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Biomedical subjects

F Velasco

Publications and source records attributed to F Velasco.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

Subacute and chronic electrical stimulation of the hippocampus on intractable temporal lobe seizures: preliminary report.

Recent animal experiments show that the application of an electrical stimulus to the amygdala or hippocampus following the kindling stimulus produced a significant and long-lasting suppressive effect on this experimental model of epilepsy. This is a preliminary report on the development of a surgical neuromodulatory procedure by chronic electrical stimulation of the hippocampus (CHCS) for control of intractable temporal lobe seizures in patients in whom anterior temporal lobectomy is not advisable, i.e., patients with bilateral temporal foci or a unilateral focus spreading to surrounding cerebral regions of the dominant hemisphere. This work was divided in two main consecutive stages. In the first stage, we demonstrated that subacute hippocampal stimulation (SAHCS) blocks intractable temporal lobe epileptogenesis with no additional damage to the stimulated tissue, and in a second stage, we attempt to demonstrate that CHCS may produce a sustained, long-lasting antiepileptic condition without additional undesirable effects on language and memory. In addition, taking advantage of this unique and ethically permissible situation, we attempt to determine whether or not the antiepileptic effects of SAHCS and CHCS are due to inhibition of the stimulation of hippocampal tissue by means of a number of electrophysiological, single photon computed tomography (SPECT) perfusion, and autoradiographic techniques.SAHCS during 3-4 weeks prior to anterior temporal lobectomy applied to a critical area located either at the anterior Pes hippocampus close to the amygdala or at the parahippocampal gyrus close to the entorhinal cortex abolished clinical seizures and significantly decreased the number of interictal spikes at focus after 5-6 days. Microscopy analysis of the stimulated tissue showed no evident histopathological differences between stimulated vs. non-stimulated hippocampal tissues. Additionally, CHCS persistently blocked temporal lobe epileptogenesis for 3-4 months with no apparent additional undesirable effects on short memory. Also, inhibition of the stimulated hippocampus seems to be one of the possible mechanisms underlying the beneficial antiepileptic effects of SAHCS and CHCS. This was revealed by increased threshold and decreased duration of the afterdischarges induced by hippocampal stimulation, flattening of the hippocampal-evoked response recovery cycles, SPECT hypoperfusion of the hippocampal region, and increased hippocampal benzodiazepine receptor binding. Future studies increasing the number and time of follow-up of patients under hippocampal stimulation are necessary before considering CHCS a reliable procedure for controlling intractable temporal lobe seizures.

Amygdala↗
PubMedDate not supplied

Subthalamic prelemniscal radiation stimulation for the treatment of Parkinson's disease: electrophysiological characterization of the area.

Previous reports have provided evidence of a reticulo-thalamic system, extending from the mesencephalic reticular formation (MRF) to the ventrolateral thalamus (VL), involved in the production of tremor. In humans, a funnel of fibers in the posterior subthalamus named the prelemniscal radiations (Raprl) has been described as an exquisite target to treat tremor in cases of Parkinson's disease. In the present study, a group of 14 patients suffering from Parkinson's disease, with prominent unilateral tremor and rigidity, were implanted with tetrapolar depth brain stimulation (DBS) electrodes in Raprl to perform chronic electrical stimulation (ES) for the treatment of patient symptoms. Electrodes were left externalized to corroborate their placement throughout MRI studies and also to perform the following electrophysiological battery: (a) recording of somatosensory-evoked responses (SEP) through different electrode contacts and scalp by means of a paradigm to study the attention process; (b) evoking scalp EEG responses by stimulation with low (3 cps, 6 cps) and high (60-120 cps) frequencies with stimuli delivered through different electrode contacts, and (c) studying recovery cycle (RC) potentials in the Raprl while the upper MRF was being stimulated and, conversely, the RC in MRF while Raprl was being stimulated, before and after subacute Raprl stimulation. Thereafter, the electrodes were internalized and connected to a pulse generator (IPG) to carry on chronic ES, while the effects of stimulation were determined through a quantitative evaluation that measured phasic and tonic muscular activity with EMG recordings during different motor tasks. Results indicate the following: (a) that late, but not early, SEP components were recorded in Raprl and modulated in different attentive conditions; (b) that bilateral recruiting responses and spike and wave complexes were elicited by Raprl through low-frequency stimulation, while bilateral positive DC shifts induced by high-frequency stimulation were recorded, similar to those obtained in animals from MRF, and (c) that Raprl-ES induced RC inhibition at Raprl, but Raprl ES did not change MRF-RC. Long-term Raprl-ES induced a significant decrease in tremor and rigidity. It was concluded that Raprl represents a subthalamic circuit electrophysiologically related to MRF in the genesis of tremor and rigidity and in the process of selective attention. Raprl-ES induced a significant improvement in tremor and rigidity by causing inhibition of the stimulated area.

