RESUMO
The temporal poles (TPs) are among the brain regions that are often considered as the brain network sustaining our ability to understand other people's mental states or "Theory of Mind" (ToM). However, so far the functional role of the left and right TPs in ToM is still debated, and it is even not clear yet whether these regions are necessary for ToM. In this study, we tested whether the left TP is necessary for ToM by assessing the mentalizing abilities of a patient (C.M.) diagnosed with semantic dementia. Converging evidence from detailed MRI and (18)F-fluoro-2-deoxy-d-glucose PET examinations showed a massive atrophy of the left TP with the right TP being relatively unaffected. Furthermore, C.M.'s atrophy encompassed most regions of the left TP usually activated in neuroimaging studies investigating ToM. Given C.M.'s language impairments, we used a battery of entirely nonverbal ToM tasks. Across five tasks encompassing 100 trials, which probed the patient's ability to attribute various mental states (intentions, knowledge, and beliefs), C.M. showed a totally spared performance. This finding suggests that, despite its consistently observed activation in neuroimaging studies involving ToM tasks, the left TP is not necessary for ToM reasoning, at least in nonverbal conditions and as long as its right counterpart is preserved. Implications for understanding the social abilities of patients with semantic dementia are discussed.
Assuntos
Mapeamento Encefálico/métodos , Demência Frontotemporal/diagnóstico , Testes de Linguagem , Testes Neuropsicológicos , Lobo Temporal/patologia , Teoria da Mente , Atrofia/diagnóstico , Atrofia/psicologia , Cognição/fisiologia , Demência Frontotemporal/psicologia , Humanos , Masculino , Pessoa de Meia-Idade , Teoria da Mente/fisiologiaRESUMO
OBJECTIVES: To retrospectively identify morphological and physiological post-operative magnetic resonance imaging (MRI) characteristics predictive of glioblastoma recurrences after gross total resection (gross-TR). METHODS: Resection margins of 24 glioblastoma were analysed immediately post-operatively (MRI ≤ 2 h) and early post-operatively (24 h ≤ MRI ≤ 48 h), and subdivided into areas with and without subtle contrast enhancement previously considered non-specific. On follow-up MRI, tumour regrowth areas were subdivided according to recurrence extent (focally/extended) and delay (≤6 and ≥12 months). Co-registration of pre-operative, immediately post-operative and early post-operative MRI with the first follow-up MRI demonstrating recurrence authorised their morphological (contrast enhancements) and physiological (rCBV) characterisation. RESULTS: Morphologically, on immediately post-operative MRI, micro-nodular and frayed enhancements correlate significantly with early recurrences (≤6 months). After gross-TR the absence of these enhancements is associated with a significant increase in progression-free survival (61 vs 15 weeks respectively) and overall survival (125 vs 51 weeks respectively). Physiologically, areas with a future focal recurrence have a trend toward higher rCBV than other areas. CONCLUSION: Immediately post-operative topography of micro-nodular and frayed enhancements is suggestive of recurrence location and delay. Absence of such enhancements is associated with a fourfold increase in progression-free survival and a 2.5-fold increase in overall survival. KEY POINTS: ⢠Immediately post-operative MRI reveals contrast enhancement after glioblastoma gross total resection. ⢠Immediately post-operative micro-nodular and frayed enhancement correlate with early recurrence. ⢠Absence of micro-nodular/frayed enhancement is associated with 61 weeks' progression-free survival. ⢠Absence of micro-nodular/frayed enhancement is associated with 125 weeks' overall survival.
