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At least 919 records · Page 51Linked to original sources
PubMed2000

[Neuroimaging and functional analyses for multiple sclerosis].

For neuroimaging studies of multiple sclerosis(MS) lesions, magnetic resonance imaging (MRI) is most useful, while evoked potentials(EPs) are commonly used for functional analyses of neural damage due to MS. This review summarizes the MRI and EP findings in MS. MS lesions are visualized as high signal intensity lesions on T2-weighted images, proton density(PD)-weighted images, and fluid-attenuated inversion recovery(FLAIR) images, while such lesions demonstrate a low signal on T1-weighted images. New MS lesions are usually enhanced by gadolinium-DTPA on T1-weighted images, and the enhancement generally lasts 4 to 8 weeks. In Asian patients with MS, opticospinal MS(Asian-type MS) shows a significantly smaller numbers of brain MRI lesions than conventional MS(Western-type MS), while opticospinal MS shows a significantly higher frequency of the spinal cord atrophy on MRI than conventional MS. EPs are useful for detecting lesions located in certain portions of the central nervous system. MRI is not sensitive enough to detect small lesions in the optic nerves and spinal cord, whereas EPs are sensitive for optic nerve and spinal cord lesions. Thus, combined use of MRI and EPs is required for the diagnosis and the optimal monitoring of disease activity in MS.

Contrast Media↗
PubMed2000

New directions in PET neuroimaging for neocortical epilepsy.

Our results and those of others demonstrate that the development of new PET probes with increasing sensitivity and specificity for epileptogenic brain regions is feasible. Further development of novel tracers guided by knowledge of the biochemical characteristics of epileptogenic cortex from basic studies is the logical next step in the application of neuroimaging to localize epileptogenic cortex. Furthermore, computational advances allowing coregistration of biochemical images with high-resolution MRI anatomic images, as well as electrophysiologic data sets, not only has practical value in guiding surgical resection of epileptogenic neocortex, but this approach contributes to further understanding of the biochemical mechanisms involved in the pathophysiology of neocortical epilepsy.

Epilepsy↗
PubMed2000

[The pathophysiology of migraine: insights from functional neuroimaging].

Over the last 20 years, functional neuroimaging has led to major advances in the understanding of the pathophysiology of migraine. The migraine aura is characterized by the occurrence of an hypoperfusion of moderate intensity which is peculiar by its initial appearance in the posterior cortex and its anterior spread at a speed of about 2 to 3mm per minute, congruent with the migrainous march of neurologic deficit and reminiscent of the phenomenon of cortical spreading depression described in the laboratory animal after various neuronal aggressions. The hypoperfusion is followed by a phase of long-lasting hyperperfusion temporally dissociated from the headache, which seems rather to result from vasodilatation and inflammation of the extra-cerebral large vessels. Although this sequence of hypoperfusion followed by hyperperfusion would be consistent with an ischemic process, there is presently no formal argument in favour of such a process being operational in migraine aura. It is however possible that migrainous subjects are genetically susceptible to the development of some unknown process at the borderline between spreading depression and classic ischemia. In migraine without aura, the data indicate only rare and mild changes in brain perfusion, although there also exist isolated observations of pauci-symptomatic spreading bilateral hypoperfusion. Physiologic imaging has also documented the occurrence during migraine without aura of a dorsal mesencephalic activation in the vicinity of the raphé and the locus coeruleus, independent of the pain itself and which might represent the long sought-after "migraine generator". It remains unknown if this phenomenon is also present in migraine with aura. The main prevalent hypotheses attempting a synthesis of all the available data are briefly presented in the conclusion.

Brain↗
PubMed2001

[Neuroimaging and electrophysiological study in epilepsy].

There exist various morphological and biochemical changes closely associated with electrophysiological phenomena which cause epileptic seizures in the brains of epilepsy patients. Recent developments in investigation methods, not only electrophysiological(EEG and MEG), but also neuroimaging involving morphological imaging(CT and conventional MRI) and functional imaging(SPECT, PET, functional MRI and MRS) is able to demonstrate these changes. SPECT and PET can particularly clarify the changes of cerebral blood flow and glucose metabolism between interictal and ictal periods. In our experience of 423 patients who underwent epilepsy surgery for intractable seizures, these interventions provide important information to identify the epileptogenic foci. However, in practice, discordance in the results of these presurgical evaluations is recognized, and invasive intracranial recordings are needed in such cases. These problems in diagnosis were shown especially in patients with mesial temporal sclerosis and focal cortical dysplasia. To detect an epileptogenic focus more clearly, a combination of morphological and functional findings, new functional imaging such as neurotransmitter receptor imaging, EEG-triggered or neuropharmacological functional MRI, as well as, statistical parametric analysis may be needed.

