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At least 469 records · Page 26Linked to original sources
PubMedDate not supplied

[Schizophrenia: a brain disease. II. Functional neuroimaging].

Functional neuroimaging techniques constitute formidable tools to investigate the human brain in vivo. This possibility has led to a growing interest in these techniques in psychiatric research, particularly in the study of neural mechanism involved in schizophrenia. Three main lines of research have been developed in this field: 1. Patterns of brain activity in a rest condition or during cognitive task performance, 2. correlations between psychopathology and brain activity, and 3. investigations of neurochemical characteristics (neurotransmitters and neuroreceptors) of schizophrenic patients. However, despite of the great effort developed lately these studies have yielded little in the way of coherent pathophysiologic theories of schizophrenia. Future studies combining molecular biology and genetic techniques with structural and functional neuroimaging studies are needed in our purpose to explore the neural mechanisms involved in schizophrenia.

Brain↗
PubMedDate not supplied

[The classical clinical and neuroimaging features of meningiomas are mimicked by other intracranial, supratentorial expansive lesions].

OBJECTIVE: To analyze the surgical neurology cases in which both the clinical and neuroimaging features suggested supratentorial meningioma, and resulted in different entities from the neuropathological point of view. PATIENTS AND METHODS: The clinical histories of patients harboring intracranial, supratentorial mass lesions diagnosed as meningioma operated in different hospitals of Maracaibo, Venezuela, during the period 1993-1997 were reviewed. RESULTS: Our analysis revealed 15 cases with different neuropathological diagnosis. They were distributed as follows: three cases of hemangiopericytoma, two cases each of anaplastic ependymoma, metastatic carcinoma, and solitary intracranial plasmacytoma, and one case each of plasma cell granuloma, pleomorphic xanthoastrocytoma, chondroma, actinomycetoma, meningeal fibroma and chronic inflammation not otherwise specified. CONCLUSION: A heterogeneous group of intracranial, supratentorial expansive mass lesions can masquerade as meningiomas both from the clinical and neuroimaging points of view.

Adolescent↗
PubMed2000

[Consideration on neuroimaging and functional diagnosis in cerebrovascular disorder].

The electroencephalogram(EEG) has been one of the important clinical examination in cerebrovascular disorder(CVD). Since X-ray computed tomography(CT) was introduced in the 1970's, the numbers of EEG examination decreased in Japan. In the present, the diagnosis of acute CVD is done by neuroimaging examinations which generally are CT, magnetic resonance imaging(MRI) and at times, single photon emission computed tomography(SPECT). But EEG examination is necessary for estimate of brain function in acute and/or chronic CVD. Only EEG examination is able to confirm epileptic seizure, sleep-wake disorder and disturbance of consciousness. alpha-coma and spindle coma are peculiar disturbance of consciousness and appear in acute CVD. REM sleep behavior disorder(RBD) sometimes appear in chronic CVD. The characteristic of RBD is violent or injurious behavior during REM sleep. Polysomnography demonstrates abnormal REM sleep without loss of atonia. Both neuroimaging and functional diagnosis have been to perform to estimate in CVD same as in the other central nervous disorders.

Cerebrovascular Disorders↗
PubMedDate not supplied

[Functional neuroimaging of emotions and bipolar disorder].

In this review we comment the results of functional neuroimaging works of emotions on normal population and some parallelisms with the emotional changes of bipolar disorder correlated with their functional neuroimaging. Initially we refer the emotional ontogenetical development of human brain based on regional cerebral sanguineous flow evolution (FSC). Secondly we describe the differences of FSC between the externally generated emotions versus internally; between positive versus negative emotions and the correlation between FSC and some facial expressions. When FSC of bipolar disorder is compared with normal emotions on general population, we observe that temporal cortex, the prefrontal medial and insular anterior cortex, change their perfusion with the switch or the change of emotional expression. It is possible to determine if the findings obtained in samples of healthy subjects and bipolar patients converge in a dimensional model, or if on the contrary they support the categorical hypotheses, moving the emotional aspects to a second term on bipolar disorder.

