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V Ibáñez

Publications and source records attributed to V Ibáñez.

At least 19 recordsLinked to original sources
PubMed2006

Frontal theta event-related synchronization: comparison of directed attention and working memory load effects.

Early studies showed that long-term encoding and retrieval of new information is associated with modulation of the theta rhythm. More recently, changes in theta power amplitude over frontal electrode sites were reported during working memory, yet their relative significance in regard to attentional and memory processes remains unclear. Event-related synchronisation responses in the 4-7.5 Hz theta EEG frequency band was studied in 12 normal subjects performing four different tasks: two working memory tasks in which load varied from one (1-back task) to two (2-back task) items, an oddball detection (attention) task and a passive fixation task. A phasic theta increase was observed following stimulus apparition on all electrode sites within each task, with longer culmination peak and maximal amplitude over frontal electrodes. Frontal theta event-related synchronization (ERS) was of higher amplitude in the 1-back, 2-back and detection tasks as compared to the passive fixation task. Additionally, the detection task elicited a larger frontal and central theta ERS than the 2-back task. By analyzing theta ERS characteristics in various experimental conditions, the present study reveals that early phasic theta response over frontal regions primarily reflects the activation of neural networks involved in allocation of attention related to target stimuli rather than working memory processes.

Adult↗
PubMed2006

[Choledocal cyst: analysis of 29 cases and review or the literature].

UNLABELLED: The aim of the present study has been to systematize the clinical presentation of the entity named choledochal cyst, in relation with its probable etiopathology and the intraoperative findings as well as its evolution after surgery, based on the revision of the literature and of our experience in 29 cases. MATERIAL AND METHODS: 29 cases of cystic dilatation of the biliar duct extra and/or intrahepatic are analyzed. In 4 cases the diagnosis was prenatal and two were excluded of the study after it has been confirmed they suffered biliary atresia type I. In the left 27 cases, 19 variables are analyzed retrospectively, like age, sex, weight, symptoms, ultrasonographic images, etc. Subsequently, intra-operative cholangiographic findings were correlated with the clinic presentation and the evolution of the patients after surgery. RESULTS: Of the 27 cases analyzed 16 (59,25%) were cystic dilatations from which 14 had a neonatal or early clinic presentation (before 2 years), however the fusiform dilatations were presented later on. From the analyzed symptoms, in relation with the age only the pain and the jaundice showed significant differences, being the pain most frequent in later presentation ande the jaundice in the early form. The two cases of type 3 of Todani or choledochocele were of later presentation. An anomaly in the bilionpacreatric junction was detected in 15 patients; the majority had a later presentation, associated to pancreatitis in 4 cases. Primary cyst excision and biliary Roux-en-Y reconstruction was the treatment of election in the majority of cases. In 3 cases we used the appendix to replace the choledocus, but all three cases were reconverted two years later because of permanent elevation of ALT and GGT. CONCLUSIONS: In favour of the literature and of our experience nowadays it would be possible to systematize this malformation and make a division in two groups, depending on the cholangiographic findings and clinical presentation: 1. Cystic dilatations with a clinical neonatal presentation or beneath 2 years. 2. Fusiform dilatations with a later clinical predominance and associated frequently to pancreatitis and anomalous pancreatobiliary junction. Choledochocele is an entity that must be considered not only for its etiology but for its clinical presentation and treatment. Primary cyst excision and biliary Roux-en-Y reconstruction is the treatment of election. Regular long-term review of these patients is mandatory in the surveillance of sub-clinic cholangitis and the risk of possible long-term malignance of this entity.

Choledochal Cyst↗
PubMed2005

[Evidence-based medicine in Spanish pediatric surgery reports].

INTRODUCTION: Pediatric surgical literature is characterized by a high prevalence of observational studies and a paucity of randomized controlled trial, comparing mainly medical therapies. AIMS: To asses scientific evidence level produced by spanish pediatric surgeons. MATERIAL AND METHODS: Articles reported in Cirugía Pediátrica, surgical reports in Anales Españoles de Pediatría, and reports from spanish authors published in the Journal of Pediatric Surgery, Pediatric Surgery International and European Journal of Pediatric Surgery, from 1997 to 2002. Internal validity was assessed through the critial guides from Sackett, and evidence level was classified through the Oxford Centre for Evidence Based Medicine classification. RESULTS: 94.5% on therapy reports, 61.5% on diagnosis, 83.3% on prognosis and 52.2% on risk factors or etiology, were classified as level 4 (descriptive studies). Only four randomized controlled trials were found, all of them comparing medical therapies (analgesia, antibiotics and surgical stress control). CONCLUSIONS: Our results are similar to those offered by previous reviews, showing up a low level of scientific evidence in most articles. Diffusion of guides on reporting descriptive studies may improve the evidence level of our reports.

