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Biomedical subjects

T H Lesser

Publications and source records attributed to T H Lesser.

At least 19 recordsLinked to original sources
PubMed2001

Otology in ancient India.

Sushrutra Samhita is essentially a multi-volume textbook reporting the surgical practices of ancient India. It covers all aspects of surgery. However, specific references are made to otorhinological conditions, their description and subsequent treatments often being described in some detail. In this paper we outline the structure of the document and attempt to explain its underlying philosophies. We highlight the specific references to otological diseases and their treatment and draw the obvious comparisons with modern otological practice.

Female↗
PubMed1998

Grommet insertion in children: a survey of parental perceptions.

Grommet insertion is a widely accepted method of treatment of glue ear in children. There have been questions raised over the last few years about the indications for grommets and whether assessing the hearing alone is an efficient outcome measure. Parental pressure accounts for one of the factors that is taken into consideration when the decision to insert grommets for glue ear is made. In this paper, a prospective questionnaire is used to investigate the parental perceptions of the effectiveness of grommet insertion in children, focusing on alternative outcome measures such as general health, language, and social skills. The results of this survey suggest that grommet insertion causes improvement in many factors other than hearing and this seems to account for the parental pressure for siblings to have grommet insertion.

Attitude↗
PubMed1997

Mode shapes of a damaged and repaired tympanic membrane as analysed by the finite element method.

This work makes use of recent finite element discretization of the human tympanic membrane where the known anisotropy of the tympanic membrane is implemented by a series of thin beam elements superimposed on thin shell membrane elements. These thin beam elements were introduced in order to simulate the fibre structure of the tympanic membrane. The onset of tympanosclerosis has been modelled as a gradual increase in tympanic membrane density and modulus in the affected area. This increased density results in a fall of 55% of the first natural frequency for only a 16% area of drum sclerosis. Additionally the amplitude response is significantly reduced. Repair of the membrane was simulated by removal of the fibre system from the affected area. Under these circumstances the natural frequencies virtually return to the healthy state but the mode shapes of vibration do not. The repair to the membrane, although not significantly altering frequency values, has resulted in a disruption to the normal mode shape patterns with consequences in the movements conveyed to the stapes and cochlear fluids.

Cochlea↗
PubMed1997

Subtotal petrosectomy in the treatment of cerebrospinal fluid fistulae of the lateral skull base.

Cerebrospinal fluid (CSF) fistulae almost invariably lead to meningitis, even in the absence of other clinically obvious sequelae of the fistula such as a CSF fluid leak. The only effective means of reducing the risk of meningitis is surgical closure of the fistula. If surgery is to be recommended to patients with CSF fistulae even if they are currently asymptomatic, the morbidity of the procedure must be a principal determinant of the chosen technique. Recovery after the extracranial approach to a CSF fistula is much more rapid than after an intracranial procedure. The extracranial route is also free of the long-term risk of epilepsy which accompanies a craniotomy. The principal disadvantage of the lateral extracranial approach, failure of treatment, has been largely eliminated following studies into the obliteration of simple bony cavities using free adipose grafts. This paper describes our use of the extracranial approach to closure of CSF fistulae of the lateral skull base.

Adult↗
PubMed1995

A simple technique to measure body sway in normal subjects and patients with dizziness.

For many years vestibular testing has relied on measurements of the vestibulo-ocular reflex (VOR). More recently quantified assessment of balance, using fixed or moving force platforms and magnetometry have been applied to clinical research. These are objective attempts to quantify the vestibulospinal reflex (VSR). This study evaluates whether SwayWeigh, a simple device which measures lateral body sway, can provide an objective assessment of balance dysfunction. Forty patients with a balance disorder and 31 subjects with normal balance were tested with eyes opened and eyes closed whilst they were standing on a flat surface and then on an air bed. The lateral sway in patients with a balance disorder was compared to that in the normal subjects and highly significant differences (p < 0.0001) were observed. The results also confirmed the importance of vision and proprioception in the maintenance of posture. The SwayWeigh balance platform is a simple and economical device which objectively measures balance dysfunction.

Adult↗
PubMed1995

Objective measurement of the benefit of walking sticks in peripheral vestibular balance disorders, using the Sway Weigh balance platform.

Following a lesion in the vestibular system visual, proprioceptive and residual vestibular information is integrated by the brain, to enable a patient to attain equilibrium. The basis of vestibular rehabilitation is to encourage these adaptive and compensatory mechanisms. Another form of rehabilitation is to provide some form of mechanical aid, and walking sticks are often used for this purpose in patients with balance disorders. There are no reported studies objectively assessing the use of walking sticks in patients with balance disorders. In this study we used the Sway Weigh balance platform (Raymar) to determine the efficacy of a walking stick in 25 patients with peripheral vestibular balance disorders. Patients were tested with their eyes opened and eyes closed whilst they were standing on a flat surface and on an air-filled bed (to alter limb proprioception) on the Sway Weigh balance platform. All the tests were carried out with, and without, a walking stick. The results demonstrate that a walking stick significantly reduces lateral body sway in patients with peripheral vestibular balance disorders.