Assuntos
Neoplasias Encefálicas/patologia , Glioblastoma/patologia , Imageamento por Ressonância Magnética/métodos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/cirurgia , Meios de Contraste/farmacologia , Intervalo Livre de Doença , Feminino , Glioblastoma/diagnóstico , Glioblastoma/cirurgia , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Recidiva Local de Neoplasia , Período Pós-Operatório , Estudos Retrospectivos , Resultado do Tratamento , Adulto JovemRESUMO
BACKGROUND AND AIM OF THE STUDY: The study aim was to define the timing of cerebral embolization events during transcatheter aortic valve implantation (TAVI), and to determine if events were more closely associated with valve implantation or with balloon inflation. METHODS: Between January 2008 and November 2011, a total of 114 patients underwent TAVI at the author's institution. Of these patients, 44 had previously undergone imaging before and after TAVI, and were included in the study (26 transfemoral (TF); 18 transapical (TA)). Eleven patients who had only balloon valvuloplasty (BV) during the same period were included, as were 22 patients who had open aortic valve replacement (AVR), as controls. All 77 patients underwent neurological examination, and all had cerebral MRIs before and after their procedures. RESULTS: Fifty of the 77 patients who underwent postprocedural MRI had new cerebral lesions, as follows: 24/26 (92%) in TF patients; 17/18 (94%) in TA patients; 3/11 (27%) in BV patients; and 6/22 (27%) in AVR patients (TF and TA versus BV and AVR, p < 0.0001). The mean number and volume of embolic lesions per patient were respectively 5.4/438 mm3 for TF, 11.6/3414 mm3 for TA, 0.7/46 mm3 for BV, and 0.4/48 mm3 for AVR (TF versus TA and BV versus AVR, p = NS; TF and TA versus BV and AVR, p < 0.0001). No association was found between either the EuroSCORE or patient age and the number of events. CONCLUSION: In the present study, an incidence of silent cerebral embolic lesions after TAVI was identified which was significantly higher than that for BV or AVR. This indicated an association of embolism with valve implantation rather than with balloon inflation.
Assuntos
Valvuloplastia com Balão/efeitos adversos , Implante de Prótese de Valva Cardíaca/efeitos adversos , Embolia Intracraniana/etiologia , Idoso , Idoso de 80 Anos ou mais , Imagem de Difusão por Ressonância Magnética , Feminino , Humanos , Masculino , Estudos ProspectivosRESUMO
BACKGROUND: Previous functional MRI studies have shown increased hippocampus activation in response to item encoding in amnestic mild cognitive impairment (aMCI). Recent behavioral studies suggested that associative memory could be more impaired than item memory in aMCI. So far, associative encoding has not been evaluated separately from item encoding in functional MRI studies. METHODS: We conducted a volumetric and functional MRI study investigating associative encoding in 16 aMCI and 16 elderly controls while controlling for item encoding. RESULTS: We confirmed the presence of associative memory impairment in aMCI even after controlling for item memory differences between groups. Associative memory but not item memory correlated with hippocampus volume in aMCI. Such a correlation was not observed in elderly controls. The left anterior hippocampus activation in response to successful associative encoding was decreased in aMCI, even after correction for hippocampus atrophy. CONCLUSION: Associative memory impairment in aMCI appears to be related to hippocampus atrophy and left anterior hippocampus hypoactivation.
Assuntos
Amnésia/patologia , Transtornos Cognitivos/patologia , Idoso , Atrofia , Feminino , Hipocampo/patologia , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Memória/fisiologia , Testes NeuropsicológicosRESUMO
Developmental dyscalculia (DD) is a deficit in number processing and arithmetic that affects 3-6% of schoolchildren. The goal of the present study was to analyze cerebral bases of DD related to symbolic number processing. Children with DD aged 9-11 years and matched children with no learning disability history were investigated using fMRI. The two groups of children were controlled for general cognitive factors, such as working memory, reading abilities, or IQ. Brain activations were measured during a number comparison task on pairs of Arabic numerals and a color comparison task on pairs of nonnumerical symbols. In each task, pairs of stimuli that were close or far on the relevant dimension were constituted. Brain activation in bilateral intraparietal sulcus (IPS) was modulated by numerical distance in controls but not in children with DD. Moreover, although the right IPS responded to numerical distance only, the left IPS was influenced by both numerical and color distances in control children. Our findings suggest that dyscalculia is associated with impairment in areas involved in number magnitude processing and, to a lesser extent, in areas dedicated to domain-general magnitude processing.
