A mixed hearing loss happens when there is the presence of both a conductive hearing loss (usually temporary hearing loss caused by a blockage) in the middle or outer ear, and a sensorineural hearing loss (hearing loss caused by damaged inner ear hair cells) in the inner ear involving either the cochlea or the auditory nerve.
Mixed hearing loss results from anything that causes conductive or sensorineural hearing loss. One situation where mixed hearing loss occurs is large vestibular aqueduct syndrome (LVAS). LVAS usually involves just sensorineural hearing loss, but it can also have a conductive component.
The conductive component in LVAS is thought to be the result of causes such as when the ossicles (the small bones in the middle ear) aren't working right because of incomplete bone formation in the inner ear. Another cause is fixation of the stapes (one of the ossicles), which means that the stapes can't transmit vibrations. One more possible cause is increased perilymphatic pressure that results from a tear in the membranes separating the middle ear from the inner ear.
There was a case of a toddler with hearing loss who showed abnormal middle ear results plus fluctuating hearing loss. A radiological test identified the presence of LVAS. Hearing aids had been tried but were not a viable long-term solution because the hearing loss was progressive. So the toddler was given a cochlear implant, and speech and language ability improved.
Mixed hearing loss can be treated with hearing aids, bone-anchored hearing implants, or cochlear implants.
Sources:
American Speech-Language-Hearing Association. Mixed Hearing Loss. http://www.asha.org/public/hearing/Mixed-Hearing-Loss/. Accessed March 2011.
Christensen, Lisa. New bone-anchored amplification options for children. A S H A Leader. July 14, 2009 v14 i9 p5(2). Accessed March 2011.
Jackie L. Clark, Ross J. Roeser. Large vestibular aqueduct syndrome: a case study. Journal of the American Academy of Audiology. Nov-Dec 2005 v16 i10 p822(7). Accessed March 2011.