Child↗
PubMed2004

Aging and working memory: early deficits in EEG activation of posterior cortical areas.

Using the n-back task, we recently identified, in young subjects, a positive-negative event related potential component (PN(wm)) in a time-range window between 140 and 280 ms after stimulus onset representing an electrophysiological correlate of working memory load. To evaluate age-related electrophysiological changes in working memory processing, we applied the same neuropsychological paradigm and compared densities of the PN(wm) component in 17 young (mean age: 26) and 17 healthy elderly individuals (mean age: 75). Both age groups displayed a PN(wm) component during the two working memory tasks. For the 1-back task, densities were similar in both young and elderly individuals. In contrast, PN(wm) densities increased with higher memory load (2-back>1-back) in the younger but not in the older group. This difference was mainly observed over parietal electrodes suggesting an impaired activation of neural generators within this brain region. The present results are consistent with the hypothesis of decreased brain reserve in the elderly and provide evidence for age-related deficits in the recruitment of posterior cortical neurons with increasing working memory load.

Adult↗
PubMed2001

The effect of brain atrophy on cerebral hypometabolism in the visual variant of Alzheimer disease.

BACKGROUND: Brain glucose metabolic rates measured by positron emission tomography can be more affected by partial volume effects in Alzheimer disease (AD) than in healthy aging because of disease-associated brain atrophy. OBJECTIVE: To determine whether the distinct distribution of cerebral metabolic lesions in patients with the visual variant of AD (AD + VS) represents a true index of neuronal/synaptic dysfunction or is the consequence of brain atrophy. SETTING: Government research hospital. DESIGN: Resting cerebral metabolic rate for glucose was measured with positron emission tomography in a cross-sectional study of AD and AD + VS groups and in healthy control subjects. Segmented magnetic resonance images were used to correct for brain atrophy. PATIENTS: Patients with AD + VS had prominent visual and visuospatial symptoms. There were 15 patients with AD, 10 with AD + VS, and 37 age-matched control subjects. MAIN OUTCOME MEASURE: Measurement of the rate of cerebral glucose metabolism. RESULTS: Before atrophy correction, the AD + VS group, compared with the control subjects, showed hypometabolism in primary and extrastriate visual areas and in parietal and superior temporal cortical areas. Compared with the AD group, the AD + VS group showed hypometabolism in visual association areas. After atrophy correction, hypometabolism remained significantly different between patients and controls and between the 2 AD groups. CONCLUSIONS: The reductions in cerebral hypometabolism represent a true loss of functional activity and are not simply an artifact caused by brain atrophy. The different patterns of hypometabolism indicate the differential development of the lesions between the AD and AD + VS groups.

Aged↗
PubMed2001

Urgent distal splenorenal shunt in low-body weight patients.

The authors report two patients with extrahepatic portal hypertension and repeated massive bleeding from esophageal varices who underwent urgent distal splenorenal shunting (DSRS) after having proved refractory to medical treatment, endoscopic sclerotherapy, and ligation of esophageal varices. Their ages and weights were 18 months/10 kg, and 11 months/6.4 kg, respectively. The splenic veins were 6 and 4 mm in diameter. During follow-up of 4 and 3 years, respectively, the shunts have remained patent in both patients as demonstrated by Doppler Ultrasound. Gastrointestinal hemorrhage has not recurred, splenomegaly regressed, and platelet and white blood cell counts increased gradually. Neither patient developed a significant encephalopathy, and liver function tests showed no significant changes throughout the observed period. The authors considered the shunting feasible despite the relatively narrow splenic veins. In both patients the anatomic position of the splenic vein--more caudal to the posterior wall of the pancreas--facilitated its isolation. In the smaller infant, the inferior mesenteric vein was sutured to gain a satisfactory segment of splenic vein. The successful use of a DSRS to control actively bleeding varices in a child weighing 6.4 kg has not been previously reported.

Angiography, Digital Subtraction↗
PubMed2001

[Acute gastric volvulus secondary to asplenia in a child with Smith-Lemli-Opitz syndrome].

