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1.
J Neurol Sci ; 368: 402-7, 2016 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-27538672

RESUMO

BACKGROUND: 4-aminopyridine (4-AP) is a potassium-channel blocker able to enhance walking speed in MS improving the action potentials of demyelinated axons on which internodal potassium channels are exposed. OBJECTIVE: to study early 4-AP effect with clinical, subjective, neurophysiological and neuroradiological tools. METHODS: Clinical (Timed 25-Foot Walk - T25FW, Timed Up-And-Go - TUG), subjective (MS Walking Scale-12 - MSWS-12), neurophysiological (Motor Evoked Potentials - MEPs) and imaging (Diffusion Tensor Imaging - DTI) evaluations were performed before (T0) and after (T1) 14days of 4-AP treatment. MEPs were recorded from Abductor Hallucis of both legs. A Tract-Based-Spatial-Statistics (TBSS) was performed on DTI. RESULTS: We found a significant difference between T0 and T1 for T25FW, TUG, MSWS-12 (p≤0.001) in the whole patients' sample (23 subjects, median EDSS 6.0) and decrease of Central Motor Conduction Time and increase of mean Amplitude (Amp) at T1 (p=0.008 and p=0.006). We also recorded a significant difference of T25FW, TUG, MSWS-12 and Amp in clinical responder (CR) patients (CR: amelioration >20% at T25FW). TBSS showed a significant Mean and Radial Diffusivity reduction in the corticospinal tracts (p<0.05) of the whole group of patients; this reduction was also found in the CR subgroup. CONCLUSION: Neurophysiological and neuroradiological parameters were modified in MS patients treated with 4-AP, and most of them reported a subjective improvement of their motor performances after treatment. The use of clinical, subjective, neurophysiological and neuroradiological tools could help to better explore MS patients responsiveness to 4-AP.


Assuntos
4-Aminopiridina/uso terapêutico , Esclerose Múltipla/tratamento farmacológico , Avaliação de Resultados em Cuidados de Saúde/métodos , Bloqueadores dos Canais de Potássio/uso terapêutico , Adulto , Imagem de Tensor de Difusão , Potencial Evocado Motor/efeitos dos fármacos , Teste de Esforço , Feminino , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Esclerose Múltipla/diagnóstico por imagem , Esclerose Múltipla/fisiopatologia , Índice de Gravidade de Doença , Estatística como Assunto , Estatísticas não Paramétricas , Estimulação Magnética Transcraniana , Caminhada/fisiologia
2.
Eur J Neurol ; 23(3): 605-12, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26616102

RESUMO

BACKGROUND AND PURPOSE: Previous studies have demonstrated that individuals suffering from disorder of consciousness (DOC) maintain some minor neural processing of percepts mediated by senses that early in their pathway intersect the thalamus, a key dysfunctional area in DOC patients. Here the degree of sensory preservation within the olfactory system, a system that lacks an obligatory thalamic relay, and its relationship to the consciousness level in DOC patients of various etiologies was assessed. METHODS: Clinical Coma Recovery Scale - Revised (CRS-R) as well as cerebral responses to odors by means of functional magnetic resonance were obtained in a group of vegetative state/unresponsive wakefulness syndrome (n = 26) patients, minimally conscious state (n = 7) patients and healthy controls (n = 25). RESULTS: A majority of vegetative state/unresponsive wakefulness syndrome patients (58%) and 100% of minimally conscious state patients demonstrated a significant preservation of olfactory neural processing, manifested by activation within the piriform cortex, an area considered as a primary olfactory region. Degree of preservation of olfactory processing differed linearly in line with the patients' etiologies where groups demonstrating greater conscious awareness demonstrated more significant processing. Viewed over all DOC patients, there was a significant negative association between odor-related activity in the orbitofrontal cortex and CRS-R scores. CONCLUSIONS: It is demonstrated that DOC patients exhibit a significant preservation of olfactory neural processing with a clear relationship to etiopathologies and clinical measures even years after of chronification of DOC.