Assuntos
Mapeamento Encefálico , Córtex Cerebral/fisiopatologia , Transtornos Cognitivos/patologia , Deficiências do Desenvolvimento/patologia , Matemática , Simbolismo , Córtex Cerebral/irrigação sanguínea , Criança , Transtornos Cognitivos/fisiopatologia , Percepção de Cores/fisiologia , Deficiências do Desenvolvimento/fisiopatologia , Feminino , Lateralidade Funcional/fisiologia , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Masculino , Testes Neuropsicológicos , Oxigênio/sangue , Reconhecimento Visual de Modelos/fisiologia , Estimulação Luminosa/métodos , Tempo de Reação/fisiologiaRESUMO
AIM: To design a simple and affordable device that could apply standardized mechanical punctuate stimuli to trigger the periodontal mechanoreceptors during functional magnetic resonance imaging (fMRI). MATERIAL AND METHODS: A new manually controlled device using von Frey monofilaments was tested on a phantom and on eight volunteers. Four block design paradigms with different timing were compared. Teeth 11, 12, 13, 21, 22, 23 and the thumb were stimulated. RESULTS: The device did not induce any artefacts in MR images. The most efficient protocol included an epoch duration of 24 s and stimuli delivered at 1 Hz. When stimulating the teeth, activations of the primary (S1) and secondary (S2) somatosensory areas were consistently obtained, either on the ipsilateral, contra-lateral or both sides. Stimulation of the thumb led to activations of the contra-lateral S1 area and either ipsilateral or contra-lateral S2 area. CONCLUSION: The use of this innovative tool should allow to perform fMRI studies aimed to unveil the neural correlates of periodontal neural receptors, and to understand their plasticity induced by tooth loss and their eventual replacement by endosseous oral implants.
Assuntos
Imageamento por Ressonância Magnética , Mecanorreceptores/fisiologia , Ligamento Periodontal/fisiologia , Estimulação Física/instrumentação , Dente/inervação , Adulto , Dente Canino/inervação , Imagem Ecoplanar/métodos , Desenho de Equipamento , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Incisivo/inervação , Masculino , Pessoa de Meia-Idade , Vias Neurais/fisiologia , Imagens de Fantasmas , Limiar Sensorial/fisiologia , Córtex Somatossensorial/fisiologia , Polegar/inervação , Fatores de Tempo , Percepção do Tato/fisiologia , Adulto JovemRESUMO
We describe the development and evaluation of a computer-controlled system for delivering odors in a magnetic resonance imaging (MRI) environment. The system allows a timely presentation of different odors in synchrony with MRI sequences and participant's inspiration phase. The rise/fall time of odor deliverance has been optimized to generate prompt and strong stimulations. Equipped with a user-friendly programming interface, the system can be used reliably in a wide range of experimental paradigms. We have paid particular attention to developing a portable system that is relatively easy, rapid, and inexpensive to replicate. The equipment has been tested in a 3-Tesla MRI in a boxcar paradigm, in which stimulation conditions alternated with rest periods (no stimulation). The experiment demonstrated the good functioning of the device and its efficiency in producing the expected activation in the olfactory cortex; it also revealed some methodological and technical aspects to be improved.
Assuntos
Automação Laboratorial/instrumentação , Encéfalo/fisiologia , Imageamento por Ressonância Magnética , Odorantes , Percepção Olfatória/fisiologia , Mapeamento Encefálico , Humanos , Processamento de Imagem Assistida por ComputadorRESUMO
We investigated with fMRI the cortical correlates of recovery of semantic processing in a patient (DL) with left temporal damage. Names of animals, plant, and artifacts (semantic conditions) and reversed words (baseline condition) were auditorily presented to the patient and nine control subjects in a category monitoring task. Data analyses showed large differences between the patterns of domain-specific semantic activation observed in DL and the control subjects, which could be attributed to a cortical reorganization compensating for the damaged part of the semantic processing system in DL. Such reorganization relied on three main mechanisms, first, upholding of a subset of the structurally intact domain-specific regions, second, functional changes (both decreases and increases) of the domain specificity in several structurally intact regions that are normally engaged in the domain-specific network and, third, recruitment of supplementary domain-specific areas. Thus, in DL, animal-specific processing engaged supplementary areas in the left lingual gyrus and right cuneus, which correspond to animal-specific regions usually engaged in more demanding semantic tasks whereas the supplementary areas recruited for artifact-specific processing within the left superior/middle occipital lobe and right angular gyrus probably are endowed with a related but not domain-specific, semantic function. In contrast, no supplementary area contributed to plant-specific processing in DL. These findings suggest that the pattern of cortical reorganization consecutive to damage to the semantic processing network depends on the particular domain-specific function sustained by the damaged areas and the capacity of the remaining areas to assume this function.
