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

MRI Screening in Vestibular Schwannoma: A Deep Learning-based Analysis of Clinical and Audiometric Data

Objective

To find a more objective method of assessing which patients should be screened for a vestibular schwannoma (VS) with magnetic resonance imaging (MRI) using a deep-learning algorithm to assess clinical and audiometric data.

Materials and Methods

Clinical and audiometric data were collected for 592 patients who received an audiogram between January 2015 and 2020 at Duke University Health Center with and without VS confirmed by MRI. These data were analyzed using a deep learning-based analysis to determine if the need for MRI screening could be assessed more objectively with adequate sensitivity and specificity.

Results

Patients with VS showed slightly elevated, but not statistically significant, mean thresholds compared to those without. Tinnitus, gradual hearing loss, and aural fullness were more common in patients with VS. Of these, only the presence of tinnitus was statistically significant. Several machine learning algorithms were used to incorporate and model the collected clinical and audiometric data, but none were able to distinguish ears with and without confirmed VS. When tumor size was taken into account the analysis was still unable to distinguish a difference.

Conclusions

Using audiometric and clinical data, deep learning-based analyses failed to produce an adequately sensitive and specific model for the detection of patients with VS. This suggests that a specific pattern of audiometric asymmetry and clinical symptoms may not necessarily be predictive of the presence/absence of VS to a level that clinicians would be comfortable forgoing an MRI.

Finding more than what you are looking for: a retrospective study of incidental findings in magnetic resonance imaging (MRI) scans performed for patients suspicious of vestibular schwannoma

Background

Nearly 20% of the patients presenting to ENT department with audiovestibular symptoms are considered potential candidates for vestibular schwannoma screening. MRI scan done on these patients can also detect a large number of incidental findings. We did a retrospective descriptive study of incidental findings identified on MRI scans done on patients presenting to the ENT department in a county hospital in United Kingdom from April 2020 to April 2021. All MRI reports were scrutinised and various incidental findings tabulated. The further management of patients with these findings were also analysed.

Results

A total of 159 MRIs were reviewed. The most common incidental finding was small vessel disease followed by old infarcts. Fifteen patients were found to have significant incidental findings. The detection rate of vestibular schwannoma was 3.1%.

Conclusion

With the increased use of imaging technology, the incidence of incidental findings has risen. Understanding the significance of these findings is important so that clinicians can counsel their patients and make appropriate management plans. Categorising the incidental findings into groups based on their level of significance may help in making these clinical decisions.

The Diagnostic Accuracy of Pure-Tone Audiometry Screening Protocols for Vestibular Schwannoma in Patients with Asymmetrical Hearing Loss-A Systematic Review and Meta-Analysis

(1) Background: Magnetic resonance imaging (MRI) is the gold standard investigation for all patients who present with asymmetrical hearing loss (AHL) and a high index of suspicion for vestibular schwannoma (VS). However, pure-tone audiometry (PTA) is an investigation that can be used for the screening of these patients in order to reduce the costs. The aim of this systematic review and meta-analysis was to evaluate the diagnostic accuracy of different PTA protocols for VS in patients with ASHL, when compared with MRI; (2) Methods: Medline, Embase, and Cochrane databases were used to find relevant studies. All prospective and retrospective observational studies that evaluated the accuracy of PTA protocols for the screening of VS were assessed, according to the international guidelines; (3) Results: We analyzed seven studies (4369 patients) of poor-to-moderate quality. Their pooled sensitivity was good (0.73-0.93), but their specificity was low (0.31-0.60). All protocols were located in the right lower quadrant on the likelihood scattergram, and the post-test probabilities for positive and negative diagnosis of these protocols were extremely low; (4) Conclusions: PTA protocols cannot be used for a proper screening or diagnosis of vestibular schwannoma despite their good sensibility, and MRI remains the gold standard for this purpose.

Machine Learning for Vestibular Schwannoma Diagnosis Using Audiometrie Data Alone

OBJECTIVE

The aim of this study is to compare machine learning algorithms and established rule-based evaluations in screening audiograms for the purpose of diagnosing vestibular schwannomas. A secondary aim is to assess the performance of rule-based evaluations for predicting vestibular schwannomas using the largest dataset in the literature.

STUDY DESIGN

Retrospective case-control study.

SETTING

Tertiary referral center.

PATIENTS

Seven hundred sixty seven adult patients with confirmed vestibular schwannoma and a pretreatment audiogram on file and 2000 randomly selected adult controls with audiograms.

INTERVENTIONS

Audiometric data were analyzed using machine learning algorithms and standard rule-based criteria for defining asymmetric hearing loss.

