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PubMed1996

Neuroimaging and the cognitive neuroscience of schizophrenia.

The Carmel Workshop on Cognitive Psychophysiology began in 1980, and the focus of the 1996 workshop was on schizophrenia. Research into schizophrenia is in the midst of a period of unparalleled advance, driven in large part, by improvements in neuroimaging technology that make detailed examination of in vivo brain structure and function possible. Neuroimaging studies may help provide a bridge between investigations demonstrating molecular and cellular abnormalities in schizophrenia and those demonstrating cognitive dysfunction. The workshop brought together experts in different neuroimaging modalities to present the strengths and advantages of each, as well as the insights each modality might bring into normal and schizophrenic cognitition. It began with a series of tutorials to inform participants of the state of the art in various disciplines. It then broke into four panels, each given a very specific topic assignment related to neuroimaging and/or the cognitive neuroscience of schizophrenia. After 1 1/2 days of discussion, each panel reported its conclusions to the workshop. Group I presented cellular models of the pathophysiology of schizophrenia. Group II examined experimental paradigms for studying cognitive function and schizophrenia. Group III examined technical issues in image processing and combining data across different modalities. Group IV sought to survey the current state of knowledge about the pathophysiology of schizophrenia. The conclusions of each of the groups are presented in this report.

California↗

PubMedDate not supplied

Multimodal neuroimaging approaches to disorders of consciousness.

Advances in neuroimaging techniques hold significant promise for improving understanding of disorders of consciousness arising from severe brain injuries. We review neuroimaging studies of the vegetative state (VS) and minimally conscious state (MCS), and findings in an unusual case of late emergence from MCS. Multimodal neuroimaging studies using positron emission tomography techniques, functional magnetic resonance imaging, and quantitative electroencephalography and magnetoencephalography quantify variations of residual cerebral activity across these patient populations. The results suggest models to distinguish the pathophysiologic basis of VS and MCS. Less clear are potential brain mechanisms underlying late recovery of communication in rare MCS patients. Diffusion tensor magnetic resonance imaging studies and recent experimental findings suggest that structural remodeling of the brain following severe injury may play a role in late functional recoveries. More generally, relatively long time courses of recovery following severe brain injury emphasize the need to develop markers for identifying patients who may harbor potential for further meaningful recovery. Introduction of neuroimaging into the clinical evaluation process will require developing frameworks for longitudinal assessments of cerebral function. Although limited in number, available studies already provide important insights into underlying brain mechanisms that may help guide development of such assessment strategies.

Arousal↗

PubMed2000

Review of neuroimaging studies of child and adolescent psychiatric disorders from the past 10 years.

OBJECTIVES: To review recent neuroimaging studies of serious emotional disorders in youth and identify problems and promise of neuroimaging in clinical practice. METHOD: Published reports from refereed journals are briefly described, critiqued, and synthesized into a summary of the findings to date. RESULTS: Childhood-onset schizophrenia shows progressive ventricular enlargement, reduction in total brain and thalamus volume, changes in temporal lobe structures, and reductions in frontal metabolism. Autistic disorder is associated with cerebellar changes, greater total brain and lateral ventricle volume, and asymmetry. The prefrontal cortex and the basal ganglia are consistently reported as abnormal in attention-deficit/hyperactivity disorder. Patients with anorexia nervosa show enlarged CSF spaces and reductions in gray and white matter that are only partially reversible with weight recovery. CONCLUSIONS: Results from neuroimaging studies of childhood-onset psychiatric disorders suggest consistency in the structures found to be abnormal, but inconsistencies in the nature of these abnormalities. Although neuroimaging technology holds great promise for neurodevelopmental research, it is not yet a diagnostic instrument.

Adolescent↗

PubMed1993

Neuroimaging of epilepsy, movement disorders, and degenerative diseases.