Assuntos
Percepção Auditiva , Encefalite/fisiopatologia , Potenciais Evocados Auditivos , Rememoração Mental , Semântica , Análise e Desempenho de Tarefas , Lobo Temporal/fisiopatologia , Mapeamento Encefálico , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
OBJECTIVES: The purpose of this research was to compare the diagnostic accuracy of three-dimensional navigator-gated magnetic resonance (MR) imaging and 16-slice multidetector row computed tomography (MDCT) versus quantitative coronary angiography (QCA) for the detection of coronary artery stenosis in patients. BACKGROUND: Both MR and MDCT are novel non-invasive tests, which have been proposed for noninvasive detection of coronary artery disease. Yet their diagnostic accuracy has not been directly compared in the same population. METHODS: Fifty-two patients underwent coronary MR and 16-slice MDCT before invasive coronary angiography. Diameter stenosis (DS) severity in vessels >1.5-mm reference diameter were graded visually and measured quantitatively on both MR and MDCT images. Diagnostic accuracy of both methods was compared using QCA as the reference test. RESULTS: According to QCA, 81 of 452 (18%) coronary segments with >1.5 mm diameter had >50% DS. By visual analysis, MR and MDCT had similar sensitivity (75% vs. 82%, p = NS), specificity (77% vs. 79%, p = NS), and diagnostic accuracy (77%, vs. 80%, p = NS) for detection of >50 % DS. Quantitative measures of DS by MR (r = 0.60, p < 0.001) and MDCT (r = 0.75, both p < 0.001) correlated well with QCA. Receiver-operating characteristic analysis demonstrated that quantification of DS severity improved the diagnostic accuracy of MDCT (area under curve [AUC] 0.81 vs. 0.92, p < 0.001) but not that of MR (AUC 0.78 vs. 0.83, p = NS). CONCLUSIONS: Visual assessment of coronary diameter stenosis severity by MR or MDCT allows identification of significant coronary artery disease with a similar high diagnostic accuracy. Quantitative analysis significantly further improves the diagnostic accuracy of MDCT but not that of MR.
Assuntos
Estenose Coronária/diagnóstico por imagem , Estenose Coronária/patologia , Imageamento Tridimensional , Imageamento por Ressonância Magnética , Tomografia Computadorizada por Raios X , Idoso , Angiografia Coronária , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Índice de Gravidade de DoençaRESUMO
BACKGROUND AND PURPOSE: Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are positron emission tomography, single photon emission computed tomography, Xenon-enhanced computed tomography, dynamic perfusion computed tomography, MRI dynamic susceptibility contrast, arterial spin labeling, and Doppler ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow or cerebral blood volume. All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. SUMMARY OF REVIEW: This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview established by consensus among specialists of the various techniques. CONCLUSIONS: For clinicians, this article should offer a clearer picture of the pros and cons of currently available brain perfusion imaging techniques and assist them in choosing the proper method for every specific clinical setting.