MAIN OUTCOME MEASURES

The primary outcome is the ability to identify patients with vestibular schwannomas based on audiometric data alone, using machine learning algorithms and rule-based formulas. The secondary outcome is the application of conventional rule-based formulas to a larger dataset using advanced computational techniques.

RESULTS

The machine learning algorithms had mildly improved specificity in some fields compared with rule-based evaluations and had similar sensitivity to previous rule-based evaluations in diagnosis of vestibular schwannomas.

CONCLUSIONS

Machine learning algorithms perform similarly to rule-based evaluations in identifying patients with vestibular schwannomas based on audiometric data alone. Performance of established rule-based formulas was consistent with earlier performance metrics, when analyzed using a large dataset.

Multiple Audiometric Analysis in the Screening of Vestibular Schwannoma

Introduction

Asymmetric sensorineural hearing loss is the main early symptom of retrocochlear lesions, hence its importance in screening for vestibular schwannomas. Currently, there is no consensus regarding its definition. The objective was to identify the audiometric pattern that would serve as a predictor for vestibular schwannoma in patients with asymmetric hearing loss.

Materials and methods

A cross-sectional study was conducted that included patients with asymmetric hearing loss attending a secondary care center and a tertiary care center. Clinical, audiometric and imaging (MRI with gadolinium) variables were collected. Asymmetric hearing loss was defined as a difference of 15 dB in one or more frequencies between both ears. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of different audiometric patterns were analyzed.

Results

A total of 107 patients were studied and divided into two groups: group 1 without vestibular schwannoma (n=98); and group 2 with vestibular schwannoma (n=9). No significant difference in demographic characteristics or audiometric patterns was found in patients with and without vestibular schwannoma. The audiometric pattern with the best sensitivity as a screening test was a difference >20 dB in the 4,000 Hz frequency, with a sensitivity of 77.78%, specificity of 30.61%, PPV of 8.33%, NPV of 93.75% and accuracy of 34.50%.

Conclusion

The audiometric pattern with the best results was a difference >20 dB in the 4,000 Hz frequency range; however, patients with asymmetric hearing loss could not be differentiated from patients with retrocochlear lesions based only on audiometry. Asymmetrical hearing loss must be studied with MRI.

The use of magnetic resonance imaging in the investigation of patients with unilateral non-pulsatile tinnitus without asymmetrical hearing loss

BACKGROUND

Tinnitus is a common condition presenting to the ENT out-patient clinic. Vestibular schwannomas are benign cerebellopontine angle tumours that usually present with unilateral sensorineural hearing loss. Magnetic resonance imaging of the internal auditory meatus is the definitive investigation in their detection. The current recommendation is for unilateral tinnitus patients to undergo magnetic resonance imaging of the internal auditory meatus to exclude vestibular schwannoma.

OBJECTIVE

To evaluate magnetic resonance imaging in the investigation of patients with unilateral non-pulsatile tinnitus without asymmetrical hearing loss.

METHOD

A retrospective case series was conducted of all patients who underwent magnetic resonance imaging of the internal auditory meatus to investigate unilateral non-pulsatile tinnitus without asymmetrical hearing loss, from 1 January 2014 to 1 January 2019.

RESULTS

Of 2066 scans, 566 (27 per cent) were performed to investigate patients (335 female, 231 male) with unilateral non-pulsatile tinnitus without asymmetrical hearing loss. Three vestibular schwannomas were detected on imaging, and 134 incidental findings were discovered.

CONCLUSION

The detection rate of vestibular schwannoma in this group was just 0.3 per cent. This paper questions the utility of magnetic resonance imaging evaluation in these patients.

Evaluation of pure-tone audiometric protocols in vestibular schwannoma screening

The objective was to evaluate the pure-tone audiogram-based screening protocols in VS diagnostics. We retrospectively analyzed presenting symptoms, pure tone audiometry and MRI finding from 246 VS patients and 442 controls were collected to test screening protocols (AAO-HNS, AMCLASS-A/B, Charing Cross, Cueva, DOH, Nashville, Oxford, Rule3000, Schlauch, Seattle, Sunderland) for sensitivity and specificity. Results were pooled with data from five other studies, and analysis of sensitivity, specificity and positive likelihood ratio (LR+) for each protocol was performed. Our results show that protocols with significantly higher sensitivity (AMCLASS-A/B, Nashville) show also significantly lowest specificity, and tend to have low association (positive likelihood ratio, LR+) to the VS. The highest LR+ was found for protocols AAO-HNS, Rule3000 and Seattle. In conclusions, knowing their properties, screening protocols are simple decision-making tools in VS diagnostic. To use the advantage of the highest sensitivity, protocols AMCLASS-A + B or Nashville can be of choice. For more reasonable approach, applying the protocols with high LR+ (AAO-HNS, Rule3000, Seattle) may reduce the overall number of MRI scans at expense of only few primarily undiagnosed VS.

