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Dive into the research topics where Juan J. Rivas is active.

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Featured researches published by Juan J. Rivas.


Journal of Neurosurgery | 1981

Observations on 82 patients with extradural hematoma

Francisco Cordobes; R.D. Lobato; Juan J. Rivas; Maria J. Muñoz; Diego Chillón; Jaime M. Portillo; Eduardo Lamas

A consecutive, unselected series of 82 patients with epidural hematoma treated between 1973 and 1980 is presented. Forty-one patients were managed before the advent of computerized tomography (CT) and the other 41 after this neuroradiological method was available. Mortality and disability rates which were 29.2% and 31.7% during the pre-CT period decreased to 12.1% and 19.5%, respectively, with the aid of CT scanning. This technique allowed a more rapid and accurate diagnosis of the hematomas than angiography, and defined better the presence and the evolutional changes of the associated cerebral lesions. As a consequence, surgery has been more effectively planned and executed during the CT era.


Acta Neurochirurgica | 1999

Risk factors predicting recurrence in patients operated on for intracranial meningioma. A multivariate analysis.

J. Ayerbe; R.D. Lobato; J. de la Cruz; R. Alday; Juan J. Rivas; P.A. Gómez; A. Cabrera

Summary The authors undertook a follow-up study of 286 patients who underwent surgical treatment for intracranial meningioma between 1973 and 1994, in order to analyse clinical, radiological, topographic, histopathological and therapeutic factors significantly influencing tumour recurrence. All patients were followed by using either computed tomography (CT) or magnetic resonance from 3 months to 17 years since first surgery (mean follow-up: 4.1 years). Forty-four (15.4%) recurrences were detected during this time period. Overall recurrence rates were 14%, 37% and 61% at 5, 10 and 15 years, respectively. Factors significantly associated with tumour relapse in bivariate analysis were: tumour location at petroclival and parasagittal (middle third) regions, incomplete surgical resection (assessed by Simpsons classification), atypical and malignant histological types (WHO classification), presence of nucleolar prominence, presence of more than 2 mitosis per 10 high-power fields, and heterogeneous tumour contrast enhancement on the CT scan. The multivariate analysis using the Coxs proportional hazards model identified the following risk factors for recurrence: incomplete surgical resection (Relative risk: 2.2; 95% Confidence interval: 1.33–3.64), non conventional histological type (RR: 2.13; 95%CI: 1–4.53), heterogeneous contrast enhancement on the CT scan (RR: 2.25; 95%CI: 1.1–4.72) and presence of more than 2 mitosis per 10 high-power fields (RR: 2.28; 95%CI: 0.99–5.27). Patients without any of these features showed low recurrence rates (4% and 18% at 5 and 10 years), and thus, they need less clinical and radiological controls through the follow-up than patients with some of these risk factors.


Acta Neurochirurgica | 1997

Sequential computerized tomography changes and related final outcome in severe head injury patients

R.D. Lobato; P.A. Gómez; R. Alday; Juan J. Rivas; J. Domínguez; A. Cabrera; F. S. Turanzas; A. Benitez; B. Rivero

SummaryThe authors analysed the serial computerized tomography (CT) findings in a large series of severely head injured patients in order to assess the variability in gross intracranial pathology through the acute posttraumatic period and determine the most common patterns of CT change. A second aim was to compare the prognostic significance of the different CT diagnostic categories used in the study (Traumatic Coma Data Bank CT pathological classification) when gleaned either from the initial (postadmission) or the control CT scans, and determine the extent to which having a second CT scan provides more prognostic information than only one scan.92 patients (13.3% of the total population) died soon after injury. Of the 587 who survived long enough to have at least one control CT scan 23.6% developed new diffuse brain swelling, and 20.9% new focal mass lesions most of which had to be evacuated. The relative risk for requiring a delayed operation as related to the diagnostic category established by using the initial CT scans was by decreasing order: diffuse injury IV (30.7%), diffuse injury III (30.5%), non evacuated mass (20%), evacuated mass (20.2%), diffuse injury II (12.1%), and diffuse injury I (8.6%).Overall, 51.2% of the patients developed significant CT changes (for worse or better) occurring either spontaneously or following surgery, and their final outcomes were more closely related to the control than to the initial CT diagnoses. In fact, the final outcome was more accurately predicted by using the control CT scans (81.2% of the cases) than by using the initial CT scans (71.5% of the cases only). Since the majority of relevant CT changes developed within 48 hours after injury a pathological categorization made by using an early control CT scan seems to be most useful for prognostic purposes.Prognosis associated with the CT pathological categories used in the study was similar independently of the moment of the acute posttraumatic period at which diagnoses were made.


