Magnetic resonance imaging screening for vestibular schwannoma: analysis of published protocols

Abstract

This study seeks to define the most appropriate guidelines for selection of patients for magnetic resonance imaging (MRI) to exclude a vestibular schwannoma. Improved selection may reduce patient anxiety and improve resource utilization. All MRIs of the internal auditory meatus, performed during the year 2000, were reviewed. Audiograms and symptoms were collated for all 'positive' scans and 100 negative scans. Information was analysed using seven published protocols and other defined frequency specific criteria. A diagnosis of vestibular schwannoma was made on 36 scans. Four criteria had a sensitivity of >95 per cent; of these the highest specificity (49 per cent) utilized an interaural difference at two adjacent frequencies of 15.dB in unilateral hearing loss and 20.dB in bilateral asymmetric loss. Applying our best protocol would have reduced the number of scans performed from 392 to 168. The one patient with a vestibular schwannoma who was excluded had trigeminal paraesthesia, an independent indication for investigation.

Incidental findings on magnetic resonance imaging of the internal auditory meatus performed to investigate audiovestibular symptoms

“…10,11 Our study has demonstrated, however, that only a small proportion (0.9 per cent) of scans requested actually demonstrated retrocochlear pathology. This is in line with other studies, which have shown that none of the various clinical criteria that exist to try to increase the pick-up rate of vestibular schwannoma are particularly effective, with none improving beyond a 4 per cent pick-up rate, [1][2][3]6 and an incidental finding is more likely to be reported.…”

“…1 Presentation is variable, with patients most commonly presenting with asymmetrical sensorineural hearing loss (SNHL). 2 Tinnitus, vertigo, disequilibrium and facial palsy can also be diagnostic indicators, making vestibular schwannoma a challenge to accurately diagnose clinically. [2][3][4] Radiological assessment is therefore crucial, with gadolinium-enhanced magnetic resonance imaging (MRI) of the internal auditory meatus recognised as the 'gold standard' for investigating asymmetrical SNHL.…”

“…2 Tinnitus, vertigo, disequilibrium and facial palsy can also be diagnostic indicators, making vestibular schwannoma a challenge to accurately diagnose clinically. [2][3][4] Radiological assessment is therefore crucial, with gadolinium-enhanced magnetic resonance imaging (MRI) of the internal auditory meatus recognised as the 'gold standard' for investigating asymmetrical SNHL. 5 With such wide-ranging symptomatology for vestibular schwannoma, increasing numbers of MRI scans of the internal auditory meatus are being performed.…”

The Agreement between Protocols for the Investigation of Asymmetrical Audiovestibular Symptoms

“…Charing Cross Protocol [10] . 20 dB asymmetry 44 between two contiguous frequencies or 15 dB if normal hearing in one ear.…”

“…However, of the scans requested, only 44%-90% met the criteria of any one individual guideline (Table 1) [8][9][10][11] . The reason for this disparity was the poor concordance between the criteria in the published scanning guidelines.…”