Asymmetric sensorineural hearing loss and vestibular schwannoma: when to image?

PURPOSE OF REVIEW

We review the literature on the use of audiometric protocols in the guidance of when to obtain MRI for detection of vestibular schwannoma. This discussion will focus on the sensitivity, specificity, and cost-effective analysis of audiometric criteria of asymmetric sensorineural hearing loss (ASNHL) when used to decide when MRI scans should be performed.

RECENT FINDINGS

The sensitivity for detecting vestibular schwannomas when invoking published audiometric protocols for triggering MRI acquisition in ASNHL ranged from 50 to 100%. Specificity of these protocols ranged from 23 to 83%. Such audiometric protocols are efficient, achieving sensitivity and specificity at these rates while reducing the screening rate to 18 to 35%. The reduced procurement of MRI while using such audiometric protocols is associated with annual cost savings of between 23 and 82%. While no definitive recommendations can be made from this review, some audiometric protocols offer a better balance of sensitivity and specificity than others.

SUMMARY

Audiometric protocols for triggering MRI acquisition in ASNHL for evaluation of vestibular schwannoma can be both sensitive and specific. These are competitive measures, and so no protocol is both 100% sensitive and specific. Such protocols become less effective in populations with increased incidence of noise-induced hearing loss. Invocation of such audiometric protocols can considerably reduce the annual cost of MRI evaluation for vestibular schwannomas.

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.

Audiologist-led screening of acoustic neuromas in patients with asymmetrical sensorineural hearing loss and/or unilateral tinnitus: our experience in 1126 patients

OBJECTIVE

To determine whether patients within an otolaryngology department presenting with asymmetrical sensorineural hearing loss and/or unilateral tinnitus can be safely and cost-efficiently screened for acoustic neuroma by audiologists as a first or only point of contact.

METHODS

A prospective case series and cost analysis were conducted at a tertiary referral centre. Between April 2013 and March 2017, 1126 adult patients presented to the audiology department with asymmetrical sensorineural hearing loss and/or unilateral tinnitus. All were screened for acoustic neuroma with magnetic resonance imaging, based on pre-determined criteria. The main outcome measure was the presence of acoustic neuroma or other pathology on magnetic resonance imaging.

RESULTS

Twenty-five patients (2.22 per cent) were found to have an acoustic neuroma (size range: 3-20 mm) and were referred to the otolaryngologist for further assessment. The remaining patients were appropriately managed and discharged by the audiologists without ENT input. This resulted in an overall cost saving of £164 850.

CONCLUSION

Patients with asymmetrical sensorineural hearing loss and/or unilateral tinnitus can be safely screened for acoustic neuroma and independently managed by audiologists as a first or only point of contact, resulting in considerable departmental cost savings.

Diagnostics and therapy of sudden hearing loss

This article reviews recent aspects of diagnostics, differential diagnostics, and evidence in systemic and local therapy of idiopathic sudden sensorineural hearing loss (ISSHL). Since a number of disorders can be accompanied by sudden hearing loss, a meaningful and targeted diagnostic strategy is of utmost importance. An important differential diagnosis of sudden hearing loss are intralabyrinthine schwannomas (ILS). The incidence of ILS is probably significantly underestimated. This may be due to the lack of awareness or lack of explicit search for an intralabyrinthine tumor on MRI or an inappropriate MRI technique for the evaluation of sudden hearing loss ("head MRI" instead of "temporal bone MRI" with too high slice thicknesses). Therefore, the request to the radiologist should specifically include the question for (or exclusion of) an ILS. With special MRI techniques, it is possibly today to visualize an endolymphatic hydrops. The evidence in the therapy of ISSHL is - with respect to the quality and not quantity of studies - unsatisfying. The value of systemically (low dose) or intratympanically applied corticosteroids in the primary treatment of ISSHL is still unclear. In order to investigate the efficacy and safety of high dose corticosteroids as primary therapy for ISSHL, a national, multicenter, three-armed, randomized, triple-blind controlled clinical trial is currently performed in Germany (http://hodokort-studie.hno.org/). After insufficient recovery of the threshold with systemic therapy of ISSHL, intratympanic corticosteroid therapy appears to be associated with a significantly higher chance of an improved hearing threshold than no therapy or placebo. Both, hearing gain and final hearing threshold, however, appear to be independent from the onset of secondary therapy. Based on currently available data from clinical studies, no recommendation can be made with respect to the type of corticosteroid and specifics of the intratympanic application protocol.

