Return to: General Clerkship Objectives

Overview

Three major types of hearing loss:

• Conductive hearing loss (CHL)
• Sensorineural hearing loss (SNHL)
• Mixed: both CHL and SNHL components

Hearing Fork Tests:

• Can help to determine type and laterality of loss
• Types of tests:
  • Weber test
    • place tuning fork at the midline of the patient's forehead
    • Normal or equal bilateral loss: localizes to midline
    • CHL: localizes to the affected ear
    • SNHL: localizes to better ear
  • Rinne test
    • place tuning fork on patient's mastoid bone (bone conduction) and then in front of the patient's ear (air conduction)
    • Normal or SNHL: air conduction > bone conduction
    • CHL: bone conduction > air conduction
    • A normal test is termed as a 'positive Rinne', and an abnormal test is termed 'negative'

Audiogram:

• Pure-tone audiometry which tests hearing threshold (dB) for different frequencies (Hz)
• Tests each ear for bone conduction and air conduction
• Hearing loss types:
  • CHL: 'air-bone gap'; difference in threshold for a given frequency in the same ear
  • SNHL: >25 dB for a given frequency
  • Mixed: Higher thresholds as well as an air-bone gap

Conductive Hearing Loss

• Trouble conducting sound, from the auricle to the inner ear 
• Location of abnormality:
  • EAC
  • Tympanic membrane
  • Middle Ear Space
  • Ossicles
•  Causes:
  • Cerumen impaction
  • Otitis Media 
  • Tympanic membrane perforation
  • Otosclerosis
  • Foreign body
  • Otitis externa
  • Tumors
• Findings:
  •  Physical abnormality
    • EAC obstructed (tumor, otitis externa)
    • TM perforation
    • Change in TM mobility
    • Fluid in ME
    • Cholesteatoma 
  • Negative Rinne (BC>AC), Weber localizing to affected ear
  • Audiogram showing air-bone gap

Sensorineural Hearing Loss

• Trouble sending neural signals, from the cochlea to CNVIII to the brain 
• Location of abnormality:
  • Inner ear
  • Eighth cranial nerve
• Causes:
  • Presbycusis
  • Noise exposure
  • Congenital
  • Infection
  • Meniere's disease
  • Ototoxicity
• Findings:
  • No physical abnormality
  • Positive Rinne (AC>BC)
  • Audiogram showing increase in hearing thresholds with no air-bone gap