Biomedical subjects
Publications and source records attributed to D M Baguley.
We report on the presentation and clinical manifestations of superior semicircular canal dehiscence in association with a large defect of the tegmen tympani in a 41-year-old woman with no previous history of trauma. Based on this case we recommend that clinicians consider the possibility of superior semicircular canal dehiscence in patients presenting with symptoms associated with tegmen defects.
INTRODUCTION: Wearing hearing aid earmoulds has been implicated as a predisposing factor in the development of chronic otitis externa. Audiologists come into contact with a large number of hearing aid earmoulds and these could potentially harbour pathogenic micro-organisms, with the risk of subsequent cross infection. Cleaning with dilute alcohol is widely used in an attempt to break the chain of infection. OBJECTIVE: To determine the presence and nature of microbial flora on hearing aid earmoulds and the efficacy of cleaning methods used to prevent cross infection. SETTING: Secondary health care within the audiology department of Addenbrooke's Hospital, Cambridge, UK. DESIGN: A prospective, observational study. METHODS: Hearing aid earmoulds were swabbed before and after cleaning. Samples were cultured to determine qualitatively and quantitatively the microbiological flora present before and after cleaning. RESULTS: Twenty out of 21 (95 per cent) earmoulds had microbes present and, of these, 19/20 (95 per cent) had a polymicrobial profile. Coagulase negative staphylococci and diphtheroids were the most frequent microbial isolates, but pathogenic bacteria and fungi were also demonstrated on earmoulds both before and after cleaning. CONCLUSIONS: The polymicrobial flora, including recognized pathogens, that colonizes earmoulds may lead to chronic otitis externa. Cleaning with 70 per cent alcohol solution was ineffective, in particular for pathogenic fungi on earmoulds.
. Acquired unilateral sensorineural hearing loss reduces the ability to localize sounds and to discriminate in background noise. . Four controlled trials attempt to determine the benefit of contralateral bone anchored hearing aids over contralateral routing of signal (CROS) hearing aids and over the unaided condition. All found no significant improvement in auditory localization with either aid. Speech discrimination in noise and subjective questionnaire measures of auditory abilities showed an advantage for bone anchored hearing aid (BAHA) > CROS > unaided conditions. . All four studies have material shortfalls: (i) the BAHA was always trialled after the CROS aid; (ii) CROS aids were only trialled for 4 weeks; (iii) none used any measure of hearing handicap when selecting subjects; (iv) two studies have a bias in terms of patient selection; (v) all studies were underpowered (vi) double reporting of patients occurred. . There is a paucity of evidence to support the efficacy of BAHA in the treatment of acquired unilateral sensorineural hearing loss. Clinicians should proceed with caution and perhaps await a larger randomized trial. . It is perhaps only appropriate to insert a BAHA peg at the time of vestibular schwanoma tumour excision in patients with good preoperative hearing, as their hearing handicap increases most.
OBJECTIVE: A preliminary study to investigate the intra-observer and inter-observer variability of measurements of vestibular schwannoma volume using an area-tracing and linear dimension measurement method. DESIGN: Prospective blinded measurements by two observers (one a consultant and one a sub-specialty trainee in neuroradiology). SETTING: Ambulatory patients with known vestibular schwannoma attending a tertiary referral centre. PARTICIPANTS: Twenty-three patients with 26 vestibular schwannomas aged 29-80 years old. MAIN OUTCOME MEASURE: Quantification of the variability in measured volume due to intra- and inter-observer measurement differences, expressed as reliability coefficients within which 95% of repeated measurements are calculated to lie from each other in relative percentage terms. RESULTS: For the linear measurement method, intraobserver variability was calculated to have a reliability coefficient of 65% and for interobserver variability this was 155%. For the area tracing method, the corresponding coefficients were 26% for intraobserver variability and 44% for interobserver variability. CONCLUSIONS: Volume measurements in vestibular schwannoma are variable even when the measurements are made by the same observer on identical images. The area tracing method, commonly regarded as the gold standard, is less variable than a linear method but still introduces more variability than commonly realized (for 95% of patients, repeated measurements by the same observer lie within around 25% of each other). Manual area tracing is not widely used in practice because it is time consuming and reliable automated methods are eagerly awaited.
