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Biomedical subjects

D A Moffat

Publications and source records attributed to D A Moffat.

At least 19 recordsLinked to original sources
PubMed1995

Rare tumours of the cerebellopontine angle.

The vast majority of cerebellopontine angle (CPA) tumours are acoustic neuromas. However, in our series of 305 CPA tumours, one in five was another pathological lesion. Of the non-acoustic tumours, the majority were meningiomas, primary cholesteatomas and glomus jugulare tumours. A variety of rarely seen but fascinating pathologies were also treated. A study of these non-acoustic tumours has been carried out, looking at their relative incidence, histology and clinical features, as well as the radiological features that make them unusual and help to distinguish them from acoustic neuromas (vestibular schwannomas). The otoneurosurgical procedures required to excise these intriguing lesions are also discussed.

Cerebellar Neoplasms↗
PubMed1995

The molecular genetics of vestibular schwannoma.

Vestibular schwannoma occurs both as a sporadic tumour and in the dominantly inherited familial cancer syndrome neurofibromatosis type 2 (NF2). The gene for NF2 has recently been isolated on chromosome 22, and the demonstration of inactivating germline mutations in NF2 patients and NF2 associated tumours suggests that it acts as a tumour suppressor. The results of recent research in Cambridge suggest that somatic mutations of the NF2 tumour suppressor gene are a critical step in the pathogenesis of both familial and indeed non-familial unilateral sporadic vestibular schwannoma and that the mechanism of tumourigenesis complies with the 'two-hit' model. This paper represents a brief review of the current status of molecular biology in relation to vestibular schwannoma in particular and is discussed in relation to the molecular pathology of skull base tumours as a whole.

Child↗
PubMed1995

Thrombosed posterior-inferior cerebellar artery aneurysm: a rare cerebellopontine angle tumour.

A case report of a thrombosed posterior-inferior cerebellar artery aneurysm is described. The tumour masqueraded as a vestibular schwannoma on imaging but the presenting features were unusual, the facial pain and weakness predominating despite well preserved hearing. This is an example of a rare cerebellopontine angle tumour and highlights the need for suspicion when lesions present atypically.

Aneurysm↗
PubMed1995

Genetics of familial and non-familial skull base tumours.

Many tumours of the skull base, including schwannomas, paragangliomas, meningiomas and anterior pituitary tumours occur both as sporadic tumours and in clear cut familial syndromes. These cancers' highly penetrant dominantly inherited syndromes have proven to be a rich resource for locating tumour genes, most of which are of the tumour suppressor type. Recently, the gene for type 2 neurofibromatosis (NF2) was isolated by the technique of positional cloning. The NF2 gene has now been demonstrated to be involved in the pathogenesis of both familial and non-familial vestibular schwannomas as well as meningiomas. The presence of inactivating mutations within this gene suggests that it acts as a tumour suppressor and the mechanism has been shown to comply with a 'two hit' mutation model. Hereditary tumours constitute a small proportion of all cases, but evidence from studies of tumours such as vestibular schwannoma and meningioma have shown that their genes are also relevant to the much more common non-familial forms of the same tumour. This paper briefly describes the approach to locating tumour genes, and reviews our current knowledge regarding the chromosomal location and function of genes responsible for familial tumours involving the skull base. The genetic mechanisms of tumourigenesis are discussed as are the prospects for the development of novel forms of diagnosis and treatment.

Adenoma↗
PubMed1995

Referral patterns in vestibular schwannomas.

The investigation and treatment of vestibular schwannomas is an increasingly specialized area in which major advances have been seen over recent years. The effect of these advances on the referral patterns to a centre specializing in such surgery is reviewed. The proportion of referrals with a known diagnosis has increased substantially, allowing the specialist centre to focus on appropriate management rather than diagnosis. The vast majority of vestibular schwannomas are referred by otolaryngologists. The caseload referred by neurologists or neurosurgeons have different presenting symptoms. The incidence of vestibular schwannoma in the Cambridge district is found to be 1 per 50,000 population per year. This is a higher incidence than that recorded in other studies. This may be due to a tight diagnostic strategy and the high level of clinical awareness of the local general practitioners.

Ear Neoplasms↗
PubMed1995

Nervus intermedius function after vestibular schwannoma removal: clinical features and pathophysiological mechanisms.

The results of facial nerve outcome following vestibular schwannoma removal have generally ignored the sensory component of the nerve. This lack of reporting occurs partly because the distress relating to these functions is less obvious to the surgeon, and partly because the facial nerve grading systems currently used do not include the functions of the nervus intermedius. We have estimated the frequency and nature of abnormalities of nervus intermedius function following vestibular schwannoma removal using a retrospective questionnaire. Questionnaires were mailed to 257 patients and correctly completed and returned by 224 (87%) of the patients. Prior to surgery 5 (2%) of the patients complained of crocodile tears, 9 (4%) noted dryness of the eye, and 15 (6%) complained of an abnormality of taste. Postoperative crocodile tears occurred in 98 (44%), an absence or significant reduction in the production of tears was noted in 162 (72%), and a taste abnormality, either a significant reduction or an alteration in character, was noted in 107 (48%). The onset of crocodile tears approximated to a bimodal distribution, and the recovery of nervus intermedius functions was variable. This study has demonstrated that nervus intermedius abnormalities are common following vestibular schwannoma removal. It also documents their natural history and discusses the underlying pathophysiological mechanisms. We suggest that appropriate preoperative counseling be given to all patients undergoing surgery and that the functions of the nervus intermedius be included in the surgical reporting of facial nerve results in cerebellopontine angle surgery.