Assuntos
Encéfalo/patologia , Angiografia por Ressonância Magnética/métodos , Tomografia por Emissão de Pósitrons/métodos , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Tomografia Computadorizada por Raios X/métodos , Ultrassonografia Doppler/métodos , Idoso , Encéfalo/irrigação sanguínea , Calibragem , Circulação Cerebrovascular , Meios de Contraste/farmacologia , Feminino , Hemodinâmica , Humanos , Angiografia por Ressonância Magnética/instrumentação , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons/instrumentação , Marcadores de Spin , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Tomografia Computadorizada por Raios X/instrumentação , Ultrassonografia Doppler/instrumentação , Xenônio/farmacologiaRESUMO
BACKGROUND: New diagnostic criteria for predemential Alzheimer's disease (AD) advocate the use of biomarkers. However, the benefit of using biomarkers has not been clearly demonstrated in clinical practice. OBJECTIVE: To investigate whether a combination of biomarkers may be helpful in classifying a population of non-demented patients attending a Memory Clinic. METHODS: Sixty non-demented patients were compared with 31 healthy elderly subjects. All subjects underwent a neuropsychological examination, brain 3T magnetic resonance imaging, [F18]-fluorodeoxyglucose and [F18]-flutemetamol positron emission tomography. According to their performance on memory, language, executive, and visuo-spatial domains, the patients were classified as mild cognitive impairment (amnestic, non-amnestic, single, or multiple domain) or subjective cognitive impairment. Patients were then classified according to the National Institute on Aging-Alzheimer's Association (NIA-AA) criteria, using the normalized mean hippocampal volume (Freesurfer), [F18]-FDG PALZAD, and [F18]-flutemetamol standard uptake value ratio (SUVr) (cut-off at the 10th percentile of controls). The standard of truth was the clinical status at study entry (patient versus control). RESULTS: The sensitivity/specificity of the clinical classification was 65/84%. The NIA-AA criteria were applicable in 85% of patients and 87% of controls. For biomarkers the best sensitivity (72%) at a fixed specificity of 84% was achieved by a combination of the three biomarkers. The clinical diagnosis was reconsidered in more than one third of the patients (42%) as a result of including the biomarker results. CONCLUSIONS: Application of the new NIA-AA AD diagnostic criteria based on biomarkers in an unselected sample of non-demented patients attending a Memory Clinic was useful in allowing for a better classification of the subjects.
Assuntos
Doença de Alzheimer/diagnóstico , Disfunção Cognitiva/diagnóstico , Memória , Idoso , Doença de Alzheimer/diagnóstico por imagem , Doença de Alzheimer/patologia , Doença de Alzheimer/psicologia , Biomarcadores , Disfunção Cognitiva/diagnóstico por imagem , Disfunção Cognitiva/patologia , Disfunção Cognitiva/psicologia , Progressão da Doença , Diagnóstico Precoce , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos , Tomografia por Emissão de Pósitrons , Sensibilidade e EspecificidadeRESUMO
Intensive rehabilitation interventions have been shown to be efficacious in improving upper extremity function in children with unilateral spastic cerebral palsy (USCP). These interventions are based on motor learning principles and engage children in skillful movements. Improvements in upper extremity function are believed to be associated with neuroplastic changes. However, these neuroplastic changes have not been well-described in children with cerebral palsy, likely due to challenges in defining and implementing the optimal tools and tests in children. Here we documented the implementation of three different neurological assessments (diffusion tensor imaging-DTI, transcranial magnetic stimulation-TMS and functional magnetic resonance imaging-fMRI) before and after a bimanual intensive treatment (HABIT-ILE) in two children with USCP presenting differential corticospinal developmental reorganization (ipsilateral and contralateral). The aim of the study was to capture neurophysiological changes and to document the complementary relationship between these measures, the potential measurable changes and the feasibility of applying these techniques in children with USCP. Independent of cortical reorganization, both children showed increases in activation and size of the motor areas controlling the affected hand, quantified with different techniques. In addition, fMRI provided additional unexpected changes in the reward circuit while using the affected hand.