Current insights in noise-induced hearing loss: a literature review of the underlying mechanism, pathophysiology, asymmetry, and management options

BACKGROUND

Noise-induced hearing loss is one of the most common forms of sensorineural hearing loss, is a major health problem, is largely preventable and is probably more widespread than revealed by conventional pure tone threshold testing. Noise-induced damage to the cochlea is traditionally considered to be associated with symmetrical mild to moderate hearing loss with associated tinnitus; however, there is a significant number of patients with asymmetrical thresholds and, depending on the exposure, severe to profound hearing loss as well.

MAIN BODY

Recent epidemiology and animal studies have provided further insight into the pathophysiology, clinical findings, social and economic impacts of noise-induced hearing loss. Furthermore, it is recently shown that acoustic trauma is associated with vestibular dysfunction, with associated dizziness that is not always measurable with current techniques. Deliberation of the prevalence, treatment and prevention of noise-induced hearing loss is important and timely. Currently, prevention and protection are the first lines of defence, although promising protective effects are emerging from multiple different pharmaceutical agents, such as steroids, antioxidants and neurotrophins.

CONCLUSION

This review provides a comprehensive update on the pathophysiology, investigations, prevalence of asymmetry, associated symptoms, and current strategies on the prevention and treatment of noise-induced hearing loss.

Evaluation of Magnetic Resonance Imaging Diagnostic Approaches for Vestibular Schwannoma Based on Hearing Threshold Differences Between Ears: Added Value of Auditory Brainstem Responses

OBJECTIVE

This study investigates the most appropriate audiometric criterion in deciding which patients with asymmetric hearing loss should be referred to MRI to exclude a lesion in the cerebellopontine angle (CPA). Careful selection of patients could improve resource utilization while preventing unnecessary investigations with accompanying burden and costs.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Of all the patients who were referred to our clinic between 1997 and 2012, the records were reviewed of those who underwent pure-tone audiometry, auditory brainstem response (ABR) testing, and had a Gadolinium-enhanced MRI of the CPA.

INTERVENTION

Regarding interaural pure-tone threshold differences at single or multiple (averaged) frequencies, we assigned multiple possible cut-off values (dB) defining an aberrant result, suggestive for CPA lesions. Results were compared with MRI to calculate sensitivity and specificity for every cut-off value. These were visualized as ROC curves enabling qualitative comparison. Added value of ABR was assessed as well.

MAIN OUTCOME MEASURES

Sensitivity and specificity of various criteria to decide which patients with asymmetric hearing loss to send to MRI to exclude a CPA lesion.

RESULTS

In total, 1016 records were reviewed. Two hundred ninety-four subjects (29%) were diagnosed with a CPA lesion on MRI. Sensitivity and specificity for audiometry results differed greatly depending on the predefined cut-off value for hearing threshold difference (40-95% sensitivity and 20-90% specificity). Best ROC curves were obtained when threshold differences at two or three higher frequencies were averaged. Adding results of ABR to the threshold criterion yielded a slightly better ROC curve, although sensitivity decreased.

CONCLUSIONS

The best criterion to decide which patient with asymmetric hearing loss should be referred to MRI is based on the average bone conduction threshold difference at multiple (two or three) higher frequencies. The extent of the average threshold difference between ears that is used as a cutoff will mainly depend on treatment modality and (eventually) on resource costs and on the burden of Gadolinium-enhanced magnetic resonance imaging. Results of ABR can have little added value when only patients with a unilateral abnormal ABR at the worse hearing ear are referred to MRI. However, a lower sensitivity must then be accepted.

Intralabyrinthine schwannomas: a case series with discussion of the diagnosis and management

OBJECTIVE

By extracting cases of intralabyrinthine schwannomas (ILS) from the sum of all vestibular schwannomas, we aim to identify and analyze unique features of its presentation. This allows us to refine the management protocol of this rare condition.

DESIGN

This is a retrospective study of all patients seen in the Department of Otorhinolaryngology-Head and Neck Surgery, Rouen University Hospital, with either ILS or ILS with intracanalicular extension (ILS-IAC) between 2001 and 2011. A literature search was performed and results combined to draw conclusions on management strategies.

METHOD

Three patients with ILS and 6 patients with ILS-IAC were identified. We retrieved data on age, sex, symptoms, audiometry, imaging, and management. Pure tone audiometry and speech discrimination score were assessed and hearing classification recorded. Facial nerve function and vestibular function were documented throughout. The diagnostic and surveillance imaging (MRI with or without CT) were reviewed.

RESULTS

The average age at presentation was 62.8 years and the sex ratio was (male: female) 4:5. An ipsilateral hearing loss was observed in all patients. Eight of 9 patients had tinnitus at presentation, 2 had rotatory vertigo, and 1 patient had a facial palsy and hemifacial spasm. In 2 cases, the labyrinthine extension was initially missed. The patient presenting with a large tumor and facial palsy was operated on without delay. The others underwent MRI surveillance, with 4 requiring surgery at a later stage. No postoperative facial palsies were encountered other than the one that had been present preoperatively.

