Conductive Hearing Loss

CONDUCTIVE HEARING LOSS
  • Caused by any disease process interfering with conduction of sound from the external ear to the stapedio-vestibular joint.
  • Tuning Fork Tests:
  1. Negative Rinne test (BC > AC)
  2. Weber lateralized to poorer ear
  3. Normal ABC test
  • Low frequencies affected more
  • Audiometry:
  1. BC better than AC with air bonegap. Greater the air-bone gap, more is the CHL
  2. Loss is not more than 60 dB
  3. Speech discrimination is good
WHO CLASSIFICATION OF DEGREE OF HEARING LOSS
  • Mild : 26 – 40 dB
  • Moderate : 41 – 55 dB
  • Moderately severe : 56 – 70 dB
  • Severe : 71– 90 dB
  • Profound : > 90 dB
CAUSES OF CONDUCTIVE HEARING LOSS
  1. Perforation of tympanic membrane
  2. Fluid in the middle ear-acute otitis media, serous otitis media, hemotympanum
  • Commonest cause of hearing loss in children is Chronic secretory otitis media.
  1. Mass in the middle ear (benign/malignant)
  2. Disruption of ossicles-trauma to ossicular chain, CSOM, cholesteatoma
  • Cause of conductive hearing loss in a patient with history of head injury with tympanic membrane normal and mobile would be Ossicular Chain Discontinuity. Fixation of ossicles-otosclerosis, tympanosclerosis
  1. Otosclerosis-Family history positive,Bilateral hearing loss,type As Tympanogram,PTA -bone conduction hearing loss with an apparent bone conduction hearing loss at 2000 
  2. Hz,hearing might worsen during pregnancy
  • Eustachian tube blockage
AVERAGE HEARING LOSS IN DIFFERENT LESIONS OF CONDUCTIVE APPARATUS
  • Complete obstruction of ear canal - 30 dB
  • Perforation of tympanic membrane - 10-40 dB
  • Ossicular interruption with intact drum - 54 dB
  • Ossicular disruption with intact tymnpanic membrane causes the maximum hearing loss
  • Ossicular interruption with perforation - 38 dB
  • Malleus fixation - 10-25 dB
  • Partial to complete fixation of Stapes - 5- 60 dB
MANAGEMENT OF CONDUCTIVE HEARING LOSS
  • Myringotomy - incision over TM
  • Myringoplasty - repair of TM
  • Ossiculoplasty - reconstruction of ossicular chain
  • Tympanoplasty - repair of TM and ossicles
CLINICAL SIGNIFICANCE OF HEARING LOSS
  • Permanent privation of the hearing of either ear comes under grievous injury .
  • Even if the hearing loss is correctable through surgery, then also it will fall under grievous injury.
  • The hearing loss when the patient fails to understand normal speech, but can understand shouted or amplified speech would be severe hearing loss.
Exam Question
  • Ossicular disruption with intact tymnpanic membrane causes maximum hearing loss.
  • After rupture of tympanic membrane, the hearing loss is 10-40 dB.
  • Permanent privation of the hearing of either ear comes under grievous injury .
  • Commonest cause of hearing loss in children is Chronic secretory otitis media.
  • The hearing loss when the patient fails to understand normal speech, but can understand shouted or amplified speech would be severe hearing loss.
  • Cause of unilateral conductive hearing loss in a patient with history of head injury with tympanic membrane normal and mobile would be Ossicular Chain Discontinuity.
  • Otosclerosis-Family history positive,Bilateral hearing loss,type As Tympanogram,PTA -bone conduction hearing loss with an apparent bone conduction hearing loss at 2000 Hz,hearing might worsen during pregnancy

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