Adam Walker- Audiological Scientist, Manchester, UK.

Hearing loss is split into groups depending upon its severity, these are: mild, moderate, severe and profound.  There are 3 main types of hearing loss, conductive, sensorineural and mixed.

Therefore, when we categorize a hearing loss we would refer to its severity and type, e.g. we may say it is a ‘mild conductive hearing loss’, or a ‘severe mixed hearing loss’ etc.

Conductive Hearing Loss

A conductive hearing loss (CHL) occurs when there is a problem with the outer or middle ear which makes it harder for the sound to reach the cochlea (hearing organ).  The most common type of conductive hearing loss in children is otitis media with effusion (OME, ‘glue ear’), which is a build-up of fluid behind the eardrum in the middle ear.  If there is fluid in the middle ear, the sound signal is dampened down as it travels through the fluid to reach the cochlea. Conductive hearing loss caused by glue ear is very common in early childhood (but can occur in young people and adults) and generally clears up itself after a few months; once the fluid has cleared the hearing returns to normal.  However, in some cases the glue ear and resulting conductive hearing loss persist for a long-time, in which case there are various ‘treatments’ to improve hearing- the 2 most common being hearing aids or ventilation tubes (grommets).

Sensorineural Hearing Loss

A sensorineural hearing loss (SNHL) is a permanent hearing loss that is caused by a problem with the cochlea.  In most cases this is because the tiny hair cells that sense sound in the cochlea are damaged or missing.  This could happen for several reasons and may be congenital (from birth) or acquired (occurring after birth).  Congenital sensorineural hearing loss is mainly caused by genetic mutations or is hereditary.  The main causes of acquired sensorineural hearing loss are childhood illnesses or as a result of life-saving medical treatment in the first few days / weeks of life.  In some cases, we do not know what has caused the sensorineural hearing loss; this is called ‘idiopathic’ – i.e. it has no apparent cause.   Sensorineural hearing loss is permanent and the only option is amplifying the sound delivered to the cochlea using some type of hearing aid (or cochlear implant if the hearing loss is severe/profound).

Mixed Hearing Loss

A mixed hearing loss is a combination of a conductive hearing loss and a sensorineural hearing loss.  The most common mixed hearing loss in childhood occurs when a child with a sensorineural hearing loss develops a case of glue ear.