CONCLUSION

Frequency of ILS is underestimated because of poor diagnostic criteria. These tumors have often been described as having features, which resemble Ménière's disease, which is not found in our series. In the absence of tumor progression or disabling symptoms, their management is surveillance/medical, and when surgery is considered, facial paralysis and recurrence rates seem low. The treatment of IAC-ILS differs from that of ILS.

Incidence of vestibular schwannoma and incidental findings on the magnetic resonance imaging and computed tomography scans of patients from a direct referral audiology clinic

OBJECTIVE

To identify the incidence of vestibular schwannoma amongst patients referred from a direct referral audiology clinic, and also the number of incidental findings, as seen on magnetic resonance imaging or computed tomography scans.

METHOD

Prospective data collection for patients referred from a direct referral audiology clinic due to audiological evidence of asymmetrical hearing loss. The audiograms, magnetic resonance imaging and computed tomography scans of patients with diagnosed vestibular schwannoma were subsequently reviewed.

RESULTS

A total of 4100 patients were seen during the study period, with 396 scans performed. Six (1.5 per cent) patients had vestibular schwannoma, while 12 (3 per cent) had significant incidental findings.

CONCLUSION

Patients referred from the direct referral audiology clinic had a low incidence of vestibular schwannoma detection. Their detection rate for significant incidental findings was similar to previous reports. If the current protocol had not been in place, over 300 patients would have been needlessly added to the ENT clinic list. Thus, general practitioner referral to direct referral audiology clinics provides a cost-effective way of managing asymmetrical sensorineural hearing loss in older patients. The number of such clinics could be expanded.

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.

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.

Incidental findings on MRI scans of patients presenting with audiovestibular symptoms

Background

The evaluation of patients presenting with audiovestibular symptoms usually includes MRI of the internal auditory meatus, the cerebellopontine angle and the brain. A significant percentage of these scans will present unexpected, incidental findings, which could have important clinical significance.

Objective

To determine the frequency and clinical significance of incidental findings on MRI scans of patients with audiovestibular symptoms.

Materials and methods

A retrospective analysis of 200 serial MRI scans.

Results

Gender distribution: equal. Age range: 17-82 years. One-hundred and four scans (52%) were normal and 1 scan (0.5%) demonstrated a unilateral vestibular schwannoma. Ninety-five scans (47.5%) demonstrated incidental findings. Sixty-six of these (33%) were considered of ishaemic origin and did not require further action. Five (2.5%) scans demonstrated significant findings which warranted appropriate referral; Two Gliomas (1%), 2 cases of extensive White Matter Lesions (1%), 1 lipoma (0.5%). The remaining scans demonstrated various other findings.

Conclusion

Investigation of patients with audiovestibular symptoms with MRI scans revealed incidental findings in a significant percentage (47.5%). The majority of these findings were benign warranting no further action and only 2.5% required further referral. It is the responsibility of the referring Otolaryngologist to be aware of these findings, to be able to assess their significance, to inform the patient and if needed to refer for further evaluation.

Should all patients referred for magnetic resonance imaging scans of their internal auditory meatus be followed up in ENT clinics?

Magnetic resonance imaging (MRI) is recognised as the "Gold Standard" investigation for symptoms pertaining to the inner ear and detection of retro-cochlear pathology. There is still no accurate clinical predictor for cerebellopontine angle lesions and increasingly more normal scans are being performed. With constantly increasing demands on ENT outpatient clinics, our aim was to investigate whether all patients referred for MRI of their internal auditory meatus (IAM) require follow-up in ENT clinics. A retrospective study was carried out in a tertiary referral centre referring patients for MRI IAM from ENT clinics and neurotology clinics on 153 patients referred for MRI IAM performed over a 4-month period. The MRI reports and the case notes of the patients were reviewed. MRI results and patient symptoms with patient follow-up schedule and follow-up situation for at least 6 months post-scan were compared. There were two patient groups, those referred from main outpatients (81) and those referred by the audiological physicians (72). Of the total number of scans, 101 were reported as normal, 45 had incidental findings, and 7 showed pathology of the cerebellopontine angle. The presenting complaints of the patients, the scan results and the follow-up since were compared. Six months later 63% of those referred from outpatients were no longer being followed up in clinic. We suggest that 56.8% of patients referred for MRI IAM do not require ENT follow-up. Their symptoms and concerns could be dealt with at the first consultation where onward referral could be made if necessary. Once checked by the requesting clinician, uncomplicated scan results could be sent to the patients and general practitioners by post or email. This would reduce the burden on general otolaryngology outpatient clinics and improve resource utilisation.

Vestibular schwannoma: when to look for it?