Aged↗
PubMed1995

A 3-D finite element analysis of the natural frequencies of vibration of a stapes prosthesis replacement reconstruction of the middle ear.

In this work, the natural frequencies of vibration of two different stapes prosthesis replacement reconstructions have been analysed using the finite element method. Prosthesis 1 was constructed of fine stainless steel wire and a Teflon base, while prosthesis 2 was made entirely of Teflon. The results have indicated that generally, the first natural frequency of vibration falls as the prostheses become larger and more bulky. However, the fall in the first natural for prosthesis 1 was modest when compared with that of the isolated tympanic membrane. An important variable influencing frequencies and mode of vibration of the reconstruction was the tightness of fit of the prostheses within the remaining ossicular chain. The tightness of fit in this work was modelled as a range of spring constants applied at the stapes pseudo footplate, together with a series of joint elements at the incus tip/prosthesis head for the Teflon implant. When these spring constraints were below approximately 10 N/mm, the reconstruction exhibited normal mode 1 vibration behaviour, but at larger spring values, an abnormal mode 1 became established resembling the normal mode 2 vibration characteristics. The formation of new geometries and surfaces following reconstruction, introduces new constraints between umbo and stapes footplate particularly at the natural/artificial interfaces. These unnatural constraints may inhibit and modify the natural movements normally occurring at the stapes footplate leading to abnormal modes of vibration.

Ear Ossicles↗
PubMed1995

Mucosal-strip/uvulectomy by the CO2 laser as a method of treating simple snoring.

The effect of stiffening the soft palate by inducing scarring after removing a central strip of mucosa with a CO2 laser was investigated in 25 heavy snorers. The results were assessed using a series of Visual Analogue Score (VAS) assessment questionnaires completed by the partner over a period of 6 months. Of the 22 patients who had the laser-strip and uvulectomy, snoring improved in 18 (82%) (median improvement of 75% at 3 months). Four patients did not improve. Between 3 and 6 months, snoring increased in one patient and decreased in four (< 10% change on VAS). Snoring did not improve in the three patients who did not undergo uvulectomy. We conclude that the laser-strip/uvulectomy can reduce snoring to a tolerable level in eight out of 10 heavy snorers, but the procedure is painful for several days.

Adult↗
PubMed1994

Day case surgery in otolaryngology: the setting up and first year of a freestanding unit.

A freestanding day case surgery unit for ENT cases is described and the first year's experience reviewed. Special attention is paid to the variety, and complications, of surgery as the freestanding unit is 17 miles from the main ENT centre. The difficulties of running the unit are reviewed. The problems encountered include arranging training for the staff and maintaining optimum throughput of cases. Consideration is also given to the setting up and running costs of the unit. Four hundred and seventy-seven patients were treated from 46 lists. This accounted for 64 per cent of the total number of patients having ENT surgery in 1992 from our area.

Adolescent↗
PubMed1994

Nasal airflow after septorhinoplasty.

The changes in nasal function which occur after septorhinoplasty for obstruction were investigated by anterior rhinomanometry in 15 subjects. Objective and subjective measures of outcome were compared. Anterior rhinomanometry was performed after nasal decongestion. These data were mathematically transformed to determine the amount of airflow asymmetry through the nostrils and the stiffness of the nasal valve. The results suggested that the presence of gross airflow asymmetry (> +/- 80%) in patients prior to surgery was a bad prognostic indicator for post-operative satisfaction with the airway. Patient satisfaction with function and cosmetic appearance post-operatively was correlated with the presence of symmetrical nasal airflow. Nasal valve stiffness did not seem to be affected by septorhinoplasty.

Adult↗
PubMed1993

Natural frequencies of vibration of a fibre supported human tympanic membrane analysed by the finite element method.

A finite element programme developed previously to calculate the natural frequencies of vibration of the human tympanic membrane, has been modified to take into account both natural and geometric rigidities. The natural rigidities take the form of internal membrane stress/strain parameters, while the geometric rigidities are the flexural and membrane stress resultants. The first six natural frequencies calculated are similar to those measured by Laser holography on cadaver membranes and analysed recently by interference techniques. Using a generalized stress/strain constitutional relationship, the natural frequencies were found to be linearly related to the square root of the forces within the membrane. It was proposed in our earlier work, that these internal stresses as well as maintaining the complex shape of the tympanic membrane, serve to enhance its frequency range and response. The role of the radial and circular fibres embedded within the ground substance of the membrane on the frequencies and mode shapes have also been examined by super-imposing beam elements on the semi-loof membrane elements. It was found that the modes of vibration of the membrane are restricted to a fairly simple pattern up to beam moduli values of approximately 50 MPa. Above this beam modulus, the normal mode shape was observed with a gradually increasing complex vibration pattern as the frequency increases. This new treatment of membrane re-enforcement suggests a non-Hookean behaviour of the drum displacements. In order to account for the earlier measured frequencies of Tonndorf & Khanna, the previously proposed internal stress/strain parameters are believed to be less important and have been calculated to be small compared with the membrane modulus.

Humans↗
PubMed1992

Problems in alloplastic middle ear reconstruction.

