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Biomedical subjects

L A Vallejo

Publications and source records attributed to L A Vallejo.

10 recordsLinked to original sources
PubMed2006

[Modelling of the geometry of the external auditory canal by the finite elements method].

The aim of this work is to design a computerized 3-D model of the human external ear, based on the finite elements method. The method consists to splitting a specific special area in a simple element net connected between themselves by nodes. The elements are associated to equations that define their physical characteristics. We realize a coupling with the middle ear model to know the behaviour of both systems with an acoustic excitation without the use of real measures or biological models. The model simulates the acoustic and biomechanic characteristics of the human external auditory canal. The development of a computerized model allows a better knowledge of the external ear mechanic-acoustic behaviour, this makes easier understand the physiology of the human external ear.

Acoustic Impedance Tests↗
PubMed2006

[Diagnosis and treatment of carotid body paragangliomas. Presentation of 9 cases and review of the literature].

Carotid body paragangliomas (CBP) are relatively rare tumors arising from the carotid body paraganglion. Clinical signs and images are necessary to establish the diagnosis. Surgery is the preferred method of treatment, paying special attention to the carotid artery. Nine patients with carotid body tumors were identified, three of them with complicated diagnosis. One patient is treated with radiotherapy. Out of the eight surgical patients, three preserved the whole arterial structure, the external carotid artery is resected in two patients, the carotid artery is replaced (safen graft, gore tex prosthesis) in other two patients, and the common carotid was tied in the remaining patient. Our objective is to show the decisions taken in the patients from our casuistic, comparing them to the literature data. We conclude that the diagnosis may be deceptive, and that the attitude forward the carotid is variable, always being prepared to do arterial replacement techniques.

Carotid Body Tumor↗
PubMed2006

Molecular and clinical characterisation of three Spanish families with maternally inherited non-syndromic hearing loss caused by the 1494C->T mutation in the mitochondrial 12S rRNA gene.

Mutations in the 12S rRNA gene of the mitochondrial genome are responsible for maternally inherited non-syndromic hearing loss (NSHL), and for increased susceptibility to the ototoxicity of aminoglycoside antibiotics. Among these mutations, 1555A-->G is the most prevalent in all populations tested so far. Recently, the 1494C-->T mutation was reported in two large Chinese pedigrees with maternally inherited NSHL. In this study, sequencing of the 12S rRNA gene in a Spanish family with maternally inherited NSHL showed the presence of the 1494C-->T mutation. An additional screening of 1339 unrelated Spanish patients with NSHL allowed the authors to find two other families with the mutation. Audiological data were obtained from 17 confirmed 1494C-->T carriers, which showed that the hearing loss was sensorineural, bilateral and symmetrical, with a remarkable variability in age of onset and severity. Three carriers were asymptomatic. Three affected carriers had a history of treatment with aminoglycoside antibiotics. The mitochondrial genome of one affected person from each of these three families was entirely sequenced, and it was established that they belong to different mitochondrial haplogroups (H, U5b, U6a). The study results further support the pathogenic role of 1494C-->T on hearing, and show that this mutation can be found in different Caucasian mitochondrial DNA backgrounds.

Adult↗
PubMed2005

[Esthesioneuroblastoma treatment].

INTRODUCTION: Esthesioneuroblastoma is an uncommon malignancy of the olfactory neuroepithelium. The best treatment has yet to be defined. The purpose of this study is to analyze the tumors's behaviour to choose the ideal treatment, the therapeutic strategy and the patterns of failure. MATERIALS AND METHODS: We carry out a revision of the series published between 1994 to 2004. In these series, we found 39 papers with 713 patients. DISCUSSION CONCLUSIONS: In this review the 5-years survival rate is 51.2%. Through the analysis of 583 partients found in 34 publications, surgery (alone or combined) is the treatment most used (78%). The commonly management is surgical in combination with radiotherapy (47%).

Esthesioneuroblastoma, Olfactory↗
PubMed2003

[Stapedotomy, stapedectomy and revision surgery performed with laser techniques. Revision of literature].