Electroencephalography↗
PubMedDate not supplied

[Neuroimaging in multiple sclerosis].

INTRODUCTION: Multiple sclerosis is currently considered to be a destructive disorder, and a certain degree of alteration in immunity is considered to occur in genetically susceptible persons. DEVELOPMENT: Magnetic resonance (MR) has become the basic technique for diagnosis and evaluation of the response to treatment. The key factor in the information obtained form MR images is the water content. There are several technical situations to be taken into account when using MR in multiple sclerosis: phase T1, phase T2, FLAIR, phase T1 with gadolinium, MR with spectroscopy, cerebral parenchymatous fraction and magnetization transfer MR. Apart from magnetic resonance, immunological changes of multiple sclerosis are seen in the CSF in over 50% of the patients with the disorder. Use of evoked potentials, with the important advantage of detecting lesions not visible on MR and asymptomatic lesions, may also be useful for establishment of the diagnosis. CONCLUSION: In this article we describe the use of neuroimaging in the diagnosis of multiple sclerosis.

Autoimmune Diseases↗
PubMed2001

[Neuroimaging study with morphometric analysis of hereditary and idiopathic ataxia].

BACKGROUND: Hereditary and idiopathic ataxias are neurodegenerative disorders affecting diverse neuronal systems, particularly the cerebellum and its tracts. They are currently classified according to clinical and genetic criteria. Neuroimaging is a useful tool to help diagnosis but studies using quantitative methodology are scarce. OBJECTIVE: To apply digital morphometry to cerebral MRI and define objective patterns for clinical evaluation and follow up. PATIENTS AND METHODS: The study was carried out on 48 patients of whom 17 were Friedreich ataxia (FA), 6 non-Friedreich early onset spinocerebellar ataxia (EOCA), 9 autosomal dominant cerebellar ataxia type 1 (ADCA 1), 7 ADCA 3 and 9 idiopathic late onset cerebellar ataxia (ILOCA); 35 controls were grouped on early (< 30 years-old) and late age. Morphometric measures were done on previously selected MRI planes by image analyser digital software. RESULTS: Six out of 21 measurements and 3 ratios were significantly discriminant. By categories, the structures mainly involved were as follows: atrophy of cervical spinal cord (p = 0.001), cerebellum (p = 0.038) and protuberance (p = 0.002) in FA; atrophy of spinal cord (p = 0.009), cerebellum (p = 0.035) and widening of IV ventricle (p = 0.044) in EOCA; shrinkage of protuberance (p = 0.009), middle cerebellar peduncles (p = 0.004) and spinal cord atrophy (p = 0.001) in ADCA 1; cerebellar atrophy (p = 0.041) in ADCA 3; and cerebellar atrophy (p = 0.041) and shortening of middle cerebellar peduncles (p = 0.038) in ILOCA. CONCLUSIONS: This quantitative morphometric study confirms the existence of different pattern of cerebral involvement that is closely related with the distints clinical forms of hereditary and idiopathic ataxias. Only a few measurements can be used to obtain a morphometric profile for diagnostic and follow up purposes.

Adult↗
PubMed2001

Facial pain: from animal models to functional neuroimaging studies.

This paper summarizes some recent findings on the physiopathology of facial pain. Over the past decade, a number of animal models of facial pain have been developed. Two of these models are discussed in more detail. The model developed by Strassman and Burstein has provided a useful tool for the study of the mechanisms underlying migraine. Single unit recordings revealed that medullary dorsal horn neurons show a long-lasting increased response to dural and cutaneous periorbital mechanical and thermal stimulation after application of inflammatory agents to the dura. In addition, dural and cutaneous receptive fields largely expanded and spontaneous ongoing activity developed. These findings suggest that the extracranial hypersensitivity that is often observed in headache may have an intracranial origin. The second model that is discussed is the model of facial neuropathic pain after infraorbital nerve ligation developed by Vos and colleagues. In contrast to the previous model which is an acute electrophysiological preparation, the infraorbital nerve model is a behavioural model. It can therefore be used both for electrophysiological and behavioural studies. In recent years, a number of functional neuroimaging studies of facial pain appeared. Studies performed in cluster headache patients seem to point to a crucial role of the hypothalamus in this syndrome. However, since hypothalamic activation has also been reported in some other types of (facial) pain, the specificity of the role of the hypothalamus in cluster headache remains to be proven.

