Assessment of brain vascularization with magnetic resonance imaging

Thèse de doctorat en sciences médicales (neurosciences) (MED 3)--UCL, 200

Developmental aspects of pediatric fMRI: Considerations for image acquisition, analysis, and interpretation

Functional MRI provides a powerful means to identify and trace the evolution, development, and consolidation of cognitive neural networks through normal childhood. Neural network perturbations due to disease and other adverse factors during development can also be explored. Studies performed to date suggest that normal children older than 5 years show activation maps comparable to adults for similar cognitive paradigms. Minor differences in adult and pediatric activation maps may reflect age dependent strategies or maturation of cognitive networks. However, there are important physiologic and anatomic differences in children, varying with age, that may affect the acquisition, analysis, and interpretation of pediatric fMRI data. Differences between children and adult fRIRI comparison studies may reflect technical aspects of data acquisition as much as developmental and brain maturation factors. (C) 2001 Academic Press

Ferristene as intestinal MR contrast agent. Distribution and safety of a fast ingestion procedure with oral metoclopramide.

PURPOSE: To compare the small bowel distribution and safety of a fast ingestion procedure of ferristene to those of the standard ingestion procedure. MATERIAL AND METHODS: Sixty-four patients received 0.5 g/l ferristene in 800 ml water. Thirty-four patients of the fast ingestion group ingested ferristene with 20 mg of oral metoclopramide during the course of 30 min before MR imaging and received an i.v. injection of an antiperistaltic agent during the MR study. Thirty patients of the standard group ingested ferristene during the course of 2 h, without additional drugs. Ferristene distribution was assessed by 2 reviewers and adverse events were recorded. RESULTS: More than 50% of the small bowel segments analyzed were filled with ferristene in 30 patients in the fast ingestion group and in 28 patients in the standard ingestion group. One patient in each group experienced nausea and/or vomiting. Some bloating or sensation of fullness was reported by 2 patients in the fast ingestion group and by 3 patients in the standard ingestion group. CONCLUSION: The distribution of ferristene in the small bowel and the safety of the procedure were thus similar in the 2 groups using either a fast ingestion procedure with oral metoclopramide or the more time-consuming standard ingestion procedure

Unusual location of an intracranial chondroma.

We describe the MR findings in a case of chondroma arising from the falx. At MR imaging, the mass appeared well defined, lobulated, hypointense to isointense on T1-weighted images, and very heterogeneous with marked hyperintense areas on T2-weighted images. After contrast administration, this tumor enhanced slightly on delayed images

Epileptic discharges in a mammillary body of a patient with refractory epilepsy

Objectives. To document epileptiform discharges recorded within a mammillary body (MB) of a patient with chronic refractory epilepsy (CRE). Materials and Methods. A 37-year-old man, whose epilepsy was not controlled by medication or vagus nerve stimulation, was enrolled in a study of the effects of deep brain stimulation of the MB and mammillothalamic tract (MTT) in CRE. Surface and deep EEG recordings were obtained for 3 days before implantation of the macroelectrodes and for 4 days after implantation of the macroelectrodes but before implantation of the stimulator battery. Results. Paroxysmal epileptiform discharges were recorded in the right MB while other surface and deep recordings, in particular from the right MTT, were silent. When these discharges were longer than 100 sec, they spread to the right MTT area and then to the left MB and MTT area. Simultaneously, the patient became agitated and confused. Conclusions. This original observation indicates that subcortical neuronal structures, such as the MB, may sustain epileptiform discharges in humans

A functional magnetic resonance imaging study of left hemisphere language dominance in children.

Functional magnetic resonance imaging is a noninvasive method of assessing language dominance in a pediatric population. To determine the pattern of receptive language lateralization in healthy children. 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. 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. Hemispheric lateralization was clearly demonstrated in 8 children. As in adults, left hemisphere lateralization of receptive language is present at age 8 years

Aphasia owing to subcortical brain infarcts in childhood

The aim of this study was to further define the clinical features of subcortical aphasia in children with deep brain infarcts and to define the sequelae associated with childhood strokes. We retrospectively studied nine children with left subcortical brain infarcts who presented with acquired language disorder and underwent, language investigations based on standardized tests. Stroke in these patients involved the left internal capsule, lenticular or thalamic nuclei, or a combination of these. Early aphasic manifestations following the deep cerebral infarcts affected language expression. These included mutism, nonfluent speech, word finding difficulties, and phonemic and semantic paraphasia. Speech comprehension was generally more preserved. All patients subsequently improved, although variably; sequelae such as dysfluency, word finding difficulties, and written language learning impairment could be detected through standardized tests in six of them (all younger than 6 years at the time of the infarct). Two of the three remaining patients (both older than 6 years at the time of the infarct) had a full recovery. Our study confirms the concept of childhood subcortical aphasia, depicts the linguistic profile in these patients, and sustains the indication of systematic formal language assessment during the follow-up of all children with subcortical infarct involving the dominant hemisphere

Cortical localization of reading in normal children: An fMRI language study

Background: fMRI provides a noninvasive means of identifying the location and organization of neural networks that underlie cognitive functions. Objective: To identify, using fMRI, brain regions involved in processing written text in children. Methods: The authors studied nine normal right-handed native English-speaking children, aged 10.2 years (range 7.9 to 13.3 years), with two paradigms: reading Aesop's Fables and "Read Response Naming" (reading a description of an object that was then silently named). Data were acquired using blood oxygen level-dependent fMRI. Group data were analyzed with statistical parametric mapping; individual data sets were analyzed with a region-of-interest approach from individual study t maps. The number of activated pixels was determined in brain regions and an asymmetry index (AI = [L - R]/[L + R]) calculated for each region. Results: The authors found strong activation in the left middle temporal gyrus and left midfrontal gyrus and variable activation in left inferior frontal gyrus for both reading tasks in the group analysis (z > 5.5 to 9.1). All subjects had strong left-sided lateralization for both tasks in middle/superior temporal gyrus, inferior frontal gyrus, and middle frontal gyrus (AI = 0.76 to 1.0 for t = 4). Reading Fables activated twice as many pixels in temporal cortex as the Read Response Naming task; activation in dorsolateral prefrontal cortex was similar for both tasks. Small homologous right middle temporal region activation was seen with reading a fable. Conclusions: The neural networks that process reading appear to be lateralized and localized by middle to late childhood. Reading text paradigms may prove useful for identifying frontal and temporal language-processing areas and for determining language dominance in children experiencing epilepsy or undergoing tumor surgery

Dissociation between Olfactory and Auditory-Verbal Processing in the Occipital Cortex of Early Blind Subjects

Despite numerous studies on cross-modal brain plasticity, it is still unclear to what extent distinct (nonvisual) sensory modalities are segregated in the reorganized occipital cortex (OC) of blind subjects. In addition, little is known about the potential role of the OC in olfactory processing that is enhanced in these subjects. Using fMRI, we monitored the brain activity in ten early blind (EB) subjects while they were discriminating or categorizing olfactory (fruit and flower odors) versus auditory-verbal stimuli (fruit and flower names). Both modalities selectively activated the ventral part of the OC and were segregated in this cortex; 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. No such occipital activation was observed in sighted controls, but the same right-olfactory/left-auditory hemispheric lateralization was found overall in their brain. These findings constitute the first evidences (1) that the OC is involved in the processing of odors in EB subjects and (2) that sensory modalities are (to some extent) segregated in the OC of EB subjects. Furthermore, the ventral stream seems to develop its designated functional role in processing stimulus identity independently of visual experience