Juan Álvarez-Linera

Brain structural changes in essential tremor: Voxel-based morphometry at 3-Tesla

BACKGROUND Abnormalities in cerebello-thalamo-cortical pathways have been suggested as a basis for essential tremor (ET). Two voxel-based morphometry (VBM) studies, each using a 1.5-T magnet, evaluated ET patients, leading to contradictory results. Using a 3-T magnet, we assessed whether white or gray matter changes occurred in ET patients vs. controls. METHODS We recruited 19 ET patients (mean age 69.8+/-9.4 years) and 20 age and gender-matched controls. 3-T MRI data were analyzed using the Statistical Parametric Mapping (SPM) 5 package. RESULTS In case-control comparisons, white matter changes were seen in several areas (right cerebellum, left medulla, right parietal lobe, and right limbic lobe); gray matter changes were seen in several areas as well (bilateral cerebellum, bilateral parietal lobes, right frontal lobe, and right insula) (p<0.001, uncorrected at a voxel level). Compared with controls, ET patients with severe tremor had white matter changes in the midbrain, both occipital lobes, and right frontal lobe, and gray matter changes bilaterally in the cerebellum (p<0.001, uncorrected at a voxel level). CONCLUSIONS Structural white and gray abnormalities may be detected in ET patients using VBM and a high-field MRI scanner. Such changes may be related to the pathological substrates associated with this disease.

Pituitary enlargement in patients with intracranial hypotension syndrome.

Article abstract—The authors analyzed whether the pituitary gland enlarges in intracranial hypotension syndrome by studying 11 consecutive patients. Initial MRI scans showed pituitary gland enlargement with a convex superior margin. Follow-up MRI studies revealed that the size of the gland invariably diminished in all patients. The authors hypothesize that pituitary gland enlargement in intracranial hypotension syndrome is due to hyperemia of dural and epidural venous sinuses.

Neuroanatomic overlap between intelligence and cognitive factors: morphometry methods provide support for the key role of the frontal lobes.

Evidence from neuroimaging studies suggests that intelligence differences may be supported by a parieto-frontal network. Research shows that this network is also relevant for cognitive functions such as working memory and attention. However, previous studies have not explicitly analyzed the commonality of brain areas between a broad array of intelligence factors and cognitive functions tested in the same sample. Here fluid, crystallized, and spatial intelligence, along with working memory, executive updating, attention, and processing speed were each measured by three diverse tests or tasks. These twenty-one measures were completed by a group of one hundred and four healthy young adults. Three cortical measures (cortical gray matter volume, cortical surface area, and cortical thickness) were regressed against psychological latent scores obtained from a confirmatory factor analysis for removing test and task specific variance. For cortical gray matter volume and cortical surface area, the main overlapping clusters were observed in the middle frontal gyrus and involved fluid intelligence and working memory. Crystallized intelligence showed an overlapping cluster with fluid intelligence and working memory in the middle frontal gyrus. The inferior frontal gyrus showed overlap for crystallized intelligence, spatial intelligence, attention, and processing speed. The fusiform gyrus in temporal cortex showed overlap for spatial intelligence and attention. Parietal and occipital areas did not show any overlap across intelligence and cognitive factors. Taken together, these findings underscore that structural features of gray matter in the frontal lobes support those aspects of intelligence related to basic cognitive processes.

Brain activation in discourse comprehension: a 3t fMRI study.

To date a very small number of functional neuroimaging studies have specifically examined the effects of story coherence on brain activation using long narratives, a procedure fundamental to the study of global coherence. These studies, however, not only yielded notably divergent results, but also featured a number of caveats. It is the purpose of the present study to try to overcome some of these limitations. A left precuneus/posterior cingulate activation related to global coherence comprehension was in consonance with a part of previous literature. However, our most important results corresponded to left parietal regions (angular gyrus, BA 39), this diverging from the previous studies. Recent developments of the situational models of narrative comprehension could explain all these apparently inconsistent results. According to these, different situation models would be created as a function of the content of the narratives, which would yield in turn different patterns of brain activity. Our data also suggest that the same content might also give place to different situation models as a function of the degree of global coherence achieved by the reader or listener.

Predicting the Histopathological Grade of Cerebral Gliomas Using High b value MR DW Imaging at 3‐Tesla

Our aim was to prospectively assess whether magnetic resonance (MR) diffusion‐weighted (DW) imaging using high b values can predict better than b value of 1,000 s/mm2 the histopathological grade of cerebral gliomas.

Subcortical regional morphology correlates with fluid and spatial intelligence.

Neuroimaging studies have revealed associations between intelligence and brain morphology. However, researchers have focused primarily on the anatomical features of the cerebral cortex, whereas subcortical structures, such as the basal ganglia (BG), have often been neglected despite extensive functional evidence on their relation with higher‐order cognition. Here we performed shape analyses to understand how individual differences in BG local morphology account for variability in cognitive performance. Structural MRI was acquired in 104 young adults (45 men, 59 women, mean age = 19.83, SD = 1.64), and the outer surface of striatal structures (caudate, nucleus accumbens, and putamen), globus pallidus, and thalamus was estimated for each subject and hemisphere. Further, nine cognitive tests were used to measure fluid (Gf), crystallized (Gc), and spatial intelligence (Gv). Latent scores for these factors were computed by means of confirmatory factor analysis and regressed vertex‐wise against subcortical shape (local displacements of vertex position), controlling for age, sex, and adjusted for brain size. Significant results (FDR < 5%) were found for Gf and Gv, but not Gc, for the right striatal structures and thalamus. The main results show a relative enlargement of the rostral putamen, which is functionally connected to the right dorsolateral prefrontal cortex and other intelligence‐related prefrontal areas. Hum Brain Mapp 35:1957–1968, 2014.