Neurosurgery | 1984

Spinal Metastatic Disease: Analysis of Factors Determining Functional Prognosis and the Choice of Treatment

Alejandro Barcena; R.D. Lobato; Juan J. Rivas; Francisco Cordobes; S. Castro; A. Cabrera; Eduardo Lamas

The authors surveyed 31 surgical and radiotherapy series comprising over 2300 patients with spinal metastases to determine the influence of factors such as tumor biology and topography, pretreatment neurological status, the presence of a myelographic block, the progression rate of symptoms, and the general medical condition of the patient on both the functional prognosis and the choice of treatment. Both life expectancy and the functional results after therapy are mainly dependent on tumor biology, which in turn determines radiosensitivity. The remaining factors seem to have only complementary predictive power. Because radiotherapy has been found to be as effective as operation plus radiotherapy in the management of the majority of patients with spinal metastases, it is very important to improve the selection of surgical candidates (less than 42% of the total cases) to prevent unnecessary surgery-related morbidity and mortality. Factors considered important in the selection of therapy are the location of the tumor within the spinal canal, the neurological status at the time of treatment, and the systemic condition of the patient.


Acta Neurochirurgica | 1996

Brain oedema in patients with intracranial meningioma. Correlation between clinical, radiological, and histological factors and the presence and intensity of oedema.

R.D. Lobato; R. Alday; P.A. Gómez; Juan J. Rivas; J. Domínguez; A. Cabrera; S. Madero; J. Ayerbe

SummaryThe authors analysed the correlation between different clinical, radiological, and pathological variables and the presence and intensity of brain oedema associated to intracranial meningioma in 400 consecutive patients studied by computerized tomography (CT).The following factors did not show significant correlation with brain oedema development: the age and sex of the patient, the occurrence of focal deficits, the presence of skull changes (endostosis, exostosis, osteolysis), the occurrence of tumour calcification, the density of the tumour on plain CT scan, the presence of a cystic component, the pathological subtype of meningioma (both conventional and non-conventional), and the presence of histological features of tumour aggressiveness, such as an increased vascularization, high cellularity, high mitotic index, pleomorphism, necrosis, and brain infiltration.Factors showing a statistically significant correlation with the presence and intensity of brain oedema at the bivariate analysis were: the presence of symptoms (p < 0.001), the duration of the clinical history (p < 0.05), the location and size of the tumour (p < 0.001), the type (heterogeneous vs homogeneous), and intensity of tumour contrast enhancement (p < 0.001), the presence of irregular tumour margins (p < 0.001), and the existence of focal low density intratumoural areas (p < 0.001).The multivariate analysis using only clinical parameters showed that the group of variables with the highest power for predicting the presence of brain oedema (concordance level of 76.8%) included: the presence of symptoms, the occurrence of seizures (focal or generalized), the presence of an intracranial hypertension syndrome, and the age of the patient. The multivariate analysis using only anatomico-radiological parameters showed that the model which included the size of the tumour, the intensity of contrast enhancement, the tumour margins, and meningioma location, predicted the presence of brain oedema in 80.8% of the cases.Though the results of the present study do not definitively support any of the major physiopathological theories proposed to explain brain oedema formation in patients with intracranial meningioma, some findings could favour the so-called hydrodynamic theory.


Neurosurgery | 1993

Comparison of the Clinical Presentation of Symptomatic Arteriovenous Malformations (Angiographically Visualized) and Occult Vascular Malformations

R.D. Lobato; Juan J. Rivas; P.A. Gómez; A. Cabrera; Rosario Sarabia; Eduardo Lamas

The authors compared the clinical presentations of angiographically apparent arteriovenous malformations (AVMs) and angiographically occult vascular malformations (AOVMs) of the brain in 188 consecutive patients treated when computed tomography and magnetic resonance were available. There were 133 patients (70.7%) with AVMs and 55 patients (29.2%) with AOVMs. AOVMs tended to occur more frequently in male patients and in the posterior fossa and to present earlier clinically than AVMs, but differences were not significant. One distinctive feature was the greater size of AVMs, as compared with AOVMs. Presentation by hemorrhage occurred in 64.3% of the patients with AVMs and in 61.8% of those with AOVMs. Malformations of both types located in the posterior fossa presented with hemorrhage more frequently (84.2% of AVMs and 78.5% of AOVMs) than similar lesions lying above the tentorium (60.8% of AVMs and 56% of AOVMs). Bleeding was more severe in patients with AVMs than in those with AOVMs, as indicated by the higher mortality associated with hemorrhage (7.5 vs. 3.6% of the cases) and the more frequent and marked decrease in the level of consciousness observed at admission (34 vs. 16.2% of drowsy or comatose patients). Brain hematomas caused by AVMs were on average bigger than those caused by AOVMs (58.8 and 20% of large hematomas, respectively), and intraventricular and subarachnoid hemorrhages were also more common and profuse in patients with AVMs. However, AOVMs bled subsequently more times than AVMs (61.7 vs. 15.6%), before they were diagnosed and treated, leading to a higher nonoperative morbidity (16.3 vs. 13.6%).(ABSTRACT TRUNCATED AT 250 WORDS)


Neurosurgery | 1986

Symptomatic Subependymoma: Report of Four New Cases Studied with Computed Tomography and Review of the Literature

