Juan Arrazola

Complutense University of Madrid, Madrid, Madrid, Spain

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Publications (7)17.61 Total impact

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    ABSTRACT: The aim of this study was to analyze the combined contribution of magnetic resonance imaging and magnetoencephalography (MEG) to the diagnosis of mild cognitive impairment (MCI) and AD. To whole-head MEG recordings were obtained from three diagnosis groups: Alzheimer disease (AD), MCI, and control. Magnetic resonance imaging volumetric data of global brain, temporal lobe, and hippocampal volumes, were also obtained. Results indicated that a reduction of volume in the hippocampal structure allowed the discrimination between AD and MCI patients as compared with controls. The percentage of correct classification was 91.3% when AD versus controls was compared, and 83.3% when we compared MCI versus control. MEG data showed that AD patients exhibit higher theta and delta activity than MCI and controls. Such higher activity was significant in parietal, temporal, and occipital areas. Left parietal theta classified controls versus MCIs with 78.3% rate of correct classification. Right occipital theta and the left parietal delta allowed the discrimination of controls versus ADs, with 81.8% rate of correct classification. Left parietal theta discriminated between ADs and MCIs with 56.6% rate of correct classification. In addition, the combination of both techniques significantly improved the rate of correct classification, thus indicating that a multidisciplinary perspective of techniques may improve the diagnostic capabilities.
    Alzheimer disease and associated disorders 07/2009; 24(1):1-10. · 2.88 Impact Factor
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    ABSTRACT: An accurate computer-assisted method able to perform regional segmentation on 3D single modality images and measure its volume is designed using a mixture of unsupervised and supervised artificial neural networks. Firstly, an unsupervised artificial neural network is used to estimate representative textures that appear in the images. The region of interest of the resultant images is selected by means of a multi-layer perceptron after a training using a single sample slice, which contains a central portion of the 3D region of interest. The method was applied to magnetic resonance imaging data collected from an experimental acute inflammatory model (T(2) weighted) and from a clinical study of human Alzheimer's disease (T(1) weighted) to evaluate the proposed method. In the first case, a high correlation and parallelism was registered between the volumetric measurements, of the injured and healthy tissue, by the proposed method with respect to the manual measurements (r = 0.82 and p < 0.05) and to the histopathological studies (r = 0.87 and p < 0.05). The method was also applied to the clinical studies, and similar results were derived of the manual and semi-automatic volumetric measurement of both hippocampus and the corpus callosum (0.95 and 0.88).
    Magnetic Resonance Imaging 10/2003; 21(8):901-12. · 2.06 Impact Factor
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    ABSTRACT: Patients with Alzheimer disease (AD) have more low-frequency activity on conventional EEG and increased focal magnetoencephalographic (MEG) dipole density (DD) in delta and theta bands. This activity concurs with atrophy and reduced metabolic and perfusion rates, particularly in temporoparietal structures. The relationship between functional and structural measures and their conjoined capability to improve the diagnosis of AD were assessed in this study. Whole-head MEG recordings were obtained in 15 patients in whom the diagnosis of AD had been made and in 16 healthy control subjects during a resting condition. MR imaging volumetric data were also obtained; these included global cerebral, temporal lobe, and hippocampal volumes. DD in the delta and theta bands was enhanced in the AD group compared with the healthy control subjects. Slow-wave activity differed significantly between the groups in the temporoparietal regions of both hemispheres. Left hippocampal volume was correlated with left temporal and parietal delta DD and left temporal theta DD. A combination of left hippocampal volume and left temporal theta DD enabled correct classification in 87.1% of the patients with AD or control subjects. Results support the predominant role of temporoparietal hypofunction as defined by DD and hippocampal structural deficits shown on MR images in patients with AD. A multidisciplinary perspective of different techniques may improve our understanding of the disease and our diagnostic abilities.
    American Journal of Neuroradiology 04/2003; 24(3):481-7. · 3.17 Impact Factor
