Long-term brain plasticity allowing a multistage surgical approach to World Health Organization Grade II gliomas in eloquent areas.

Although the goal of surgery for World Health Organization Grade II gliomas is maximal extent of resection, complete tumor removal is not always possible when the glioma involves eloquent areas. The authors propose a multistage surgical approach to highly crucial areas that are classically considered inoperable, enabling optimization of the extent of resection while avoiding permanent cognitive deficits due to induced functional reshaping in the interim between the 2 consecutive operations. To demonstrate such plasticity, the authors used a combination of sequential functional MR imaging and intraoperative electrical stimulation mapping before and during surgeries spaced by several years in 2 patients who each underwent 2 separate resections of Grade II gliomas located in the left dominant premotor area.

[Semantic dementia associated with amyotrophic lateral sclerosis].

The association semantic dementia-amyotrophic lateral sclerosis has been rarely reported in the literature. We report a case study of a patient with a severe prosopagnosia in relation with semantic dementia associated, 12 months later, with a motor neuron disease.

A locus for bilateral occipital polymicrogyria maps to chromosome 6q16-q22.

We describe the clinical, radiographic, and genetic features of a large consanguineous Moroccan family in which bilateral occipital polymicrogyria segregated as an autosomal recessive trait. Six affected members of the family had partial complex seizures often associated with behavioral abnormalities. On MRI, three patients had a thickened irregular cortex in the lateral occipital lobes with small gyri.

Visualization of disconnection syndromes in humans.

Knowledge of the relationship between structure and function is essential to the exploration of the architecture of cognition. Cognitive processes require the coordinated activity of large-scale brain networks consisting of distant cortical regions, connected by long-range white matter tracts. Despite decades of connectional tracing studies in monkeys, the backwardness of human anatomy makes it difficult to draw conclusions from lesion studies and functional neuroimaging when brain connectivity is at issue.

Structural and diffusion tensor imaging of the fornix in childhood- and adolescent-onset schizophrenia.

Objective: There is emerging evidence that aberrations in the integrity of cerebral white matter tracts, especially those connected to limbic structures, play a role in the pathophysiology of schizophrenia. The fornix is the primary efferent neural pathway of the hippocampus and has been shown to be abnormal in adults with schizophrenia.

Method: High-resolution structural magnetic resonance imaging and diffusion tensor images were obtained on 15 patients with childhood- and adolescent-onset schizophrenia and 15 age- and sex-matched controls.

Discrimination between Alzheimer disease, mild cognitive impairment, and normal aging by using automated segmentation of the hippocampus.

Purpose: To prospectively evaluate the accuracy of automated hippocampal volumetry to help distinguish between patients with Alzheimer disease (AD), patients with mild cognitive impairment (MCI), and elderly controls, by using established criteria for patients with AD and MCI as the reference standard.

Materials And Methods: The regional ethics committee approved the study and written informed consent was obtained from all participants. The study included 25 patients with AD (11 men, 14 women; mean age +/- standard deviation [SD], 73 years +/- 6; Mini-Mental State Examination (MMSE) score, 24.

VBM anticipates the rate of progression of Alzheimer disease: a 3-year longitudinal study.

Objective: To determine whether regional atrophy or neuropsychological factors can predict the rate of decline in patients with mild Alzheimer disease (AD).

Background: Despite important implications for planning the care and treatment strategy, few prognostic factors of severe AD progression are known.

Methods: Twenty-three patients with mild AD were followed up every 6 months over the course of 3 years.

Regions, systems, and the brain: hierarchical measures of functional integration in fMRI.

In neuroscience, the notion has emerged that the brain abides by two principles: segregation and integration. Segregation into functionally specialized systems and integration of information flow across systems are basic principles that are thought to shape the functional architecture of the brain. A measure called integration, originating from information theory and derived from mutual information, has been proposed to characterize the global integrative state of a network.

[Update on vascular dementias].

The concept of vascular dementia greatly evolved since Hachinski's description of multi-infarct dementia. Vascular dementias are reviewed with emphasis on current diagnostic criteria, elusive natural history, neuroradiological aspects, difficult epidemiological features and intriguing links with Alzheimer's disease. The recent proposed shift from vascular dementias to a broader definition of "vascular cognitive disorders", including non demented subjects with "vascular cognitive impairment", is described, followed by a brief review of current treatments.

Altered diffusion in the frontal lobe in Parkinson disease.

Background And Purpose: Parkinson disease (PD) is characterized by basal ganglia abnormalities. However, there are neurodegenerative changes in PD that extend beyond the basal ganglia and that are not sufficiently evaluated with standard MR imaging. The aim of this study was to characterize whole-brain gray matter (GM) and white matter (WM) changes in PD by using diffusion tensor imaging (DTI).

Lateralized parietal activity during decision and preparation of saccades.

The posterior parietal cortex is involved in numerous visuospatial tasks, but little is known about the lateralization of these functions. We used functional magnetic resonance imaging to map the posterior parietal areas involved in saccades. Cerebral activation was studied during three different steps of saccadic elaboration: internal Decision of where to direct a horizontal saccade, motor Preparation and saccade Execution.

A novel approach to clinical-radiological correlations: Anatomo-Clinical Overlapping Maps (AnaCOM): method and validation.

We present a new clinical-radiological correlation method (AnaCOM) that aims at establishing structure-function relationships. We validated AnaCOM by assessing the location of lesions that are associated with altered performances in a well-studied task: the verbal fluency task. We retrospectively reviewed 64 brain-damaged patients who had focal lesions in a variety of cortical sites due to stroke, hemorrhage or tumor surgery.

