Strategy and benefits of acoustic neuroma searching

Magnetic resonance imaging for vestibular schwannoma: cost-effective protocol for referrals

Objective

Vestibular schwannoma is the most common neoplasm in the cerebellopontine angle, and fast spin-echo T2-weighted magnetic resonance imaging is the most sensitive test for diagnosing it. This study evaluated the financial and time costs of unnecessary magnetic resonance imaging referrals before and after the application of a magnetic resonance imaging protocol.

Method

A full audit cycle was used for the assessment. The first cycle in January 2012 was retrospective and evaluated the financial impact of current selection criteria for magnetic resonance imaging referral against standard guidelines. The second cycle in January 2014 was prospective after implementation of the protocol.

Results

There were 46 and 112 patients who had magnetic resonance imaging during first and second cycle, respectively. Of the referrals for magnetic resonance imaging, 65 per cent versus 81 per cent of the referrals were appropriate in the first and second cycles, respectively. The relative risk was reduced from 0.5 to 0.2. The waiting times for magnetic resonance imaging scans improved.

Conclusion

Selection criteria for magnetic resonance imaging referral are important in reducing waiting times for scans, patient anxiety and conserving trust resources.

Early Diagnosis and Surgical Management of Acoustic Neuroma: Is it Cost Effective?

Audiological and radiological advances and refinement of microsurgical techniques have facilitated the diagnosis and excision of very small acoustic nerve tumours with a low morbidity and mortality. Is this cost effective?

In an attempt to answer this question, an analysis of 66 cases of surgically treated acoustic neuromas is presented. This represents a part of a series of otoneurosurgical procedures carried out at Addenbrooke's Hospital over the last five years. By studying the relative morbidity of early and late surgical intervention in these cases, and by costing the exercise, the justification for early diagnosis and treatment is presented both in financial and human terms.

Should initial surveillance of vestibular schwannoma be abandoned?

Early diagnosis of vestibular schwannoma (VS) has increased in recent years because of increased longevity and availability of magnetic resonance imaging (MRI). Initial conservative radiological surveillance is often requested by patients and physicians to establish whether these tumors are growing before embarking on intervention. Initial observation of at least 1 year in all small VS was therefore recommended by some authors. We evaluated our prospective skull base database of VSs that were managed with initial radiological surveillance to establish when this policy should be abandoned and what predicts future growth. Fifty-four consecutive patients with VS in our institution who were managed by initial yearly MRI scanning were studied. The MRI data were collected prospectively and analyzed by Kodak CareStream viewing software where VS maximum diameters in three perpendicular planes and volume were calculated. One patient was excluded from the analysis as he had only one MRI follow-up. The median age of the 53 patients was 59 years (range, 26 to 86 years), 25 were males and 28 were females, and 33 were under 65 years of age; 18 VSs were extracanalicular, 18 were intracanalicular, and 17 extended both inside and outside the canal; 21 VSs were 1.2 cm(3) or less, 22 were 1.2 to 4 cm(3), and the rest were >4 cm(3). Using volumetric analysis, 29.72% of conservatively managed VS grew by at least 2 mm per year, and 70.82% did not grow in 5 years. Age, gender, symptoms, and side did not predict future growth. However, growth in the first year was a strong predictor of future growth (p < 0.001) and initial volume was also a strong predictor of future growth (p < 0.05). Twenty-nine percent of observed VSs grew by at least 2 mm per year in the first 5 years of surveillance. As the growth rate is slow, initial radiological surveillance is justified in elderly patients and patients with small VSs and nonserviceable hearing. Growth in the first year was a strong predictor of future growth. The reported treatment effect should be interpreted in the light of 70.24% of VSs that either shrink or do not change in the first 5 years.

Growth of untreated vestibular schwannoma: a prospective study

Object

Small vestibular schwannomas (VSs) are often conservatively managed and treated only upon growth. Growth is usually reported in mm/year, but describing the growth of a 3D structure by a single diameter has been questioned. As a result, VS growth dynamics should be further investigated. In addition, baseline clinical parameters that could predict growth would be helpful. In this prospective study the authors aimed to describe growth dynamics in a cohort of conservatively managed VSs. They also compared different growth models and evaluated the ability of baseline parameters to predict future growth.

Methods

Between 2000 and 2006, 178 consecutive patients with unilateral de novo small-sized VSs identified among the Norwegian population of 4.8 million persons were referred to a tertiary care center and were included in a study protocol of conservative management. Tumor size was defined by MR imaging–based volume estimates and was recorded along with clinical data at regular visits. Mixed-effects models were used to analyze the relationships between observations. Three growth models were compared using statistical diagnostic tests: a mm/year–based model, a cm3/year–based model, and a volume doubling time (VDT)-based model. A receiver operating characteristic curve analysis was used to determine a cutoff for the VDT-based model for distinguishing growing and nongrowing tumors.

Results

A mean growth rate corresponding to a VDT of 4.40 years (95% CI 3.49–5.95) was found. Other growth models in this study revealed mean growth rates of 0.66 mm/year (95% CI 0.47–0.86) and 0.19 cm3/year (95% CI 0.12–0.26). Volume doubling time was found to be the most realistic growth model. All baseline variables had p values > 0.09 for predicting growth.

