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

Published online by Cambridge University Press:  24 June 2021

C Saxby*
Affiliation:
ENT Department, Northwick Park Hospital, London, UK
F Koumpa
Affiliation:
ENT Department, Northwick Park Hospital, London, UK
S Mohamed
Affiliation:
ENT Department, Northwick Park Hospital, London, UK
A Singh
Affiliation:
ENT Department, Northwick Park Hospital, London, UK
*
Author for correspondence: Ms Clair Saxby, ENT Department, Northwick Park Hospital, Harrow HA1 3UJ, London, UK E-mail: clair.saxby@nhs.net
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Abstract

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.

Type
Main Articles
Copyright
Copyright © The Author(s), 2021. Published by Cambridge University Press

Introduction

Tinnitus is the perception of sounds in the absence of an external auditory stimulus.1 Its prevalence in adults worldwide has been estimated to be between 10.1 and 14.5 per cent.Reference Tyler2 Whereas bilateral or non-localising tinnitus is common and said to affect the majority of the population at some time, unilateral tinnitus raises the concern of an underlying pathology. Unilateral tinnitus is a common presentation to the ENT out-patient clinic.

Vestibular schwannomas are benign cerebellopontine angle tumours that grow from the superior vestibular component of the vestibulocochlear nerve, usually presenting with unilateral sensorineural hearing loss.1 They may also cause vague and indistinct symptoms such as facial numbness, dizziness, headache and unilateral tinnitus.Reference Yoshimoto3

The reported incidence of vestibular schwannoma is 1 in 100 000, and the rate of growth per year is approximately 1.2 mm per annum.Reference Yoshimoto3 At least 50 per cent of vestibular schwannomas do not grow and maintain a static size.Reference Yoshimoto3 However, tumour growth at the cerebellopontine angle can lead to potentially life-threatening complications, and treatment by stereotactic radiotherapy or surgical excision is indicated.Reference Ramsden and Moffat4 Magnetic resonance imaging (MRI) of the internal auditory meatus (IAM) with intravenous gadolinium is the definitive investigation in the detection of vestibular schwannoma.Reference Tyler2

Current UK national guidelines state that a patient with unilateral tinnitus requires an MRI scan of the IAM to exclude a vestibular schwannoma.1,5 A vestibular schwannoma does not fulfil the World Health Organization criteria for population-level screening.Reference Wilson and Jungner6 The high cost and low detection rate make routine MRI of the IAM for unilateral tinnitus controversial.Reference Amiraraghi, Lim, Locke, Crowther and Kontorinis7Reference Robinette, Benscoter, Trenkle, Alapati, Jackson and Babu13 Patients with unilateral tinnitus in whom the exclusion of vestibular schwannoma is indicated place a significant burden upon ENT and radiology departments within the National Health Service (NHS). We therefore question the utility of MRI evaluation in patients with non-pulsatile unilateral tinnitus without asymmetrical hearing loss.

Aim

This study aimed to evaluate the clinical effectiveness of investigating patients with unilateral non-pulsatile tinnitus without asymmetrical hearing loss using MRI.

Materials and methods

A retrospective case review analysis was conducted of all patients who had undergone MRI of the IAM for unilateral non-pulsatile tinnitus without asymmetrical hearing loss from 1 January 2014 to 1 January 2019 (five years) within London North West University Healthcare NHS Trust. Patients aged 16 years or younger, and patients with headache, vertigo, or trigeminal and facial nerve symptoms, were excluded from the review. A secure database was created and electronic patient records were accessed. Patient demographics, history, examination and audiometric findings were collected. The main outcome measure was the presence of a vestibular schwannoma or other incidental pathology on MRI.

Results

A total of 2066 MRI scans of the IAM were performed between 2014 and 2018, of which 566 scans (27 per cent) were performed to investigate patients with unilateral non-pulsatile tinnitus without asymmetrical hearing loss. Of these patients, 59 per cent were female (n = 335) and 41 per cent were male (n = 231). The mean age was 54 years (range, 17–91 years). Three vestibular schwannomas were found on MRI, and 134 incidental findings were discovered (24 per cent) (Figure 1).