Assuntos
Paralisia Cerebral/reabilitação , Córtex Motor/fisiopatologia , Modalidades de Fisioterapia , Encéfalo/patologia , Encéfalo/fisiopatologia , Mapeamento Encefálico , Paralisia Cerebral/etiologia , Paralisia Cerebral/patologia , Paralisia Cerebral/fisiopatologia , Criança , Imagem de Tensor de Difusão , Feminino , Neuroimagem Funcional , Humanos , Imageamento por Ressonância Magnética , Córtex Motor/patologia , Projetos Piloto , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/patologia , Acidente Vascular Cerebral/fisiopatologia , Estimulação Magnética Transcraniana , Resultado do TratamentoRESUMO
BACKGROUND: Functional magnetic resonance imaging is a noninvasive method of assessing language dominance in a pediatric population. OBJECTIVE: To determine the pattern of receptive language lateralization in healthy children. DESIGN: We used functional magnetic resonance imaging to assess an auditory language task in 11 children (7 girls, 4 boys; mean age, 8.5 years). Participants alternately rested and listened to descriptors of nouns presented auditorily, naming the object described silently. Asymmetry indices ([(left - right)/(left + right)]) were calculated for a priori-determined regions of interest. RESULTS: The results showed strong activation bilaterally, with greater activation on the left in the superior and middle temporal gyri. Other areas of activation included the cuneus, the left inferior temporal gyrus, the prefrontal area, and the left fusiform and lingual gyri. Regions of interest analysis of individual scans showed additional activation in the left frontal lobe. Asymmetry indices showed strong left lateralization of the inferior frontal gyrus, middle frontal gyrus, and the Wernicke region. CONCLUSIONS: Hemispheric lateralization was clearly demonstrated in 8 children. As in adults, left hemisphere lateralization of receptive language is present at age 8 years.
Assuntos
Mapeamento Encefálico/métodos , Córtex Cerebral/fisiologia , Dominância Cerebral , Idioma , Imageamento por Ressonância Magnética , Criança , Feminino , Lateralidade Funcional , Humanos , Modelos Lineares , MasculinoRESUMO
OBJECTIVE: Magnesium sulfate is being investigated for the prevention or treatment of vasospasm following subarachnoid hemorrhage. PATIENT: A 45-year-old woman suffered subarachnoid hemorrhage and developed after 8 days symptomatic vasospasm in the left middle cerebral artery (MCA) while she was receiving nimodipine prophylactically. METHODS AND RESULTS: Transcranial Doppler monitoring was performed. Cerebral autoregulation was abolished in the left MCA. Despite this finding the administration of a bolus dose of MgSO(4), followed by a continuous infusion in order to achieve serum magnesium levels in the range of 4-4.5 mg/dl (1.65-1.85 mmol/l), resulted in a marked decrease (12.2%) of the left MCA mean blood flow velocity, without clinically relevant change in systemic blood pressure (3%). This effect was maintained for at least 4 h. It did not prevent the development of ischemic lesions.
Assuntos
Sulfato de Magnésio/administração & dosagem , Hemorragia Subaracnóidea/complicações , Vasoespasmo Intracraniano/tratamento farmacológico , Bélgica , Feminino , Humanos , Infusões Intravenosas , Imageamento por Ressonância Magnética , Pessoa de Meia-Idade , Hemorragia Subaracnóidea/fisiopatologia , Vasoespasmo Intracraniano/etiologia , Vasoespasmo Intracraniano/fisiopatologiaRESUMO
Brain plasticity was investigated in a child with a hemiplegia due to unilateral schizencephaly involving the sensorimotor cortex. This focal lesion led to a dramatic functional reorganization of the undamaged hemisphere, as evidenced by the unusual pattern of fMRI activation during paretic finger movements. The functional relevance of the activation in the undamaged motor cortex was supported by the finding that TMS of this area yielded a response in the paretic hand, indicating that it controls both hands. However, this reorganization was not restricted to the primary motor cortex, but also concerned other structures involved in the control of movements, as shown by the activation of contralesional SMA and thalamus. In contrast, the fMRI activation in the damaged sensorimotor cortex during paretic hand movements appears functionally irrelevant.