An acute gastric volvulus in a 10 years old boy with Smith-Lemli-Opitz syndrome is reported. He was immediately operated on and an organoaxial volvulus secondary to spleen agenesia was found. No other visceral malformation was present. Because of gastric ischemia, a second-look procedure was performed 48 hours later in order to asses necrosis extent. Gastric fundus had to be resected and the stomach was definitively fixed to the abdominal wall. Clinical, radiological and therapeutic characteristics of this unusual pathology are reviewed.

Acute Disease↗
PubMed2000

Wavelet analysis of dynamic PET data: application to the parametric imaging of benzodiazepine receptor concentration.

Receptor density and ligand affinity can be assessed using positron emission tomography (PET). Biological parameters (B(max)('), k(1), k(2), k(on)/V(R), k(off)) are estimated using a compartmental model and a multi-injection protocol. Parametric imaging of the ligand-receptor model has been shown to be of special interest to study certain brain disorders. However, the low signal-to-noise ratio in kinetic curves at the pixel level hampers an adequate estimation of model parameters during the optimization procedure. For this reason, mapping requires a spatial filter, resulting in a loss of resolution. Filtering the kinetic curves in the frequency domain using the Fourier transform is not appropriate, because of difficulties in choosing a correct and efficient cutoff frequency. A wavelet-based filter is more appropriate to such tracer kinetics. The purpose of this study is to build up parametric images at the pixel level while conserving the original spatial resolution, using wavelet-based filtering. Data from [(11)C]flumazenil studies, mapping the benzodiazepine receptor density, were used. An invertible discrete wavelet transform was used to calculate the time-frequency signals of the time-concentration PET curves on a pixel-by-pixel basis. Kinetic curves observed from large regions of interest in high and low receptor-density regions were used to calibrate the threshold of wavelet coefficients. The shrunken wavelet coefficients were then transformed back to the original domain in order to obtain the filtered PET signal. Maps of all binding parameters were obtained at the pixel level with acceptable coefficients of variation of less than 30% for the B(max)(') parameter in most of the gray matter. A strong correlation between model parameter estimates using the usual regions of interest and parametric imaging was observed for all model parameters (r = 0.949 for the parameter B(max)(')). We conclude that wavelet-based filters are useful for building binding parameter maps without loss of the original spatial resolution of the PET scanner. The use of the wavelet-based filtering method can be extended far beyond the multi-injection protocol. It is likely to be also effective for other dynamic PET studies.

Brain↗
PubMed2000

Correlations between reaction time and cerebral blood flow during motor preparation.

We show using positron emission tomography in normal volunteers that for four tasks involving motor preparation, regional cerebral blood flow in the ipsilateral cerebellum is negatively correlated with reaction time. Each of the tasks presented subjects with different amounts of advanced information (from none to partial to full information) prior to a signal to move one of two possible fingers in one of two possible directions. The cerebellum was the only brain area that was correlated with reaction time in all the conditions. These results are compatible with the idea that the cerebellum plays an important role in the preparation and initiation of motion.

Adult↗
PubMed2000

Similarity and robustness of PET and SPECT binding parameters for benzodiazepine receptors.

The single photon emission computed tomography (SPECT) radiotracer [123I]iomazenil is used to assess benzodiazepine receptor binding parameters. These measurements are relative indices of benzodiazepine receptor concentration (B'max). To evaluate the ability of such indices in accurately accessing the B'max the authors compared them with absolute values of B'max, measured using positron emission tomography (PET). The authors performed SPECT, PET, and magnetic resonance imaging (MRI) studies on a group composed of seven subjects. For SPECT studies, the authors administered a single injection of [123I]iomazenil and estimated the total and specific distribution volumes (DV(T SPECT), DV(S SPECT)) and the binding potential (BP) using unconstrained (BP(SPECT)) and constrained (BP(C SPECT)) compartmental models. For PET studies, the authors used a multiinjection approach with [11C]flumazenil and unlabeled flumazenil to estimate absolute values of receptor concentration, B'max, and some other binding parameters. The authors studied the correlation of different binding parameters with B'max. To study the robustness of the binding parameter measurements at the pixel level, the authors applied a wavelet-based filter to improve signal-to-noise ratio of time-concentration curves, and the calculated kinetic parameters were used to build up parametric images. For PET data, the B'max and the DV(PET) were highly correlated (r = 0.988). This confirms that it is possible to use the DV(PET) to access benzodiazepine receptor density. For SPECT data, the correlation between DV(SPECT) estimated using a two- and three-compartment model was also high (r = 0.999). The DV(T SPECT) and BP(C SPECT) parameters estimated with a constrained three-compartment model or the DV(T''SPECT) parameter estimated with a two-compartment model were also highly correlated to the B'max parameter estimated with PET. Finally, the robustness of the binding parameters allowed the authors to build pixel-by-pixel parametric images using SPECT data.

