-SPID project, here discussed, concerns the processing of neuroimages and attached components stored in an object-relational multimedia database management system (DBMS). Advanced bioinformation concepts are exploited in this project such as large scale data storage, high level graphical user interfaces and 3D graphical processing and display of data. Our database implementation is based on standard programming components, runs on several UNIX platforms and is written to be evolutive. Queries on this database are designed to obtain and display from neuroimaging data several types of results (pictures, text, or 3D graphical shapes) on heterogeneous systems.

Brain Mapping↗

PubMed2000

Structural and functional neuroimaging of electroconvulsive therapy and transcranial magnetic stimulation.

Neuroimaging has long been utilized to provide a measure of the effects of electroconvulsive therapy (ECT) on brain structure and function as well as to better understand its mechanisms of action. In a similar fashion, functional neuroimaging may provide the means to elucidate both the underlying neurobiological effects and therapeutic potential of transcranial magnetic stimulation (TMS). This article will review findings of neuroimaging studies of both TMS and ECT, concentrating on how such studies may help guide treatment.

Brain↗

PubMed2002

Nonparametric permutation tests for functional neuroimaging: a primer with examples.

Requiring only minimal assumptions for validity, nonparametric permutation testing provides a flexible and intuitive methodology for the statistical analysis of data from functional neuroimaging experiments, at some computational expense. Introduced into the functional neuroimaging literature by Holmes et al. ([1996]: J Cereb Blood Flow Metab 16:7-22), the permutation approach readily accounts for the multiple comparisons problem implicit in the standard voxel-by-voxel hypothesis testing framework. When the appropriate assumptions hold, the nonparametric permutation approach gives results similar to those obtained from a comparable Statistical Parametric Mapping approach using a general linear model with multiple comparisons corrections derived from random field theory. For analyses with low degrees of freedom, such as single subject PET/SPECT experiments or multi-subject PET/SPECT or fMRI designs assessed for population effects, the nonparametric approach employing a locally pooled (smoothed) variance estimate can outperform the comparable Statistical Parametric Mapping approach. Thus, these nonparametric techniques can be used to verify the validity of less computationally expensive parametric approaches. Although the theory and relative advantages of permutation approaches have been discussed by various authors, there has been no accessible explication of the method, and no freely distributed software implementing it. Consequently, there have been few practical applications of the technique. This article, and the accompanying MATLAB software, attempts to address these issues. The standard nonparametric randomization and permutation testing ideas are developed at an accessible level, using practical examples from functional neuroimaging, and the extensions for multiple comparisons described. Three worked examples from PET and fMRI are presented, with discussion, and comparisons with standard parametric approaches made where appropriate. Practical considerations are given throughout, and relevant statistical concepts are expounded in appendices.

Brain↗

PubMed2004

Impacts of neuroimaging on psycho-oncology.

Non-invasive neuroimaging has become important in the field of psycho-oncology. Positron emission tomography (PET) is a highly advanced form of scintigraphy and used for observation of regional tissue activities such as metabolism and perfusion. Nowadays, PET measurement of glucose consumption has been widely used not only for cancer diagnosis but also for evaluation of brain activity in various psychiatric and neurological disorders. Recently, it has been used for evaluation of relatively mild depression among cancer patients. In addition, magnetic resonance imaging (MRI) has been used for detection of brain metastasis in cancer patients, but also useful for evaluation of stressful events by measuring the sizes of tiny neural structures such as hippocampus and amygdala. In this report, recent findings of non-invasive neuroimaging in cancer patients are overviewed, putting emphasis on the possible impacts of neuroimaging on psycho-oncology.

Depression↗

PubMed2002

Lateral asymmetry in phonological processing: relating behavioral measures to neuroimaged structures.