Bipolar Disorder↗
PubMed2000

The use of neuroimaging techniques for clinical detection of neurotoxicity: a review.

Although toxins exert their impact on a molecular level, they may yield molar effects by affecting areas large enough to be visualized by neuroimaging techniques. Therefore, neuroimaging of the brain may be used to render the macroscopic sequelae of neurotoxins visible. Toxic agents may induce brain edema or atrophy, demyelination, infarctions, calcifications, hemorrhages, or changes of perfusion, metabolism or receptor density. Although they do not readily disclose their nature, clues as to the offending agent may in some instances be gleaned from the pattern, distribution, and appearance of the cerebral changes. Intoxication, however, has always to be proved or substantiated independently by appropriate means. This paper deals with the extent and certainty to which conclusions as to some of the most common offending substances may be drawn from pictures of the brain.

Brain↗
PubMed2001

[A case of juvenile pilocytic astrocytoma with unusual neuroimaging features].

We present a case of cerebellar juvenile pilocytic astrocytoma(JPA) with unusual neuroimaging features. The patient was a 14-year-old male who suffered from chronic headaches for a couple of weeks. Plain craniogram showed a decalcification and bulging of the occipital bone. Computed tomography(CT) scans demonstrated low density multiple components with small calcifications in the right cerebellar hemisphere extending to the left. These calcifications were found at the margin of these multi-lobular components. Magnetic resonance imaging(MRI) revealed iso or low intensity on T1 weighted image, and slightly high intensity on T2 weighted image. The lesion indicated more heterogeneous and higher intensity than brain parenchyma on FLAIR imaging, and remarkable higher intensity than brain parenchyma with some small low intensity areas on diffusion weighted imaging. He underwent the complete resection except for the cranial tissue surrounding the pons. Histologic diagnosis was juvenile pilocytic astrocytoma, because of biphasic pattern of bipolar cells and a number of Rosenthal fibers. Generally JPA has sharp and smooth demarcated cysts with well-enhanced mural nodule. It was difficult to diagnose the presented tumor as JPA before operation, since its unusual neuroimaging resembled both dermoid and high grade gliomas.

Adolescent↗
PubMed2001

[Contribution of positron emission tomography to functional neuroimaging in Alzheimer's disease].

When combined with cognitive investigations, functional neuroimaging methods such as positron emission tomography allow to depict the neural substrates that underlie the neuropsychological alterations in Alzheimer's disease. Capitalising on the variance in both cognitive performances and resting cerebral metabolic rate of glucose (CMRGlc) in Alzheimer's disease, it is possible to correlate these two quantitative variables on a pixel-by-pixel basis and to generate maps showing the significant correlations in stereotaxic space. Some examples using this approach in the domain of memory disorders are presented in this brief review. We notably show that the localisation of the significant correlations differs from one memory system to another, as evaluated by clinical memory tasks. This approach also unravels the compensatory mechanisms that take place with evolution of the disease. Over and above its interest in clinical neuropsychology, this method constitutes a new source of inferences complementary to the classic activation paradigm in normal subjects, as the latter identifies the cerebral structures that are involved with, but not necessarily indispensable for, the normal execution of the task. This approach highlights the interest of combining functional neuroimaging and neuropsychology to better understand the neural substrates of cognitive deficits in both patients with memory disorders and elderly normal subjects.

Alzheimer Disease↗
PubMed2001

Pharmacologic modulation of human cerebral activity: contribution of functional neuroimaging.

This article highlights the following: (1) How the tools of functional neuroimaging analyze the effect of drug therapy on the central nervous system; (2) how the interactions between the drugs and the cortical neuronal networks have illustrated new aspects of the concepts of cerebral neuroplasticity; and (3) how functional neuroimaging has proved to be a valuable tool in understanding the mechanisms that govern the therapeutic activity of experimental drugs.