Neuroimaging has improved the understanding, diagnosis, and management of several neurologic diseases and syndromes. Recent advances in the neuroimaging of epilepsy, movement disorders, and degenerative diseases of the nervous system are reviewed. Current research confirms that structural and functional neuroimages each provide unique, clinically useful information in these disorders. Quantification of images improves their diagnostic sensitivity and specificity. Presymptomatic or early neurochemical changes have been identified and followed longitudinally in several neurodegenerative diseases, providing a method for monitoring response to therapeutic intervention and pathophysiologic hypothesis testing. Functional activation studies and receptor-specific radioligands continue to advance our understanding of these disorders. Future methods will take increasing advantage of both the ability to measure neuropharmacological and neurochemical changes in vivo, and the ability to combine images and information obtained with distinct structural and functional neuroimaging modalities.

Brain↗

PubMed2003

Neuroimaging of stroke: a review.

Advances in neuroimaging technology during the past 30 years have resulted in a virtual explosion in the amount of pathologic information that can be obtained in the clinical stroke setting. This neuroimaging revolution has led to a much better understanding of cerebrovascular and tissue pathology, creating a wide array of opportunities for acute treatment and secondary prevention. Advances include early and accurate detection of ischemic and infarcted tissue and the ability to reveal hypoperfused tissue at risk. Clinicians are increasingly able to noninvasively detect embolic and atherothrombotic intravascular lesions. Vascular lesions associated with stroke can be characterized through endovascular neuroimaging techniques and repaired by various means. In this article, we provide an overview and update on the various techniques used in the neuroimaging of stroke and intracranial hemorrhage, including computed tomography, magnetic resonance imaging, ultrasound, and catheter angiography. We outline the specific role of each modality in clinical practice.

Acute Disease↗

PubMed2001

Neuroimaging studies of autobiographical event memory.

Commonalities and differences in findings across neuroimaging studies of autobiographical event memory are reviewed. In general terms, the overall pattern across studies is of medial and left-lateralized activations associated with retrieval of autobiographical event memories. It seems that the medial frontal cortex and left hippocampus in particular are responsive to such memories. However, there are also inconsistencies across studies, for example in the activation of the hippocampus and dorsolateral prefrontal cortex. It is likely that methodological differences between studies contribute to the disparate findings. Quantifying and assessing autobiographical event memories presents a challenge in many domains, including neuroimaging. Methodological factors that may be pertinent to the interpretation of the neuroimaging data and the design of future experiments are discussed. Consideration is also given to aspects of memory that functional neuroimaging might be uniquely disposed to examine. These include assessing the functionality of damaged tissue in patients and the estimation of inter-regional communication (effective connectivity) between relevant brain regions.

Autobiographies as Topic↗

PubMed2005

Neuroimaging in the evaluation of patients with non-acute headache.

Available studies offer only limited guidance on neuroimaging of non-acute headache patients. The aim of this study was to estimate the frequency of significant intracranial lesions in patients with headache and to determine the clinical variables helpful in identifying patients with intracranial lesions. All patients aged >or= 15 years attending the Neurology Clinic with non-acute headache were included in the study and followed prospectively. Every patient was investigated by neuroimaging studies, either computed tomography or magnetic resonance imaging. Neuroimaging results were classified as 'significant abnormalities', 'non-significant abnormalities' or 'normal'. Significant abnormalities included neoplastic disease, hydrocephalus, vascular malformations, Chiari malformation, large arachnoid cysts, intracranial haemorrhage, and acute cerebral infarcts. Consecutive patients (n=1876; 1243 women and 633 men) were included. Their mean age was 38 years (range 15-95 years). Neuroimaging studies detected significant lesions in 22 patients [1.2%, 95% confidence interval (CI) 0.7, 1.8]. The rate of significant intracranial abnormalities in patients with headache and normal neurological examination was 0.9% (95% CI 0.5, 1.4). The only clinical variable associated with a higher probability of intracranial abnormalities was neurological examination. The proportion of patients with headache and intracranial lesions is relatively small, but neither neurological examination nor the features in the clinical history permit us to rule out such abnormalities.

Adolescent↗

PubMed2005

Renewal of the neurophysiology of language: functional neuroimaging.