Conclusions

Based on the actual measurements, VDT was the most correct way to describe VS growth. The authors found that a cutoff of 5.22 years provided the best value to distinguish growing from nongrowing tumors. None of the investigated baseline predictors were usable as predictors of growth.

Three-Year Ear, Nose, and Throat Cross-sectional Analysis of Audiometric Protocols for Magnetic Resonance Imaging Screening of Acoustic Tumors

Objectives. (1) Evaluate audiometric protocols and recommend protocols with best sensitivity and specificity for magnetic resonance imaging (MRI) screening of acoustic tumors; (2) determine clinical risks (false negative) of missing acoustic tumors and potential wastes in screening (false positive) nonacoustic tumors or radiologically “normal” cases; and (3) identify the decibel difference and range of frequencies compared by the best-performing protocols.

Study Design. Cross-sectional study with chart review.

Setting. Ear, nose, and throat (ENT); audiology; and radiology departments in a tertiary-care hospital.

Subjects and Methods. Three-year cohort (2006-2009) of 1751 ENT patients underwent MRI screening and pure-tone audiometry indicating sensorineural hearing loss. Audiometric protocols were ranked by highest sensitivity to acoustic tumors, specificity A to nonacoustic tumors, and specificity B to “radiologically normal” cases.

Results. No audiometric protocols achieved 100% sensitivity or specificity rates. Only 2 protocols achieved ≥90% sensitivity: the AMCLASS-A-Urben protocol (93.16%) and the Mangham protocol (91.58%). Eleven of 15 protocols for specificity A and 12 of 15 protocols for specificity B achieved ≥50%. Clinical risks ranged from 6.84% to 18.95%, whereas potential wastes ranged from 33.56% to 68.37% for specificity A and 31.76% to 66.86% for specificity B. Interaural difference parameters indicating highest mean sensitivity were on the order of ≥10 dB, ≥15 dB, and ≥20 dB. For frequency comparison parameters, “2 or more adjacent frequency” and “single-frequency” comparison indicated higher mean sensitivity than the “averaged multifrequency” comparison. Mean specificity showed an opposite pattern.

Conclusions. For optimum sensitivity, the Mangham protocol is preferred (sensitivity, 91.58%; specificity A, 44.23%; specificity B, 44.91%), which proposes a ≥10-dB interaural difference, averaging 1 to 8 kHz. For optimum specificity, the American Academy of Otolaryngology–Head and Neck Surgery protocol is preferred (sensitivity, 87.37%; specificity A, 65.38%; specificity B, 66.04%), which proposes ≥15 dB between ears, averaging 0.5 to 3 kHz.

The clinical characteristics of tinnitus in patients with vestibular schwannoma

OBJECTIVES

To review the symptoms, signs, and clinical findings in a large series of patients diagnosed with unilateral sporadic vestibular schwannoma (VS) to describe the clinical characteristics of tinnitus in this population. Further, to ascertain which of the proposed mechanisms of tinnitus generation in VS was supported.

DESIGN

Retrospective case note and database review.

SETTING

Tertiary university teaching hospital departments of audiology and neuro-otology.

PARTICIPANTS

Nine hundred forty-one patients with unilateral sporadic VS, diagnosed during the period 1986 to 2002. Twenty-three additional patients were excluded due to missing clinical data.

MAIN OUTCOME MEASURES

The presence or absence of tinnitus, and its rated subjective severity were analyzed in conjunction with data regarding patient demographics, symptoms, signs, and diagnostic audiovestibular test findings.

RESULTS

No statistical association at the 5% level was found between tinnitus presence/absence and patient age, gender, 2- to 4-kHz audiometric thresholds, ipsilateral auditory brainstem response abnormality, length of history, tumor side, nor caloric test abnormality. Statistically significant associations were found between tinnitus presence/absence and tumor size (p = 0.012) and type of hearing loss (progressive, sudden, fluctuant, nil) with a tendency for patients without hearing loss to be less likely to experience tinnitus. Statistically significant associations were identified between classification of tinnitus severity and age at diagnosis (p < 0.001) (greater age being associated with greater tinnitus severity), abnormal findings on caloric testing (p = 0.01) (abnormal calorics being associated with greater tinnitus severity), and tinnitus as a principal presenting symptom (p < 0.001) (this being associated with greater tinnitus severity).

CONCLUSIONS

The analysis does not identify any single one of the proposed mechanisms for tinnitus as being the obvious culprit. In fact, even in a homogeneous group of patients such as this, there is evidence of multiple mechanisms that are not mutually exclusive. The association between increased tinnitus severity in older patients, patients with canal pareses on caloric testing, and with tinnitus as a principal presenting symptom should be borne in mind by the clinician.

Beyond audiofacial morbidity after vestibular schwannoma surgery

Object

Outcomes following vestibular schwannoma (VS) surgery have been extensively described; however, complication rates reported in the literature vary markedly. In addition, the majority of reports have focused on outcomes related to cranial nerves (CNs) VII and VIII. The objective of this study was to analyze reported morbidity unrelated to CNs VII and VIII following the resection of VS.

Methods

The authors performed a comprehensive search of the English language literature, identifying and aggregating morbidity and death data from patients who had undergone microsurgical removal of VSs. A subgroup analysis based on surgical approach and tumor size was performed to compare rates of CSF leakage, vascular injury, neurological deficit, and postoperative infection.