The concept of the 'learning curve' in the early years of consultant appointment is no longer acceptable and yet, for most complex operations, learning is a career-long process. Sub-specialization offers part of the solution to this problem by concentrating expertise, but there remains the question of how to introduce new team members without adversely affecting patient outcome. Shortened training and an increasingly aware public, who are more questioning of the experience and outcomes of those treating them, has required the surgical profession to move away from individual consultant practice and embrace team-working. When, in 1997, a second neurosurgeon joined the skull base team at Addenbrooke's Hospital, his introduction to acoustic neuroma surgery was mentored and operative cases were carefully selected at first. In this article, we discuss our experience with consultant mentoring, and compare the results of the first 100 translabyrinthine acoustic neuroma operations performed under this system with the first cohort of a similar number of patients published from Cambridge in 1989.
OBJECTIVES: To determine whether mental alerting (MA) makes a significant difference to nystagmus recorded during gaze testing using electronystagmography (ENG). DESIGN: A prospective study, blinded interpretation of test results, alternate order of testing sequence. SETTING: Vestibular assessment clinic in a tertiary referral centre. PARTICIPANTS: A total of 80 patients were seen by the authors (R.L.H., K.F.L.M.) for vestibular assessment, between August 2002 and February 2004. Patients cognitively unable to perform MA tasks or with limited English were omitted. Patients all underwent gaze-testing using ENG. Each patient was tested twice, once without MA and once with an MA task, in an alternate test order. MAIN OUTCOME MEASURES: Slow-phase velocity values of recorded nystagmus, number of patients with clinically significant nystagmus (slow-phase velocity > or = 6 deg/s). RESULTS: A total of eight patients had significant gaze-evoked nystagmus when tested without MA and a total of six patients when tested with MA. Only four of these patients were common to both groups. When all nystagmus values (regardless of significance) were considered, no statistically significant differences between nystagmus measured with and without alerting were found (Wilcoxon signed rank test, P > 0.05). CONCLUSIONS: Mental alerting during gaze testing did not result in a significant difference in nystagmus and is just as likely to result in an exacerbation as a reduction in slow-phase velocity. In addition, MA is likely to result in a noisy (and therefore difficult to interpret) recording and increases the impact of the test on the patient. In view of these findings, we propose that MA is contraindicated during the gaze-testing component of the vestibular test battery.
The objective of the present study was to determine the prevalence of hyperventilation syndrome in patients seen for vestibular assessment and to assess the clinical utility of the Nijmegen Questionnaire in this group. The Nijmegen Questionnaire and Dizziness Handicap Inventory (DHI) were administered prospectively to a consecutive series of 100 patients identified as candidates for vestibular assessment within the University Hospital Neuro-otology practice. Twenty-three per cent of patients seen for vestibular assessment were diagnosed with hyperventilation syndrome using the Nijmegen Questionnaire. Seventeen of these (74%) would have remained undetected had the Nijmegen questionnaire not been used. No relationship was found between vestibular assessment results and either Nijmegen or DHI scores. A significant correlation was found between DHI scores and Nijmegen Questionnaire scores (rho = 0.348, P = 0.0005). In conclusion, the Nijmegen Questionnaire is a quick, easy to administer and low-impact assessment tool for hyperventilation syndrome and is a useful adjunct to the otological consultation. Diagnosed patients can then be offered breathing control exercises as part of a vestibular rehabilitation programme.
Diagnostic imaging techniques, symptom awareness and education of local sources of referral in vestibular schwannomas, including general practitioners, have all improved in the last 10 years. The referral patterns in vestibular schwannomas in Cambridgeshire in the period 1981-1993 has been reported.(1) A direct comparison was made with regard to referral patterns seen in the last 10 years paying particular emphasis to source of referral, diagnosis at referral and symptoms/size at presentation. The incidence of vestibular schwannomas in the region is compared and discussed. Patients' managed by the 'watch and wait' policy were particularly scrutinized, as they were not discussed previously. Retrospective analysis of computerized database was used. We have demonstrated an increase in the proportion of referrals with known vestibular schwannoma to 90% of all referrals. No significant change in length of history prior to referral, source of referral or principal presenting symptom were found. An overall decrease in tumour size was found but an increase in the percentage with larger tumours (>4.5 cm). We attribute the significant findings to an increase in availability of magnetic resonance (MR) scanners in the country during the past 10 years. It appears that some tumours would still present with no symptoms until late and therefore will elude identification until large in spite of a low threshold for MR scanning.