Structural abnormalities in the cerebellum and sensorimotor circuit in writer's cramp.

Background: Structural abnormalities were detected in bilateral primary sensorimotor areas in writer's cramp. Evidence in other primary dystonia, including blepharospasm and cervical dystonia, suggest that structural abnormalities may be observed in other brain areas such as the cerebellum in writer's cramp.

Objective: To test the hypothesis that structural abnormalities are present along the sensorimotor and cerebellar circuits in patients with writer's cramp.

Diffusion tensor imaging and voxel based morphometry study in amyotrophic lateral sclerosis: relationships with motor disability.

The aim of this study was to investigate the extent of cortical and subcortical lesions in amyotrophic lateral sclerosis (ALS) using, in combination, voxel based diffusion tensor imaging (DTI) and voxel based morphometry (VBM). We included 15 patients with definite or probable ALS and 25 healthy volunteers. Patients were assessed using the revised ALS Functional Rating Scale (ALSFRS-R).

Prefrontal cortex is involved in internal decision of forthcoming saccades.

Deciding where to look is mandatory to explore the visual world. To study the neural correlates subserving the cognitive phase of self-initiated eye movements in humans, we tested 12 healthy participants, using event-related functional MRI. Changes in the frontal-cortical activity preceding voluntary saccades were studied when the participants freely decided the direction of a forthcoming saccade, compared with a condition in which they had only to prepare an externally cued saccade.

[Neuroimaging in dementia].

Imaging is a part of the work-up for all types of dementia. X-ray computed tomography (CT) is a first-line examination to rule out causes of surgical, and thus reversible, dementia (for example, subdural hematoma or normal pressure hydrocephalus). MRI (magnetic resonance imaging) is preferred for work-ups of dementia.

[Functional magnetic resonance imaging: physiopathology, techniques and applications].

Brain functional MRI (fMRI) provides an indirect mapping of cerebral activity, based on the detection of local changes in blood flow and oxygenation levels that are associated with neuronal activity (BOLD contrast). fMRI allows noninvasive studies of normal and pathological aspects of the brain's functional organization. It is based on the comparison of two or more cognitive states.

A Riemannian approach to diffusion tensor images segmentation.

We address the problem of the segmentation of cerebral white matter structures from diffusion tensor images. Our approach is grounded on the theoretically well-founded differential geometrical properties of the space of multivariate normal distributions. We introduce a variational formulation, in the level set framework, to estimate the optimal segmentation according to the following hypothesis: Diffusion tensors exhibit a Gaussian distribution in the different partitions.

Postoperative recovery of hippocampal contralateral diffusivity in medial temporal lobe epilepsy.

Purpose: To search for a recovery after surgery of mean diffusivity (MD) values in the contralateral nonsclerotic hippocampus of patients with medial temporal lobe epilepsy (MTLE) and hippocampal sclerosis (HS).

Methods: Twenty-four MTLE patients (12 right-sided and 12 left-sided MTLE) and 36 healthy volunteers were investigated using diffusion tensor imaging. A region-of-interest approach was used to measure pre- and postoperative interictal hippocampal MD values in patients.

Disruption of hippocampal connectivity in children and adolescents with schizophrenia--a voxel-based diffusion tensor imaging study.

Introduction: One hypothesis that unifies the diversity of symptoms associated with schizophrenia involves the disruption of connectivity between brain regions. As white matter provides rapid and efficient communication between brain regions, this study was initiated to assess the early disruption of white matter pathways in children and adolescent with schizophrenia.

Materials And Methods: Diffusion tensor images were acquired on 14 children and adolescents with schizophrenia, one subject with schizoaffective disorder, and 15 age and gender matched controls.

Magnetic resonance imaging of Alzheimer's disease.

A modern challenge for neuroimaging techniques is to contribute to the early diagnosis of neurodegenerative diseases, such as Alzheimer's disease (AD). Early diagnosis includes recognition of pre-demented conditions, such as mild cognitive impairment (MCI) or having a high risk of developing AD. The role of neuroimaging therefore extends beyond its traditional role of excluding other conditions such as neurosurgical lesions.

[Functional magnetic resonance imaging in clinical practice].

In the last decade, functional MRI (fMRI) has become one of the most widely used functional imaging technique in neurosciences. However, its clinical applications remain limited. Despite methodological and practical issues, fMRI data has been validated by different techniques (magnetoencephalography, Wada test, electrical and magnetic stimulations, and surgical resections).

Partial correlation for functional brain interactivity investigation in functional MRI.

Examination of functional interactions through effective connectivity requires the determination of three distinct levels of information: (1) the regions involved in the process and forming the spatial support of the network, (2) the presence or absence of interactions between each pair of regions, and (3) the directionality of the existing interactions. While many methods exist to select regions (Step 1), very little is available to complete Step 2. The two main methods developed so far, structural equation modeling (SEM) and dynamical causal modeling (DCM), usually require precise prior information to be used, while such information is sometimes lacking.

The role of the supplementary motor area (SMA) in word production.

The supplementary motor area (SMA) is a key structure for behavioral planning and execution. Recent research on motor control conducted with monkeys and humans has put to light an anatomical and functional distinction between pre-SMA and SMA-proper. According to this view, the pre-SMA would be involved in higher level processes while the SMA-proper would be more closely tied to motor output.