Results

One hundred articles met the inclusion criteria, providing data for 32,870 patients. The overall mortality rate was 0.2% (95% CI 0.1–0.3%). Twenty-two percent of patients (95% CI 21–23%) experienced at least 1 surgically attributable complication unrelated to CNs VII or VIII. Cerebrospinal fluid leakage occurred in 8.5% of patients (95% CI 6.9–10.0%). This rate was markedly increased with the translabyrinthine approach but was not affected by tumor size. Vascular complications, such as ischemic injury or hemorrhage, occurred in 1% of patients (95% CI 0.75–1.2%). Neurological complications occurred in 8.6% of cases (95% CI 7.9–9.3%) and were less likely with the resection of smaller tumors (p < 0.0001) and the use of the translabyrinthine approach (p < 0.0001). Infections occurred in 3.8% of cases (95% CI 3.4–4.3%), and 78% of these infections were meningitis.

Conclusions

This study provides statistically powerful data for practitioners to advise patients about the published risks of surgery for VS unrelated to compromised CNs VII and VIII.

The role of the trigeminocardiac reflex in postoperative hearing function in non-vestibular schwannoma cerebellopontine angle tumors

The trigeminocardiac reflex (TCR) is a common event during skull base surgery that can lead to intraoperative arterial hypotension and bradycardia. Arterial hypotension associated with TCR can be a negative prognostic factor for postoperative auditory function and ipsilateral tinnitus in patients undergoing surgery for vestibular schwannoma (VS). In this study, the contribution of TCR to postoperative auditory function in non-VS cerebellopontine angle (CPA) tumor surgery was investigated. From a consecutive series of 102 patients with CPA tumors, we studied the occurrence of TCR and its influence on postoperative auditory function in patients with non-VS tumors. Pre- and postoperative auditory function, pre- and intraoperative mean arterial blood pressure, as well as preoperative medication, tumor size, and occurrence of TCR were evaluated. Of the 35 patients evaluated, four developed intraoperative TCR, of whom one was preoperatively deaf. Preoperative functional hearing was detected in 30/35 patients (85.7%): preoperative deafness was documented in one patient in the TCR group and in four patients in the non-TCR group. Of the 30 patients with preoperative functional hearing, 1/3 (33.3%) patients in the TCR group and 23/27 (85.2%) patients in the non-TCR group had functional hearing postoperatively. When patients with large tumors and functional, hearing were considered, only 33.3% of patients in the TCR group and 77.8% of patients in the non-TCR group remained within the same hearing classes following surgical treatment (p=0.1573). TCR may be a negative prognostic factor for postoperative auditory function in patients with large, non-VS CPA tumors.

Magnetic resonance imaging screening in acoustic neuroma

OBJECTIVES

Magnetic resonance imaging (MRI) is the definitive investigation for detection of an acoustic neuroma. It is however an expensive resource, and pick-up rate of a tumor can be as low as 1% of all patients scanned. This study aims to examine referral patterns for MRI screening for patients presenting with asymmetrical sensorineural hearing loss (ASHL). A second aim was to suggest appropriate screening criteria.

METHOD

All 132 MRI scans performed for ASHL in the year 2005 were reviewed retrospectively along with their case records and audiograms. In addition, MRI scans and case records were reviewed for the last 30 patients diagnosed with acoustic neuromas. Information was analyzed using 2 published protocols and additional frequency-specific defined criteria.

RESULTS

Two acoustic neuromas were picked up out of 132 scans performed. Of the scans performed for ASHL, a third did not fit with any of the published criteria. Of the 30 positive scans for a tumor, the patients/audiograms revealed that 10% did not fit the published criteria despite the patients having no other audiovestibular symptoms.

CONCLUSIONS

There appears to be no universally accepted guidelines on screening in ASHL with clinical acumen being used by most ENT consultants in this region. Applying protocols may reduce the amount of scans performed, but up to 10% of tumors may be missed by this approach.

Analysis of causes for late presentation of Indian patients with vestibular schwannoma

OBJECTIVE

To determine the causes of delay in diagnosis and treatment of Indian patients with vestibular schwannomas.

METHODS

In a prospective study from 2003 to 2005, 50 patients with a confirmed diagnosis of vestibular schwannoma were interviewed to determine the causes for (1) the delay between the patient noting the initial symptom and the definitive diagnosis, and (2) the reasons for delayed diagnosis.

RESULTS

In 90 per cent of patients, the initial symptom was either hearing loss (62 per cent), vertigo (24 per cent) or tinnitus (4 per cent). However, most patients had been diagnosed and had presented for surgery only after neurological symptoms had became apparent. The delay between the initial medical consultation and the final diagnosis ranged from one month to 204 months (mean +/- standard deviation, 32.2 +/- 38.9 months). After the patient had noted symptoms, the diagnosis of vestibular schwannoma was delayed due to doctor-related causes in 80 per cent of cases, and due to patient-related causes in 20 per cent. Delay following diagnosis was minimal.

CONCLUSIONS

Delay in the diagnosis of vestibular schwannoma in Indian patients is due to both doctor- and patient-related factors.

Incidence of vestibular schwannoma and neurofibromatosis 2 in the North West of England over a 10-year period: higher incidence than previously thought

OBJECTIVE

To determine the incidence of vestibular schwannoma (VS) in sporadic, neurofibromatosis type 2 (NF2) germ-line and mosaic form in a 10-year period.

