Conductive hearing loss is a hearing loss where the ears' ability to conduct sound into the inner ear is blocked or reduced. It can be caused by a range of developmental, congenital, or acquired pathology to the external, middle, or inner ear.
Pathology
Essentially any process that obstructs or disrupts the passage of sound waves through the outer or middle ear can cause conductive hearing loss and the list of causes is very long. The most common are included below.
External ear
cerumen (earwax) or external auditory canal foreign body
congenital, e.g. external acoustic canal (EAC) atresia
trauma, e.g. tympanic membrane perforation (not seen radiologically)
otitis externa
external auditory canal benign lesions, e.g. osteoma, exostosis, keratosis obturans and medial canal fibrosis
external acoustic canal tumors, e.g. cholesteatoma, squamous cell carcinoma
barotrauma (unequal air pressure in the external and middle ear)
Middle ear
congenital, e.g. congenital ossicular fixation
trauma, e.g. ossicular chain disruption
inflammatory, e.g. otomastoiditis
middle ear tumors, e.g. tympanic paraganglioma, cholesteatoma, middle ear schwannoma
Inner ear
congenital, e.g. oval window atresia (rare)
fenestral otosclerosis
Treatment and prognosis
A stapes prosthesis may help improve conductive hearing loss.