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Biomedical subjects

D A Moffat

Publications and source records attributed to D A Moffat.

At least 55 records · Page 3Linked to original sources
PubMed1997

Audio-vestibular findings in meningioma of the cerebello-pontine angle: a retrospective review.

The aim of this study was the determination of the incidence of symptoms of audio-vestibular dysfunction and of abnormalities on audio-vestibular testing in patients found to have a unilateral meningioma of the cerebello-pontine angle (CPA). The case notes of 25 patients diagnosed with unilateral, sporadic and histologically proven CPA meningioma were retrospectively reviewed. The age range of this series was 31-71 years, with a mean age of 50 years. Two patients were male (eight per cent) and 23 were female (92 per cent). The mean length of history was 44.7 months. The distribution of tumour size was skewed toward larger tumours, with 15 cases (60 per cent) having tumours with a maximum diameter greater than 3.5 cm on imaging. Pure tone audiometry was normal in five cases (20 per cent), and no patients exhibited the high frequency sensorineural hearing loss that is characteristic of vestibular schwannoma. Speech audiometry was normal in 50 per cent of cases. Caloric testing was abnormal in 77 per cent of the 18 cases tested, whilst auditory brainstem responses (ABR) were abnormal in 100 per cent of the 18 cases who had sufficient hearing for this test to be possible. The presence of normal audiometry in patients with a proven CPA lesion indicates that, if in a protocol for investigation, asymmetry of hearing is mandatory then some pathology will be missed. Any suspicion of a CPA lesion warrants investigation even in the absence of hearing loss. The investigation of choice for the identification of CPA lesions has become magnetic resonance imaging (MRI). If this technique is not available then this study indicates that ABR is a suitable and sensitive investigation. It should be borne in mind however that the data in this study has been derived from a series of predominantly large tumours, and the sensitivity of ABR to smaller CPA meningiomata may fall, as is the case for vestibular schwannoma.

Adult↗
PubMed1997

Endolymphatic mastoid shunt surgery in unilateral Menière's disease.

One-hundred endolymphatic mastoid shunt operations in patients with classic unilateral Meniere's disease were analyzed. The patients were carefully preselected with a comprehensive protocol of audiovestibular and metabolic investigations. All patients had definitive electrophysiologic evidence of endolymphatic hydrops with an enhanced negative summating potential on transtympanic electrocochleography. The surgical results were analyzed both by the original American Academy of Ophthalmology and Otolaryngology Guidelines (AAOO, 1972), and the more recent modifications of the American Academy of Otolaryngology-Head and Neck Surgery (AA-HNS, 1985). Control of vertigo was achieved in 79% of the patients overall, with 42% sustaining complete control and 37% substantial control. A significant hearing improvement was obtained in 15% of cases, there was no change in 56% of patients, and hearing became worse in 29%. Tinnitus improved following surgery in 35% of patients, was the same in 56%, and worse in 9%. Postoperatively, there was no disability in 42% of the patients, some degree of disability in 50%, and severe disability and inability to sustain gainful employment in only 8%.

Adolescent↗
PubMed1997

Somatic neurofibromatosis type 2 gene mutations and growth characteristics in vestibular schwannoma.

BACKGROUND: The growth of hereditary and sporadic vestibular schwannomas shows wide variation, but what determines this is poorly understood. HYPOTHESIS: In neurofibromatosis type 2 (NF2), there is some correlation between the nature of the germline NF2 gene mutation and phenotype. Somatic mutations in the NF2 gene occur in sporadic tumors, but their relation to tumor behavior is unknown. METHODS: This study has investigated the molecular pathogenesis of vestibular schwannoma by looking for NF2 gene mutations. The authors have screened 17 exons of the NF2 gene in 91 sporadic vestibular schwannomas, 2 NF2, and 1 vagal schwannoma. These data have been correlated with a clinical growth index and a tumor cell proliferation index, determined using a monoclonal antibody to the proliferating cell nuclear antigen. RESULTS: Of the 94 tumors studied, 40 somatic gene mutations (38%) have been sequenced in 36 tumors. The mutations included 36 protein truncating mutations, 1 in-frame deletion, 2 splice site mutations, and 1 missense mutation. Regression analysis showed no correlation between the nature of the NF2 gene mutation and either the clinical (R2 = 0.006) or the proliferative index (R2 = 4 x 10(-8). CONCLUSION: The results of this study show no association between the nature of the intragenic NF2 gene mutation and tumor behavior. It is likely therefore that NF2 gene inactivation is not the only determinant of tumor behavior in vestibular schwannoma.