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    ABSTRACT: Many reports support the clinical validity of volumetric MRI measurements in Alzheimer's disease. To integrate functional brain imaging data derived from magnetoencephalography (MEG) and volumetric data in patients with Alzheimer's disease and in age matched controls. MEG data were obtained in the context of a probe-letter memory task. Volumetric measurements were obtained for lateral and mesial temporal lobe regions. As expected, Alzheimer's disease patients showed greater hippocampal atrophy than controls bilaterally. MEG derived indices of the degree of activation in left parietal and temporal lobe areas, occurring after 400 ms from stimulus onset, correlated significantly with the relative volume of lateral and mesial temporal regions. In addition, the size of the right hippocampus accounted for a significant portion of the variance in cognitive scores independently of brain activity measures. These data support the view that there is a relation between hippocampal atrophy and the degree of neurophysiological activity in the left temporal lobe.
    Journal of Neurology Neurosurgery &amp Psychiatry 03/2003; 74(2):208-12. · 4.92 Impact Factor
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    ABSTRACT: Magnetoencephalography (MEG) is suggested as a localizing technique of epileptogenic areas in drug-resistant seizure patients due to intracraneal lesions. A male 42-year-old patient who begins at 26 with partial complex drug-resistant seizures is put forward. MRI shows a 9 mm diameter lesion located in left superior temporal gyrus which seems compatible with cavernoma. Both conventional and sleep deprivation EEGs have proved normal. Sleep EEG shows sharp waves in left temporal region. MEG helps to localize interictal spike and spike-wave activity, as well as wide slow wave (2-7 Hz) activity areas. Craniotomy under analgesia and aware sedation conditions is carried out. Intrasurgery cortical electric stimulation assisted by neuronavigator causes a limited partial complex seizure which the patient recognizes to be exactly like his. Thus, MEG localization of the epileptogenic area is confirmed. Surgical resection of both the lesion and the epileptogenic area is carried out. The patient remains free from seizures 9 months after surgery. A control MEG study reveals no epileptogenic nor slow wave activity. CONCLUSION: in this particular case, MEG has proven to be a useful presurgical evaluation technique to localize epileptogenic activity, validated by intrasurgical cortical stimulation.
    Seizure 02/2003; 12(1):19-22. · 2.00 Impact Factor
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    ABSTRACT: The brain magnetic activity patterns in a high load probe-letter (targets and distractors) memory task were examined in patients with Alzheimers's disease (AD) and elderly controls. Control subjects showed a higher number of activity sources over the temporal and parietal cortex between 400 and 700 ms after stimulus onset. However, AD patients showed a higher number of sources over the frontal motor areas, including Broca's and the insula. The number of activity sources on the left parietal areas in response to the target stimuli predicted the AD score oncognitive (MMSE, CAMCOG) and functional staging (FAST) scales. These results suggest that a high information load reveals a deficient functioning of phonological store and reduced task-related activity in temporal and parietal areas, manifesting in a rapid information trace decay. The increased levels of activity in motor areas may reflect a compensatory strategy in an attempt to facilitate rehearsal speed.
    Neuroreport 01/2002; 12(18):3917-22. · 1.40 Impact Factor
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    ABSTRACT: In Alzheimer s disease, together with cognitive changes (loss of memory, lack of orientation in time and space, difficulty in carrying things out, etc.) non cognitive disorders also occur, seriously disturbing the patient s behavioral and emotional balance. Depression, delirious ideas, hallucinations and behavior changes (habits regarding sex, feeding and movement) are amongst the commonest features of this disease from its earliest stages. Several studies have described how initially the histopathological changes selectively involve different structures of the medial temporal lobe ( entorinal cortex, hippocampal formation, amygdala) and gradually includes neocortical association areas. Thus, the amygdala complex, a structure related to processes of memory and emotional control, is severely affected in this disease from the initial stages. Therefore, to find any possible relationship between involvement of the amygdala and the psychiatric expression of Alzheimer s type dementia, we did a radiological study, using magnetic resonance, together with a neuropsychological study of a group of 24 persons with Alzheimer s disease who had mild moderate deterioration. Analysis of the amygdala area and the scores on the subtest Alzheimer s Disease Assessment Scale Non cognitive (ADAS NC) were the variables chosen for measurement of the anatomical and psychiatric aspects of the subjects under investigation. The results of our study show a close relation between involvement of the amygdala (atrophy) and the presence of neuropsychiatric changes in persons with Alzheimer s disease.
    Revista de neurologia 01/2001; 33(5):477-82. · 1.18 Impact Factor