This is an extract of our Hearing Loss document, which we sell as part of our ENT Notes collection written by the top tier of University Of Leicester students.
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Hearing Loss Classification
- Deafness = subjective decline in hearing acuity affecting one or both ears
- Conductive hearing loss ("Obstructive") o Pathology external or middle ear amenable to surgery
- Sensory-neural hearing loss ("failure of transmission") o Pathology affecting cochlear, auditory nerve or auditory centers in the brain o Often involves loss of hair cells from the Organ of Corti, therefore is usually permanent
Conductive hearing lossExternal ear occlusion e.g wax, foreign body, congenital agenesis of the ear Infection (otitis media/externa) Glue ear Trauma (direct blow, acoustic trauma) Osteosclerosis - fixation of stapes on oval window (runs in families, associated with tinnitus and mild vertigo) Iatrogenic (surgery)
Sensorineural hearing loss-
Idiopathic Presbycusis o Age-related hearing loss, usually loss of high-frequency sounds initially, because hair cells responding to high-frequency sounds are most easily damaged) Viral infections (measles, mumps, meningitis) Tumours affecting the cochlear nerve Trauma - temporal bone fractures Drugs - aminoglycosides e.g gentamycin Central - brainstem CVA
Investigations Tuning Fork Test-
o 512 Hz, middle C - so heard not felt) Rinnes o Place tuning fork on mastoid bone and acoustic meatus and ask which is loudest (normally air conduction > bone conduction =
positive Rinne's test) o Negative test = pathology where bone conduction > air conduction = conductive hearing pattern o In sensorineural loss both AC and BC are decreased therefore AC should still be > BC Webers o Place tuning fork in middle of forehead o Normal sound is equally loud in both ears o In unilateral conductive hearing loss the sound will lateralise to the affected side
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