Assuntos
Adaptação Fisiológica/fisiologia , Lateralidade Funcional/fisiologia , Córtex Motor/anormalidades , Córtex Motor/fisiopatologia , Malformações do Sistema Nervoso/fisiopatologia , Vias Neurais/fisiologia , Plasticidade Neuronal/fisiologia , Encéfalo/anatomia & histologia , Encéfalo/fisiologia , Mapeamento Encefálico , Criança , Estimulação Elétrica , Potencial Evocado Motor/fisiologia , Dedos/inervação , Dedos/fisiologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Córtex Motor/patologia , Movimento/fisiologia , Malformações do Sistema Nervoso/patologia , Vias Neurais/anatomia & histologia , Paresia/etiologia , Paresia/patologia , Paresia/fisiopatologia , Tempo de Reação/fisiologia , Recuperação de Função Fisiológica/fisiologiaRESUMO
BACKGROUND AND PURPOSE: Our goal was to compare the sensitivity of CT and three MR sequences in detecting and categorizing early (48 hours) hemorrhagic transformation (HT) in hyperacute ischemic stroke. METHODS: Twenty-five consecutive patients with hyperacute ischemic stroke (<6 hours) without MR signs of cerebral bleeding at admission were included. Twenty-one underwent thrombolytic therapy. A standardized follow-up protocol, performed 48 hours after admission, combined brain CT scan and MR examination (1.5 T) including fast spin-echo-fluid-attenuated inversion recovery (FSE-FLAIR), echo-planar spin-echo (EPI-SE) T2-weighted, and EPI-gradient-recalled echo (GRE) T2*-weighted sequences. Both CT scans and MR images were obtained within as short a time span as possible between techniques (mean delay, 64 minutes). CT scans and MR images were independently rated as negative or positive for bleeding and categorized for bleeding severity (five classes) by two blinded observers. Prevalence of positive cases, intra- and interobserver agreement, and shifts in bleeding categorization between respective modalities and sequences were assessed. RESULTS: Twelve patients (48%) were rated positive for HT on the basis of findings of at least one technique or sequence. From this subset of bleeding patients, seven (58%) had positive CT findings, nine (75%) had positive FSE-FLAIR and EPI-SE T2-weighted findings, and 12 (100%) had positive EPI-GRE T2*-weighted findings. CT had lower intra- and interobserver agreement for positivity than did MR imaging. Among the seven patients with positive CT and MR findings, only two had convergent ratings for bleeding category based on findings of two modalities. The five remaining had upward grading from CT to MR, which varied according to pulse sequence. CONCLUSION: MR imaging depicted more hemorrhages and had higher intra- and interobserver agreement than did CT. The EPI-GRE T2*-weighted sequence demonstrated highest sensitivity. Equivocal upward shifts in bleeding categorization were observed from CT to MR imaging and between MR images.
Assuntos
Isquemia Encefálica/diagnóstico , Hemorragias Intracranianas/diagnóstico , Imageamento por Ressonância Magnética , Acidente Vascular Cerebral/diagnóstico , Tomografia Computadorizada por Raios X , Doença Aguda , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Fatores de TempoRESUMO
INTRODUCTION: Crossmodality (i.e., the integration of stimulations coming from different sensory modalities) is a crucial ability in everyday life and has been extensively explored in healthy adults. Still, it has not yet received much attention in psychiatry, and particularly in alcohol-dependence. The present study investigates the cerebral correlates of crossmodal integration deficits in alcohol-dependence to assess whether these deficits are due to the mere accumulation of unimodal impairments or rather to specific alterations in crossmodal areas. METHODS: Twenty-eight subjects [14 alcohol-dependent subjects (ADS), 14 paired controls] were scanned using fMRI while performing a categorization task on faces (F), voices (V) and face-voice pairs (FV). A subtraction contrast [FV-(F+V)] and a conjunction analysis [(FV-F) â© (FV-V)] isolated the brain areas specifically involved in crossmodal face-voice integration. The functional connectivity between unimodal and crossmodal areas was explored using psycho-physiological interactions (PPI). RESULTS: ADS presented only moderate alterations during unimodal processing. More centrally, in the subtraction contrast and conjunction analysis, they did not show any specific crossmodal brain activation while controls presented activations in specific crossmodal areas (inferior occipital gyrus, middle frontal gyrus, superior parietal lobule). Moreover, PPI analyses showed reduced connectivity between unimodal and crossmodal areas in alcohol-dependence. CONCLUSIONS: This first fMRI exploration of crossmodal processing in alcohol-dependence showed a specific face-voice integration deficit indexed by reduced activation of crossmodal areas and reduced connectivity in the crossmodal integration network. Using crossmodal paradigms is thus crucial to correctly evaluate the deficits presented by ADS in real-life situations.