Anticonvulsants↗
PubMed2001

Investigating the pathogenesis of posttraumatic stress disorder with neuroimaging.

Rapidly evolving brain neuroimaging techniques such as magnetic resonance imaging (MRI) and positron emission tomography (PET) are proving fruitful in exploring the pathogenesis and pathophysiology of posttraumatic stress disorder (PTSD). Structural abnormalities in PTSD found with MRI include nonspecific white matter lesions and decreased hippocampal volume. These abnormalities may reflect pretrauma vulnerability to develop PTSD, or they may be a consequence of traumatic exposure, PTSD, and/or PTSD sequelae. Functional neuroimaging symptom provocation and cognitive activation paradigms using PET measurement of regional cerebral blood flow have revealed greater activation of the amygdala and anterior paralimbic structures (which are known to be involved in processing negative emotions such as fear), greater deactivation of Broca's region (motor speech) and other nonlimbic cortical regions, and failure of activation of the cingulate cortex (which possibly plays an inhibitory role) in response to trauma-related stimuli in individuals with PTSD. Functional MRI research has shown the amygdala to be hyperresponsive to fear-related stimuli in this disorder. Research with PET suggests that cortical, notably hippocampal, metabolism is suppressed to a greater extent by pharmacologic stimulation of the noradrenergic system in persons with PTSD. The growth of knowledge concerning the anatomical and neurochemical basis of this important mental disorder will hopefully eventually lead to rational psychological and pharmacologic treatments.

Brain↗
PubMed2001

Use trends and geographic variation in neuroimaging: nationwide medicare data for 1993 and 1998.

BACKGROUND AND PURPOSE: Powerful tools, including CT and MR imaging, have revolutionized neuroimaging. These are routinely used, but the extent and variation of use has not been studied. Our purposes were to determine the use rates of MR imaging and CT (of spine, brain, or head and neck), myelography, conventional angiography, and MR angiography in diagnosing neurologic disorders; to study trends in use; and to determine regional variations in use. METHODS: We used the National Part B Medicare Database for 1993 and 1998 to compare rates of use for these procedures in 10 geographic regions. RESULTS: In 1993 and 1998, respectively, 13,897 and 19,431 (39.8% increase) neuroimaging procedures were performed per 100,000 Medicare beneficiaries nationwide. Use of brain or head and neck CT (30.4%) and MR imaging (43.6%), spinal CT (3.5%) and MR imaging (83.0%), myelography (56.6%), and conventional angiography (24.3%) increased in 1998 versus 1993. Increases in MR angiography were not assessed, because this procedure was not reimbursable in 1993. Regional use of brain or head and neck and spinal CT and MR studies varied considerably; ratios of highest and lowest rates were 1.38-1.56. Use of MR angiography, myelography, and conventional angiography varied three- to fourfold. CONCLUSION: Use of MR and CT studies of the brain or head and neck and of the spine increased considerably in the Medicare population between 1993 and 1998. Use of conventional invasive procedures such as myelography and angiography increased strikingly, contrary to the expected decline. Regional use varied substantially.

Angiography↗
PubMed2002

Open access neuroimaging for general practitioners--diagnostic yield and influence on patient management.

This study assessed the first year of a regional general practitioner (GP) open-access neuroimaging service, to determine diagnostic yield and influence on patient management. Overall, 48.1% of examinations demonstrated a radiologically significant abnormality with 64.1% of spinal imaging examinations demonstrating significant findings. Utilised appropriately, a regional open-access neuroimaging service has good diagnostic yield and may influence the management of most referred patients.

Brain Diseases↗
PubMed2002

Neuroimaging of NREM sleep in primary insomnia: a Tc-99-HMPAO single photon emission computed tomography study.