Assuntos
Transtornos da Consciência/fisiopatologia , Percepção Olfatória/fisiologia , Córtex Piriforme/fisiopatologia , Adulto , Coma/fisiopatologia , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Adulto Jovem
3.
J Neurooncol ; 126(2): 279-88, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26468137

RESUMO

MRI grading of grade II and III gliomas may have an important impact on treatment decisions. Occasionally,both conventional MRI (cMRI) and histology fail to clearly establish the tumour grade. Three cMRI features(no necrosis; no relevant oedema; absent or faint contrast enhancement) previously validated in 196 patients with supratentorial gliomas directed our selection of 68 suspected low-grade gliomas (LGG) that were also investigated by advanced MRI (aMRI), including perfusion weighted imaging (PWI), diffusion weighted imaging(DWI) and spectroscopy. All the gliomas had histopathological diagnoses. Sensitivity and specificity of cMRI preoperative diagnosis were 78.5 and 38.5 %, respectively, and 85.7 and 53.8 % when a MRI was included, respectively. ROC analysis showed that cut-off values of 1.29 for maximum rCBV, 1.69 for minimum rADC, 2.1 for rCho/Cr ratio could differentiate between LGG and HGG with a sensitivity of 61.5, 53.8, and 53.8 % and a specificity of 54.7, 43 and 64.3 %, respectively. A significantly longer OS was observed in patients with a maximum rCBV<1.46 and minimum rADC>1.69 (80 vs 55 months, p = 0.01; 80 vs 51 months, p = 0.002, respectively). This result was also confirmed when cases were stratified according to pathology (LGG vs HGG). The ability of a MRI to differentiate between LGG and HGG and to predict survival improved as the number of a MRI techniques considered increased. In a selected population of suspected LGG,classification by cMRI underestimated the actual fraction of HGG. aMRI slightly increased the diagnostic accuracy compared to histopathology. However, DWI and PWI were prognostic markers independent of histological grade.


Assuntos
Neoplasias Encefálicas/mortalidade , Neoplasias Encefálicas/patologia , Glioma/mortalidade , Glioma/patologia , Imageamento por Ressonância Magnética/métodos , Gradação de Tumores/métodos , Adulto , Imagem de Difusão por Ressonância Magnética/métodos , Feminino , Humanos , Angiografia por Ressonância Magnética/métodos , Masculino , Sensibilidade e Especificidade , Análise de Sobrevida
4.
Neurol Sci ; 36 Suppl 1: 47-50, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-26017511

RESUMO

The pathophysiology of cluster headache (CH) is not well-known. For several years, the most widely accepted theory was that CH was triggered by hypothalamus with secondary activation of the trigeminal-autonomic reflex. However, it was recently suggested that the posterior hypothalamus might be an actor of the pain modulating network more involved in terminating rather than triggering attacks. To investigate this hypothesis, resting state fMRI could provide valuable information on functional connectivity between brainstem and hypothalamus, as well as other brain structures that could be involved in CH pathophysiology. In this framework, here we review recent studies investigating functional connectivity by means of resting state fMRI. Despite the important findings of these studies, we suggest that important steps in the comprehension of CH pathophysiology will be done when the scientific community will use the new methodological approaches recently suggested to study functional connectivity in the brainstem.


Assuntos
Encéfalo/irrigação sanguínea , Encéfalo/patologia , Cefaleia Histamínica/diagnóstico , Imageamento por Ressonância Magnética , Descanso , Humanos , Processamento de Imagem Assistida por Computador , Oxigênio/sangue
5.
Neuroimage Clin ; 3: 73-83, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24179851

