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Aetiological investigations of permanent hearing loss in adults and children

Permanent hearing loss is common in children and adults. The incidence in children is 1 per 750 births and, one in six adults in the UK has some form of hearing loss, with an increasing prevalence with age.[1] The common causes of permanent childhood hearing loss include genetic (the commonest being mutations in GJB2), intrauterine infections (the commonest being cytomegalovirus), perinatal causes (e.g. neonatal jaundice), malformations of the ear, acquired infections (e.g. meningitis) and head trauma among others. Permanent hearing loss in adults is related to presbyacusis, otosclerosis, Meniere’s disease, ototoxicity, noise exposure, autoimmune causes, head trauma, cerebellopontine angle tumours, and a range of genetic causes. Aetiological investigations are aimed mainly at identifying the causes of hearing loss that are preventable (e.g. m1555A>G mutation), serious (Jervell–Lange– Neilsen syndrome, cerebellopontine angle tumours), potentially treatable (e.g. congenital cytomegalovirus infection, autoimmune diseases), or need genetic counselling (e.g. Pendred syndrome). The urgency of conducting the investigations is apparent in conditions such as meningitis (where rapid cochlear ossification may limit or prevent insertion of a cochlear implant) and congenital cytomegalovirus (where treatment is most effective in a narrow time window during the neonatal period). It follows that all children and selected adults with permanent hearing loss should be offered these investigations in a timely way, failing which, there is risk of clinical harm and potential for litigation. The British Association of Audiovestibular Physicians (BAAP) have reviewed their guidance on aetiological investigations for hearing loss based on recent evidence. The process of producing these guidelines is detailed in the ‘BAAP manual for producing guidelines’ [2] and granted accreditation by NICE (National Institute for Health and Care Excellence) in March 2016. The guidelines published here are produced by the NICE accredited process and bear the NICE accreditation mark. Further good quality studies and systematic reviews will be needed to strengthen the evidence base for supporting aetiological investigations, which are currently based on level 2–4 studies. Recent advances in genetic testing and wider availability of these tests is likely to improve the diagnostic yield of the investigations and decrease the proportion of hearing losses of ‘unknown aetiology’. It cannot be emphasized enough that the process of aetiological investigations is not just a tick-box exercise, but one of the judicious use of test procedures tailored to clinical need, with a patientand family-friendly approach and careful counselling of results. The process is a continuous one, and will often require a periodic review based on clinical findings, patient and family expectations.