Adult↗
PubMed1996

Epithelial-myoepithelial carcinoma of the parotid gland. An unusual cause of ear canal stenosis.

Epithelial-myoepithelial carcinoma (EMC) accounts for approximately one per cent of salivary gland tumours. This tumour is gaining wider recognition following inclusion into the WHO histological classification of salivary gland tumours in 1990. Salivary gland tumours characteristically present with an enlarging mass. We describe an unusual presentation of a salivary gland tumour with stenosis of the external ear canal in the absence of a palpable mass. EMC usually arises from the salivary glands but isolated cases have been described arising primarily from the paranasal sinuses, trachea and lacrimal gland. The management of this tumour is still evolving with surgical excision being the main-stay of treatment. The efficacy of radiotherapy has not yet been established but high local recurrence rates despite apparently adequate excision and the possibility of a multicentric origin of the tumour may herald an increasing role for radiotherapy in the future. We stress the importance of awareness of adjacent structures when considering the cause of cartilaginous canal stenosis.

Carcinoma↗
PubMed1996

Factors which influence the facial nerve outcome in vestibular schwannoma surgery.

A series of 276 patients with a unilateral vestibular schwannoma has been analysed with respect to the factors affecting post-operative facial nerve outcome. Age, tumour size, operative approach and the use of intra-operative facial nerve monitoring have been examined. The tumours were removed via either a translabyrinthine or a retrosigmoid approach. In this series increasing age and increasing tumour size were associated with a worse facial nerve outcome. The use of intra-operative facial nerve monitoring and the retrosigmoid approach were both associated with a better facial nerve outcome. Those patients having a retrosigmoid approach had a facial nerve result that was over one House grade better than those having translabyrinthine tumour removal.

Facial Nerve↗
PubMed1996

The surgical management of patients with glomus tumours of the skull base.

Total surgical excision is the only treatment modality that offers a cure for patients with glomus tumours of the skull base. The vascularity, inaccessibility and frequently extensive local spread, all contribute to the difficulties encountered in the management of patients with these complex lesions. Owing to the rarity of skull base glomus tumours, experience in their management can only be attained over long periods of time. We describe the surgical management of 20 patients with large glomus tumours of the skull base treated by an otoneurosurgical team over an 11-year period. Overall, 70% of patients had an excellent outcome, 10% a good outcome and 20% a poor outcome at a mean follow-up of 3.1 years. Poor outcomes were due to severe facial nerve palsies in two cases, and poorly accommodated palsies of the bulbar cranial nerves in a further two patients. The management of postoperative neurological deficits is discussed in detail. We conclude that in the majority of patients with skull base glomus tumours, complete surgical excision can be safely achieved.

Adult↗
PubMed1996

Surgical results in unusual cerebellopontine angle tumours.

Vestibular schwannomas account for 84% of cerebellopontine angle (CPA) lesions. The remaining CPA tumours comprise a fascinating group of lesions which may present in a similar fashion. Fortunately, advances in neuroradiology have increased our diagnostic accuracy of these lesions. This paper describes the surgical results of a series of 69 CPA lesions which were not vestibular schwannomas. The majority of these unusual CPA tumours were meningiomas, cholesteatomas and neuromas of other cranial nerves in the posterior fossa.

Adult↗
PubMed1996

Molecular genetic investigation of the neurofibromatosis type 2 tumor suppressor gene in sporadic meningioma.