STUDY DESIGN

Review of all incident cases of VS presenting to the four main neurosurgical centers for a population of 4.1 million from 1990 to 1999 and cross-referencing with the regional cancer registry.

SETTING

Population based.

PATIENTS

All patients presenting with VS detected on magnetic resonance imaging scan.

RESULTS

A total of 419 sporadic and 64 NF2-related VS were identified over the study period. This represented an incidence of 10.4 per million per year for sporadic VS and 11.8 per million per year including NF2-related tumors. The incidence rose to 14 per million per year in the latter 5 years. The NF2 patient diagnoses represent an estimated birth incidence of 1 in 25,000, and 7% of the patients with VS had NF2, which is higher than previous estimates.

CONCLUSIONS

The incidence of VS is rising almost certainly due to increasing diagnosis in the magnetic resonance imaging era. At current rates, 1 per 1,000 individuals will be diagnosed with VS in their lifetime. More VS than previously thought are due to NF2, which may be because of recognition of mosaic forms of the disease.

Referral patterns in vestibular schwannomas --10 years on

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.

Conservative management of vestibular schwannomas - second review of a prospective longitudinal study

Vestibular schwannomas have been traditionally managed with microsurgical removal and in recent years, stereotactic radiotherapy. However, there is a group of patients in whom a conservative management approach might represent a desirable alternative. The aim of this study was to determine the natural history and outcome following the conservative management of 72 patients with unilateral vestibular schwannomas. This is a prospective cohort review of a previously published group of patients [Clin. Otolaryngol. (2000) 25, 28-39] with unilateral vestibular schwannoma that were initially analysed at our institution in 1998 [Walsh R.M., Bath A.P., Bance M.L. et al., Clin. Otolaryngol. (2000) 25, 28]. The mean duration of follow-up was 80 months (range 52-242 months). All the patients in the study underwent serial magnetic resonance imaging (MRI) for assessment of tumour growth. Patients were deemed to have failed conservative management if there was evidence of rapid radiological tumour growth and/or increasing signs and symptoms, which necessitated active intervention. The mean tumour growth rate for the entire group at the second review was 1 mm/year (range -0.84-9.65 mm/year). The mean growth rate for cerebellopontine angle tumours (1.3 mm/year) was significantly greater than that of internal auditory canal (IAC) tumours (0 mm/year) (P = 0.005). The majority of tumours (87.14%) grew <2 mm/year. There was significant tumour growth seen in 38.9%, no or insignificant growth in 41.7%, and negative growth in 19.4%. Twenty-three patients (32%) failed conservative management at the second review. There was no difference in the outcome of these failed patients in comparison with patients who underwent primary treatment without a period of conservative management. The mean growth rate of tumours in patients that failed conservative management (3.1 mm/year) was significantly greater than that in patients who did not fail (0.2 mm/year) (P < 0.001). No factors predictive of tumour growth or failure of conservative management were identified. Hearing deterioration with pure tone averages (0.5, 1, 2, 3 kHz) and speech discrimination scores occurred irrespective of tumour growth. This prospective study further emphasizes the role of conservative management in selected cases of vestibular schwannomas. Tumours in this study confined to the IAC typically demonstrated minimal or no growth on serial MRI scanning. Regular follow-up with interval scanning is mandatory in all patients.

Fascicle preservation surgery for facial nerve neuromas involving the posterior cranial fossa

OBJECTIVE

To assess facial nerve function after fascicle preservation surgery in cases of facial nerve neuroma involving the cerebellopontine angle.

STUDY DESIGN

Retrospective case series and literature review.

SETTING

Tertiary referral center.

PATIENTS

Seven patients with facial nerve neuroma involving the posterior cranial fossa were reviewed from a single neurotologist's practice and combined with a review of 648 cases reported in the literature.

INTERVENTIONS

Translabyrinthine resection was used in all patients for complete tumor removal. Nerve reconstruction was accomplished with fascicle preservation (three cases), cable nerve interposition grafting (three cases, one of which involved using cranial nerve VIII as the graft), or direct anastomosis (one case).

MAIN OUTCOME MEASURE

Facial nerve function as measured by the House-Brackmann grading system. RESULTS A postoperative facial nerve (House-Brackmann) grade of II/VI was obtained in two of our three patients who underwent fascicle preservation reconstruction and in two of eight cases reported by other authors. One case reported elsewhere resulted in grade I/VI, and four other cases reported elsewhere achieved grade III/VI; only two cases were grade V/VI. There were no tumor recurrences at 5 to 19 years of follow-up.

CONCLUSION

Most cases of facial nerve neuroma require facial nerve resection. In rare cases, these tumors can be dissected away from the nerve fascicles, allowing the surgeon to preserve the facial nerve. This method resulted in better long-term postoperative facial nerve function (House-Brackmann grade II/VI vs. grade III/VI) compared with other techniques for patients in this small series, and no tumor recurrence.

Vestibular schwannomas in children

OBJECTIVE

This article highlights the clinical presentation and management issues of unilateral vestibular schwannomas in children. We demonstrate how the presentation differs from neurofibromatosis type 2 (NF2) and from adult unilateral vestibular schwannomas.

STUDY DESIGN

This article is composed of a series of three cases and a literature review.

SETTING

The study was performed at a university hospital (tertiary referral center).