Action Potentials↗
PubMedDate not supplied

Acute and chronic electrical stimulation of the centromedian thalamic nucleus: modulation of reticulo-cortical systems and predictor factors for generalized seizure control.

The present report recapitulates the clinical and electrophysiologic studies we have performed on patients with certain forms of medically intractable epilepsy to investigate the basic mechanisms and predictor factors for seizure control of the electrical stimulation of the thalamic centromedian nucleus (CM) procedure. Acute electrical stimulation of CM reveals that in humans, as in other animals, CM represents a thalamic relay of a reticulo-cortical system that participates crucially in wakefulness and attentive processes and in regulation of cortical excitability, as well as in the physiopathology of genuine generalized epileptic seizures. For example, unilateral, threshold, low-frequency (6/sec) stimulation of CM produced electrocortical incremental responses, while high-frequency (60/sec) stimulation of CM produced electroencephalogram (EEG) desynchronization and electronegative DC shifts with no behavioral counterparts. In contrast, combined suprathreshold low-frequency (3/sec) stimulation of CM on one side and of mesencephalic reticular stimulation on the other produced generalized spike-wave complex discharges accompanied by the symptoms of a typical absence attack, including motionless stare, eye blinking, and unresponsiveness of patients to a series of flashes under a simple response task. Chronic bilateral, threshold, high-frequency (60/sec) stimulation of CM significantly decreased the number of primary and secondary generalized tonic-clonic seizures and atypical absence attacks and the amount of interictal generalized EEG discharges in both. In addition, it improved the psychological performance of patients and normalized the EEG by increasing the frequency of background EEG activity. In contrast, chronic stimulation of CM reduced neither the number of complex partial seizures nor the epileptic EEG activities localized in the temporal region. Good outcomes of the chronic CM stimulation procedure were achieved depending on correct selection of patients and accuracy of ventriculographic stereotactic targets, as well as on periodic clinical and EEG evaluation and electrophysiologic monitoring of CM electrical stimulation reliability. However, the presence of 3- to 6-month long-lasting effects of CM stimulation made statistical evaluation of ON-OFF effects of CM stimulation under placebo, double-masked randomized experiments difficult.

Cerebral Cortex↗
PubMedDate not supplied

Electrical stimulation of the centromedian thalamic nucleus in the treatment of convulsive seizures: a preliminary report.

Five patients with clinical and EEG primary generalized or multifocal uncontrollable seizures underwent stereotaxic implantation of electrodes in both centromedian thalamic nuclei (CM). Each electrode consisted of a semiflexible array of three platinum-iridium wires, isolated except at their tips, which were separated by 4 mm. Bipolar, biphasic rectangular pulses were delivered in trains of 1 min every 5 min, alternating right and left side for sessions 2 h/day. Patients were followed for 3 months with charting of clinical seizures, daily 4-h EEG recordings from scalp and depth for 5 days and weekly thereafter. Baseline and 3-month evaluation of psychological performance through selected Beta R, Wechsler memory scale, visual discrimination, MMPI, and Zung's rated depression scale. Tests were evaluated for significant changes by the parametric student's t test and Mann Whitney nonparametric test. Clinical seizures were significantly reduced by electrical stimulation (ES), as were EEG interictal spikes and EEG slow waves. Psychological performance improved beyond that expected by reduction in seizure activity. ESCM induced a local afterdischarge (AD) that progressively developed in time and intensity, and the beneficial effects outlasted ES for periods of weeks to months, suggesting that a state of hyperexcitability of stimulated tissue, similar to "kindling," was created by chronic ES.