Recent neuroimaging studies have revealed neuroanatomical centers of activation that appear to be linked specifically to phonological processes. Furthermore, there is evidence that these centers of activation are more likely to be bilaterally represented in women than in men. However, behavioral evidence of such hemispheric asymmetries or of related sex differences is somewhat inconsistent. Two experiments were carried out to determine whether behavioral correlates of the neuroimaging findings could be demonstrated. The first experiment employed a rhyme-matching task used in a recent neuroimaging study, in which two nonsense words were projected successively to the left or right sides of the visual field. The results indicated that the left hemisphere was superior for this task. An analysis of gender effects, however, revealed that the asymmetry was restricted to men. The second experiment employed a lateralized pseudohomophone detection task that was designed to determine whether the results of the first experiment could be confirmed in the context of a phonological task with a simpler structure. This experiment broadly supported the findings of the first experiment. The results support the specialization of the left hemisphere for phonological processing, and the existence of gender differences with respect to these processes.

Adult↗

PubMed2002

Classical and Bayesian inference in neuroimaging: theory.

This paper reviews hierarchical observation models, used in functional neuroimaging, in a Bayesian light. It emphasizes the common ground shared by classical and Bayesian methods to show that conventional analyses of neuroimaging data can be usefully extended within an empirical Bayesian framework. In particular we formulate the procedures used in conventional data analysis in terms of hierarchical linear models and establish a connection between classical inference and parametric empirical Bayes (PEB) through covariance component estimation. This estimation is based on an expectation maximization or EM algorithm. The key point is that hierarchical models not only provide for appropriate inference at the highest level but that one can revisit lower levels suitably equipped to make Bayesian inferences. Bayesian inferences eschew many of the difficulties encountered with classical inference and characterize brain responses in a way that is more directly predicated on what one is interested in. The motivation for Bayesian approaches is reviewed and the theoretical background is presented in a way that relates to conventional methods, in particular restricted maximum likelihood (ReML). This paper is a technical and theoretical prelude to subsequent papers that deal with applications of the theory to a range of important issues in neuroimaging. These issues include; (i) Estimating nonsphericity or variance components in fMRI time-series that can arise from serial correlations within subject, or are induced by multisubject (i.e., hierarchical) studies. (ii) Spatiotemporal Bayesian models for imaging data, in which voxels-specific effects are constrained by responses in other voxels. (iii) Bayesian estimation of nonlinear models of hemodynamic responses and (iv) principled ways of mixing structural and functional priors in EEG source reconstruction. Although diverse, all these estimation problems are accommodated by the PEB framework described in this paper.

Algorithms↗

PubMed1997

Understanding functional neuroimaging methods based on neurovascular coupling.

Functional neuroimaging techniques are usually grouped according to the employed apparatus into functional magnetic resonance imaging techniques (fMRI), nuclear medicine approaches such as single photon emission tomography (SPET) or positron emission tomography (PET), and optical approaches (measurement of intrinsic signals, near infrared spectroscopy (NIRS)). However, the physiological parameters that are measured with these methods do not necessarily follow this technical classification. On the one hand, using different imaging modalities the same physiological parameters are measured and on the other hand, using the same imaging devices completely different physiological parameters can be assessed. The present article covers those functional neuroimaging methods which measure the vascular response to functional brain activation (PET, SPET, fMRI and NIRS). First, starting with the traditional grouping of these methods, it is outlined how the specific methods assess vascular changes associated with brain activation in order to localize brain function. Based on the understanding of the underlying physiological events, subsequently, a new classification of functional neuroimaging methods is proposed.

Animals↗

PubMed1995

Adolescent schizophrenia: a methodologic review of the current neuroimaging and neuropsychologic literature.

This paper reviews all relevant articles that reported structural neuroimaging or neuropsychological data in adolescent patients with schizophrenia. These papers were subsequently examined from a methodological perspective. Few papers have been written that have examined whether adolescent schizophrenia is associated with structural neuroimaging abnormalities or cognitive dysfunction. In these studies, major methodologic issues exist. Therefore, at present, firm conclusions cannot be made regarding the presence or absence of neuropsychologic dysfunction or structural neuroimaging abnormalities in this population. Attention to certain methodologic issues may improve future studies of this topic.

Adolescent↗