Higher Glutamate to Glutamine Ratios in Occipital Regions in Women With Migraine During the Interictal State

Glutamate (Glu) and glutamine (Gln) are strongly compartmentalized (in neurons for Glu and in astrocytes for Gln). The visual cortex is the brain region with a higher neuron/astrocyte ratio (the highest neuronal density and the relatively lowest density of astrocytes). Elevations in extracellular Glu or potassium above certain thresholds are likely candidates to be the final common steps in the multiple distinct processes that can lead to cortical spreading depression. Astrocytes play a key role in this phenomenon, by acting as a sink for extracellular Glu and potassium, as well as generally acting as a buffer for the ionic and neurochemical changes that initiate and propagate cortical spreading depression.

Changes in resting-state functionally connected parietofrontal networks after videogame practice

Neuroimaging studies provide evidence for organized intrinsic activity under task‐free conditions. This activity serves functionally relevant brain systems supporting cognition. Here, we analyze changes in resting‐state functional connectivity after videogame practice applying a test–retest design. Twenty young females were selected from a group of 100 participants tested on four standardized cognitive ability tests. The practice and control groups were carefully matched on their ability scores. The practice group played during two sessions per week across 4 weeks (16 h total) under strict supervision in the laboratory, showing systematic performance improvements in the game. A group independent component analysis (GICA) applying multisession temporal concatenation on test–retest resting‐state fMRI, jointly with a dual‐regression approach, was computed. Supporting the main hypothesis, the key finding reveals an increased correlated activity during rest in certain predefined resting state networks (albeit using uncorrected statistics) attributable to practice with the cognitively demanding tasks of the videogame. Observed changes were mainly concentrated on parietofrontal networks involved in heterogeneous cognitive functions. Hum Brain Mapp 34:3143–3157, 2013.

Altered Functional Connectivity in Essential Tremor: A Resting-State fMRI Study.

AbstractEssential tremor (ET) has been associated with a spectrum of clinical features, with both motor and nonmotor elements, including cognitive deficits. We employed resting-state functional magnetic resonance imaging (fMRI) to assess whether brain networks that might be involved in the pathogenesis of nonmotor manifestations associated with ET are altered, and the relationship between abnormal connectivity and ET severity and neuropsychological function.Resting-state fMRI data in 23 ET patients (12 women and 11 men) and 22 healthy controls (HC) (12 women and 10 men) were analyzed using independent component analysis, in combination with a “dual-regression” technique, to identify the group differences of resting-state networks (RSNs) (default mode network [DMN] and executive, frontoparietal, sensorimotor, cerebellar, auditory/language, and visual networks). All participants underwent a neuropsychological and neuroimaging session, where resting-state data were collected.Relative to HC, ET patients showed increased connectivity in RSNs involved in cognitive processes (DMN and frontoparietal networks) and decreased connectivity in the cerebellum and visual networks. Changes in network integrity were associated not only with ET severity (DMN) and ET duration (DMN and left frontoparietal network), but also with cognitive ability. Moreover, in at least 3 networks (DMN and frontoparietal networks), increased connectivity was associated with worse performance on different cognitive domains (attention, executive function, visuospatial ability, verbal memory, visual memory, and language) and depressive symptoms. Further, in the visual network, decreased connectivity was associated with worse performance on visuospatial ability.ET was associated with abnormal brain connectivity in major RSNs that might be involved in both motor and nonmotor symptoms. Our findings underscore the importance of examining RSNs in this population as a biomarker of disease.

Gait disorders of unknown cause in the elderly: Clinical and MRI findings

BACKGROUND Disequilibrium of unknown cause in older people has been associated with white matter lesions on neuroimaging studies. OBJECTIVE To investigate the relationship between gait and balance problems in the elderly, white matter hyperintensities, and vascular risk factors. METHODS We studied clinical and neuroimaging features in 30 people older than 65 years of age with gait disorders of unknown cause and 30 age- and sex-matched controls. Patients and controls underwent the same extensive quantitative test battery. White matter lesions on MRI scans were graded in different brain regions. RESULTS History of hypertension was more common among patients than controls (60% vs. 27%, p=0.012). On all scales, patients with gait disorders scored worse than controls. The frequency of white matter lesions was significantly higher in patients than in controls (p<0.001). In a multivariate logistic regression analysis in which diagnosis (patient vs. control) was the dependent variable, there was an association between diagnosis and white matter signal hyperintensity score (p<0.001) and history of hypertension (p=0.039). CONCLUSIONS Gait disorders of unknown cause in older people are associated both with white matter lesions on MRI scans and with history of hypertension.