Adult↗
PubMed1999

Deficient activation of the motor cortical network in patients with writer's cramp.

OBJECTIVE: To study regional cerebral blood flow (rCBF) in patients with simple writer's cramp using PET to identify regions that malfunction. BACKGROUND: Several lines of evidence indicate impaired cortical function in patients with focal dystonia, but the precise pathophysiology is still unknown. METHODS: Seven patients with writer's cramp were compared with seven age- and sex-matched control subjects. Control subjects and patients were scanned during sustained contraction, tapping, and writing with the right hand. After realignment and stereotactic normalization of the scans, all tasks were compared with a rest condition. For each task, an intra- and intergroup comparison was performed using statistical parametric mapping. For each condition and within groups, rCBF correlation analysis was performed between some selected regions that were activated during movement. RESULTS: In control subjects and patients, significant increases of rCBF were observed for each task in areas already known to be activated in motor paradigms. The intergroup comparison disclosed less activation in writer's cramp patients for several areas for all three tasks. This decrease reached significance for the sensorimotor cortex during the sustained contraction task and for the premotor cortex during writing. rCBF correlation analysis showed different patterns between control subjects and patients. At rest and during writing, the correlations between the putamen and premotor cortical regions and between the premotor cortical regions themselves were stronger in control subjects. CONCLUSIONS: Deficient activation of premotor cortex and decreased correlation between premotor cortical regions and putamen suggest a dysfunction of the premotor cortical network in patients with writer's cramp possibly arising in the basal ganglia. The dysfunction is compatible with a loss of inhibition during the generation of motor commands, which in turn could be responsible for the dystonic movements.

Adult↗
PubMed1999

[Laparoscopic transsection of Ladd's bands: a new indication for therapeutic laparoscopy in neonates].

Within the last ten years and by the introduction of some new instruments, laparoscopy is a safe and effective method that has been further extended in children. We report our experience in the treatment of laparoscopy on a seven day old newborn affected by malrotation with an intermittent duodenal obstruction. The treatment consisted of a duodenal liberation after the section was easily performed in congenital Ladd's bands. The spiral twists of the small intestine found in the upper gastrointestinal series, disappeared in a new study done after surgery. We consider this operation as a new indication for an operative laparoscopy. It allows a good visualization of this congenital abnormality, and it is easy to perform with a significantly reduced operative trauma.

Duodenal Obstruction↗
PubMed1999

[High-frequency jet ventilation with a proximal injector in a case of surgery of the tracheal carina].

A 44-year-old man underwent surgery requiring medial sternotomy of resection of a tracheal carcina tumor. High frequency jet ventilation was used during tumor resection and reconstruction of the carina in order to shorten the time of surgery and to provide a nearly immobile and unobstructed surgical field. The only noteworthy complication was a tendency to respiratory acidosis that resolved without sequelae in the operating room once the trachea was closed. The anesthetic challenges presented by the various techniques used throughout history for such an interesting and complex type of surgery are briefly summarized. We also discuss the role of high frequency jet ventilation on surgery involving the major airways.

Adult↗
PubMed1999

[Single-system ectopic ureters. A review of 19 cases].

Single system ectopic ureters are usually associated with multiple congenital abnormalities and the corresponding renal units is frequently abnormal. 19 cases of single system ectopic ureters were diagnosed and treated in our hospital during the last 20 years. The patients were less than 11 years old. The abnormality was bilateral in two cases and the 63% of all had associated malformations, being the anorectal abnormalities the most frequent. The incidence of reflux into the ectopic ureter was 57%, and the association to unilateral or contralateral renal agenesis, 26.3%. Thirteen ectopic ureters were reimplanted successfully into the bladder, and the cases of nonfunctioning kidneys were removed (nephroureterectomy). The follow-up period was 10 months to 14 years, developing the 68% of the cases without any complication and a good renal function. Two patients were transplanted due to a kidney failure. Diagnosis is often extremely difficult and requires a high degree of suspicion. This diagnosis may be incidental, and it may be made during investigation of patients with other malformations. An early diagnosis and treatment must be made in order to avoid a disturbance of renal function. We wish to point up the high incidence of reflux into the ectopic ureter and the high association to renal agenesis in the single system ectopic ureters in comparison with ectopic ureter of duplex system.