Animals↗
PubMed2001

Interactions among neuronal systems assessed with functional neuroimaging.

Cortical organisation is based on the principles of functional specialisation and functional integration. Those two concepts exist at multiple spatial scales. For example at a macroscopic level, functionally segregated areas V1 and V5 are integrated within the dorsal visual stream. At a microscopic level, it is possible to infer the functional integration of (segregated) ocular dominance columns within area V1. At the macroscopic level functional specialisation and integration can be tested with functional neuroimaging, using fMRI/PET or EEG/MEG. A framework that allows making inferences on functional integration between brain regions using fMRI will be presented. The common feature of all techniques within that framework is that they can incorporate second order terms and therefore explicitly allow for contextual modulations. Two examples demonstrate how attention and paired associates learning can modulate effective connectivity within the visual system. Furthermore these models can incorporate non-linear modulatory (feedback) connections that can account for the changes in effective connectivity observed.

Attention↗
PubMedDate not supplied

[Relation of the cerebellum with cognitive function: neuroanatomical, clinical and neuroimaging evidence].

INTRODUCTION: Published studies in the last decades, employing a variety of methodologies, suggest that the cerebellum function is not only limited to motor control but also has an important role in cognition and emotion. DEVELOPMENT: In the present paper we review the main neuroanatomical and functional neuroimaging studies supporting the idea that the cerebellum has a role in non motor behavior. On the other hand, we expound the results of the neuropsychological studies of patients with cerebellar lesions. The deficits showed after cerebellar lesions include disturbances in executive functions, learning, memory, attention, visuo-spatial functions, language and personality change. Some studies propose that the cerebellum, through its afferent and efferent circuits with the cerebrum, perform a global function capable to influencing motor behavior, in cognitive functions and in emotion. A fault in this function would cause the behavioral deficits shown in patients with cerebellar lesions. CONCLUSION: The evidence available in the anatomical, functional and clinical studies support the conclusion that the cerebellum participates not only in motor functions, but also in cognitive functions and in emotion.

Brain↗
PubMed2001

[Creutzfeldt-Jakob disease with unilateral onset: clinical profile and neuroimaging].

The usual clinical profile of Creutzfeldt-Jakob disease (CJD) is that of subacute dementia and intractable myoclonus. Occasionally, some cases present peculiar clinical features. We report on a case of CJD with an unilateral onset showing remarkable neuroimaging features. The patient, aged 72 years, began to suffer from sudden anomia, initially restricted to persons; but in a few weeks it evolved into a global aphasia, right hemiparesis, severe gait disorder, and finally akinetic mutism and intractable myoclonus. He died 11 weeks after onset. Early in the course, an analysis of 14-3-3 protein in CSF was positive. In advanced disease, the EEG showed the typical periodic activity of CJD. FLAIR MRI study showed a mesencephalic and focal cortical hyperintensity. Autopsy was performed and confirmed the diagnosis of CJD with an extensive presence of generalised spongiosis in cerebral grey matter. This case illustrates the usefulness of the life recent paraclinical methods to diagnose CJD in life. New MRI techniques seems to be particularly relevant, as they are not limited to exclude other conditions but can also offer data with validity to a positive diagnosis, like grey matter hyperintensity, that in this case was present also in the midbrain.

14-3-3 Proteins↗
PubMed2002

Neuroimaging in pediatric brain tumors: Gd-DTPA-enhanced, hemodynamic, and diffusion MR imaging compared with MR spectroscopic imaging.

