A voxel-based analysis of FDG-PET in traumatic brain injury: regional metabolism and relationship between the thalamus and cortical areas.

The objective was to study the correlations and the differences in glucose metabolism between the thalamus and cortical structures in a sample of severe traumatic brain injury (TBI) patients with different neurological outcomes. We studied 49 patients who had suffered a severe TBI and 10 healthy control subjects using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET). The patients were divided into three groups: a vegetative or minimally-conscious state (MCS&VS) group (n=17), which included patients who were in a vegetative or a minimally conscious state; an In-post-traumatic amnesia (In-PTA) group (n=12), which included patients in PTA; and an Out-PTA group (n=20), which included patients who had recovered from PTA. SPM5 software was used to determine the metabolic differences between the groups. FDG-PET images were normalized and four regions of interest were generated around the thalamus, precuneus, and the frontal and temporal lobes. The groups were parameterized using Student's t-test. Principal component analysis was used to obtain an intensity-estimated-value per subject to correlate the function between the structures. Differences in glucose metabolism in all structures were related to the neurological outcome, and the most severe patients showed the most severe hypometabolism. We also found a significant correlation between the cortico-thalamo-cortical metabolism in all groups. Voxel-based analysis suggests a functional correlation between these four areas, and decreased metabolism was associated with less favorable outcomes. Higher levels of activation of the cortico-cortical connections appear to be related to better neurological condition. Differences in the thalamo-cortical correlations between patients and controls may be related to traumatic dysfunction due to focal or diffuse lesions.

Voxel-based statistical analysis of thalamic glucose metabolism in traumatic brain injury: relationship with consciousness and cognition.

OBJECTIVE: To study the relationship between thalamic glucose metabolism and neurological outcome after severe traumatic brain injury (TBI). METHODS: Forty-nine patients with severe and closed TBI and 10 healthy control subjects with (18)F-FDG PET were studied. Patients were divided into three groups: MCS&VS group (n = 17), patients in a vegetative or a minimally conscious state; In-PTA group (n = 12), patients in a state of post-traumatic amnesia (PTA); and Out-PTA group (n = 20), patients who had emerged from PTA. SPM5 software implemented in MATLAB 7 was used to determine the quantitative differences between patients and controls. FDG-PET images were spatially normalized and an automated thalamic ROI mask was generated. Group differences were analysed with two sample voxel-wise t-tests. RESULTS: Thalamic hypometabolism was the most prominent in patients with low consciousness (MCS&VS group) and the thalamic hypometabolism in the In-PTA group was more prominent than that in the Out-PTA group. Healthy control subjects showed the greatest thalamic metabolism. These differences in metabolism were more pronounced in the internal regions of the thalamus. CONCLUSIONS: The results confirm the vulnerability of the thalamus to suffer the effect of the dynamic forces generated during a TBI. Patients with thalamic hypometabolism could represent a sub-set of subjects that are highly vulnerable to neurological disability after TBI.

Increased amygdala and parahippocampal gyrus activation in schizophrenic patients with auditory hallucinations: an fMRI study using independent component analysis.

OBJECTIVE: Hallucinations in patients with schizophrenia have strong emotional connotations. Functional neuroimaging techniques have been widely used to study brain activity in patients with schizophrenia with hallucinations or emotional impairments. However, few of these studies have investigated the association between hallucinations and emotional dysfunctions using an emotional auditory paradigm. Independent component analysis (ICA) is an analysis method that is especially useful for decomposing activation during complex cognitive tasks in which multiple operations occur simultaneously. Our aim in this study is to analyze brain activation after the presentation of emotional auditory stimuli in patients with schizophrenia with and without chronic auditory hallucinations using ICA methodology. It was hypothesized that functional connectivity differences in limbic regions responsible for emotional processing would be demonstrated. METHODS: The present functional magnetic resonance imaging (fMRI) study compared neural activity in 41 patients with schizophrenia (27 with auditory hallucinations, 14 without auditory hallucinations) with 31 controls. Neural activity data was generated while participants were presented with an auditory paradigm containing emotional words. The comparison was performed using a multivariate approach, ICA. Differences in temporo-spatial aspects of limbic network were examined in three study groups. RESULTS: Limbic networks responded differently in patients with auditory hallucinations compared to healthy controls and patients without auditory hallucinations. Unlike control subjects and non-hallucinators, the group of hallucinatory patients showed an increase of activity in the parahippocampal gyrus and the amygdala during the emotional session. CONCLUSIONS: These findings may reflect an increase in parahippocampal gyrus and amygdala activity during passive listening of emotional words in patients with schizophrenia and auditory hallucinations.

MR and genetics in schizophrenia: focus on auditory hallucinations.