PATIENTS

Three children, aged 9, 11, and 13 years, with histologically confirmed vestibular schwannomas were studied. All children under 16 years of age in the world literature with unilateral vestibular schwannomas were reviewed.

INTERVENTION

Analysis of presentation and surgical management of these three children and those children reported in the literature.

MAIN OUTCOME MEASURE

Pattern of presentation relative to children with NF2 and people with adult unilateral vestibular schwannomas.

RESULTS

Two patients had multiple cranial nerve weakness and recurrence, and one patient had successful removal of the tumor with preservation of all functions of the cranial nerves, including the facial nerve.

CONCLUSION

Vestibular schwannomas in children are very uncommon. It is likely that it is the first manifestation of NF2, but it may also be a variant of sporadic vestibular schwannomas. A presentation of three cases and a review of 36 other cases in the literature demonstrates how the presentation is different from adult sporadic vestibular schwannomas and NF2 because it lacks primary audiological symptoms. The study also provides evidence of non-NF2 vestibular schwannomas presenting in children and suggests that it is likely that these are a variant of unilateral sporadic vestibular schwannomas. The search for the features of NF2 in these cases remains mandatory.

The incidence of symptoms consistent with cerebellopontine angle lesions in a general ENT out-patient clinic

To quantify the potential burden for screening for cerebellopontine angle lesions, all adult new patients attending the ENT outpatient department of a district general hospital were documented to see if their presenting symptom(s) could be consistent with the presence of a cerebellopontine angle lesion. Of the patients, 19.7 per cent were found to be potential candidates for screening. A 15 decibel asymmetry at one frequency was found in 11.8 per cent of patients. The burden of screening with a variety of audiological and symptomatic protocols was quantified. Effective age limits to reduce the burden for screening were found to be either 65 or 75 years of age. With such a large potential pool of patients for further investigation, the results of this study could be used to suggest protocols which are likely to produce a load of cases, which matches local resources for screening.

Acoustic neuroma: correlations between morphology and otoneurological manifestations

Forty-two patients with acoustic neuroma (AN) were studied to determine whether different types of neuroma could be correlated with specific signs and symptoms of the disease. Based on gadolinium-enhanced TI-weighted MRI sequences, the 42 cases of AN could be divided into three groups, either by size (small: 11.9%, medium: 50%, and large: 38.1%) or by site of origin of the tumour (lateral: 16.7%, intermediate: 69%, and medial: 14.3%). Relations were found between the size and the site of origin of the neuromas and certain clinical, audiological and vestibular findings. The clinical presentation seemed to vary with the site of origin and the size of the tumour: patients with lateral neuromas generally had small tumours, sometimes only located in the internal auditory canal (IAC), and presented early subjective hearing loss while patients with medial neuromas had larger tumours which grew without causing significant audiological symptoms. Normal hearing function was seen only in the patients with medial ANs; however, a significant relation between the size or the site of origin of the AN and the average hearing threshold was not demonstrated. The sensitivity of the stapedial reflex test (SR) was higher for lateral ANs. Anomalies in the brainstem auditory evoked potentials (BAEPs) did not seem to be related to either the size or the site of origin of the AN. The vestibular tests demonstrated a higher frequency of central vestibular involvement in the large tumours, while normal function was more frequent in the lateral tumours. In the group studied the combination of BAEPs and vestibular tests allowed us to identify all the ANs with an optimal level of sensitivity.

A cost effective screening protocol for vestibular schwannoma in the late 90s

Magnetic resonance imaging (MRI) is the imaging modality of choice in diagnosing vestibular schwannoma (VS). Perceived high costs have prevented clinicians from using it as a screening investigation, although MR scanners are now widely available in the United Kingdom. In a retrospective study, the clinical records of all the patients who presented to the ENT department of Taunton and Somerset NHS Trust with suspected symptoms of VS during the year 1994 were analysed. The cost of confirming or refuting the diagnosis of VS in each patient ranged from 220.72 pounds to 580.31 pounds depending on the number of hospital visits and investigations performed. This study shows that the routine use of MR scanning for detection of VS is cost effective and more effective than the use of conventional tests.

MRI in the detection of acoustic neuromas--a suggested protocol for screening

Magnetic resonance imaging (MRI) is the definitive investigation in the detection of an acoustic neuroma and its use is becoming increasingly widespread for this purpose. In the Oxford region, this facility has been available for 3 years, resulting in the scanning of the internal auditory meati and cerebellopontine angles of 892 patients and the detection of 38 acoustic neuromas. Based on our use of this investigation over this time period, we have attempted to rationalize our entry protocol for screening by limiting the availability of the test to those patients up to 70 years of age presenting with unilateral audiovestibular symptoms in the absence of significant neurological symptoms or signs, with an average difference in hearing threshold of 15 dB between normal and symptomatic ears or unilateral tinnitus with normal hearing. By following these entry criteria, we would hope to maximize the available resources.