Electric Stimulation Therapy↗
PubMedDate not supplied

Epileptiform EEG activities of the centromedian thalamic nuclei in patients with intractable partial motor, complex partial, and generalized seizures.

Centromedian thalamic nuclei (CM) epileptiform EEG activities were recorded in patients with intractable partial motor, complex partial, and generalized seizures through implanted recording-stimulating electrodes, used for seizure control. CM epileptiform activities showed either little or no correlation to focal surface cortical and amygdaloid activities in patients with partial motor and complex partial seizures: CM paroxysmal discharges were correlated to focal epileptiform ictal activities only during the contraversive movements of partial motor and complex partial seizures. In contrast, CM epileptiform activities were consistently correlated to widespread surface cortical activities and clinical symptoms of fully developed nonconvulsive and convulsive tonic-clonic generalized seizures; i.e., unilateral CM double spike-wave complex discharges significantly preceded (p less than 0.001) the contralateral CM and bilateral surface cortical discharges and symptoms of nonconvulsive generalized seizures. Unilateral CM fast-slow-fast paroxysmal discharges significantly preceded (p less than 0.005) those of the contralateral CM and bilateral surface cortical regions and symptoms of the convulsive tonic-clonic generalized seizures. Individual spike-wave complexes from the frontal region preceded (p less than 0.001 and p less than 0.005) those at CM and other cortical regions during the nonconvulsive and clonic generalized attacks. No correlations between CM and cortical epileptiform activities were found, however, in the case of abortive, subclinical thalamocortical EEG discharges.

Electroencephalography↗
PubMedDate not supplied

Epileptiform EEG activity of the centromedian thalamic nuclei in children with intractable generalized seizures of the Lennox-Gastaut syndrome.

Centromedian thalamic nuclei (CM) epileptiform EEG activities were recorded in children with intractable generalized seizures of Lennox-Gastaut syndrome (LGS) through implanted recording-stimulating electrodes used for seizure control. Ictal CM epileptiform activities were consistently correlated to widespread surface cortical EEG activities and symptoms in all patients and all types of generalized seizures; i.e., fast spike discharges at CM correlated at onset of tonic and tonic-clonic generalized seizures; slow (1-2 Hz) spike-wave complex discharges at CM correlated for atypical absence seizures; slow polyspike-wave complex discharges correlated for myoclonic seizures; and spike bursts and suppression patterns correlated for combined tonic-atonic-myoclonic seizures. Ictal EEG activities occurred simultaneously at right and left CM and surface at onset of all seizure types, with the exception of myoclonic seizures where CM complete discharges and individual spike-wave complexes significantly lead those of the surface. Brief tonic-atonic spasms clinically undistinguishable from "real" epileptic seizures showed no EEG counterparts at CM and surface. Interictal CM spike-wave complete discharges and individual spike-wave complexes showed variable amplitude-temporal patterns. Amplitude emphasis on CM and frontopolar regions was observed in most of complete discharges, however, and phase shifts between CM and frontopolar regions were observed in individual spike-wave complexes.

Adult↗
PubMedDate not supplied

Effect of chronic electrical stimulation of the centromedian thalamic nuclei on various intractable seizure patterns: I. Clinical seizures and paroxysmal EEG activity.

Twenty-three patients with various intractable seizure patterns were divided into four groups based on their most frequent seizure type and their clinical and EEG response to chronic electrical stimulation of the centromedian thalamic nuclei (ESCM): group A, generalized tonic-clonic (GTC, n = 9); group B, partial motor (Rasmussen type) (n = 3); group C, complex partial seizures (CPS, n = 5); and group D, generalized tonic seizures (Lennox-Gastaut type) (n = 6). CM were radiologically and electrophysiologically localized by means of stereotaxic landmarks and by thalamically induced scalp recruiting-like responses and desynchronization. ESCM consisted of daily 2-h stimulation sessions for 3 months. Each stimulus consisted of a 1-min train of square pulses with a 4-min interstimulus interval, alternating right and left CM. Each pulse was 1.0 ms in duration at 60/s frequency and 8-15 V (400-1,250 microA) amplitude. Voltage (V), current flow (microA) and impedance (k omega) at the electrode tips were kept constant. A significant decrease in the number of seizures per month and paroxysmal EEG waves per 10-s spochs occurred in group A patients between the baseline period (BL) and the ESCM period. These changes persisted for > 3 months after discontinuation of ESCM (poststimulation period, Post). Post was accompanied by a significant decrease in the number of paroxysmal EEG discharges. A substantial decrease in seizures and paroxysmal discharges was also observed in patients of group B. In contrast, patients of groups C and D showed no significant changes from BL to ESCM and Post periods, except for a significant decrease in the number of seizures in group D patients from BL to Post periods.

