conductive hearing loss

what is conductive hearing loss?

mechanical dysfunction of outer or middle ear which prevents transmission of sound waves from reaching the inner ear

what are the different causes of conductive hearing loss? (7)

- tympanic membrane perforation - trauma, infection

- problems with ossicular chain - otosclerosis, trauma, infection

- failure of eustachian tube to equalise pressure of middle ear - throat, nose, ear infections

- otitis media/externa

- cholesteatoma

- cerumen impaction (earwax)

- congenital - external auditory canal atresia

what is external auditory canal atresia?

malformation of external auditory canal

what are the clinical features of conductive hearing loss?

- hearing IMPROVES in noisy environments

- volume of own voice remains the same

- external canal obstruction

why does the volume of your own voice stay the same in CHL?

inner ear and auditory nerve are unaffected

what can cause external canal obstruction?

- cerumen (earwax)

- pus

- debris

- foreign body

what are the results of the Rinne's test in CHL?

- rinne's NEGATIVE

- bone conduction > air conduction

- so the pt will say they can hear better when the tuning fork is placed on mastoid process over directly next to their ear

what are the results of Weber's test in CHL?

- it will sound louder on the affected side

what is the hypothesis explaining why sound is louder on the affected side in Weber's in CHL?

affected side perceives sound to be louder due to up-regulation of inner ear which makes it more sensitive to stimuli received via bone conduction

what other investigations can be done for CHL?

- otoscopy

- audiogram

- speech audiogram

- impedance audiometry

what are audiograms?

pure tone testing - can decipher between bone and air conduction

what are the results in speech audiograms with CHL?

increasing volume increases speech comprehension and no discrimination loss (loss of word comprehension)

what is impedance audiometry?

assesses the middle ear ossicular transmission

what would the impedance audiometry results of CHL be?

elevated acoustic reflex - involuntary stapedius + tensor tympani muscle contraction in response to high-intensity sound stimuli