The authors investigated the role of somatic mutations of the neurofibromatosis type 2 (NF2) gene in sporadic meningioma. Neurofibromatosis 2 is a dominantly inherited familial tumor syndrome predisposing affected patients to a variety of central nervous system tumors including vestibular schwannoma and meningioma. Neurofibromatosis type 2 is caused by germline mutations in the NF2 tumor suppressor gene. In addition, the authors and others have reported that somatic NF2 gene mutations occur frequently in nonfamilial vestibular schwannoma. In this study, molecular genetic analysis was performed on 23 nonfamilial meningiomas. Paired DNA samples extracted from the blood and tumors of the patients were analyzed for loss of heterozygosity (LOH) in the region of the NF2 gene on chromosome 22 using closely linked DNA markers. The NF2 gene mutations were sought by single-stranded conformation polymorphism analysis and DNA sequencing. Fourteen (61%) of 23 meningiomas showed LOH in the region of the NF2 gene on chromosome 22. Somatic NF2 gene mutations were detected in eight meningiomas (35%) after screening all 17 exons. All tumors with NF2 gene mutations showed simultaneous chromosome 22 LOH. Review of the histopathological findings of the cases studied did not demonstrate any predominance of genetic abnormalities in a particular histological type of meningioma. These results are compatible with the hypothesis that the NF2 gene acts as a tumor suppressor and that its inactivation is important in the pathogenesis of sporadic meningioma.

Chromosomes, Human, Pair 22↗
PubMed1996

Audiovestibular results after surgery for cerebellopontine angle meningiomas.

Meningiomas are the second most common cerebellopontine angle (CPA) tumor. The reported rates of hearing preservation following surgical removal vary between 32% and 100%. There is only one recent report discussing vestibular function after CPA meningioma removal. In this series of 31 patients with CPA meningiomas, 16 patients had their tumors removed via the retrosigmoid approach. All 16 had audiovestibular assessment pre- and postsurgery and were the subjects of this study. Class A hearing is socially useful hearing and is defined as a pure tone average (PTA; average of 500 Hz and 1, 2 and 4 kHz) of < 30 dB and speech discrimination scores (SDS) of > 70%. Class B hearing is serviceable hearing, defined as PTA of < 50 dB and SDS of > 50%. Nine patients had class A hearing, and two had class B hearing presurgery. Socially useful hearing was preserved in six of nine (67%) patients in whom it was present before surgery, and serviceable or better hearing was preserved in eight of 11 (73%). Vestibular symptomatology and examination findings improved despite a decrease in the number of patients with intact caloric function postsurgery. Patients who retained vestibular function on caloric testing were symptomatically better than those who lost caloric function. These results confirm that excellent audiovestibular function is possible after CPA meningioma surgery.

Adult↗
PubMed1996

The operative learning curve and its effect on facial nerve outcome in vestibular schwannoma surgery.

The successful removal of vestibular schwannomas requires a team approach by skillful and appropriately trained surgeons. It is generally perceived that the results of surgery, especially facial nerve outcome, will improve as the surgical team acquires more experience. This study of 300 patients undergoing surgical removal of vestibular schwannomas confirms that there was a significant learning curve for facial nerve outcome. In the first 50 cases, 52% had satisfactory outcomes (House grades I-III), whereas in the last 50 cases 92% had satisfactory outcomes. The major improvement came between the first 50 cases and the second 50 cases (House grades I-III results at 12 months improved from 52% to 78%). After the second 50 patients there was a gradual, but continued improvement, which is also attributable to increased surgical experience. Most of this learning curve was related to the translabyrinthine approach. House grades I-III results were attained for 45% of the first 40 and 70% of the second 40 translabyrinthine tumor removals.

Ear Neoplasms↗
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↗
PubMed1995

The patient's perspective after vestibular schwannoma removal: quality of life and implications for management.

A postal survey was conducted, using a standardized quality of life questionnaire, of patients who had undergone surgery for removal of vestibular schwannoma between 1981 and 1992. Of 257 questionnaires, 227 (88%) were returned completed. The questionnaire was based on the European Organisation for Research into the Treatment of Cancer (EORTC) core questionnaire. A series of five functional gradings were used to assess the quality of life, and specific questions were also asked. The results were numerically scored and have been correlated with patient and tumor characteristics. There was a significant difference (p = .0001) between the subjective functional outcome for small and intracanalicular tumors when compared with tumors larger than 1.5 cm maximum diameter. However, there was no significant difference when tumors 1.5 to 2.5 cm in diameter were compared to larger tumors. Poor functional outcome did not correlate with the age of the patient, position in the series, or postoperative facial nerve motor function. There also was no significant difference when younger patients (age < 65 yr) were compared with older patients (age 65 - 76 yr). In general, the quality of life following vestibular schwannoma surgery was excellent. Patients with a poor functional outcome were evenly distributed over the medium and large tumor size groups, and patients with small tumors ( < or = 1.5 cm) had a significantly better outcome.

Activities of Daily Living↗