See also the study selection flow chart in appendix E, forest plots of sensitivity and specificity in appendix K, study evidence tables in appendix H and excluded studies list in appendix L. Evidence from these studies is summarised in the clinical evidence summary ( Table 15). Seven studies were included in the review 20, 27, 66, 75, 102, 104, 111 these are summarised in Table 13 below. Studies with mixed populations, but the majority having hearing loss at presentation were included but downgraded for indirectness. Studies were excluded if they included mixed populations (a mix of people with hearing loss and with other audiovestibular symptoms) and the proportion with hearing loss was unclear. We initially sought cohort (single-gate) studies, but if these were not available for a specific test, case–control (2-gate) studies were also considered. We searched for prospective and retrospective studies assessing the diagnostic test accuracy of referral criteria or risk assessment tools to identify the presence (as indicated by MRI) of vestibular schwannoma (or other causative lesions) in people under investigation in secondary care for hearing loss (symmetric or asymmetric). There is no clear consensus on the clinical and audiological parameters which should prompt MRI referral in order to optimise the diagnostic efficacy for clinically relevant pathology. There is also a potential cost to the ‘overdiagnosis’ of asymptomatic vestibular schwannomas (or other abnormalities) which do not require intervention, in terms of increased resources required for clinical follow-up or MRI monitoring and increased patient anxiety. When developing referral guidelines for MRI it is important to maximise diagnostic yield without missing pathologies which would benefit from earlier diagnosis, monitoring or treatment however, it should be noted that vestibular schwannomas only grow in the medium term in 30–90% of cases 107 and are frequently managed conservatively. 54 This has contributed to an increased incidence of vestibular schwannoma detection in the past 30 years, 46, 106, 107, 114 and the average tumour size at detection has decreased from 3 cm to 1 cm. It has been noted that up to 20% of new ENT referrals with audiovestibular symptoms are deemed appropriate for MRI. 117 MRI is increasingly performed in this clinical field due to wider availability of scanners, quicker scanning protocols, changes in diagnostic algorithms and easier access to audiological testing, as well as due to heightened patient awareness and expectations. 117 In a paper by Vandervelde in 2009 looking at 881 consecutive MRI scans performed for audiovestibular symptoms 1.4% were positive for vestibular schwannomas, 0.4% identified other relevant pathology and in 1.4% incidental pathologies were found which were irrelevant to the presenting complaint. Whilst the main focus of investigation with MRI is on the detection of vestibular schwannomas or similar tumours, other abnormalities may be demonstrated with a similar frequency. Small tumours may be very slow growing in older people, requiring observation only, but in younger people growth can be quicker and surgical removal may be needed. These tumours can cause hearing loss by compressing the cochlear nerve in this narrow bony channel or in the inner ear, or they can grow into the posterior cranial fossa and cause brain stem compression giving neurological symptoms and signs, and, in time, can be life-threatening if not treated. The vestibular nerves run with the nerve of hearing (cochlear nerve) in the internal auditory meatus. Vestibular schwannoma (also known as acoustic neuroma) is a rare benign tumour of the cells that form the sheath around the nerve of balance (vestibular nerve). Hearing loss (asymmetric or unilateral) as a clinical symptom or as demonstrated on pure tone audiometry (PTA) is an important consideration when selecting patients for MRI. Such pathologies may be accurately diagnosed with MRI. Acquired audiovestibular symptoms may be an indicator of cerebellopontine angle (CPA), internal auditory meatus (IAM) or inner ear disorders, such as meningioma, vestibular schwannoma (VS), cholesterol granuloma or fibrosis of the labyrinth.

Mri internal auditory canal cpt code