Efficiency of tests used to screen for cerebello-pontine angle tumours: a prospective study

With increasing use of imaging in the investigation of cerebello-pontine angle (CPA) tumours, the role of audio-vestibular and electrophysiological testing has changed. Field performance data on the efficiencies of these tests to screen for CPA tumours are lacking, but must be known to choose an appropriate testing strategy. A prospective observational study of 237 patients attending a neuro-otology clinic for audio-vestibular investigation was carried out. The aim was to provide field performance data on which to base an effective protocol to screen for CPA tumours. All patients presenting at the ENT department and meeting any of the following criteria were referred to the neuro-otology clinic and included in the study: (1) asymmetrical sensorineural hearing loss, (2) unexplained asymmetrical tinnitus with normal bearing thresholds, (3) unilateral bearing difficulties with normal hearing thresholds and (4) other neurological indications. In addition to audio-vestibular and auditory brainstem response (ABR) investigation, every patient underwent computed tomography (CT), with magnetic resonance imaging (MRI) in cases having marginal results on CT, to exclude or confirm the presence of a tumour. Pass or fail on each test was based on a priori criteria from other studies. Eighteen patients were found to have CPA tumours. ABR testing was the only effective procedure for screening, but had some limitations. A contingent protocol using ABR in all cases except those with asymmetrical tinnitus and normal bearing thresholds, those with severe hearing loss, and those with neurological signs, was retrospectively defined: the exceptions would go straight to CT. This protocol would have missed two of the 18 tumour patients. CT scanning alone would have missed one small intra-canalicular tumour, which was picked up on MRI triggered by abnormal ABR. Based on the results from the present study we conclude there is no effective screening protocol for detecting CPA tumours, as MRI scanning with gadolinium enhancement will identify virtually all tumours. Where MRI is available but waiting lists are long, the described strategy using ABR to select priority referrals for MRI scanning is recommended.

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.

Sudden Hearing Loss in Acoustic Neuroma Patients

Patients with acoustic neuroma may have sudden sensorineural hearing loss. Most patients with sudden hearing loss seek medical attention promptly, but the diagnosis of an acoustic neuroma may be delayed for months or years because sudden hearing loss is an unusual initial symptom of an acoustic neuroma. In a retrospective review of 836 cases of sudden hearing loss, we found 13 patients with acoustic neuromas. The prevalence of acoustic neuromas for those screened with auditory brain stem response or magnetic resonance imaging was 2.5%. In addition to these 13 patients, 79 acoustic neuroma patients treated in our clinic had well-documented sudden hearing loss as the initial symptom. Hearing loss in these 92 patients ranged from mild to profound. Associated symptoms of pain, facial paresthesia, or unilateral tinnitus preceding the sudden hearing loss were suggestive of an acoustic neuroma, as was a midfrequency (U-shaped) hearing loss. A history of other diseases or events that might explain the sudden hearing loss, a normal electronystagmogram, or recovery of hearing does not eliminate the possibility of a tumor. Because there are no clinical findings that clearly distinguish those patients with acoustic neuromas from other patients with sudden hearing loss, we recommend either an evaluation with auditory brain stem response or gadolinium-enhanced magnetic resonance imaging for any patient with sudden hearing loss.

Hearing loss associated with weapons noise exposure: when to investigate an asymmetrical loss

The air conduction thresholds in the right and left ears, and the interaural asymmetry of thresholds at 0.5, 1, 2, 3, 4 and 6 kHz were measured in a group of 225 soldiers exposed to a variety of weapon noise who were referred for assessment because of a deterioration in hearing on routine testing. At 0.5 and 1 kHz the threshold levels rarely exceeded 25 dB and the interaural asymmetry was 10 dB or less in 90 per cent of cases. The degree of hearing loss and interaural asymmetry increased as the frequency increased, with the average loss being significantly greater in the left ear at 2, 3, 4 and 6 kHz. Recommendations are made for the selection of cases of asymmetrical hearing loss exposed to weapon noise which require further investigation to exclude a retrocochlear cause or to define spurious hearing threshold levels.

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.

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.

Presentation and diagnosis of small acoustic tumors

With the recent advent of magnetic resonance imaging and auditory brain stem response, it is now possible to diagnose acoustic tumors while they are still quite small. As a result, it is becoming obvious that the clinical presentation of these smaller lesions can be somewhat variant to what is considered typical for an acoustic neuroma. Likewise, although the sensitivity of auditory brain stem response for larger tumors is believed to be quite good, the sensitivity for smaller tumors has recently been questioned, particularly when the patient is first seen early in the course of the disease with only mild otologic complications. To assess auditory brain stem response results as well as clinical and audiologic presentations, we conducted a retrospective study of patients treated for small acoustic tumors (less than 1 cm). Of the 70 patients included in the study, auditory brain stem response was abnormal in 65 (93%), on the basis of wave V latency prolongation and interaural latency differences. This would indicate that auditory brain stem response is a valid screening test for acoustic tumors, even in early stages of development. The clinical presentation of patients with small acoustic tumors was similar to that reported for acoustic tumors in general, but with vertigo occurring more frequently in patients with smaller tumors. Several atypical patterns of hearing loss were also noted.

The burden of screening for acoustic neuroma: asymmetric otological symptoms in the ENT clinic

The rising numbers of legal cases relating to delay in the diagnosis of acoustic neuroma, combined with the increasing availability of magnetic resonance, is increasing pressure on otologists to make an early definitive diagnosis of cerebellopontine angle tumours. Unilateral or asymmetrical otologic symptoms not explained by external or middle ear disease are elicited in 16.6% of 500 consecutive attenders to an otolaryngology clinic. An agreed policy of risk stratification of patients with unexplained asymmetric otological symptoms is required if expense is to be limited and litigation minimized.