Assuntos
Alcoolismo/fisiopatologia , Alcoolismo/psicologia , Rede Nervosa/fisiopatologia , Percepção/fisiologia , Estimulação Acústica , Adulto , Córtex Cerebral/fisiologia , Escolaridade , Emoções , Face , Lateralidade Funcional/fisiologia , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Vias Neurais/fisiopatologia , Estimulação Luminosa , Desempenho Psicomotor/fisiologia , Tempo de Reação/fisiologia , Sensação/fisiologia , Percepção Social , VozRESUMO
In number comparison tasks, the performance is better when the distance between the numbers to compare increases. It has been shown that this so-called numerical distance effect (NDE) decreases with age but the neuroanatomical correlates of these age-related changes are poorly known. Using functional magnetic resonance imaging (fMRI), we recorded the brain activity changes in children aged from 8 to 14 years while they performed a number comparison task on pairs of Arabic digits and a control color comparison task on non-numerical symbols. On the one hand, we observed developmental changes in the recruitment of frontal regions and the left intraparietal sulcus (IPS), with lower activation as age increased. On the other hand, we found that a behavioral index of selective sensitivity to the NDE was positively correlated with higher brain activity in a right lateralized occipito-temporo-parietal network including the IPS. This leads us to propose that the left IPS would be engaged in the refinement of cognitive processes involved in number comparison during development, while the right IPS would underlie the semantic representation of numbers and its activation would be mainly affected by the numerical proximity between them.
RESUMO
Using functional magnetic resonance imaging (fMRI) in ten early blind humans, we found robust occipital activation during two odor-processing tasks (discrimination or categorization of fruit and flower odors), as well as during control auditory-verbal conditions (discrimination or categorization of fruit and flower names). We also found evidence for reorganization and specialization of the ventral part of the occipital cortex, with dissociation according to stimulus modality: the right fusiform gyrus was most activated during olfactory conditions while part of the left ventral lateral occipital complex showed a preference for auditory-verbal processing. Only little occipital activation was found in sighted subjects, but the same right-olfactory/left-auditory-verbal hemispheric lateralization was found overall in their brain. This difference between the groups was mirrored by superior performance of the blind in various odor-processing tasks. Moreover, the level of right fusiform gyrus activation during the olfactory conditions was highly correlated with individual scores in a variety of odor recognition tests, indicating that the additional occipital activation may play a functional role in odor processing.
Assuntos
Cegueira/fisiopatologia , Lobo Occipital/fisiologia , Odorantes , Percepção Olfatória/fisiologia , Estimulação Acústica , Adulto , Comportamento/fisiologia , Feminino , Neuroimagem Funcional , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de Tempo , Adulto JovemRESUMO
The authors describe a rare case of central auditory dysfunction induced by cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH). A 55-year-old woman who was admitted after aneurysmal SAH developed cerebral vasospasm on Day 3 affecting mainly the right middle cerebral artery (MCA) and partly the left MCA. The vasospasm became refractory to conventional therapy and was ultimately improved by intraarterial infusion of nimodipine in the right MCA and angioplasty. Severe auditory dysfunction was apparent from Day 10 as the patient was not reactive to speech or environmental sounds. Brain MRI on Day 17 demonstrated infarcted areas mainly in the right hippocampus, medial occipital lobe, and thalamus. The patient underwent further examination using audiometry, speech testing, auditory evoked potentials, functional MRI, and cerebral PET. The initial diagnosis was extended nonverbal agnosia and total pure word deafness. The central auditory dysfunction improved over 6 months, with persisting hyperacusis, tinnitus, and amusia. Central auditory dysfunction is a rare complication after SAH. While cortical deafness may be associated with bilateral lesions of the temporal cortex, partly reversible central auditory dysfunction was observed in this patient after prominently unilateral right temporal lesions. The role of the interthalamic connections can be discussed, as well as the possibility that a less severe vasospasm on the left MCA could have transiently impaired the left thalamocortical auditory pathways.