RESUMO

In patients with temporal lobe epilepsy (TLE), assessment of language lateralization is important as anterior temporal lobectomy may lead to language impairments. Despite the widespread use of fMRI, evidence of its usefulness in predicting postsurgical language performance is scant. We investigated whether preoperative functional lateralization is related to the preoperative language performance, peri-ictal aphasia, and can predict language outcome one year post-surgery. We studied a total of 72 TLE patients (42 left, 30 right), by using three fMRI tasks: Naming, Verb Generation and Fluency. Functional lateralization indices were analyzed with neuropsychological scores and presence of peri-ictal aphasia. The key findings are:1)Both left and right TLE patients show decreased left lateralization compared to controls.2)Lateralization correlates with language performance before surgery. In left TLE, decreased left lateralization correlates with better fluency performance. In right TLE, increased left lateralization during the Naming task correlates with better naming.3)Left lateralization correlates with peri-ictal aphasia in left TLE patients.4)Lateralization correlates with language performance after surgery. In a subgroup of left TLE who underwent surgery (17 left), decreased left lateralization is predictive of better naming performance at 6 and 12 months after surgery. The present study highlights the clinical relevance of fMRI language lateralization in TLE, especially to predict language outcome one year post-surgery. We also underline the importance of using fMRI tasks eliciting frontal and anterior temporal activations, when studying left and right TLE patients.

6.
Q J Nucl Med Mol Imaging ; 56(2): 112-37, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22617235

RESUMO

Imaging plays a crucial role in the management of patients with brain tumors. The technical improvement of computed tomography (CT) and magnetic resonance (MRI) with the development of, new imaging techniques strongly improved the detection and characterization of brain tumors. For the optimal therapeutic management of the oncologic patient not only the recognition of the lesion is needed, but also the exclusion of other diseases that can mimic brain tumors. The preoperative assessment of malignancy and of relationships of the tumor with surrounding eloquent structures are also necessary to allow the correct choice of therapy and to warn surgeons of possible risks of the surgical approach. This article is an overview of the current state of neuroimaging of the most frequent brain tumors including CT and MRI, perfusion weighted imaging (PWI), diffusion weighted imaging (DWI), diffusion tensor imaging (DTI), proton magnetic resonance spectroscopy (1H-MRS) and functional MRI based on blood oxygen level (fMRI BOLD). Indeed, in the last years, a transition took place from a purely anatomy-based radiology to one that incorporates functional, hemodynamic, metabolic, cellular, and cytoarchitectural alterations. Neuroimaging has evolved into a comprehensive diagnostic tool that allows the characterization of morphologic as well as biologic alterations to diagnose and grade brain tumors and to monitor and assess treatment response and patient prognosis.


Assuntos
Neoplasias Encefálicas/diagnóstico , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Aumento da Imagem/métodos , Imageamento por Ressonância Magnética/métodos , Tomografia Computadorizada por Raios X/métodos , Humanos
7.
AJNR Am J Neuroradiol ; 33(1): 180-7, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21998099

RESUMO

BACKGROUND AND PURPOSE: The connectivity across brain regions can be evaluated through fMRI either by using ICA or by means of correlation analysis of time courses measured in predefined ROIs. The purpose of this study was to investigate quantitatively the correspondence between the connectivity information provided by the 2 techniques. MATERIALS AND METHODS: In this study, resting-state fMRI data from 40 healthy participants were independently analyzed by using spatial ICA and ROI-based analysis. To assess the correspondence between the results provided by the 2 methods, for all combinations of ROIs, we compared the time course correlation coefficient with the corresponding "ICA coactivation index." RESULTS: A strongly significant correspondence of moderate intensity was found for 20 ICA components (r = 0.44, P < .001). Repeating the analysis with 10, 15, 25, 30, 35, and 40 components, we found that the correlation remained but was weaker (r = 0.35-0.41). CONCLUSIONS: There is a significant but not complete correspondence between the results provided by ICA and ROI-based analysis of resting-state data.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/fisiologia , Interpretação de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Rede Nervosa/fisiologia , Descanso/fisiologia , Adulto , Feminino , Humanos , Aumento da Imagem/métodos , Masculino , Vias Neurais/fisiologia , Análise de Componente Principal , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Estatística como Assunto
8.
Neurol Sci ; 32(3): 473-7, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21234777

RESUMO

Hemophagocytic lymphohistiocytosis (HLH) is a rare disease with rarer neurological presentation. When this occurs, diagnosis may be delayed. This report aims to call attention to clinical, laboratory, and radiological features that should prompt the correct diagnosis. A 13-year-old girl presented with progressive increase in intracranial pressure and ataxia. MRI showed a diffuse tumor-like swelling of the cerebellum with tonsillar herniation and patchy white matter post-contrast enhancement. Regression of swelling with steroids ruled out glioma and medulloblastoma, and brain lymphoma was considered. Diagnosis of HLH was reached 2 months after onset when uncontrolled fever and severe elevation of liver enzymes occurred. Two bone marrow biopsies were needed to demonstrate hemophagocytosis. Familial HLH was confirmed by perforin gene mutations. Bone marrow transplantation was performed. The early diagnosis of HLH may be life saving. Awareness of the disease is necessary to investigate its characteristic findings, thus avoiding a delay in diagnosis.