Unusual cerebello-pontine angle tumours

Fifty-nine unusual cerebello-pontine angle tumours have been studied. These lesions represent 19.3 per cent or 1 in 5 of a series of 305 cerebello-pontine angle tumours of which the rest, 246 (80.7 per cent), were acoustic neuromas. An analysis of the relative incidence, histology and presenting clinical features has been carried out. The various radiographical features and imaging techniques used to diagnose these fascinating tumours have been described and also the otoneurosurgical procedures necessary to excise them.

MRI as a Single Screening Procedure for Acoustic Neuroma: A Cost Effective Protocol

Magnetic resonance imaging (MRI) is accepted as the ‘gold standard’ in diagnosing acoustic neuromas. Limited availability and perceived high costs have prevented clinicians from using it as a first-line investigation. A prospective study was set up in a specially designated screening session to audit the cost effectiveness and accuracy of audiovestibular investigations compared to MRI. Ninety-nine patients with asymmetrical audiovestibular symptoms or signs were investigated. Of these 54 evoked response audiometry tests, and 39 calorics were either not performed or were inconclusive. One patient refused to enter the MRI machine. All others received an unequivocal report after MRI and four tumours (three intracanalicular) were detected. The total cost of the audiovestibular protocol was £12 545 compared to £12 900 for the MRI protocol, which is a diagnostic and well-tolerated procedure. This study shows that MRI can be cost effective, as well as accurate, when used as a single screening procedure for acoustic neuromas.

The effective use of magnetic resonance imaging in the diagnosis of acoustic neuromas

The diagnostic approach to acoustic neuromas is complex but these tumours are infrequent in patients even with a suggestive clinical picture. Easy access to an efficient, reliable and cost effective investigation is desirable. Magnetic resonance imaging is now the imaging modality of choice and this paper shows that it may be used effectively as the sole investigation. T2-weighted (T2W) fast spin echo axial images taking 1 min 37 s to acquire were compared with T1-weighted (T1W) gadolinium-enhanced axial images, taking 5 min 11 s to acquire, in 157 patients. The T2W images were satisfactory alone in 43% of patients and allowed confident diagnosis of seven of the nine acoustic neuromas. Partial volume artefact and CSF flow artefact resulted in equivocal examinations in the remaining patients. Using both sequences in every patient, imaging time was 7 min 41 s and at least 40 patients could be examined in 1 day, thus ensuring efficient patient throughput. We suggest that T2W fast spin echo axial images be routinely obtained and that only when they are equivocal should T1W gadolinium-enhanced axial sequences be employed.

Clinical correlates of acoustic neuroma morphology

Thirty-eight patients with vestibular schwannomas were reviewed. A correlation was found between tumour morphology and clinical presentation. Based on our knowledge of the variability in the neurilemmal-neurologlial junction and therefore the site of origin of these tumours in relation to the internal auditory canal, a classification into three different appearances on magnetic resonance imaging was possible. Dumbbell shaped tumours (21 per cent) represented laterally arising schwannomas, lollipop shaped tumours (18 per cent) were medially arising and cone shaped tumours (61 per cent) were the more common intermediate form. Patients with laterally arising dumb-bell shaped tumours were more likely to present early with hearing loss and had smaller tumours than patients with medially arising lollipop shaped ones. The relatively well preserved hearing in patients with medially arising tumours made them more likely to present at a later stage with signs of trigeminal compression, cerebellar dysfunction and raised intracranial pressure.

The changing clinical presentation of acoustic tumors in the MRI era

The application of magnetic resonance imaging (MRI) scanning in the diagnosis of acoustic neuroma (AN) has increased the relative incidence of smaller tumors and has impacted on the typical clinical presentation of AN patients. The charts of 126 patients treated at the University of California, San Francisco for newly diagnosed AN from 1986 to 1990 were reviewed. Twenty-four percent of tumors fell into the smallest size category (< 1 cm); this was a substantial improvement over earlier series. However, 16% of tumors remained undiagnosed until they achieved large size (> 3 cm). The incidence of hearing loss, dysequilibrium, headache, facial numbness, and diplopia all increased with increasing tumor size, while the incidence of vertigo decreased. Diagnosticians should not overemphasize "typical" symptom complexes, as substantial variability in clinical manifestations exists. An improved awareness by clinicians of the variability of AN presentation will improve diagnostic efficiency and continue the trend toward earlier diagnosis of these lesions.

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.

Clinical and financial audit of diagnostic protocols for lesions of the cerebellopontine angle

OBJECTIVE

To assess the diagnostic efficiency and costs of protocols used for investigating patients with suspected lesions of the cerebellopontine angle.

DESIGN

Prospective evaluation of tests of auditory brain stem responses and acoustic reflex thresholds, electronystagmography, and calorics. Positive test results were confirmed or refuted by high resolution computed tomography with intravenous enhancement.

SETTING

Single general otolaryngology clinic in a teaching hospital.

PATIENTS

270 consecutive patients with sensorineural hearing loss requiring investigation to exclude a lesion of the cerebellopontine angle.

MAIN OUTCOME MEASURES

Estimated costs of various diagnostic protocols and performance in detecting tumours of the cerebellopontine angle.

RESULTS

Protocols including tests of auditory brain stem responses and acoustic reflex thresholds as sifting tests before computed tomography were clinically acceptable and presented considerable savings over the use of computed tomography in all patients (74,000 pounds or 84,000 pounds v 122,000 pounds). The use of electronystagmography and calorics could not be justified on clinical or financial grounds.