OBJECTIVES

(1) To compare audiometric parameters in patients with vestibular schwannoma and in those with asymmetric hearing loss from other causes; and (2) to assess proposed screening criteria by comparing published protocols.

METHODS

Audiometric data from 199 vestibular schwannoma patients and 225 non-tumour patients were compared. Eight screening protocols were tested on these 424 patients.

RESULTS

Vestibular schwannoma and non-tumour patients with little or no hearing loss in the unaffected ear were inseparable; however, vestibular schwannoma patients with hearing loss in the unaffected ear had greater audiometric asymmetry, compared with non-tumour patients with the same pattern of hearing loss. The sensitivity of screening protocols varied from 73 to 100 per cent; parallelism was observed between sensitivity and screening rate.

CONCLUSION

As regards vestibular schwannoma screening protocols, the best compromise between sensitivity and screening rate was offered by a criterion comprising either: (1) > or =20 dB asymmetry at two neighbouring frequencies, or unilateral tinnitus, or (2) > or =15 dB asymmetry at two frequencies between 2 and 8 kHz.

Asymmetric hearing loss: rule 3,000 for screening vestibular schwannoma

OBJECTIVE

To assess the diagnostic yield of audiograms associated to electronystagmography (ENG) for screening vestibular schwannomas (VSs), to determine what definition of asymmetric sensorineural hearing loss (ASNHL) fits best for the diagnosis of VS, and to determine if cochleovestibular symptoms and atherosclerotic potential risk factors play a role in the VS screening.

STUDY DESIGN

Retrospective chart review in a tertiary care center.

METHODS

One hundred twenty-two patients were included in the study and divided into 2 groups: 1) patients presenting a VS (n = 74) and 2) patients without VS (n = 48). They had received an audiometry assessment, an ENG, and a posterior fossa magnetic resonance imaging (MRI). In addition, a variety of risk factors and clinical data were collected. Mean hearing threshold by frequency, mean asymmetries by frequency, speech discrimination score (SDS), ENG results, and presence or absence of vertigo are studied. Cochleovestibular symptoms and atherosclerotic potential risk factors were collected. Characteristics were studied with analysis of variance, chi2 test, or a paired t test. A receiver operating characteristic curve was obtained. A logistic regression with a step-wise selection based on the likelihood ratio was used to identify the best subgroup of predictors of the VS.

RESULTS

The most revealing data were the mean ASNHL at 3,000 Hz (p < 0.001), the interaural SDS asymmetry (p < 0.001), the vestibular deficit (p < 0.049), and the absence of vertigo (p < 0.001). The ASNHL at 3,000 Hz was the most representative value of all the frequencies and for the SDS asymmetry. Interaural difference of 15 dB or more at 3,000 Hz is sufficient to consider hearing loss as asymmetric. When the cutoff for a positive test was placed at 50% probability, the receiver operating characteristic curve shows a sensitivity of 73%. The grade of the tumor was also related with the degree of ASNHL at 3,000 Hz. Caloric test does not predict the localization or the grade of the VS. Tinnitus and atherosclerotic potential risk factors were not considered significantly linked with VS.

CONCLUSION

To reduce the number of negative MRI performed in the investigation of an ASNHL, we propose the "rule 3,000," ASNHL of 15 dB or more at the 3,000-Hz frequency. In this case, an investigation with MRI is crucial. If this ASNHL is less than 15 dB, we recommend a biannual audiometric follow-up.

Screening patients with sensorineural hearing loss for vestibular schwannoma using a Bayesian classifier

OBJECTIVES

Selecting patients with asymmetrical sensorineural hearing loss for further investigation continues to pose clinical and medicolegal challenges, given the disparity between the number of symptomatic patients, and the low incidence of vestibular schwannoma as the underlying cause. We developed and validated a diagnostic model using a generalisation of neural networks, for detecting vestibular schwannomas from clinical and audiological data, and compared its performance with six previously published clinical and audiological decision-support screening protocols.

DESIGN

Probabilistic complex data classification using a neural network generalization.

SETTINGS

Tertiary referral lateral skull base and a computational neuroscience unit.

PARTICIPANTS

Clinical and audiometric details of 129 patients with, and as many age and sex-matched patients without vestibular schwannomas, as determined with magnetic resonance imaging.

MAIN OUTCOME MEASURES

The ability to diagnose a patient as having or not having vestibular schwannoma.

RESULTS

A Gaussian Process Ordinal Regression Classifier was trained and cross-validated to classify cases as 'with' or 'without' vestibular schwannoma, and its diagnostic performance was assessed using receiver operator characteristic plots. It proved possible to pre-select sensitivity and specificity, with an area under the curve of 0.8025. At 95% sensitivity, the trained system had a specificity of 56%, 30% better than audiological protocols with closest sensitivities. The sensitivities of previously-published audiological protocols ranged between 82-97%, and their specificities ranged between 15-61%.