Functional neuroimaging methods have reached maturity. It is now possible to start to build the foundations of a physiology of language. The remarkable number of neuroimaging studies performed so far illustrates the potential of this approach, which complements the classical knowledge accumulated on aphasia. Here we attempt to characterize the impact of the functional neuroimaging revolution on our understanding of language. Although today considered as neuroimaging techniques, we refer less to electroencephalography and magnetoencephalography studies than to positron emission tomography and functional magnetic resonance imaging studies, which deal more directly with the question of localization and functional neuroanatomy. This review is structured in three parts. 1) Because of their rapid evolution, we address technical and methodological issues to provide an overview of current procedures and sketch out future perspectives. 2) We review a set of significant results acquired in normal adults (the core of functional imaging studies) to provide an overview of language mechanisms in the "standard" brain. Single-word processing is considered in relation to input modalities (visual and auditory input), output modalities (speech and written output), and the involvement of "central" semantic processes before sentence processing and nonstandard language (illiteracy, multilingualism, and sensory deficits) are addressed. 3) We address the influence of plasticity on physiological functions in relation to its main contexts of appearance, i.e., development and brain lesions, to show how functional imaging can allow fine-grained approaches to adaptation, the fundamental property of the brain. In closing, we consider future developments for language research using functional imaging.

Aphasia↗

PubMed1997

Structural neuroimaging in learning disability.

BACKGROUND: Neuroimaging has proven useful in confirming diagnoses of certain neuropsychiatric conditions, but neuroimaging studies in learning disability are at an early stage. METHOD: A review of recent structural neuroimaging research in relation to learning disability was carried out. RESULTS: Brain abnormalities can be detected in cases of idiopathic and non-idiopathic learning disability, but their significance is not clear due to discrepancies in study findings and the small cohorts involved. CONCLUSION: Although the role of structural neuroimaging in the assessment of people with learning disability is not clear, new magnetic resonance imaging technology holds great promise for future research.

Autistic Disorder↗

PubMed1998

Neuroimaging in autism.

BACKGROUND: Childhood autism is a developmental disorder with distinctive clinical features and characteristic cognitive deficits. Neuroimaging techniques have been extensively used in the study of autism and related disorders. METHOD: Recent important literature reported on structural and functional neuroimaging in autism was reviewed and discussed in the context of other neurobiological research findings. RESULTS: Various abnormalities of brain structure and function have been proposed, but no focal defect has been reliably demonstrated. Important findings, so far, include increased brain volume, structural abnormality in frontal lobe and corpus callosum in a proportion of autistic individuals. Functional neuroimaging findings emphasised the imbalance in inter-regional and inter-hemispheric brain metabolism and blood flow as well as abnormality in the anterior cingulate gyrus. CONCLUSION: The research to date has been hindered by methodological difficulties. However, hypothesis-driven research, particularly involving activation studies and neurotransmitter/neuroreceptor activities, using functional neuroimaging will be very useful in unravelling the enigma associated with this intriguing and distressing condition.

Autistic Disorder↗

PubMed2006

The role of functional neuroimaging in pediatric brain injury.

The aim of this article is to review empirical studies published in the last 10 years that used various functional neuroimaging techniques to assess pediatric patients with brain injury. Overall, these studies have demonstrated the ability of functional neuroimaging to offer unique information concerning the diagnosis, clinical outcome, and recovery mechanisms after pediatric brain injury. Future research using functional neuroimaging is recommended to better understand the functional reorganization and neurodevelopmental consequences resulting from brain injury. Such research might allow clinicians to design tailored early-intervention and rehabilitation programs to maximize the recovery process for pediatric patients. Limitations and advantages associated with the use of functional neuroimaging in pediatric populations are discussed.

Brain Injuries↗

PubMed2005

Neuroimaging biomarkers for clinical trials of disease-modifying therapies in Alzheimer's disease.