STUDY OBJECTIVES: The objectives of this study were to: 1) demonstrate the feasibility of combining polysomnography and SPECT neuroimaging to study NREM sleep in primary insomnia and 2) evaluate possible functional CNS abnormalities associated with insomnia. DESIGN: Patients with insomnia and good sleeper controls were studied polysomnographically for three nights with a whole brain SPECT Scan of NREM sleep on Night 3. Groups were screened for medical/psychiatric history, substance use, and matched on age, body mass index, and education. SETTING: Sleep Research Laboratory and Nuclear Medicine Center PARTICIPANTS: Nine females, 5 patients with chronic psychophysiologic insomnia and 4 healthy good sleepers (mean age 36 years, SD 12, range 27-55). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Tomographs of regional cerebral blood flow during the 1st NREM sleep cycle were successfully obtained. Contrary to our expectations, patients with insomnia showed a consistent pattern of hypoperfusion across all 8 pre-selected regions of interest, with particular deactivation in the basal ganglia (p=.006). The frontal medial, occipital, and parietal cortices also showed significant decreases in blood flow compared to good sleepers (p<.05). Subjects with insomnia had decreased activity in the basal ganglia relative to the frontal lateral cortex, frontal medial cortex, thalamus, occipital and parietal cortices (p<.05). CONCLUSIONS: This study demonstrated the feasibility of combining neuroimaging and polysomnography to study cerebral activity in chronic insomnia. These preliminary results suggest that primary insomnia may be associated with abnormal central nervous system activity during NREM sleep that is particularly linked to basal ganglia dysfunction.

Adult↗
PubMed2002

[Investigation of the dopamine dysregulation hypothesis of schizophrenia with neuroimaging techniques].

The most elaborated biochemical concept of schizophrenia is the dopamine hypothesis. However, this classical theory is based on indirect observations. It has recently become possible to study this theory directly by means of advanced functional neuroimaging techniques, the development of specific radioligands and study protocols that are eligible to monitor dynamic changes in the neurotransmitter systems. According to the early concept, the essence of schizophrenia is the hyperactivity of the dopamine system. Nevertheless, this idea has gone through many modifications. In accordance with the modified dopamine hypothesis, the cognitive deficit and negative symptoms are related to the hypoactivity of the dorsolateral prefrontal cortex while the acute phases of the disease associates with hyperactivity of the ventral striatal elements of the dopaminergic system. Between these dysfunctions there is causality via their exuberant connections. Beyond that, the interactions between the prefrontal and striatal anomalies implicate the involvement of other neurotransmitters than dopamine. Observations from model psychosis induced by N-methyl-D-aspartate antagonists and in vivo neuroimaging investigations in humans support primarily the role of glutamatergic system. Our developing knowledge about the neurochemical mechanism of schizophrenia can significantly affect therapeutic strategies as well.

Amphetamine↗
PubMedDate not supplied

[Transient ischemic attacks: risk factors, duration and neuroimaging in a series of 173 patients].

INTRODUCTION: The appearance of transient ischemic attacks (TIA) is an important sign of vascular risk. The maximum time the deficit lasts has been set arbitrarily at 24 hours. It is assumed that TIA does not entail permanent vascular lesions. PATIENTS AND METHODS: A retrospective review of the clinical records of patients diagnosed as suffering from TIA in our centre between 1996 and 1997. Analysis of associated risk factors (RF), duration and findings in neuroimaging. RESULTS: The clinical records of 173 patients (106 males) were examined. The RF identified were similar to those described for ischemic strokes. 45.6% of patients with a history of vascular pathologies received no preventative treatment. 58% of the TIA were resolved within the first 30 minutes and 71% within the first hour. Cranial CT was normal in 69%, showed old lesions in 26% and lesions that were compatible with the clinical signs of TIA in 5% (in the latter case the duration of the episodes was greater). CONCLUSIONS: TIA shares the same RF and aetiopathogenic mechanisms as ischemic stroke and should, therefore, be considered as such. There is a need to revise the concept of TIA paying special attention to the findings of neuroimaging or to establish duration limits that are better matched to the practical reality. TIA maintains a practical interest since it provides a simple method of identifying patients with a high vascular risk.