Adolescent↗
PubMedDate not supplied

Effect of chronic electrical stimulation of the centromedian thalamic nuclei on various intractable seizure patterns: II. Psychological performance and background EEG activity.

We studied the effect of electrical stimulation of centromedian thalamic nuclei (ESCM) on seizure control and paroxysmal EEG activity in 23 patients. We report the effect of chronic ESCM on psychological performance and background EEG activity of patients with various intractable seizure patterns. In each patient, a simple specifically designed neuropsychological scales (one for adults and one for children) was administered at the end of the baseline (BL), ESCM, and poststimulation (Post) periods; and 14 consecutive EEG recordings during these periods were performed to determine the degree of neuropsychological improvement and the temporal course of EEG changes. A significant increase in psychological scores and the number of background EEG waves per 10 s was noted in groups A (generalized tonic-clonic seizures, GTC), C (complex partial seizures, CPS), and D (generalized tonic seizures) and the total group of patients from BL to ESCM and from BL to Post periods. Group B patients showed a substantial increase (partial motor seizures) during the same periods. Improvement on psychological performance correlated better with age and baseline degree of deterioration than with the nature of the particular psychological improvement in any given subtest. The improvement in EEG background rhythm was most noticeable at the end of ESCM and at the beginning of the Post periods. Complete normalization of neuropsychologic scores and EEG rhythms was rare, but improvement was significant for both. Psychological scores increased from BL 14 +/- 2 to ESCM 21 +/- 2 and Post 23 +/- 2 (normal expected 26), and EEG background rhythm increased from BL 42 +/- 2 to ESCM 62 +/- 2 and Post 54 +/- 2 EEG waves/10 s. (normal expected > 80).

Adolescent↗
PubMedDate not supplied

Electroencephalographic and magnetic resonance correlations in children with intractable seizures of Lennox-Gastaut syndrome and epilepsia partialis continua.

A study was performed of EEG-magnetic resonance imaging (MRI) abnormalities in 7 Lennox-Gastaut syndrome (LGS) children and 3 epilepsia partialis continua (EPC) children with intractable generalized and partial motor seizures, respectively. In 4 children with LGS and 3 children with EPC, depth electrodes were implanted in the centromedian thalamic nuclei (CM) for seizure control. In all children with LGS, hyperdense, T2-weighted MRI signals were observed at the mesencephalic level of the brainstem, whereas none of the 3 children with EPC had this finding. Patients with idiopathic LGS without cerebral hemisphere MRI abnormalities showed generalized bilateral and symmetrical spike-wave EEG activity. Patients with symptomatic LGS with unilateral hemispheric MRI abnormalities demonstrated asymmetrical EEG activity with higher amplitude spike-and-wave over the normal hemisphere. Patients with EPC with unilateral hemispheric lesions had lateralized higher amplitude spike-wave over the damaged hemisphere. These data suggest that abnormal mesencephalic MRIs are a sign of bad prognosis in patients with LGS but not with EPC. Maximal amplitude paroxysmal EEG activities may indicate the abnormal hemisphere in patients with EPC or the normal hemisphere in those with LGS.

Cerebellum↗
PubMedDate not supplied

Coagulation, fibrinolytic and kallikrein systems in neonates with uncomplicated sepsis and septic shock.