The pathophysiologic process leading to neurodegeneration in Alzheimer's disease (AD) is thought to begin long before clinical symptoms develop. Existing therapeutics for AD improve symptoms, but increasing efforts are being directed toward the development of therapies to impede the pathologic progression of the disease. Although these medications must ultimately demonstrate efficacy in slowing clinical decline, there is a critical need for biomarkers that will indicate whether a candidate disease-modifying therapeutic agent is actually altering the underlying degenerative process. A number of in vivo neuroimaging techniques, which can reliably and noninvasively assess aspects of neuroanatomy, chemistry, physiology, and pathology, hold promise as biomarkers. These neuroimaging measures appear to relate closely to neuropathological and clinical data, such as rate of cognitive decline and risk of future decline. As this work has matured, it has become clear that neuroimaging measures may serve a variety of potential roles in clinical trials of candidate neurotherapeutic agents for AD, depending in part on the question of interest and phase of drug development. In this article, we review data related to the range of neuroimaging biomarkers of Alzheimer's disease and consider potential applications of these techniques to clinical trials, particularly with respect to the monitoring of disease progression in trials of disease-modifying therapies.

Alzheimer Disease↗

PubMed2004

Neuroimaging of HIV and AIDS related illnesses: a review.

Neuroimaging technology continues to unfold in a very exciting way, providing almost limitless information about the structural and functional integrity of the nervous system. In patients with an immunocompromised state such as those infected with human immunodeficiency virus (HIV) and subsequently developing acquired immunodeficiency syndrome (AIDS), neurologic complications represent an important manifestation requiring vigilance. Many of the central nervous system (CNS) disorders related to HIV and AIDS are treatable and without prompt diagnosis and treatment, will lead to significant morbidity or death. Neuroimaging plays an increasingly pivotal role in the early diagnosis and longitudinal monitoring of these conditions. The author intends to provide an overview of neuroimaging technology and its applications including various magnetic resonance imaging (MRI) and functional imaging techniques in the evaluation of patients with HIV and AIDS related CNS disorders. The role of neuroimaging in this population includes early detection of direct HIV infection, opportunistic infections, neoplasia, or cerebrovascular diseases. In addition, through a wide breadth of imaging techniques, the pathology, neurochemistry and metabolism of lesions can be studied to clarify the differential diagnosis, such as discriminating infection vs. neoplasia.

AIDS Dementia Complex↗

PubMedDate not supplied

Clinical neuroimaging in psychiatry.

The practical aspects of contemporary neuroimaging techniques relevant to clinical psychiatry are reviewed. In particular, the structural imaging modalities of computed axial tomography (CT) and magnetic resonance imaging (MRI) are described and compared. Likewise, functional neuroimaging modalities including the nuclear imaging techniques of positron emission tomography (PET) and single photon emission computed tomography (SPECT), as well as the newer magnetic resonance techniques of functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy (MRS), are reviewed. Although structural imaging techniques are most useful for ruling out medical etiologies of mental status disturbances, functional neuroimaging techniques currently have an adjunctive role in the evaluation of dementia and seizure disorders and show promise for the evaluation of primary psychiatric disorders in the future. Specific guidelines are suggested regarding the use of these neuroimaging studies.

Brain Diseases↗

PubMedDate not supplied

Neuroimaging and neurobiological models of depression.

We review the data from structural neuroimaging studies (computed tomography and magnetic resonance imaging) related to depressive disorders. In addition, we review the relevant functional neuroimaging research, including studies of normal emotional processing, studies of the functional neuroanatomy of major depression, and neurochemical neuroimaging studies of depression. Finally, we discuss existing neurobiological models of depression and offer modifications based upon the body of neuroimaging research we have presented.

Depressive Disorder↗

PubMed2005

Modified boron neutron capture therapy for malignant gliomas performed using epithermal neutron and two boron compounds with different accumulation mechanisms: an efficacy study based on findings on neuroimages.