BACKGROUND AND PURPOSE: Gadolinium-enhanced MR images assist in defining tumor borders; however, the relation between tumor cell extent and contrast-enhanced regions is unclear. Our aim was to improve conventional neuroimaging of pediatric brain tumors with hemodynamic, diffusion, and spectroscopic MR imaging. METHODS: We performed conventional MR and MR spectroscopic imaging in 31 children with neuroglial brain tumors. Hemodynamic MR imaging was performed in 16 patients with a first-pass intravenous bolus of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA); apparent diffusion coefficients (ADCs) were measured in 12 patients. To account for multiple measurements in a patient, we used a nested analysis of variance. RESULTS: At MR spectroscopy, choline (Cho)-containing compounds (indicating tumor) and lipid levels (indicating necrosis) did not correlate with percent Gd-DTPA enhancement on MR images. Percent enhancement was positively correlated with relative cerebral blood volumes (rCBVs) (P =.05) and negatively correlated with ADCs (P <.001). Stepwise multiple linear regression revealed that rCBV (P =.008), ADC (P =.022), and lipid (P <.001) levels were significant independent predictors of percent enhancement. Tumor spectral patterns were detected in tumor regions and outside enhancing tumor beds in patients with clinical progression; these were confirmed at neuropathologic analysis. CONCLUSION: MR spectroscopic imaging improves the assessment of pediatric brain tumors by adding biochemical information regarding tumor involvement and by depicting residual or recurrent tumor outside the Gd-DTPA-enhanced tumor bed. rCBV and ADC mapping complemented MR spectroscopic imaging. We recommend the use of MR spectroscopic imaging in addition to conventional MR imaging in assessing pediatric brain tumors.

Adolescent↗
PubMedDate not supplied

[Neuroimaging features associated with AIDS].

Due to the nonspecific clinical presentation of Central Nervous System disorders that may come out during the course of Human Immunodeficiency Virus infection, we emphasize the importance of neuroimaging on the differential diagnosis of these situations. Review and illustration of the most typical imaging patterns of the main Central Nervous System disorders in Acquired Immunodeficiency Syndrome.

Acquired Immunodeficiency Syndrome↗
PubMed2002

[Neuroimaging and neurochemical studies of Rett syndrome].

We review here the current status of neuroimaging and neurochemical research on Rett syndrome (RTT), with reference to neurophysiological, neuropathological, and immuno-histochemical changes previously described. Abnormalities have been reported in the intermediates of the biogenic amine neurotransmitters/receptor systems, and of beta-phenylethylamine (PEA), an endogenous amine synthesized by the decarboxylation of phenylalanine in dopaminergic neurons of the nigrostratal system. We also discuss the roles of other neurotransmitters including beta-endrophin, substance P and neurotrophic factors including nerve growth factors. Recently, mutations in the gene encoding methyl-CpG binding protein 2 (MeCP2), mapped to Xq28, have been identified in patients with RTT. Multiple abnormalities in various neurotransmitter/receptor systems may accounts for the pervasive defects in RTT.

Biogenic Amines↗
PubMed2002

Neuroimaging and obesity: mapping the brain responses to hunger and satiation in humans using positron emission tomography.

The hypothalamus has a major role in the control of food intake. However, neurotracing studies have shown that the hypothalamus receives input from several other regions of the brain that are likely to modulate its activity. Of particular interest to the understanding of human eating behavior is the possible involvement of the cortex. Using positron emission tomography (PET), we generated functional brain maps of the neuroanatomical correlates of hunger (after a 36-h fast) and satiation (after oral administration of a liquid formula meal) in lean and obese subjects. Results in lean individuals indicate that the neuroanatomical correlates of hunger form a complex network of brain regions including the hypothalamus, thalamus, and several limbic/paralimbic areas such as the insula, hippocampal/parahippocampal formation, and the orbitofrontal cortex. Satiation was associated with preferentially increased neuronal activity in the prefrontal cortex. Our studies also indicate that the brain responses to hunger/satiation in the hypothalamus, limbic/paralimbic areas (commonly associated with the regulation of emotion), and prefrontal cortex (thought to be involved in the inhibition of inappropriate response tendencies) might be different in obese and lean individuals. In conclusion, neuroimaging of the human brain is proving to be an important tool for understanding the complexity of brain involvement in the regulation of eating behavior. PET studies might help to unravel the neuropathophysiology underlying human obesity.

Adolescent↗
PubMedDate not supplied

[Dementia with frontal lobe atrophy: clinical study from 18 patients with cognitive impairment and frontal lobe involvement detected by structural and functional neuroimaging].

OBJECTIVE: To characterize clinically patients with cognitive impairment and frontal lobe degeneration at neuroimaging. PATIENTS AND METHODS: Patients diagnosed of dementia or mild neurocognitive impairment by DSM IV criteria and neuropsychological tests with frontal lobe atrophy and hipoperfusion detected by computed tomography and single photon emission computed tomography. RESULTS: 18 patients, 5:1 on behalf of women; mean age at onset, 74 years; hereditary for dementia, 38%; mean duration of illness at first testing, 2 years; the most common initial symptoms, memory loss. At initial examination, psychotic or behavioral impairment was found in 61% and parkinsonism in 38%, the commonest cognitive troubles at this moment was the executive function, language and anterograde memory dysfunctions at the same rate. Frontal lobe atrophy and hypoperfusion was found in 100%, temporal in 88% and parietal in 38%. Electroencephalogram was pathological in 33%. The course of the disease was progressive but with fluctuation in 27%. Frontotemporal dementia clinical criteria in 13 patients, 4 of them clinical criteria of dementia with Lewy bodies too, and clinical criteria of Alzheimer s disease in 5.