Although many structural and functional abnormalities have been related to schizophrenia, until now, no single biological marker has been of diagnostic clinical utility. One way to obtain more valid findings is to focus on the symptoms instead of the syndrome. Auditory hallucinations (AHs) are one of the most frequent and reliable symptoms of psychosis. We present a review of our main findings, using a multidisciplinary approach, on auditory hallucinations. Firstly, by applying a new auditory emotional paradigm specific for psychosis, we found an enhanced activation of limbic and frontal brain areas in response to emotional words in these patients. Secondly, in a voxel-based morphometric study, we obtained a significant decreased gray matter concentration in the insula (bilateral), superior temporal gyrus (bilateral), and amygdala (left) in patients compared to healthy subjects. This gray matter loss was directly related to the intensity of AH. Thirdly, using a new method for looking at areas of coincidence between gray matter loss and functional activation, large coinciding brain clusters were found in the left and right middle temporal and superior temporal gyri. Finally, we summarized our main findings from our studies of the molecular genetics of auditory hallucinations. Taking these data together, an integrative model to explain the neurobiological basis of this psychotic symptom is presented.

Chronic auditory hallucinations in schizophrenic patients: MR analysis of the coincidence between functional and morphologic abnormalities.

PURPOSE: To prospectively evaluate if functional magnetic resonance (MR) imaging abnormalities associated with auditory emotional stimuli coexist with focal brain reductions in schizophrenic patients with chronic auditory hallucinations. MATERIALS AND METHODS: Institutional review board approval was obtained and all participants gave written informed consent. Twenty-one right-handed male patients with schizophrenia and persistent hallucinations (started to hear hallucinations at a mean age of 23 years +/- 10, with 15 years +/- 8 of mean illness duration) and 10 healthy paired participants (same ethnic group [white], age, and education level [secondary school]) were studied. Functional echo-planar T2*-weighted (after both emotional and neutral auditory stimulation) and morphometric three-dimensional gradient-recalled echo T1-weighted MR images were analyzed using Statistical Parametric Mapping (SPM2) software. Brain activation images were extracted by subtracting those with emotional from nonemotional words. Anatomic differences were explored by optimized voxel-based morphometry. The functional and morphometric MR images were overlaid to depict voxels statistically reported by both techniques. A coincidence map was generated by multiplying the emotional subtracted functional MR and volume decrement morphometric maps. Statistical analysis used the general linear model, Student t tests, random effects analyses, and analysis of covariance with a correction for multiple comparisons following the false discovery rate method. RESULTS: Large coinciding brain clusters (P < .005) were found in the left and right middle temporal and superior temporal gyri. Smaller coinciding clusters were found in the left posterior and right anterior cingular gyri, left inferior frontal gyrus, and middle occipital gyrus. CONCLUSION: The middle and superior temporal and the cingular gyri are closely related to the abnormal neural network involved in the auditory emotional dysfunction seen in schizophrenic patients.

Investigación Radiológica: necesidad de una aproximación colaborativa / Radiology research: the need for a collaborative approach

La creciente importancia de la imagen en todos los procesos médicos hace que el desarrollo de trabajos cooperativos en red sea una obligación social. Mediante la creación de una plataforma conjunta, multidisciplinar y colaborativa se pueden aunar datos, esfuerzos, capacidades y recursos. Los profesionales de la imagen médica deben profundizar en la calidad de la información que se extrae de las exploraciones que se realizan y de las nuevas terapias mínimamente invasivas guiadas por la imagen, en un entorno distribuido y seguro de compartición de conocimietno y recursos. Este entorno se debe construir sobre una capa de servicios desplegados en una “ciberinfraestructura” con un sistema de acceso distribuido a las bases de datos estructuradas y seguras sobre las que aplicar técnicas avanzadas de “posproceso” y de “minería de datos” para extraer conocimiento en un entorno seguro. Las ciberinfraestructuras son los nuevos entornos de investigación avanzada que dan soporte a los procesos de adquisición, almacenamiento, gestión, integración, minería y visualización de datos, así como otros servicios de computación y procesamiento de la información a través de Internet. Para que la investigación radiológica sea eficaz, deben crearse grupo de trabajo donde se interrelacionen no sólo médicos de diversas especialidades, sino también otros profesionales no sanitarios relacionados con la imagen médica (ingenieros, informáticos, telecomunicaciones, química-física, farmacología). El grado de complejidad de estos grupos, su multidisciplinaridad, será un medida de las necesidades de la investigación (AU)

The growing importance of the image in all medical processes means that the development of cooperative work in network is a social obligation. Multi-disciplinarity is a key factor to increasing the quality of information which is extracted from radiology explorations and the new minimally invasive therapies guided by imaging. The cyber-infrastructures are the new advanced research settings which give support to the processes of acquisition, storing, management, integration, mining and visualization of data (AU)