This study evaluates the contact system, coagulation inhibitors and fibrinolysis in 23 full-term newborns with sepsis (8 with septic shock). The results were compared with a group of 20 healthy newborns. Blood samples were obtained at the time of clinical diagnosis and 3 days after the antibiotic therapy was started. The results showed that: severe infection was associated with activation of the contact system, depletion of anticoagulant proteins and elevation of C4b-binding protein levels. There was a shift in protein S to the complexed inactive form, and the thrombin-antithrombin complexes increased. These changes occurred in parallel to both activation and inhibition of fibrinolysis. These changes were more pronounced in the septic shock patients than in nonshock neonates. After therapy, this procoagulant state decreased among survivor patients while in those who died, the abnormalities in coagulation did not improve. Our study suggests that neonatal sepsis induces a hypercoagulable state that persists in nonsurvivor neonates despite a correct treatment.

Anti-Bacterial Agents↗
PubMedDate not supplied

Low prevalence of the factor V Leiden among patients with ischemic stroke.

The aim of the study is to determine if a novel thrombophilia mechanism (factor V Leiden) that is associated with resistance to activated protein C (APC) is in itself a risk factor for the development of ischemic stroke (IS). Sixty-six controls and 66 patients with IS were included in an unmatched case-control study. In the group of patients selected for this study, other causes of IS were ruled out. APC resistance was considered if activated partial thromboplastin time (aPTT) measured in the presence of APC was less than 2.2 times prolonged when compared to aPTT in the absence of APC (APC ratio < 2.2). Digestion with a restriction enzyme of a previously amplified exon 10 of the gene that encodes for factor V was used to detect the presence of the factor V mutation. We identified 5 patients (prevalence: 7.5%) with APC resistance (mean age: 31 years, range: 6-52 years). Mutation in factor V gene was confirmed in three of them. In the control group we detected 3 (4.5%) low APC ratios, all of them carrying specific factor V mutation. We cannot conclude a significant association between APC resistance and IS [odds ratio: 1.72; chi 2 Mantel and Haenszel was 0.53 (p = 0.4673) and exact Fisher's test p = 0.3589] but these 5 young adults suffered an episode of IS having APC resistance as the only prothrombotic condition. In conclusion, these results cannot prove a statistical association between APC resistance and IS. Further studies must be done in order to confirm that there is no relationship between APC resistance and IS in young adults when major risk factors are excluded.

Adolescent↗
PubMedDate not supplied

[Cerebrovascular disease in a tertiary care hospital. The current situation and points to be improved].

INTRODUCTION: Caring for patients suffering from a cerebrovascular diseases requires a large quantity of resources which must be optimised. The aim of this study is to analyse the management of stroke in a tertiary care hospital. PATIENTS AND METHODS: All admissions with a diagnosis of stroke were analysed retrospectively for the year 2003. Length of stay, computed tomography in the Emergency Room, origin, previous admissions during the last year, presence of vascular risk factors, stroke subtype, complications and mortality during admission and destination when discharged from hospital, were all recorded. RESULTS: 936 patients were admitted to hospital with a diagnosis of stroke. 80.22% corresponded to acute ischaemic strokes (27.14% lacunar, 18.57% transient ischaemic attacks, 10.25% cardioembolic, 15.44% aterothrombotic, 8.44% infarct of undetermined cause, 0.24% unusual aetiology) and 19.78% corresponded to haemorrhagic strokes (13.99% intraparenchymatous hemorrhage, 5.79% subarachnoid hemorrhage). Intra-hospital mortality was 5.3%. 11% suffered from complications while in hospital, and average length of stay was 10.4 days, being much longer for those patients discharged to a medium-long stay centre (17.5 days). Compared to other series, the incidence of cardioembolic and aterothrombotic subtypes of stroke is low. However, because of the inclusion of neurosurgical patients, an increase of cerebral haemorrhages is observed. CONCLUSIONS: Intra-hospital morbidity and mortality and average length of stay in our series are consistent with those from other centres of similar characteristics. A better coordination with medium-long stay centres along with the presence of neurologists on call, would certainly improve these variables.

Adolescent↗
PubMedDate not supplied

[Quantification of bacteria in the small intestine of malnourished children with chickenpox].

The purpose of the present study was to determine whether a high number of bacteria could be demonstrated in the upper small bowel during the chickenpox infection. Intestinal juice was drawn in nine malnourished children, during and two weeks after the acute period of the disease. The results of the study fail to demonstrate quantitative differences in the bacterial flora of the small bowel in both periods. Besides that, the bacterial overgrowth previously reported in malnutrition, is confirmed.

Bacteria↗