Aged↗
PubMed2002

[Neural areas of emotions in normal and brain pathology assessed by functional neuroimaging methods].

The investigation into neural back-ground of emotions in normal and brain pathology using functional brain imaging techniques (fMRI, PET, SPECT) remains one of the most interesting scientific challenges in the area of psychiatry. The aim of the current study is: 1) to present the recent neuroimaging findings concerning functioning of "emotional brain" in normal and brain pathology with particular emphasis on psychiatric disorders, 2) to consolidate knowledge of neuroimaging techniques and experimental designs used in the assessment of human affect.

Adult↗
PubMed2000

Episodic memory meets working memory in the frontal lobe: functional neuroimaging studies of encoding and retrieval.

Recent functional-neuroimaging studies have provided a wealth of new information suggesting that regions of the prefrontal cortex play a role in episodic memory encoding and retrieval. This review seeks to evaluate the results of these studies in the context of one general model that has proposed that the left prefrontal cortex is preferentially involved in episodic memory encoding, whereas the right prefrontal cortex is preferentially involved in episodic memory retrieval, irrespective of the type (e.g., modality) of information being remembered. The origins of this framework are considered in some detail and then all relevant functional-neuroimaging studies are critically reviewed. The results of this review fail to provide support for the functional-asymmetry model, suggesting instead that episodic memory encoding and retrieval may actually involve similar regions of the lateral prefrontal cortex when all factors relating to the type of stimulus material (i.e., modality), are appropriately controlled.

Brain Mapping↗
PubMed2003

Comparative evaluation of concomitant structural and functional neuroimages in Rasmussen's encephalitis.

BACKGROUND AND PURPOSE: Rasmussen's encephalitis (RE) is a rare condition of unknown cause characterized by intractable seizures, progressive hemiparesis, mental impairment, and inflammatory histological findings in the cortex. The primary diagnosis is based on biopsy to confirm the typical clinical, electroencephalography, and brain imaging findings. The main objective of this study was to compare simultaneous structural and functional neuroimages in RE. METHODS: Concomitant magnetic resonance imaging and 2-deoxy-2-[18F]-fluoro-D-glucose positron emission tomography data from the authors' series of 5 children and 8 patients described in the literature were analyzed and compared. RESULTS: Typical early findings of RE include metabolic abnormalities (hypermetabolism and hypometabolism) starting in the frontal or temporal regions or, occasionally, involving the whole hemisphere. Focal abnormalities of cerebral glucose metabolism indicate lesions sooner and depict their extent better than concomitant magnetic resonance images. The major structural abnormality remains unilateral; however, contralateral frontal lobe hypometabolism or crossed cerebellar diaschisis can be a finding of this disease. Basal ganglia involvement and whole hemispheric metabolic abnormality appear typically only after several months of disease onset. CONCLUSION: Concomitant structural and functional neuroimaging provide possibly complementary information in the early noninvasive workup of RE and may facilitate the early diagnosis of this rare disorder.

Adolescent↗
PubMed1995

Neuropsychological outcome and quantitative neuroimaging in mild head injury.

Four cases of well-documented mild traumatic brain injury (Glasgow Coma scores > or = 13) in whom preinjury neuroimaging studies were available (three with computerized tomography and one with magnetic resonance [MR] imaging) were examined in terms of postinjury MR imaging and neuropsychological outcome. All scans were subjected to quantitative analysis by measuring ventricular volumes and calculating a ventricle-to-brain ratio. Since ventricular measurements provide an index of parenchymal integrity, any systematic increase in postinjury ventricle size would be an indication of tissue loss. In addition to using the preinjury scan for a within-subject design in comparing postinjury changes, similar MR measures were obtained on a group of medical controls. Despite neuropsychological findings that suggested significant sequelae, quantitative postinjury MR studies did not show differences between preinjury neuroimaging or medical control subjects.

Clinical Conference↗