Fig. 1. The incidental findings on magnetic resonance imaging of the internal auditory meatus. MCA = middle cerebral artery

Discussion

Our detection rate for vestibular schwannoma in patients with unilateral non-pulsatile tinnitus without asymmetrical hearing loss was 0.5 per cent. The incidental finding rate on MRI was 24 per cent. The three patients found to have a vestibular schwannoma on MRI of the IAM are discussed.

Patient one

A 73-year-old male presented with left-sided non-pulsatile tinnitus and otalgia in 2014. Pure tone audiogram showed bilateral high frequency sensorineural hearing loss. An MRI scan of the IAM revealed a 3 mm vestibular schwannoma on the left side. Patient one was referred to the skull base team. Since then, he has been monitored with annual MRI of the IAM. In 2017, the scan showed that the vestibular schwannoma had increased in size to 3.9 mm. It was decided to continue active monitoring with annual MRI of the IAM.

Patient two

A 61-year-old female presented with left-sided unilateral non-pulsatile tinnitus in 2015. An MRI scan of the IAM revealed a 4 mm vestibular schwannoma on the right side (contralateral to the patient's symptoms). Pure tone audiogram showed symmetrical hearing within the normal range. The patient was referred to the skull base team, where she has been monitored with annual MRI of the IAM. There has been no growth of the vestibular schwannoma.

Patient three

A 45-year-old female presented with left-sided non-pulsatile tinnitus and otalgia in 2014. An MRI revealed a 5.1 mm vestibular schwannoma on the left side. Pure tone audiogram showed symmetrical hearing within the normal range. The patient was referred to the skull base team, where she has been monitored with annual MRI. There has been no growth of the vestibular schwannoma.

Overall findings

Our detection rate for vestibular schwannoma in patients investigated with unilateral non-pulsatile tinnitus was extremely low. One vestibular schwannoma was detected on the contralateral side to the tinnitus (patient two) and was therefore an incidental finding, which would lower the detection rate further to just 0.3 per cent. Patients one and three also had the additional symptom of otalgia alongside the unilateral non-pulsatile tinnitus. All three patients have been managed conservatively, undergoing annual MRI. Only one vestibular schwannoma (patient one) has shown growth (of 0.9 mm) since detection over four years ago.

There have only been two published series reporting detection rates for vestibular schwannoma in patients with unilateral tinnitus. Dawes et al., in Sunderland, UK, reported a vestibular schwannoma detection rate on MRI of 0.5 per cent.Reference Dawes and Basiouny12 The Michigan Ear Institute found a 0 per cent detection rate for vestibular schwannoma in patients scanned for unilateral tinnitus.Reference Robinette, Benscoter, Trenkle, Alapati, Jackson and Babu13 Our figure of 0.3 per cent is in keeping with these findings, and an overall detection rate of 0.2 per cent can be established. Published data in the UK have revealed a vestibular schwannoma detection rate of 1.6–4 per cent for all MRI scans of the IAM ordered.Reference Amiraraghi, Lim, Locke, Crowther and Kontorinis7,Reference Sheppard, Milford and Anslow11,Reference Harcourt, Vijaya-Sekaran, Loney and Lennox14

As current national UK guidelines state that patients who present with unilateral tinnitus should undergo MRI, failure of the clinician to order this could be difficult to defend medicolegally.5,Reference Nouraei, Huys, Chatrath, Powles and Harcourt8 It presents a challenge, and may lead to clinicians simply ordering the MRI both to reassure and to protect themselves against litigation. It is difficult to put a value on reassuring patients; however, clinical acumen is paramount, unnecessary imaging is putting an ever-increasing strain on our health service, and it is our duty to improve resource utilisation. A careful history eliciting whether the tinnitus is constant or occasionally present and its relationship to factors such as stress, and clinical examination along with audiological screening, in the absence of other signs and symptoms of a cerebellopontine angle lesion, does not require MRI investigation.