Facial Nerve↗
PubMed1994

Surgical emphysema: a novel complication of aural exostosis surgery.

We present the case of a 40-year-old male Caucasian patient who developed surgical emphysema of the neck five weeks after surgery for exostoses of the external auditory canal. Imaging of the temporal bone demonstrated that the surgery had resulted in entry into the temporomandibular joint. A mechanism is proposed for this novel complication.

Adult↗
PubMed1994

Somatic NF2 gene mutations in familial and non-familial vestibular schwannoma.

Vestibular schwannoma occurs both as a sporadic tumour and in the dominantly inherited familial cancer syndrome neurofibromatosis type 2 (NF2). The gene for NF2 has recently been isolated on chromosome 22, and the demonstration of inactivating germline mutations in NF2 patients and NF2 associated tumours suggests that it act as a tumour suppressor. We have investigated 85 sporadic and 2 NF2 associated vestibular schwannomas, and one vagal schwannoma for chromosome 22 allele loss and NF2 gene mutations. A further 7 vestibular schwannomas were investigated for NF2 mutations only. Chromosome 22 allele loss was detected in 34 of 87 vestibular schwannomas and in the vagal nerve schwannoma. Six exons of the NF2 gene were investigated by SSCP analysis in all 95 tumours. Somatic NF2 gene mutations were detected in 13 non-familial vestibular schwannomas and in one of the NF2 vestibular schwannomas. Seven non-familial tumours with an NF2 gene mutation also displayed a chromosome 22 allele loss. Thirteen of the mutations were predicted to produce truncation of the NF2 protein. These results suggest that somatic mutations of the NF2 tumour suppressor gene are a critical step in the pathogenesis of both familial and non-familial vestibular schwannoma and that the mechanism of tumourigenesis complies with a 'two-hit' mutation model.

Adult↗
PubMed1994

Mastoid obliteration using bone pâté.

The technique of mastoid revision and obliteration using bone pâté and a superiorly based temporalis musculo-periosteal flap is described in detail. This method has evolved and been employed in our department over the past 10 years.

Bone Transplantation↗
PubMed1994

Bone pâté obliteration or revision mastoidectomy: a five-symptom comparative study.

A survey of 47 patients who underwent surgical treatment for persistent symptomatic mastoid cavities following mastoidectomy for cholesteatoma, was carried out. There were two groups comprising 26 patients who underwent revision mastoidectomy (14 with meatoplasty); the technique favoured early in the series, and 21 managed by mastoid revision and obliteration with autologous bone pâté and a superiorly based temporalis musculo-periosteal flap. A questionnaire was used to assign a symptom score to each patient's pre and post-operative condition, with a maximum score of 15 and minimum of zero. The pre-operative scores for the two groups were not significantly different, but the patients treated by obliteration with bone pâté had a significantly lower (P = 0.05) postoperative symptom score than those who had their mastoids simply revised. This study suggests that revision mastoidectomy with bone pâté obliteration achieves a more favourable result than revision mastoidectomy alone, and is, we believe, the technique of choice for the patient with a symptomatic mastoid cavity.

Adult↗
PubMed1994

Endolymphatic sac surgery: analysis of 100 operations.

One hundred endolymphatic mastoid shunt operations in 89 patients with classical Menière's disease were analysed. The disease was bilateral in 18 patients (20%). The patients were carefully pre-selected by a comprehensive protocol of audiovestibular and metabolic investigations. All patients had definite electrophysiological evidence of endolymphatic hydrops with an enhanced negative summating potential on transtympanic electrocochleography. The surgical results were analysed both by the original American Academy of Ophthalmology and Otolaryngology Guidelines (AA00, 1972) and the more recent modifications of the American Academy of Otolaryngology, Head and Neck Surgery (AA-HNS, 1985). Control of the vertigo was achieved in 81% of the patients overall, in 88% of the patients with unilateral disease and in 63% of the patients with bilateral disease. A significant hearing improvement was obtained in 19% of patients, no change in 55% and hearing became worse in 26%. Tinnitus improved in 38% of patients, was unchanged in 52% and became worse in 10%. Disability was assessed and there was no disability in 44% of the patients post-operatively, some degree of disability in 48% but only 8% were severely disabled and unable to sustain gainful employment.

Disability Evaluation↗
PubMed1994

Audiological findings in glomus tumours.