DISCUSSION

The Gaussian Process ORdinal Regression Classifier increased the flexibility and specificity of the screening process for vestibular schwannoma when applied to a sample of matched patients with and without this condition. If applied prospectively, it could reduce the number of 'normal' magnetic resonance (MR) scans by as much as 30% without reducing detection sensitivity. Performance can be further improed through incorporating additional data domains. Current findings need to be reproduced using a larger dataset.

Screening for cerebellopontine angle tumors: is a CISS sufficient?

This study attempted to evaluate the reliability of ultra-thin T2-weighted imaging with a constructive interference in steady state (CISS) sequence as a screening method for tumors in the cerebellopontine angle. A retrospective study of 200 CISS examinations was made by five investigators. The examinations were inspected on plain film supported by clinical information. The interobserver agreement in the detection of lesions was analyzed. Fourteen cases (50% of the contrast-enhancing lesions) were rated pathological by all five readers. One case of subarachnoid lymphoma infiltration was overlooked by all five readers. Overall, six pathological lesions (median = 6, range 1-9) were not identified. The interobserver agreement for all pathological lesions was moderate (kappa=0.53; 95% CI, 0.43-0.62). The mean sensitivity was 77.8% (range 72.0-96.3%), and the mean specificity was 97.6% (range 94.8-100%). The median sensitivity for pathological lesions concerning only patients with acute sensorineural hearing loss (n=148, patients with 20 contrast-enhancing cases) was 86.6% (range 80-100%), and median specificity was 95.2% (range 84.4-96.9%) with a moderate interobserver agreement (kappa=0.55; 95% CI, 0.44-0.66). In our opinion the CISS sequence is a valuable addition to the examination of the cerebellopontine angle but lacks sufficient reliability for the detection of tumors of small size or of tumors adjacent to brain parenchyma or the temporal bone.

Should patients with asymmetrical noise-induced hearing loss be screened for vestibular schwannomas?

The Peterborough ENT department receives many referrals for MoD personnel who have suffered hearing loss from occupational noise exposure. Those patients with asymmetrical sensorineural hearing loss are routinely screened for vestibular schwannomas by MRI scanning. Scan reports from the past 5 years have been reviewed and out of 152 scans, four revealed vestibular schwannomas giving a pick-up rate of 2.5%, which compares favourably with other published pick-up rates. Review of the audiograms in these cases suggests that they can be misleading in this context. The conclusion is that patients with noise-induced asymmetrical hearing loss should be screened for acoustic neuromas.

[Magnetic resonance: first choice test in the screening of internal auditory canal and cerebellopontine angle tumors]

Although internal auditory canal (IAC) and cerebellopontine angle (CPA) tumors are rare, their clinical suspicion is quite common in the otolaryngology office. MRI is the imaging modality of choice in diagnosing these tumors. Perceived high costs may prevent clinicians from using it as a screening tool. A protocol designed to improve cost-effectiveness in such diagnosis results in a more rationale clinical practice. Our aim was to evaluate the usefulness of MRI as screening tool in diagnosis of IAC and CPA tumors in our population. Between March 1998 and March 2000, a prospective series of 200 cases had a MRI screening requested. MRI were performed following Fast Spin Echo technique, providing T2-weighted images. Gadolinium enhanced MRI was reserved for selected cases. We report on 190 MRI done. We found 7 neuromas (3.5%), one CPA metastasis, one epidermoid cyst and 9 IAC vascular anomalies. Only 138 cases (69%) had normal MRI images. When used following a designed protocol, MRI is our procedure of choice while screening IAC and CPA tumors because it is a cost-effective tool.

Efficacy of serologic testing in asymmetric sensorineural hearing loss

PURPOSE

The goal of this study was to determine the efficacy of a detailed questionnaire, auditory brain stem response testing (ABR), MRI, and an extensive battery of serologic tests in diagnosing asymmetric sensorineural hearing loss (ASNHL).

METHODS AND MATERIAL

Patients with audiograms demonstrating ASNHL of 10 dB or greater in 2 consecutive frequencies or 15 dB in any 1 frequency between 250 and 6000 Hz were asked to participate. Patients underwent MRI scanning of the cerebellopontine angle, internal auditory canals, and posterior fossa with gadolinium contrast, ABR, and an extensive battery of tests. The causative diagnosis was made by the individual clinician based on each patient's history, physical examination, and test results.