Assuntos
Neoplasias Cerebelares/diagnóstico , Cerebelo/patologia , Erros de Diagnóstico/prevenção & controle , Linfo-Histiocitose Hemofagocítica/diagnóstico , Adolescente , Cerebelo/fisiopatologia , Diagnóstico Diferencial , Feminino , Humanos , Linfo-Histiocitose Hemofagocítica/genética , Linfo-Histiocitose Hemofagocítica/fisiopatologia
9.
Brain Topogr ; 24(1): 65-77, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21107673

RESUMO

Electrophysiological studies indicate that Unverricht-Lundborg's disease (ULD), the most common form of progressive myoclonus epilepsy in Europe, is characterized by the involvement of multiple cortical regions in degenerative changes that lead to enhanced excitation and deficient inhibition. We searched for the haemodynamic correlates of these effects using functional MRI (fMRI) of self-paced index extensions, a well-accepted task highlighting significant differences. EEG and fMRI were simultaneously acquired in 11 ULD patients and 16 controls, performing the index extensions individually (event-related task) as well as repetitively (block task). ERD/ERS analysis was performed for the EEG data in the alpha and beta bands. fMRI time-series were analyzed using the traditional general linear model, as well as with an assumption-free approach, and by means of cross-region correlations representing functional connectivity. In line with the existing literature, ULD patients had enhanced desynchronization in the alpha band and reduced post-movement synchronization in the beta band. By contrast, fMRI did not reveal any difference between the two groups; there were no activation intensity, latency or extent effects, no significant engagement of additional regions, and no changes to functional connectivity. We conclude that, so long as the patients are executing a task which does not induce obvious action myoclonus, the hypothesized abnormalities in pyramidal neuron and interneuron dynamics are relatively subtle, embodied in processes which are not metabolically-demanding and take place at a time-scale invisible to fMRI.


Assuntos
Circulação Cerebrovascular/fisiologia , Eletroencefalografia/métodos , Potenciais Evocados/fisiologia , Imageamento por Ressonância Magnética/métodos , Córtex Motor/fisiopatologia , Síndrome de Unverricht-Lundborg/fisiopatologia , Adulto , Feminino , Humanos , Masculino , Síndrome de Unverricht-Lundborg/diagnóstico , Adulto Jovem
10.
AJNR Am J Neuroradiol ; 31(4): 706-10, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19942704

RESUMO

BACKGROUND AND PURPOSE: The neostriatum is known to be affected in HD. In this work, our aim was to determine whether microstructural and volumetric alterations occur in the neostriatum of presymptomatic HD gene carriers and in patients with early-stage HD. MATERIALS AND METHODS: We studied a group of 15 presymptomatic gene carriers who were far from the estimated symptom onset (16% probability of developing the disease within 5 years), a group of 9 patients with early symptomatic HD, and 2 groups of age-matched controls. Volumetric MR imaging and DWIs were acquired, and statistical analyses were performed on the volumes of the caudate nucleus and putamen and on the corresponding MD measurements. RESULTS: Neostriatal volumes were significantly smaller in both presymptomatic HD gene carriers and symptomatic patients with respect to controls. However, whereas the diffusivity in the caudate nucleus was increased in the symptomatic patients, it was decreased in the presymptomatic gene carriers. CONCLUSIONS: Altered diffusivity and reduced volume of the caudate nucleus in presymptomatic HD gene carriers indicate that the neostriatum is affected well before the onset of symptoms. The observed initial decrease and subsequent increase of MD might be related to the combined effect of increased oligodendroglial population, putatively a developmental abnormality, and incipient neurodegeneration.