OBJECT: To improve the effectiveness of boron neutron capture therapy (BNCT) for malignant gliomas, the authors used epithermal rather than thermal neutrons for deep penetration and two boron compounds-sodium borocaptate (BSH) and boronophenylalanine (BPA)-with different accumulation mechanisms to increase the boron level in tumors while compensating for each other's faults. METHODS: Thirteen patients, 10 of whom harbored a glioblastoma multiforme (GBM), one a gliosarcoma, one an anaplastic astrocytoma, and one an anaplastic oligoastrocytoma, were treated using this modified BNCT between January 2002 and December 2003. Postoperatively, neuroimaging revealed that only one patient with a GBM had no lesion enhancement postoperatively. The patients underwent 18F-BPA positron emission tomography, if available, to assess the accumulation and distribution of BPA before neutron radiotherapy. The neutron fluence rate was estimated using the Simulation Environments for Radiotherapy Applications dose-planning system before irradiation. The patients' volume assessments were performed using magnetic resonance (MR) imaging or computerized tomography (CT) scanning. Improvements in the disease as seen on neuroimages were assessed between 2 and 7 days after irradiation to determine the initial effects of BNCT; its maximal effects were also analyzed on serial neuroimages. The mean tumor volume before BNCT was 42.3 cm3. Regardless of the pre-BNCT tumor volume, in every patient harboring an assessable lesion, improvements on MR or CT images were recognized both at the initial assessment (range of volume reduction rate 17.4-71%, mean rate 46.4%) and at follow-up assessments (range of volume reduction rates 30.3-87.6%, mean rate 58.5%). More than 50% of the contrast-enhanced lesions disappeared in eight of the 12 patients during the follow-up period. CONCLUSIONS: This modified BNCT produced a good improvement in malignant gliomas, as seen on neuroimages.

Adult↗

PubMed1999

[Progressive multifocal leukoencephalopathy associated with human immunodeficiency virus infection: the clinical, neuroimaging, virological and evolutive characteristics in 35 patients].

BACKGROUND: The clinical, neuroimaging, virologic and evolutive characteristics of progressive multifocal leukoencephalopathy (PML) in 35 AIDS patients are studied. PATIENTS AND METHODS: PML was diagnosed by clinical and neuroimaging criteria in 32 patients and by autopsy in other three. The detection of JC virus (JCV) was done by PCR and further hybridization of the amplified DNA in peripheral blood lymphocytes, urine and CSF. RESULTS: 127 of 930 HIV positive patients were admitted by neuropsychiatric symptoms and of them 35 (SD 27.6%) by PML. The PML patients had a mean CD4 lymphocytes count of 75.3 (82.0)/x 10(6)/l and a HIV viral load of 330,698 (538,971) copies of RNA/ml. Thirty patients did not receive any anti-retroviral therapy or only transcriptase inhibitors monotherapy and five triple anti-retroviral therapy, including a proteases inhibitor. Multiple hypodense lesions on CT (53.1%) and T2 hyperintense lesions on MRI (58.3%) were the most frequent neuroimaging findings. JCV was detected in 20/21 (95.2%) LMP patients: 18/19 detections in lymphocytes, 6/8 in CSF and 4/6 in urine. The mean survival without and with antiretroviral therapy were 3.0 (0.47) and 21.4 (4.4) months (p < 0.001) in 34 patients followed. PML progressed to death in 31/34 patients (91.2%), and remained stable in 3/34 (8.8%). A patient was lost for follow-up. CONCLUSIONS: The application of clinical and neuroimaging criteria and the detection of JCV in CSF are useful for high presumption diagnosis of PML without brain biopsies. JCV detection in lymphocytes and in urine have a much lower predictive value. The evolution and survival of this disease can improve with triple anti-retroviral therapy including a protease inhibitor.

AIDS-Related Opportunistic Infections↗

PubMed2001

Neuroimaging, memory and the human hippocampus.

The hippocampus has long been implicated in mnemonic function, although its precise role is still keenly debated. Neuroimaging techniques such as positron emission tomography, functional magnetic resonance imaging and structural MRI, provide the means to examine in vivo the dynamic nature of human memory. Here, I briefly discuss how neuroimaging has investigated complex real-world memories of the kind typically reported lost by patients in the clinical context. A role, paralleling that documented in animals, for the right hippocampus in navigation is clearly apparent from functional and structural neuroimaging findings. In contrast, the left hippocampus is more responsive to memories for events that occur in a specific time and place (episodic memory) that characterise one's personal, or autobiographical, memory store from throughout the lifetime. Neuroimaging is well-placed to extend our understanding of the differential contributions the left and right hippocampi make to aspects of memory and how they interface to produce a unitary representation of the past.

Amnesia↗