Glomus tumours of the skull base are rare, but as they present with symptoms of hearing loss and tinnitus they are a clinical entity of which audiologists should be aware. This paper describes the findings of the major series of skull base glomus tumours found in the literature, and notes that the contribution of conductive and sensorineural components varies with tumour classification. The reported incidence of hearing loss and tinnitus in glomus tympanicum and glomus jugulare is reviewed and compared with the Cambridge series, in which two tumours were Fisch type A, four type B, two type C and five type D. In each case a mixed hearing loss was found, though the extent of sensorineural impairment was variable. The length of history of tumours limited to the middle-ear was far shorter (mean 8 months) than for more extensive lesions (type B, mean 64 months; C, 48 months; and D, 23 months). Eleven patients (85%) reported the symptom of hearing loss, and 12 (92.5%) of tinnitus, and some patients had experienced these symptoms for some time without seeking the advice of an otologist. It may be concluded that the presence of subjective pulsatile tinnitus or a retrotympanic mass should be considered an indication for an otological opinion, wherein the use of high resolution imaging techniques and arteriography will be considered in conjunction with detailed audiological assessment. Audiologists should be aware of the possibility of glomus tumour in such cases.

Adult↗
PubMed1994

Reduction in junior doctors' hours in an otolaryngology unit: effects on the 'out of hours' working patterns of all grades.

This study aimed to assess the effects of recent controls on juniors' duty hours (the 'New Deal') on the work performed by all grades of ENT medical staff 'out of hours'. For 100 days in 1993 the out of hours duties of all grades of doctor in the Otolaryngology Unit were monitored using daily logs. Three patterns of cover were run in parallel and subjected to comparison: Light: Senior House Officer (SHO)--Consultant (CON); Traditional: SHO-Intermediate (Registrar or Senior Registrar)--Consultant; Cross-cover--Pre-Registration House Officer (PRHO)--Intermediate-Consultant. The SHO 'out of hours' daily workload did not differ significantly between the traditional and light systems (median hours: 5.6 versus 5.0). There was an increase in working hours for the intermediate (registrar or senior registrar) grade of 84 per cent when the cross-cover system was in operation compared with the traditional system (median hours: 5.0 versus 2.8; p < 0.0001--Mann-Whitney U test). Consultant working hours increased by an average of 132 per cent as a result of removal of the intermediate tier (median hours: 1.7 versus 0.80; p < 0.0001). Reduction in on-call hours of junior staff resulted in a need for cross-cover and also in the frequent removal of an intermediate tier of staff. This has been shown to have a considerable effect on working patterns for intermediate and senior grades in an ENT unit of average size. Further reductions would be expected to have major effects on the working patterns of the consultant grade and considerably dilute the emergency experience of trainees.

Consultants↗
PubMed1992

Speech in noise: a practical test procedure.

A simple and effective speech in noise test is described with clinical findings for patients with normal hearing, cochlear and retrocochlear pathologies and auditory dysacusis. The test utilizes material readily available in Audiology and ENT Departments. It was possible to obtain useful diagnostic information in patients who complain of hearing loss, but who demonstrate normal audiometric thresholds and normal speech in quiet discrimination.

Adolescent↗
PubMed1992

What is the effect of translabyrinthine acoustic schwannoma removal upon tinnitus?

A series of 129 patients who had undergone translabyrinthine removal of a unilateral acoustic schwannoma completed a postal questionnaire about pre- and post-operative tinnitus. A simple grading system was devised from which it was possible to determine the likely outcome of translabyrinthine acoustic schwannoma surgery upon tinnitus. The results have been analyzed in detail, and as a result it is possible to advise a patient undergoing this form of surgery that if they have no tinnitus pre-operatively they are unlikely to develop it, and if they do it will not be severe enough to significantly affect their quality of life. If they have mild or moderate tinnitus it is most likely to stay the same, or become less intense. If a patient has severe tinnitus it is very likely to improve and not affect their future quality of life.

Humans↗
PubMed1992

Bilateral optic nerve sheath meningiomas in a patient with neurofibromatosis type 2.

A 34-year-old woman who presented with hearing loss and tinnitus was found to have reduced vision bilaterally. Computed tomography scan revealed bilateral acoustic neuromas and bilateral optic nerve sheath meningiomas. The presence of bilateral acoustic neuromas fulfils the criteria for the diagnosis of central neurofibromatosis (neurofibromatosis type 2). Although this is the first report of bilateral optic nerve sheath meningioma in neurofibromatosis type 2, meningiomas are commoner in this dominantly inherited disorder, than in its absence and both forms of central nervous system tumour may be caused by loss of tumour suppressor genes on chromosome 22.

Adult↗
PubMed1992

Bilateral electrocochleographic findings in unilateral Menière's disease.

At present, electrocochleography is the only proven investigation that can demonstrate objectively the presence of endolymphatic hydrops. The electrophysiologic recordings in response to sound stimuli show an enhancement of the negative summating potential in these cases. It is well established that patients with unilateral Meniere's disease have a high likelihood of development of the disease bilaterally in the fullness of time. Using transtympanic electrocochleography in 40 patients who manifested unilateral clinical Meniere's disease, we have recorded bilateral abnormalities indicative of endolymphatic hydrops in 35% of cases. The early recognition of incipient Meniere's disease in the asymptomatic contralateral ear of a patient with known unilateral disease has obvious profound implications for patient management.

Action Potentials↗