Assuntos
Núcleo Caudado/patologia , Imagem de Difusão por Ressonância Magnética/métodos , Triagem de Portadores Genéticos , Doença de Huntington/diagnóstico , Doença de Huntington/genética , Processamento de Imagem Assistida por Computador/métodos , Adulto , Diagnóstico Precoce , Feminino , Predisposição Genética para Doença/genética , Humanos , Masculino , Pessoa de Meia-Idade , Putamen/patologia , Valores de Referência
11.
AJNR Am J Neuroradiol ; 30(8): 1482-7, 2009 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-19589886

RESUMO

BACKGROUND AND PURPOSE: In progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), postmortem studies show different topographic involvement of the thalamus, basal ganglia, and their cortical connections. Diffusion tensor imaging (DTI) is an MR imaging technique sensitive to gray and white matter microstructure integrity. This study was performed to determine whether DTI may demonstrate microstructural differences between PSP and CBD, particularly within the thalamus and its cortical connections. MATERIALS AND METHODS: Nine patients with probable PSP, 11 with probable CBD, and 7 controls formed the study group. Apparent diffusion coefficient average (ADC(ave)) and fractional anisotropy (FA) values were measured in regions of interest positioned in the ventrolateral (motor), medial, anterior, and posterior regions of the thalami, basal ganglia, fronto-orbital white matter, cingulum, supplementary motor area (SMA), and precentral and postcentral gyri in patients and controls. RESULTS: In PSP, ADC(ave) values were increased in several areas: the thalamus, particularly in its anterior and medial nuclei; cingulum; motor area; and SMA. FA values were particularly decreased in the fronto-orbital white matter, anterior cingulum, and motor area. In CBD, ADC(ave) was increased in the motor thalamus, in the precentral and postcentral gyri, ipsilateral to the affected frontoparietal cortex, and in the bilateral SMA. FA was mainly decreased in the precentral gyrus and SMA, followed by the postcentral gyrus and cingulum. CONCLUSIONS: In patients with PSP, thalamic involvement was diffuse and prevalent in its anterior part, whereas in CBD involvement was asymmetric and confined to the motor thalamus. DTI may be useful in the differential diagnosis of these 2 parkinsonian disorders.


Assuntos
Córtex Cerebral/patologia , Imagem de Difusão por Ressonância Magnética/métodos , Doenças Neurodegenerativas/patologia , Paralisia Supranuclear Progressiva/patologia , Tálamo/patologia , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Vias Neurais/patologia
12.
Neurol Sci ; 30 Suppl 1: S71-4, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19415430

RESUMO

Withdrawal is the first step for treating patients with chronic migraine and medication overuse. Recent studies confirmed common elements in personality between these patients and subjects addicted; some neuroimaging researches showed that abnormalities revealed are related to a specific cerebral pattern and that they can return to the normal state after withdrawal. Aim of the study was to submit a group of patients suffering from chronic migraine and medication overuse (the diagnosis was made according to Silberstein-Lipton criteria) to a withdrawal, to evaluate by f-MRI the presence of specific cerebral patterns before treatment and their possible changes after withdrawal. f-MRI seems to be a useful technique to obtain information on particular neuronal changes of the pain network involved in this type of patients. The activated areas are congruent with some data of the literature and the data emerged are discussed according to preceding reports.


Assuntos
Analgésicos/efeitos adversos , Encéfalo/fisiopatologia , Transtornos da Cefaleia Secundários/fisiopatologia , Transtornos de Enxaqueca/fisiopatologia , Dor/fisiopatologia , Adulto , Analgésicos/uso terapêutico , Mapeamento Encefálico , Doença Crônica , Feminino , Transtornos da Cefaleia Secundários/terapia , Humanos , Imageamento por Ressonância Magnética , Transtornos de Enxaqueca/tratamento farmacológico , Medição da Dor , Limiar da Dor , Psicofísica , Síndrome de Abstinência a Substâncias/fisiopatologia
13.
AJNR Am J Neuroradiol ; 30(6): 1222-6, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19342541