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The Tinnitus Handicap Inventory (THI; C. W. Newman, G. P. Jacobson, & J. B. Spitzer, 1996) is widely used in a clinical context to assess tinnitus-related self-reported handicap and to report treatment outcomes. Test-retest reliability has been reported to be high, and high convergent validity with other measures of tinnitus distress has been reported. Factor analysis of the subscales of the THI has previously been reported for a Danish translation, but not for the English version. In the present study, the THI was factor analyzed using data collected from a group of 80 clinical tinnitus patients and 116 patients with unilateral vestibular schwannoma. The factor analysis yielded strong support for a unifactorial structure of the scale, with a majority of items loading on the first factor, and high internal consistency of the total score. The authors recommend use of the total score in research and in clinical practice.
The aim of this study was to calculate the sensitivity of the head-shake test for peripheral and central vestibular dysfunction associated with unilateral sporadic vestibular schwannoma and to discuss the feasibility of using the head-shake test as a screening test. The study group consisted of 102 patients with unilateral sporadic vestibular schwannomas, who were seen consecutively for preoperative vestibular assessment, including the head-shake test. The sensitivity of the head-shake test for vestibular schwannoma was found to be 22%, and the sensitivity and specificity of the head-shake test for canal paresis (>/=25%) were found to be 27% and 88%, respectively. Patients with abnormalities in the central vestibular system and with a greater canal paresis were more likely to have head-shake nystagmus, although, even for severe canal paresis, the sensitivity of the test remained low at 36%. The direction of nystagmus was found to be contra-lateral to the side of the tumour in 86% of patients. It was concluded that the head-shake test is of insufficient sensitivity to be used as a screening test either for vestibular schwannoma or for vestibular-system abnormalities associated with vestibular schwannoma. The deduction is made that the head-shake test is of insufficient sensitivity or specificity to be of clinical value as a screening test for vestibular dysfunction in a general population with symptoms of imbalance.
The investigation of a complaint of unilateral right sensorineural hearing loss led to the identification of a right 3 mm vestibular schwannoma arising from the inferior division of the right vestibular nerve. On investigation the patient was found to have normal caloric function, this being mediated by the superior vestibular nerve. Both transient and distortion product otoacoustic emissions were absent in the right ear, and ABR was abnormal on this side. These findings are of interest as they indicate that this small lesion produced a hearing loss that was both cochlear and retrocochlear. The anatomical finding that the medial auditory efferents run within the inferior vestibular nerve is considered. This patient did not experience tinnitus or hyperacusis despite the site of the lesion arising from the inferior vestibular nerve.
This paper reviews the published evidence regarding the effect of vestibular nerve section upon tinnitus. This is of relevance not only for those performing and undergoing this procedure, but also for those considering the hypothesis that auditory efferent system dysfunction may be influential in tinnitus perception. The auditory medial efferent fibres within the internal auditory canal run within the inferior vestibular nerve, only joining the cochlear nerve at the anastomosis of Oort, a bundle of 1300 fibres running from the saccular branch of the inferior vestibular nerve to the cochlear nerve. Vestibular nerve section procedures therefore section this efferent olivocochlear pathway, and ablate efferent influence upon that cochlear. If auditory efferent dysfunction is involved in tinnitus perception, this ablation might influence the tinnitus status of that patient. A literature search identified 18 papers mentioning tinnitus status after vestibular nerve section, describing the experiences of a total of 1318 patients. The proportion of patients in whom tinnitus was said to be exacerbated postoperatively ranged from 0% to 60%, with a mean of 16.4% (standard deviation 14.0). The proportion of patients in whom tinnitus was unchanged was 17% to 72% (mean 38.5%, standard deviation 15.6), and in whom tinnitus was said to be improved was 6% to 61% (mean 37.2%, standard deviation 15.2). In the majority of patients undergoing this procedure, ablation of auditory efferent input (and thus total efferent dysfunction) to the cochlea was not associated with an exacerbation of tinnitus. The finding of this review is that efferent dysfunction after vestibular nerve section does not consistently worsen tinnitus.