CONCLUSIONS

Audiological tests of auditory brain stem responses and acoustic reflex thresholds followed by computed tomography constitute the most cost effective protocol for determining suspected lesions of the cerebellopontine angle.

IMPLICATIONS

The cost effectiveness of diagnostic protocols should be evaluated throughout the health service.

Acoustic neuroma (schwannoma) surgery 1978-1990

A series of 151 patients with 154 acoustic schwannomas have been operated upon in Manchester Royal Infirmary by a joint Otological and Neurosurgical team, employing either the translabyrinthine or the suboccipital approach. The perioperative mortality rate was 3 per cent. Anatomical preservation of the facial nerve was achieved in 89 per cent of tumour removals and a good to normal functional result in 79 per cent of cases. Attempts at hearing preservation have been unsuccessful, largely because of the small number of patients in the series in whom useful hearing was present preoperatively. Complications included major brain stem ischaemia (1.2 per cent), CSF fistula (5 per cent) and facial dysaesthesia (7 per cent). The incidence of mortality and morbidity is directly related to tumour size and to the experience of the surgeons. A number of patients experienced an unusual type of post-operative dreamlike state which appeared to be a form of hypnagogic hallucination, and the possible neurophysiological mechanism responsible for this phenomenon is discussed. The continuing failure to attain the ideal of early diagnosis is lamented, and the importance of a flexible bidisciplinary surgical approach emphasized.

Surgical management of large glomus jugulare tumours: infra- and trans-temporal approach

Surgery may have to be considered in the management of large glomus tumours since other modalities of treatment are not curative. The judicious use of surgical intervention is imperative since a neurological deficit involving the last four cranial nerves may ensue and consideration of the quality of life of the patient in the post-operative period is of paramount importance. A brief description of the historical aspects and pathology of these tumours is followed by an analysis of the clinical presentation, investigation and assessment of a series of 10 patients. Six patients underwent surgery and their tumours were removed by the infra- and trans-temporal approach. This is described and illustrated in detail and the surgical results presented.

Surgery for acoustic neurinoma. An analysis of 100 translabyrinthine operations

A consecutive series of 100 translabyrinthine operations for removal of acoustic neurinoma is reported. Complete tumor removal was achieved in 97% of cases. There were three perioperative deaths, and the postoperative morbidity rate was low. The facial nerve was preserved anatomically in 82% of patients. Preoperative facial weakness and tumor size larger than 2.5 cm were predictive of poor facial recovery. In patients with an intact nerve but complete facial palsy 1 week after surgery, electroneuronography was a good predictor of the final facial outcome and may influence the timing of rehabilitative procedures. With the exception of patients who have small tumors and good speech discrimination (where a suboccipital approach may preserve hearing acuity), the translabyrinthine operation is the procedure of choice for removal of acoustic neurinomas in patients who have normal hearing in the contralateral ear.

Mastoid ache in acoustic neuroma

In a series of 100 patients with unilateral acoustic neuroma the incidence of mastoid aching was found to be 25 per cent, though none of the patients reported this as their principal symptom. Mastoid ache was not related to tumour size, hydrocephalus, or duration of symptoms. However, there was a significantly higher incidence of facial numbness and diminished facial sensation, but not facial weakness, compared with the whole series. Since motor fibres are more resistant to pressure than sensory fibres, mastoid ache may signify the pressure of an expanding cerebellopontine angle tumour.

Contralateral auditory brainstem response abnormalities in acoustic neuroma

Contralateral Auditory Brainstem Response (ABR) findings in a series of 79 patients with unilateral acoustic neuroma are presented. Sixty-four patients (81 per cent) had a normal contralateral ABR, thirteen (16.4 per cent) had latency abnormalities contralaterally and in two patients (2.6 per cent) no consistent responses could be recorded despite good hearing. Abnormalities in the contralateral ABR were analysed and five patients had abnormal III-V interwave intervals, in seven patients the I-III intervals were abnormal and in one patient, only the fifth wave was present and of abnormal latency. The tumour size was assessed by computed axial tomography (CT) and the relationship between tumour size and contralateral ABR findings established. Large tumours (greater than 2.5 cm.) were associated with contralateral ABR abnormalities in 25.6 per cent of the patients, medium tumours (1.0-2.5 cm.) with ABR abnormalities in 14 per cent and there were no abnormalities in the small group (intracanalicular). The implications for interpretation of ABR recordings contralateral to an acoustic neuroma are discussed in relation to brainstem compression and its effect on the wave generator sites.

Facial nerve recovery after acoustic neuroma removal

A retrospective analysis of 76 patients who underwent acoustic neuroma removal is reported. Facial nerve function prior to surgery and tumour size are assessed with respect to final facial nerve recovery and the need for surgical rehabilitation. Both pre-operative facial weakness and tumour size greater than 2.5 cm. are shown to be predictive factors of poor facial nerve recovery. Multiple surgical rehabilitative procedures are often required when inadequate function and/or cosmetic results are obtained. Primary nerve repair and facial-hypoglossal anastomosis give better rehabilitative results than dynamic and static procedures. The association of tumour size greater than 2.5 cm. with increased risk of poor facial recovery re-emphasizes the need to detect and remove acoustic neuromas at an early stage.