RESUMO

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) offers a unique window on the connectivity changes, extending beyond the basal ganglia, which accompany the cognitive symptoms of Parkinson disease (PD). The primary purpose of this study was to assess the microstructural damage to cerebral white matter occurring in idiopathic PD. MATERIALS AND METHODS: Our sample included patients with PD without dementia (n = 10; Hoehn and Yahr stages I and II; Unified Parkinson Disease Rating Scale, 20.5 +/- 8.3; and Mini-Mental State Examination, 28.3 +/- 1.5) and age-matched healthy control subjects (n = 10). DTI was performed on a 1.5T scanner, and mean diffusivity (MD) and fractional anisotropy (FA) maps were obtained. Regions of interest (ROIs) were drawn on the major fiber bundles as well as on gray matter nuclei. RESULTS: In patients, the MD was increased at borderline significance in the substantia nigra but was unaltered in the thalamus, globus pallidus, putamen, and in the head of the caudate nucleus. The FA and MD were unaltered in the corticospinal tract in the midbrain and at the level of the internal capsule, and in the splenium of the corpus callosum. By contrast, the MD was increased and the FA was decreased in the genu of the corpus callosum and in the superior longitudinal fasciculus; in the cingulum, only the MD was altered. The observed changes were not significantly lateralized. CONCLUSIONS: Widespread microstructural damage to frontal and parietal white matter occurs already in the early stages of PD.


Assuntos
Encéfalo/patologia , Demência/complicações , Demência/patologia , Imagem de Difusão por Ressonância Magnética/métodos , Fibras Nervosas Mielinizadas/patologia , Doença de Parkinson/complicações , Doença de Parkinson/patologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Sensibilidade e Especificidade
14.
AJNR Am J Neuroradiol ; 30(6): 1134-41, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19357387

RESUMO

BACKGROUND AND PURPOSE: The hippocampus and parahippocampal gyrus have a central role in the acquisition of new memories. Although functional MR imaging (fMRI) can provide information on the functional status of these brain regions, it has not reached widespread use in the presurgical assessment of patients undergoing temporal lobectomy. We aimed to evaluate whether simple memory-encoding paradigms could be used to elicit robust activations in the hippocampus and parahippocampal gyrus and to determine the lateralization of verbal and nonverbal memory. We also studied the relative contribution of the anterior and posterior portions of these structures. MATERIALS AND METHODS: We conducted this study on 16 healthy subjects by performing event-related fMRI using 3 memory encoding tasks with words, objects, and faces. In addition to a second-level group analysis, region-of-interest (ROI)-based measurements of the signal intensity percent change and of the percentage of activated voxels, determined at 2 thresholds, were performed. ROIs were drawn on the hippocampus and parahippocampal gyrus, divided into anterior and posterior segments. RESULTS: We found overall left-lateralized activation with words, bilateral activation with objects, and right-lateralized activation with faces. In particular, significant hippocampal activations were observed with all 3 categories of stimuli, and the head of the hippocampus was generally more engaged than its body and tail. Data on the signal intensity percent change and percentage of activated voxels are provided for each ROI and task. CONCLUSIONS: The combination of these 3 undemanding memory tasks could be considered, following appropriate validation, as a tool to assess the functional status of the medial temporal lobe in clinical settings.


Assuntos
Mapeamento Encefálico/métodos , Potenciais Evocados/fisiologia , Imageamento por Ressonância Magnética/métodos , Rememoração Mental/fisiologia , Lobo Temporal/fisiologia , Aprendizagem Verbal/fisiologia , Adulto , Feminino , Humanos , Masculino , Valores de Referência , Sensibilidade e Especificidade , Adulto Jovem
15.
NMR Biomed ; 21(1): 2-14, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17458921