The usefulness of laser in otologic surgery, and specifically the suitability of its use in stapes surgery, is still under discussion. We intend to support the use of this method in the surgical treatment of otosclerosis, as well as to elucidate which type of laser is the most advisable one, establishing also in which stages of surgery it should be used. For this, we carry out a revision of the main opinions published in this regard in the international literature, commenting on the results and observations gathered in it. We end by setting out a number of conclusions which are the result of the analysis of the criteria put forward in the bibliography.

Humans↗
PubMed2002

[Computerized 3-D model to study biomechanics of the middle ear using the finite element method].

Based on known data about the behavior of the sound transmission mechanism, we generate a model that reproduces the real mechanics of the middle ear by the finite elements method in the most exact manner possible. We designed a computerized model to simulate the biomechanic behavior of the ear drum/ossicular chain. The investigation focused on a possible clinical application, given that the variables necessary for simulation of several conditions can be introduced in our model: tympanic perforation, fixation of the ossicular chain, chain interruption, etc. Introducing the characteristics of the lesion virtually in a simulator program market is possible to reach conclusions about the conductive hypoacusis created and about therapeutic possibilities. The 3-D modelling of the tympanic membrane, malleus, incus and stapes is presented, considering form, weight, density, Young's module (N/m2) and Poisson coefficient for the different parts of each ossicle. The modeling of the union of the different tympanic-ossicular elements, including muscles and ligaments, is also shown.

Biomechanical Phenomena↗
PubMed2000

Effects of unilateral deprivation in postnatal development of the olfactory bulb in an altricial rodent, the gerbil (Meriones unguiculatus).

To establish if olfactory bulb sensitivity to functional deprivation is related to the degree of development at birth, we studied the effects of surgical closure of one naris in the gerbil olfactory bulb development. The naris closure was performed at three different ages: at birth, P7 and P14 and maintained for 30 or 60 days. In coronal sections we measured total bulbar surface area and surface area of the different bulbar layers establishing an estimate multiple regression model for the percentage of surface area decrease in the deprived bulb related to non deprived one. The internal and external plexiform layers are the most sensitive layers to deprivation and age and duration of deprivation were factors in their mathematical models. The glomerular layer showed a surface reduction of about 25% without dependence either on age or duration. The deprived glomerular layer showed a much lower tyrosine hydroxylase-immunoreactivity and immunoreactive cell density than those in the non deprived one. However, differences in calbindin-immunoreactive and NADPH-diaphorase positive cell density between deprived and non deprived glomerular layer were not significant. Our results indicate that olfactory bulb sensitivity to functional deprivation is not related to the degree of precocity and changes in age and duration of deprivation cause different effects on the olfactory bulb layers.

Animals↗
PubMed2000

Structure of the principal olfactory tract.

Although the purpose and importance of the sense of smell in human beings has not been totally clarified, it is one of the principal information channels in macrosmatic animals. It was the first long-distance information system to have appeared in phylogenetic evolution. The objective of this article is to deepen the knowledge of the pathways that join the olfactory epithelium with the cortical olfaction areas, to better understand olfactory dysfunction in human beings. Differential staining and marking techniques were applied to histologic sections obtained from 155 animals of different species, to study the different connections existing among olfactory tract components. Our study of the connections between the olfactory mucosa and the principal olfactory bulb deserves special mention. The distribution of second neuron connections of the olfactory tract with the central nervous system is quite complex and diffuse. This indicates an interrelation between the sense of smell and a multitude of functions. These connections seem to be of different quantitative importance according to species, but qualitatively they exist in both human beings and other macrosmatic animals.

Animals↗
PubMed1999

Proposed classification scheme for quantitative olfactory function alterations.

Given the need for a clinical classification for daily patient examinations to refer to each type of quantitative alteration in the sense of smell, we have created a topographic classification of such alterations, establishing groups to distinguish among patients with decreased or total loss of olfaction. Because the classification is based on the diagnosis of the different causes of anosmia, it implicitly includes etiologic and topographic considerations. We have established 3 main groups on the basis of the site of the causal lesion: conduction, sensorineural, and mixed anosmias. In addition, within the sensorineural anosmias, we distinguish between the epithelial, retroepithelial, and central anosmias.

Adolescent↗