Aged↗
PubMedDate not supplied

Are behaviour and motor performances of rheumatoid arthritis patients influenced by subclinical cognitive impairments? A clinical and neuroimaging study.

OBJECTIVE: To determine whether some behavioural manifestations and poor motor performances in patients affected by rheumatoid arthritis (RA) are due to subclinical cognitive defects. METHODS: We performed a psychometric assessment of 30 patients affected by RA exploring several cognitive domains such as memory, visual-spatial integration, motor planning, mental flexibility, relating performances with morphological and functional neuroimaging (MRI and SPECT). We also related the cognitive data with the Ritchie and Lee indexes and other clinical parameters. RESULTS: We found an impairment in visual-spatial tasks in 71% of patients with a high correlation to activity and disease severity as expressed by the Ritchie and Lee indexes (p < 0.005; p < 0.01). Furthermore, we detected in 38% of patients some difficulties in mental flexibility related to the Lee Index (p < 0.05). These poor performances are related to hypoperfusion of the frontal and parietal lobes as detected by brain SPECT; this finding is more evident in patients with brain white matter alterations on MRI. CONCLUSIONS: Our data allow us to hypothesize that manual dexterity could be due to a disconnection between subcortical white matter and parietal-frontal lobes because of microangiopathy; furthermore, a chronic reduction in sensorial stimuli by impaired joints could lead to produce an alteration in motor planning cognitive processes.

Adult↗
PubMedDate not supplied

Schizencephaly: correlation between clinical and neuroimaging features.

Schizencephaly is an uncommon congenital brain malformation. We report our experience of 13 patients with schizencephaly and evaluate the clinical, neuroradiologic, electroencephalographic (EEG), and nosological features. Of these 13 patients, 8 were unilateral forms, 5 were bilateral forrms and 11 were open-lip type schizencephaly. One patient was proven to have cytomegalovirus (CMV) infection. The clinicalfeatures and neurodevelopmental outcomes are variable. Although seizure developed in 9 patients (5 patients from unilateral and 4 from bilateral forms), the severity of epilepsy was not totally related to the degree of malformations. The neurodevelopmental outcome depended on the extent of schizencephaly as well as the seizure control. Those with bilateral forms and intractable seizures had the worst outcome. Other central nervous system (CNS) anomalies were observed in 11 patients. Six out of 11 patients had focal cortical dysplasia. We conclude that children with schizencephaly usually have variable neurological impairment. Earlier diagnosis of schizencephaly and related CNS malformation with neuroimaging is helpful in predicting the neurodevelopmental outcomes in these patients.

Adolescent↗
PubMed2002

Neuroimaging reveals automatic speech coding during perception of written word meaning.

The extent to which visual word perception engages speech codes (i.e., phonological recoding) remains a crucial question in understanding mechanisms of reading. In this study, we used functional magnetic resonance imaging techniques combined with behavioral response measures to examine neural responses to focused versus incidental phonological and semantic processing of written words. Three groups of subjects made simple button-pressing responses in either phonologically (rhyming-judgment) or semantically (category-judgment) focused tasks or both tasks with identical sets of visual stimuli. In the phonological tasks, subjects were given both words and pseudowords separated in different scan runs. The baseline task required feature search of scrambled letter strings created from the stimuli for the experimental conditions. The results showed that cortical regions associated with both semantic and phonological processes were strongly activated when the task required active processing of word meaning. However, when subjects were actively processing the speech sounds of the same set of written words, brain areas typically engaged in semantic processing became silent. In addition, subjects who performed both the rhyming and the semantic tasks showed diverse and significant bilateral activation in the prefrontal, temporal, and other brain regions. Taken together, the pattern of brain activity provides evidence of a neural basis supporting the theory that in normal word reading, phonological recoding is automatic and facilitates semantic processing of written words, while rapid comprehension of word meaning requires devoted attention. These results also raise questions about including multiple cognitive tasks in the same neuroimaging sessions.

Adult↗