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Juan Alvarez-Linera

Publications and source records attributed to Juan Alvarez-Linera.

4 recordsLinked to original sources
PubMed2006

MRI volumetry and proton MR spectroscopy of the brain in Lafora disease.

PURPOSE: To determine brain involvement in Lafora disease by means of 3-T MRI volumetry and 1H magnetic resonance (MR) spectroscopy. METHODS: Ten patients with Lafora disease and 10 healthy controls were included in the study. The diagnosis of Lafora disease was proven genetically by the presence of mutations in the EPM2A gene in all patients, and their evolution was staged in three groups according to their functional state. MRI volumetry was performed by means of AX3DT1 images with assessment of the cerebellum and the brainstem, by using the program Stereonauta, and all the brain structures, by using voxel-based morphometry. [1H]MR spectroscopy was performed by using an Eclipse PRESS sequence probe system with 8-cc voxels positioned in the occipital and frontal cortexes, basal ganglia, pons, and cerebellar hemispheres. Spectral peak areas corresponding to NAA (N-acetylaspartate), creatine, and choline were obtained. RESULTS: MRI volumetry showed no statistically significant differences in patients compared with healthy controls in any of the analyzed structures. Analysis of [1H]MR spectroscopy data showed a statistically significant reduction in the NAA/creatine ratio in patients compared with controls in the frontal (p = 0.001) and occipital cortex (p = 0.043), basal ganglia (p = 0.002), and cerebellar hemispheres (p = 0.007). The NAA/choline and choline/creatine ratios were statistically significantly different in the frontal cortex (p = 0.005). No correlation was observed between the disease-evolution stage and MRI-measured volumes (range, -0.92 to 0.44) or [1H]MR spectroscopy values (range, -0.29 to 0.50). CONCLUSIONS: In our series of Lafora disease patients, [1H]MR spectroscopy was more sensitive than structural MRI to detect brain involvement. The brain cortex, especially frontal cortex, cerebellum, and basal ganglia, showed the greatest metabolic changes.

Aspartic Acid↗
PubMed2005

Could activity in anterior frontal regions predict performance on declarative memory tests?

Few studies have tested the correlation between traditional declarative memory scores and functional brain imaging measures of memory. We examined the predictable capabilities of magnetoencephalography-derived measures, scanned during a high-load encoding-memory task, in the immediate (LM-1) and delayed (LM-2) recall from the Wechsler memory scale. The number of activity sources on the left frontal pole (between 300 and 600 ms) predicted scores in LM-1 and LM-2. Collapsing the activity in the left frontal pole and the orbitofrontal cortex increased the goodness of the solution for the LM-2 scores. The fact that rostral-frontal measures achieved significant values highlights the importance of executive processes, such as the implementation of memory strategies and top-down control mechanisms, in the performance of high-load memory tasks.

Adult↗
PubMed2003

Prospective evaluation of carotid artery stenosis: elliptic centric contrast-enhanced MR angiography and spiral CT angiography compared with digital subtraction angiography.

BACKGROUND AND PURPOSE: Although digital subtraction angiography (DSA) is the reference standard for assessing carotid arteries, it is uncomfortable for patients and has a small risk of disabling stroke and death. These problems have fueled the use of spiral CT angiography and MR angiography. We prospectively compared elliptic centric contrast-enhanced MR angiography and spiral CT angiography with conventional DSA for detecting carotid artery stenosis. METHODS: Eighty carotid arteries (in 40 symptomatic patients) were assessed. Elliptic centric MR and spiral CT angiographic data were reconstructed with maximum intensity projection and multiplanar reconstruction techniques. All patients had been referred for DSA evaluation on the basis of findings at Doppler sonography, which served as a screening method (degree of stenosis > or = 70% or inconclusive results). Degree of carotid stenosis estimated by using the three modalities was compared. RESULTS: Significant correlation with DSA was found for stenosis degree for both elliptic centric MR and spiral CT angiography; however, the correlation coefficient was higher for MR than for CT angiography (r = 0.98 vs r = 0.86). Underestimation of stenoses of 70-99% occurred in one case with elliptic centric MR angiography (a 70% stenosis was underestimated as 65%) and in nine cases with spiral CT angiography, in comparison to DSA findings. Overestimation occurred in two cases with MR angiography (stenoses of 65-67% were overestimated as 70-75%). With CT, overestimation occurred in seven cases; a stenosis of 60% in one case was overestimated as 70%. Both techniques confirmed the three cases of carotid occlusion. With elliptic centric MR angiography, carotid stenoses of 70% or greater were detected with high sensitivity, 97.1%; specificity, 95.2%; likelihood ratio (LR) for a positive test result, 20.4; and ratio of LR(+) to LR(-), -0.3. With spiral CT angiography, sensitivity, specificity, LR(+), and LR(+):LR(-) were 74.3%, 97.6%, 31.2, and 0.3, respectively. CONCLUSION: Elliptic centric contrast-enhanced MR angiography is more accurate than spiral CT angiography to adequately evaluate carotid stenosis. Furthermore, elliptic centric contrast-enhanced MR angiography appears to be adequate to replace conventional DSA in most patients examined.

Adult↗