RESULTS

Forty-five patients completed the study. A review of the data confirmed the utility of a detailed history and physical examination, MRI, and fluorescent treponemal antibody test in all cases. Erythrocyte sedimentation rate, glycosylated hemoglobin, Lyme antibody titers, and total hemolytic component (CH50) were helpful in selected cases. Thyroid function testing, complete blood count, Sequential Multiple Analysis-7, prothrombin time/partial thromboplastin time, lipid profile, and ABR were of no value in these patients.

CONCLUSION

A careful history and physical examination, MRI, and fluorescent treponemal antibody test should be performed for the evaluation of all patients with ASNHL; however, more extensive serologic testing, including sedimentation rate, glycosylated hemoglobin, Lyme antibody titers, and CH50, should be selectively performed, based on a suggestive history or suspicious physical findings.

Langerhans' cell histiocytosis--a rare cause of sudden onset unilateral sensorineural hearing loss

Langerhans' cell histiocytosis is a rare disorder of unknown aetiology in which pathological Langerhans' cells accumulate and destroy local tissue. We report a 38-year-old female who presented with a sudden onset of left sensorineural hearing loss. Magnetic resonance imaging (MRI) revealed a contrast-enhancing lesion in the left mastoid and a second lesion in the hypothalamus. Following left mastoid exploration and biopsy a definitive diagnosis of Langerhans' cell histiocytosis was made and the patient was treated with external beam radiotherapy. Subsequent right femur and right mastoid involvement were successfully treated with steroids and cytotoxic chemotherapy. At one year follow-up the patient had residual left-sided sensorineural hearing loss with normal hearing in the right ear. To our knowledge, Langerhans' cell histiocytosis has not been previously reported as a cause of unilateral sudden onset sensorineural hearing loss. It should be considered in the differential diagnosis of this condition.

Outcome of using magnetic resonance imaging as an initial screen to exclude vestibular schwannoma in patients presenting with unilateral tinnitus

The improved cost-effectiveness of gadolinium-enhanced magnetic resonance imaging (MRIg) as a diagnostic tool for vestibular schwannoma has resulted in smaller tumours being diagnosed. There has been a change in the clinical presentation of these tumours and up to four per cent may present with unilateral tinnitus. The limitation of auditory brain stem response (ABR) as a screening tool that detects small tumours is recognized and there is a strong argument for using MRIg as the initial investigation. Various screening guidelines have been proposed, some include submitting patients with unilateral tinnitus for MRIg. This report describes the findings in a group of 174 patients presenting with unilateral tinnitus who underwent MRIg as part of a guideline-directed screen to exclude vestibular schwannoma. Five patients had a cause for their tinnitus diagnosed, one a vestibular schwannoma. Two had intracranial aneurysms and another three had pathology revealed that merited onward referral. A further nine patients had incidental findings that neither accounted for their symptoms nor needed further investigation or referral. The rationale for screening these patients with MRIg is discussed.

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.

A study of the effects of cochlear loss on the auditory brainstem response (ABR) specificity and false positive rate in retrocochlear assessment

The auditory brainstem response (ABR) test is widely used as a screen for retrocochlear dysfunction in individuals suffering idiopathic auditory and vestibular disturbance. Although its sensitivity for lesions of the lower brainstem is well established, hearing loss is known to have significant effects upon the test's specificity and false positive rate. This study analysed the effects of aspects of cochlear hearing loss including level, slope and general audiogram shape on these properties of the ABR test in a large clinical group. The study comprised 306 patients (153 male, 153 female) referred for ABR screening to exclude retrocochlear dysfunction. Of 566 ears meeting the inclusion criteria, 85 (15 per cent) failed the test. On follow-up eight ears (3 per cent) were confirmed to have some form of retrocochlear abnormality, seven of which were pathological. All had abnormal ABR results. No cases of retrocochlear abnormality were found in the ABR pass group. In those patients diagnosed as free of retrocochlear problems, the importance of the I-V interval as a primary index of function was confirmed. It displayed a high specificity (>90 per cent) which was largely independent of the level or slope of high-frequency hearing loss. In contrast wave V specificity decreased with increasing loss and increasing slope. Its value as a functional index was limited with losses greater than 70 dB HL in whom specificity fell below 70 per cent. The study concluded that, despite reducing interval availability above 60 dB HL, wave V latency cannot be used as an alternative index because it displays weakening specificity over this range of loss. With the problems inherent in applying latency corrections, the author advocates the use of improved procedures for wave I identification in these cases.

Audit of regional screening guidelines for vestibular schwannoma

An audit of 334 patients who underwent magnetic resonance imaging (MRI) as investigation for a possible diagnosis of vestibular schwannoma was carried out to assess adherence to previously agreed screening guidelines. This represents one year's activity. A posterior fossa tumour was identified in 12 patients. Scan requests were judged to be inappropriate for 28 cases. The issues surrounding the screening for acoustic neuroma are discussed.