Common aetiological investigations into bilateral hearing loss
| Investigation | Possible finding |
|---|---|
| MRI IAMs and brain | > Absent auditory nerve |
| > Mondini dysplasia | |
| > Widened vestibular aqueduct | |
| Genetic testing | > Connexin 26 and 30 – commonest genetic mutation causing non-syndromic hearing loss |
| > A1555G, which predisposes to aminoglycoside ototoxicity | |
| Blood tests | CMV IgG: a negative result excludes congenital CMV, a positive result requires retrieval of the Guthrie card (newborn bloodspot) to test for CMV DNA to confirm congenital CMV |
| Positive test commonest non-genetic cause of childhood hearing loss in UK | |
| Autoimmune screen in cases of sudden/progressive/fluctuating hearing loss | |
| Opthalmology review | 40% of children with permanent congenital hearing loss have ophthalmic conditions, such as refractive errors 26 |
| Particularly important to identify retinitis pigmentosa to detect Usher syndrome | |
| Urine dipstick | Haematuria and proteinuria are found in Alport syndrome |
| Renal ultrasound | Especially if signs of Branchio-Oto-Renal syndrome |
| Family audiograms | Approximately half of hearing impairment is genetic |
| ECG | If hearing loss is severe to profound, to identify Jervell Lange Nielsen syndrome (a cause of sudden death) |
Causes of hearing loss that can be progressive are shown in bold
CMV = cytomegalovirus; ECG = electrocardiogram; IAM = internal auditory meati; IgG = immunoglobulin G; MRI = magnetic resonance imaging