RESUMO

Rank-2 tensors are unable to represent multi-modal diffusion associated with intra-voxel orientational heterogeneity (IVOH), which occurs where axons are incoherently oriented, such as where bundles intersect or diverge. Under this condition, they are oblate or spheroidally shaped, resulting in artefactually low anisotropy, potentially masking reduced axonal density, myelinisation and integrity. Higher rank tensors can represent multi-modal diffusion, and suitable metrics such as generalised anisotropy (GA) and scaled entropy (SE) have been introduced. The effect of tensor rank was studied through simulations, and analysing high angular resolution diffusion imaging (HARDI) data from two volunteers, fit with rank-2, rank-4 and rank-6 tensors. The variation of GA and SE as a function of rank was investigated through difference maps and region of interest (ROI)-based comparisons. Results were correlated with orientation distribution functions (ODF) reconstructed with q-ball, and with colour-maps of the principal and second eigenvectors. Simulations revealed that rank-4 tensors are able to represent multi-modal diffusion, and that increasing rank further has a minor effect on measurements. IVOH was detected in subcortical regions of the corona radiata, along the superior longitudinal fasciculus, in the radiations of the genu of the corpus callosum, in peritrigonal white matter and along the inferior fronto-occipital and longitudinal fascicula. In these regions, elevating tensor rank increased anisotropy. This was also true for the corpus callosum, cingulum and anterior limb of the internal capsule, where increasing tensor rank resulted in patterns that, although mono-modal, were more anisotropic. In these regions the second eigenvector was coherently oriented. As rank-4 tensors have only 15 distinct elements, they can be determined without acquiring a large number of directions. By removing artefactual underestimation of anisotropy, their use may increase the sensitivity to pathological change.


Assuntos
Encéfalo/fisiologia , Imagem de Difusão por Ressonância Magnética/métodos , Adulto , Anisotropia , Simulação por Computador , Entropia , Feminino , Humanos , Masculino
16.
AJNR Am J Neuroradiol ; 28(10): 1996-2000, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17998418

RESUMO

BACKGROUND AND PURPOSE: Structural MR imaging does not enable reliable differentiation of spinocerebellar ataxia (SCA) types 1 and 2 (SCA1 and SCA2), and imaging may be normal during the first years after the onset of symptoms. We aimed at determining whether measurements of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) may enable their differentiation. MATERIALS AND METHODS: We enrolled 14 patients with SCA1, 11 with SCA2, and 9 age-matched controls. Diffusion tensor imaging (DTI) was performed on a 1.5T scanner, with b = 1000s/mm2 and 12 directions. ADC and FA were measured by means of regions of interest, positioned in the corticospinal tract at the level of the cerebral peduncle and at the level of the pons, in the transverse pontine fibers, in the superior and middle cerebellar peduncle, and in the hemispheric cerebellar white matter. RESULTS: With respect to controls, the ADC was significantly elevated in the middle cerebellar peduncle and in hemispheric white matter in SCA1, and in all regions under consideration in SCA2. It was significantly higher in SCA2 than in SCA1 in all regions under consideration. With respect to controls, the FA was significantly reduced in all regions under consideration in SCA1 and in SCA2. It was significantly lower in SCA2 than in SCA1 in the transverse pontine fibers and in the corticospinal tract at the level of the cerebral peduncle. Correlations with clinical scores were found. CONCLUSIONS: DTI did not enable differentiation between SCA1 and SCA2. However, strongly significant differences between the 2 subtypes and with respect to controls and correlations with clinical scores were found.


Assuntos
Cerebelo/patologia , Imagem de Difusão por Ressonância Magnética , Ataxias Espinocerebelares/diagnóstico , Adulto , Anisotropia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ponte/patologia , Tratos Piramidais/patologia , Ataxias Espinocerebelares/patologia
17.
J Geriatr Psychiatry Neurol ; 20(1): 3-21, 2007 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-17341766

RESUMO

In vivo magnetic resonance spectroscopy (MRS), functional magnetic resonance imaging (fMRI), and diffusion-tensor imaging (DTI) have recently opened new possibilities for noninvasively assessing the metabolic, functional, and connectivity correlates of aging in research and clinical settings. The purpose of this article is to provide a conceptual review intended for a multidisciplinary audience, covering physical principles and main findings related to normal aging and senile cognitive impairment. This article is divided into 3 sections, dedicated to MRS, to fMRI, and to DTI. The spectroscopy section surveys physiological function of the observable metabolites, concentration changes in normal aging and their interpretation, and correlation with cognitive performance. The functional MRI section surveys the hemispheric asymmetry reduction model from compensation and de-differentiation viewpoints, memory encoding, retrieval and consolidation, inhibitory control, perception and action, resting-state networks, and functional deactivations. The DTI section surveys age-related changes, correlation with behavioral scores, and transition to cognitive impairment.