Abnormalities, Multiple↗
PubMed1998

Long-gap esophageal atresia: reconstruction preserving all portions of the esophagus by Schärli's technique.

For distances of over 4-5 cm, esophageal replacement is almost always necessary in esophageal atresias. We present the technical details and describe our experience with esophageal reconstruction by elongation of the lesser curvature (Schärli's technique) in four cases of very long atresias. A retrosternal transposition was made without a thoracotomy in two children, and an orthotopic mediastinal route through a right thoracotomy was done in two others. There were two main complications: anastomotic leaks in three patients that closed spontaneously, and too-rapid gastric emptying, resulting in dumping symptoms that improved with time and diet. One patient developed an anastomotic stricture that responded to bouginage, while another had temporary feeding problems. Esophageal reconstruction by elongation of the lesser curvature provides a relatively simple method of esophageal replacement in children in that all portions of the esophagus are preserved. We propose this technique for early establishment of esophageal continuity in neonates.

Child, Preschool↗
PubMed1998

Dynamic cortical involvement in implicit and explicit motor sequence learning. A PET study.

We examined the dynamic involvement of different brain regions in implicit and explicit motor sequence learning using PET. In a serial reaction time task, subjects pressed each of four buttons with a different finger of the right hand in response to a visually presented number. Test sessions consisted of 10 cycles of the same 10-item sequence. The effects of explicit and implicit learning were assessed separately using a different behavioural parameter for each type of learning: correct recall of the test sequence for explicit learning and improvement of reaction time before the successful recall of any component of the test sequence for implicit learning. Regional cerebral blood flow was measured repeatedly during the task, and a parametric analysis was performed to identify brain regions in which activity was significantly correlated with subjects' performances: i.e. with correct recall of the test sequence or with reaction time. Explicit learning, shown as a positive correlation with the correct recall of the sequence, was associated with increased activity in the posterior parietal cortex, precuneus and premotor cortex bilaterally, also in the supplementary motor area (SMA) predominantly in the left anterior part, left thalamus, and right dorsolateral prefrontal cortex. In contrast, the reaction time showed a different pattern of correlation during different learning phases. During the implicit learning phase, when the subjects were not aware of the sequence, improvement of the reaction time was associated with increased activity in the contralateral primary sensorimotor cortex (SM1). During the explicit learning phase, the reaction time was significantly correlated with activity in a part of the frontoparietal network. During the post-learning phase, when the subjects achieved all components of the sequence explicitly, the reaction time was correlated with the activity in the ipsilateral SM1 and posterior part of the SMA. These results show that different sets of cortical regions are dynamically involved in implicit and explicit motor sequence learning.

Adult↗
PubMed1998

Regional glucose metabolic abnormalities are not the result of atrophy in Alzheimer's disease.

OBJECTIVE: To determine whether the hypometabolism observed in PET images of patients with Alzheimer's disease (AD) is due entirely to brain atrophy. BACKGROUND: Reduced brain glucose metabolism in AD patients measured using PET has been reported by numerous authors. Actual glucose metabolic values in AD may be reduced artificially because of brain atrophy, which accentuates the partial volume effect (PVE) on data collected by PET. METHODS: Using segmented MR images, we corrected regional cerebral metabolic rates for glucose for PVEs to evaluate the effect of atrophy on uncorrected values for brain metabolism in AD patients and healthy control subjects. RESULTS: Global glucose metabolism was reduced significantly before and after correction in AD patients compared with controls. Before PVE correction, glucose metabolic values in patients were lower than in control subjects in the inferior parietal, frontal, and lateral temporal cortex; in the posterior cingulate; and in the precuneus. These reductions remained significantly lower after PVE correction, although in the posterior cingulate the difference in metabolism between AD patients and control subjects lessened. Regional glucose metabolism of these areas with PVE correction was lower in moderately-severely demented patients than in mildly demented patients. CONCLUSION: Reduced glucose metabolism measured by PET in AD is not simply an artifact due to an increase in CSF space induced by atrophy, but reflects a true metabolic reduction per gram of tissue.

Aged↗