The objective of this study was to evaluate the short-term and long-term effect of the obliteration of the middle ear and the Eustachian tube on its function and on middle ear anatomy. Forty-two patients who underwent a translabyrinthine removal of a vestibular schwannoma were randomly selected from the 329 patients operated on in the last 5 years. According to the length of follow-up they were divided in two groups. The Eustachian tube was found to open in 40% of cases 8 months (group mean) after the operation and at 4 years in 70% of cases (group mean) after the operation. The mechanisms leading to the opening of the tube are discussed. In addition the absence of long-term middle ear disorders in those with a permanently closed Eustachian tube showed that the presence of atrophied connective tissue and scar tissue in the middle ear prevented the retraction of the tympanic membrane. Obliteration of the Eustachian tube and middle ear is an easy and rapid procedure, which is temporary in most cases and does not increase the risk of long-term middle ear disease.
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Autosomal recessive distal renal tubular acidosis (rdRTA) is characterised by severe hyperchloraemic metabolic acidosis in childhood, hypokalaemia, decreased urinary calcium solubility, and impaired bone physiology and growth. Two types of rdRTA have been differentiated by the presence or absence of sensorineural hearing loss, but appear otherwise clinically similar. Recently, we identified mutations in genes encoding two different subunits of the renal alpha-intercalated cell's apical H(+)-ATPase that cause rdRTA. Defects in the B1 subunit gene ATP6V1B1, and the a4 subunit gene ATP6V0A4, cause rdRTA with deafness and with preserved hearing, respectively. We have investigated 26 new rdRTA kindreds, of which 23 are consanguineous. Linkage analysis of seven novel SNPs and five polymorphic markers in, and tightly linked to, ATP6V1B1 and ATP6V0A4 suggested that four families do not link to either locus, providing strong evidence for additional genetic heterogeneity. In ATP6V1B1, one novel and five previously reported mutations were found in 10 kindreds. In 12 ATP6V0A4 kindreds, seven of 10 mutations were novel. A further nine novel ATP6V0A4 mutations were found in "sporadic" cases. The previously reported association between ATP6V1B1 defects and severe hearing loss in childhood was maintained. However, several patients with ATP6V0A4 mutations have developed hearing loss, usually in young adulthood. We show here that ATP6V0A4 is expressed within the human inner ear. These findings provide further evidence for genetic heterogeneity in rdRTA, extend the spectrum of disease causing mutations in ATP6V1B1 and ATP6V0A4, and show ATP6V0A4 expression within the cochlea for the first time.
Tympanometry is well established as a useful tool in the field of otological diagnosis. There have been sporadic reports, however, of bizarre tympanograms in the presence of small perforations of the tympanic membrane. A model of the outer and middle ears was fabricated which was able to produce normal and pathological tympanograms. This model was used to investigate tympanometry in the presence of microperforations. A hypothesis for the mechanism of generation of sawtooth tympanograms in the presence of micro-perforations is postulated.
Stickler syndrome is a dominantly inherited disorder characterized by arthropathy, midline clefting, hearing loss, midfacial hypoplasia, myopia, and retinal detachment. These features are highly variable both between and within families. Mutations causing the disorder have been found in the COL2A1 and COL11A1 genes. Premature termination codons in COL2A1 that result in haploinsufficiency of type II collagen are a common finding. These produce a characteristic congenital "membranous" anomaly of the vitreous of all affected individuals. Experience has shown that vitreous slit-lamp biomicroscopy can distinguish between patients with COL2A1 mutations and those with dominant negative mutations in COL11A1, who produce a different "beaded" vitreous phenotype. Here we characterize novel dominant negative mutations in COL2A1 that result in Stickler syndrome. Both alter amino acids in the X position of the Gly-X-Y triple-helical region. A recurrent R365C mutation occurred in two unrelated sporadic cases and resulted in the membranous vitreous anomaly associated with haploinsufficiency. In a large family with linkage to COL2A1, with a LOD score of 2.8, a unique L467F mutation produced a novel "afibrillar" vitreous gel devoid of all normal lamella structure. These data extend the mutation spectrum of the COL2A1 gene and help explain the basis for the different vitreous phenotypes seen in Stickler syndrome.