Assuntos
Doença de Alzheimer/fisiopatologia , Encéfalo/fisiopatologia , Imagem de Difusão por Ressonância Magnética , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Adulto , Fatores Etários , Idoso , Doença de Alzheimer/diagnóstico , Dominância Cerebral/fisiologia , Metabolismo Energético/fisiologia , Humanos , Transtornos da Memória/diagnóstico , Transtornos da Memória/fisiopatologia , Pessoa de Meia-Idade , Rede Nervosa/fisiopatologia , Testes Neuropsicológicos , Oxigênio/sangue , Tomografia por Emissão de Pósitrons
18.
AJNR Am J Neuroradiol ; 28(2): 309-13, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17297002

RESUMO

BACKGROUND AND PURPOSE: Visualizing with MR imaging and obtaining quantitative indexes of degeneration of the substantia nigra in Parkinson disease have been long-sought goals. We investigated the potential role of area and T1 contrast measurements in differentiating patients from controls and their age-related changes. METHODS: Eight patients with Parkinson disease, 8 age-matched controls, and 8 young controls were imaged. We obtained the pixel-wise difference between 2 sets of inversion-recovery images, acquired parallel to the bicommissural plane, with different inversion times. Pixel-intensity ratios between lateral and medial nigral regions, and nigral area and substantia-nigra/midbrain area ratios were computed. RESULTS: Compared with that of controls, loss of substantia nigra was evident in patients, its borders taking a smoother and more irregular appearance. Patients were characterized by a lateral-to-medial gradient, due to reduced hypointensity of the lateral portion of the substantia nigra and relative sparing of its medial portion. The visible nigral area was significantly smaller in patients compared with matched controls (P = .04). The substantia nigra/midbrain area ratio enabled considerably better separation (P = .0001). The lateral/medial pixel-intensity ratio was significantly higher in patients compared with matched controls (P = .01) and in young controls compared with age-matched controls (P = .01). CONCLUSION: Inversion-recovery sequences may provide a convenient way to visualize nigral degeneration. Relative area and pixel-intensity measurements may integrate other techniques (such as diffusion-tensor imaging on nigrostriatal pathways) in the neuroradiologic diagnosis and follow-up of Parkinson disease by quantitatively assessing the degeneration of the substantia nigra.


Assuntos
Imageamento por Ressonância Magnética/métodos , Degeneração Neural/patologia , Doença de Parkinson/patologia , Substância Negra/patologia , Adulto , Fatores Etários , Idoso , Diagnóstico Diferencial , Humanos , Pessoa de Meia-Idade , Transtornos Parkinsonianos/patologia
19.
J Digit Imaging ; 20(1): 32-41, 2007 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16953339

RESUMO

Advanced neuroimaging techniques, such as functional magnetic resonance imaging (fMRI), chemical shift spectroscopy imaging (CSI), diffusion tensor imaging (DTI), and perfusion-weighted imaging (PWI) create novel challenges in terms of data storage and management: huge amounts of raw data are generated, the results of analysis may depend on the software and settings that have been used, and most often intermediate files are inherently not compliant with the current DICOM (digital imaging and communication in medicine) standard, as they contain multidimensional complex and tensor arrays and various other types of data structures. A software architecture, referred to as Bio-Image Warehouse System (BIWS), which can be used alongside a radiology information system/picture archiving and communication system (RIS/PACS) system to store neuroimaging data for research purposes, is presented. The system architecture is conceived with the purpose of enabling to query by diagnosis according to a predefined two-layered classification taxonomy. The operational impact of the system and the time needed to get acquainted with the web-based interface and with the taxonomy are found to be limited. The development of modules enabling automated creation of statistical templates is proposed.


Assuntos
Diagnóstico por Imagem , Armazenamento e Recuperação da Informação/métodos , Neurorradiografia/métodos , Sistemas de Informação em Radiologia , Software , Humanos , Neurorradiografia/tendências
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