Alloplastic materials have been used in middle ear reconstruction since 1952. Biologically, biomaterials and specifically ceramics can be defined as being bioinert, bioactive or biodegradable; these terms being descriptive of the biochemical response provoked by the material in the host tissue. Various ceramics, carbons and polymers and their reactions have been studied by the author and his colleagues over the past 5 years utilising animal implantation and fibroblast culture studies aligned with experience from clinical usage. The qualities of the ideal alloplastic implant namely: biocompatibility, stabilisation and incorporation, the consistency of the implant and bioactive bonding and the biofunctionality or mechanics, are applied to the materials currently available. No single alloplastic material fulfills all criteria, the problems encountered in relation to the biomaterials are reported. A better understanding of the microstresses, fatigue and microfractures is necessary, before the ideal alloplastic biomaterial becomes available.

Animals↗
PubMed1992

A dynamic and natural frequency analysis of the Fisch II spandrel using the finite element method.

The recent introduction of the Fisch II spandrel total ossicular replacement prosthesis (TORP), has provided impressive initial hearing benefits in patients. The design, based on a combination of soft plastic and a highly flexible metal shaft, has been analysed in terms of its sound collecting and conducting behaviour using the finite element method. The analysis has examined the mode shapes, displacements and natural frequencies of the prosthesis for a variety of material properties and geometries. The results indicate the optimum vibration characteristics are obtained with a Polycell elastic modulus of 100 N/mm2, with the natural frequency independent of modulus above this value. Furthermore, the diameter of the spandrel shaft is crucially important, with an increase in magnitude of the first natural frequency of 54% for a 25% increase in shaft diameter. At a Polycell membrane thickness of 0.07 mm and a shaft diameter of 0.12 mm, the tympanic membrane and Fisch II prosthesis have almost identical frequencies over the 1st to 6th frequency range. This fact, together with the flexibility of clinical procedures involved in its use, may be the reason for its success.

Animals↗
PubMed1991

Clinical growth rate of acoustic schwannomas: correlation with the growth fraction as defined by the monoclonal antibody ki-67.

The growth rate of acoustic tumors, although slow, varies widely. There may be a continuous spectrum or distinct groups of tumor growth rates. Clinical, audiologic, and conventional histologic tests have failed to shed any light on this problem. Modern immunohistochemical methods may stand a better chance. The Ki-67 monoclonal antibody stains proliferating cells and is used in this study to investigate the growth fraction of 13 skull base schwannomas. The acoustic tumors can be divided into two different growth groups, one with a rate five times the other. The literature is reviewed to see if this differentiation is borne out by the radiologic studies. Distinct growth rates have been reported: one very slow, taking 50 years to reach 1 cm in diameter, a second rate with a diameter increase of 0.2 cm/year, and a third rate five times the second, with a 1.0 cm increase in diameter per year. A fourth group growing at 2.5 cm/year is postulated, but these tumors cannot be followed for long radiologically, since symptoms demand surgical intervention. The clinical implications of these separate growth rates are discussed.

Journal Article↗
PubMed1991

Mechanics and materials in middle ear reconstruction.

The normal anatomy and physiology of the middle ear is not reproduced in ossiculoplasty and an artificial mechanism for the transmission of sound results. This is true for all types of graft, be they of natural or man-made material. There are, therefore, 2 areas for consideration when looking at the problems encountered in such reconstructions: first, the materials' biocompatability and, secondly, the mechanical effects of the positioning of the graft in the reconstructed ossicular chain. The present work examines these mechanical effects using the finite element method to determine stress and displacement levels in the reconstructed ossicular chain. It is found that the stress levels at the implant-stapedial joint increases as the implant is gradually moved down the malleus. In contrast there is thought to be an increase in sound transmission as the implant is moved down the malleus. Changes in rigidity and hardness of the implant appear to make only modest stress attenuations at the implant-stapes interface.

Biomechanical Phenomena↗
PubMed1990

Acoustic schwannoma of traumatic origin? A temporal bone study.

A tumour of the singular nerve was found on examination of the temporal bones of a child who died 13 months after meningitis. The tumour consisted of a main mass with the appearance of an acoustic neuroma but close by and not connected were some nests of tumour cells inside the vestibule. This very unusual finding raises questions of the aetiology of this tumour which may have a bearing on the aetiology of other tumours of the VIIIth. nerve.

Cranial Nerve Neoplasms↗
PubMed1990

Ear, nose and throat manifestations of Lyme disease.

The manifestations of Lyme disease as they may present to the ENT surgeon are discussed. The most important ENT symptom is facial palsy. Particularly when combined with other cranial palsies, systemic illness or signs of meningeal irritation, the diagnosis must be considered. Three case reports are used to illustrate the presentation and diagnosis and treatment of Lyme disease. The characteristics of the disease are reviewed and the limitations of serological testing outlined. The literature has concentrated on bilateral or relapsing facial palsy. A review of palsies in Zurich that presented to the ENT clinic found only unilateral and partial palsies. The diagnosis should be considered in every case of facial palsy of unknown aetiology especially in children.

Adult↗