Vestibular schwannomas have been associated with a range of vestibular symptoms, which sometimes can be vague, from light-headedness and disequilibrium to true rotatory vertigo mimicking either benign positional paroxysmal vertigo or Ménière's disease.Reference Harcourt, Vijaya-Sekaran, Loney and Lennox14 Unilateral tinnitus alone is an uncommon presenting symptom of vestibular schwannoma. Morrison and Sterkers found that just 2.8 per cent of their series of vestibular schwannoma actually presented with tinnitus.Reference Morrison and Sterkers15 Lustig et al. found that 5 per cent of vestibular schwannoma patients had normal or symmetrical pure tone audiograms between 0.5 and 4 kHz.Reference Lustig, Rifkin, Jackler and Pitts16

Several protocols have been devised to try to rationalise and aid the decision as to which patients from the large population with audiovestibular symptoms warrant an MRI, to improve detection rates. Harcourt et al. have devised a protocol for the degree of hearing threshold asymmetry.Reference Harcourt, Vijaya-Sekaran, Loney and Lennox14 Sheppard et al. have set an age limit (70 years) for screening with MRI.Reference Sheppard, Milford and Anslow11 Dawes and Basiouny limited MRI to patients without significant co-morbidities that would prevent them from having surgery.Reference Dawes and Basiouny12 Previously, auditory brainstem response (ABR) testing had been used to detect a vestibular schwannoma.Reference Hentschel, Scholte, Steens, Kunst and Rovers17 However, one-third of the intracanalicular vestibular schwannoma patients had normal ABRs; therefore, this was not an appropriate primary test to screen for vestibular schwannoma.Reference Anderson, Loevner, Bigelow and Mirza18 Anderson et al. found 7 incidental vestibular schwannomas per 10 000 MRI studies (0.07 per cent).Reference Anderson, Loevner, Bigelow and Mirza18 Vestibular schwannoma can cause indistinct symptoms and occasionally be asymptomatic; therefore, the only way to identify every single vestibular schwannoma would be to perform MRI in all patients presenting with any audiovestibular symptoms, which would amount to a population-level screening programme.Reference Nouraei, Huys, Chatrath, Powles and Harcourt8

We have shown a large number (24 per cent) of incidental findings detected on MRI scans of the IAM. This has warranted in some cases unnecessary investigations and referral to other medical teams, causing anxiety and stress for the patient involved and further cost pressures on the NHS. Patients often find the process of undergoing an MRI scan unpleasant, causing symptoms of claustrophobia. There is also a potential adverse reaction to the gadolinium contrast given.

In the current environment, we need to improve our resource utilisation within the NHS. The average cost for an MRI scan of the IAM is £200. Our department has spent £113 200 on investigating patients with unilateral non-pulsatile tinnitus in the five-year period investigated, and this does not include the costs for scan reporting, follow-up appointments and further investigation into the 134 incidental findings discovered on MRI.

Study limitations

The large series was reviewed and analysed by three authors to minimise bias. The data were collected retrospectively. Our study is single-centred, which limits the generalisability of our findings. We aim to collaborate with other ENT departments to develop a multi-centre study.

  • Tinnitus is a common condition presenting to the ENT out-patient clinic

  • This study evaluated the use of magnetic resonance imaging (MRI) in the investigation of patients with unilateral non-pulsatile tinnitus without asymmetrical hearing loss

  • The detection rate of vestibular schwannoma in this group was just 0.3 per cent

  • The utility of MRI evaluation in this patient group is therefore questioned

Conclusion

Our study highlighted the very low detection rate of vestibular schwannoma in patients with unilateral non-pulsatile tinnitus without asymmetrical hearing loss; it emphasises that unilateral tinnitus is an uncommon presenting symptom of vestibular schwannoma. We call for the national UK guidelines to be updated so that clinical history, examination and audiological testing can guide the clinician as to whether MRI of the IAM is indicated.

Competing interests

None declared

Footnotes

Ms C Saxby takes responsibility for the integrity of the content of the paper

References

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Figure 0

Fig. 1. The incidental findings on magnetic resonance imaging of the internal auditory meatus. MCA = middle cerebral artery