R.D. Lobato; Maria Sarabia; S. Castro; J. Esparza; Francisco Cordobes; Jaime M. Portillo; Juan J. Rivas

The authors describe four cases of subependymoma studied with computed tomography (CT) and review 18 previously reported cases in an attempt to define the most characteristic CT presentation of this rare, benign tumor. Subependymoma usually appears as an isodense, or even hypodense, intraventricular tumor on plain CT scan and shows minimal or no enhancement in postcontrast studies. Differential diagnosis between subependymoma and the more malignant true ependymoma is difficult, particularly when the tumor occurs in the posterior fossa. Recognition of subependymoma should prompt the surgeon to attempt radical tumor removal because it can be achieved without sacrificing contiguous tissue and carries a good prognosis.


Acta Neurochirurgica | 1997

Giant intrasacral schwannomas: Report of six cases

J. Domínguez; R.D. Lobato; Ana Ramos; Juan J. Rivas; P.A. Gómez; S. Castro

SummaryOnly 4 of the 30 previously reported cases of giant sacral schwannomas have been studied with Magnetic Resonance Imaging (MRI). We are reporting 6 more cases, 5 of which had MRI studies. There were 5 women and 1 man (average age 45 years) with long lasting symptoms consisting of lumbosacral and radicular pain accompanied by urinary disturbances and dysaesthetic sensations in the lower limbs. CT clearly defined sacral bone involvement but poorly demonstrated intraspinal tumour extension which was more evident in MRI studies. MRI also clearly showed the intrapelvic extension of the tumour, its relationship with the neighbouring structures and the dumbell growth pattern due to tumour extension through sacral foramina which are important data for making a properative diagnosis and surgical planning. Surgical treatment consisted of piecemeal tumour resection through a posterior approach in four cases. Two patients underwent operation through an abdominal transperitoneal approach followed by a sacral laminectomy. Total intracapsular resection was apparently achieved in 5 cases. Through an average follow-up period of 9.2 years and despite a rather conservative approach, the recurrence rate has been very low in our series and only one patient had to be re-operated on for tumour recurrence.


Acta Anaesthesiologica Scandinavica | 1987

Intraventricular morphine for intractable cancer pain: rationale, methods, clinical results

R.D. Lobato; J.L. Madrid; Lorenza V. Fatela; Rosario Sarabia; Juan J. Rivas; Adolfo Gozalo

The experience with the administration of intraventricular morphine for the control of malignant pain in 197 patients is analyzed. Small doses of morphine injected via a ventricular reservoir provided satisfactory control of otherwise intractable pain in terminal cancer patients. Complete analgesia together with a favourable behavioral response was obtained without noticeable neurological changes or side‐effects annoying or severe enough for the patients to discontinue therapy. Tolerance was much less marked than with parenteral opiates. Chronic intraventricular therapy can be safely performed on an outpatient basis by injecting the opiate once or twice a day. The method may be improved by using refillable continuous‐infusion devices and new drugs able to retain the analgesic effects of morphine while eliminating the unwanted ones.


Acta Neurochirurgica | 1989

Subarachnoid haemorrhage of unknown aetiology.

P.A. Gómez; R.D. Lobato; Juan J. Rivas; A. Cabrera; Rosario Sarabia; S. Castro; M. Castañeda; J. M. Cañizal

SummaryThe authors review the literature on subarachnoid haemorrhage of unknown aetiology (SAHUE) and analyze a personal series of 212 patients diagnosed as SAHUE. These patients represent 30% of all cases of primary SAH admitted over a 14.5 year period.The age, sex, antecedents and initial clinical presentation of patients with SAHUE were indistinguishable from those of patients with subarachnoid haemorrhage due to ruptured aneurysm (SAHRA). However, the present series of SAHUE compare favourably with both a personal and a previously reported series of SAHRA insofar as clinical grade on admission (94% of patients in grades I–II of Botterell), presence of blood on CT (51%), vasospasm (5%), ischaemic deficits (3.3%), persistent hydrocephalus (3.5%), rebleeding (6%) and fatal result (3.9%) are concerned.The amount of blood on CT scan in our patients with SAHUE was associated with a significantly higher incidence of brain ischaemia and hydrocephalus but did not correlate with the Botterell grade on admission or final outcome, which were good in the majority of cases regardless of the presence or not of visible cisternal haemorrhage. The results of the present series confirm that the final prognosis of patients with primary SAH showing normal four-vessel cerebral angiography is essentially favourable.

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R.D. Lobato

Complutense University of Madrid

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P.A. Gómez

Complutense University of Madrid

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A. Cabrera

Complutense University of Madrid

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Alfonso Lagares

Complutense University of Madrid

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R. Alday

Complutense University of Madrid

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Eduardo Lamas

Complutense University of Madrid

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Francisco Cordobes

Complutense University of Madrid

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Rosario Sarabia

Complutense University of Madrid

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Ana Ramos

Complutense University of Madrid

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S. Castro

Complutense University of Madrid

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