Diagnostic

Purpose:

To determine the softest sound (threshold) a person can hear at various frequencies (pitches), usually between 250 Hz and 8000 Hz.

Procedure:

1. The person is seated in a soundproof booth.
2. They wear headphones (for air conduction testing) and/or bone oscillator (for bone conduction testing). 
3. Pure tones are presented at different intensity levels. ( instead of played at varying volumes) 
4. The person signals (usually by pressing a button or raising a hand) whenever they hear a sound.
5. The lowest volume at which a sound is heard 50% of the time is recorded as the threshold.

Types of Conduction Tested:

1. Air Conduction – via headphones; tests the entire hearing pathway.
2. Bone Conduction – via bone oscillator on the mastoid bone; bypasses outer and middle ear, directly stimulating the cochlea.

Results:

• Recorded on an audiogram, a graph plotting hearing thresholds (in decibels, dB HL) against frequencies (in Hertz, Hz). 
• Normal hearing: 0–25 dB HL across frequencies.
  

 Interpretation:

It helps to determine:

• Degree of hearing loss (mild, moderate, severe, profound)
  
• Type of hearing loss:
  
  • Conductive (problem in outer/middle ear)
  • Sensorineural (inner ear or nerve)
    
  • Mixed
     

Clinical Uses:

• Diagnosing hearing loss 
• Fitting hearing aids
• Monitoring hearing (e.g., in noise-exposed workers or patients on ototoxic meds)

Part of pre-surgical assessment for ear conditions

 Purpose:

Impedance audiometry evaluates the function of the middle ear, including:

• Tympanic membrane (eardrum) mobility
  
• Ossicular chain movement (middle ear bones)
  
• Eustachian tube function
  
• Presence of fluid, perforation, or pressure issues
  

It helps differentiate conductive hearing loss causes and checks for middle ear pathologies. 

Clinical Significance:

• Detects:
  
  • Otitis media (middle ear infection)
    
  • Eustachian tube dysfunction
    
  • Tympanic membrane perforation
  • Ossicular chain discontinuity
  • Otosclerosis
    
• Can be used in infants and uncooperative patients as it is objective.
  

Advantages:

• Non-invasive
  
• Quick (usually 2–5 minutes per ear)
  

Objective (no need for patient response)

Purpose of ECochG:

• Diagnose Meniere’s disease (endolymphatic hydrops)
  
• Assess auditory nerve function
• Intraoperative monitoring during ear surgery
• Evaluate cochlear and auditory nerve integrity in hearing-impaired patients
   

 How It Works:

• A click or tone burst sound stimulus is presented to the ear.
  
• Electrodes record the resulting electrical activity:
  
  • Transtympanic (needle electrode through the eardrum; more invasive, more accurate)
    
  • Extratympanic (electrodes placed in the ear canal or on the eardrum)
    

Main Components Measured:

1. Cochlear Microphonic (CM):
• Mimics the sound stimulus. 
• Generated by outer hair cells in the cochlea.


2. Summating Potential (SP): 
• A direct current (DC) shift during stimulation.
  
• Reflects hair cell activity, especially inner hair cells.
  


3. Action Potential (AP): 
• Corresponds to Wave I of the auditory brainstem response (ABR).
  
• Represents auditory nerve firing.
   

 Clinical Uses:

Condition	Role of ECochG
Meniere’s disease	Detects elevated SP/AP ratio
Auditory neuropathy	Helps differentiate sensory vs. neural issue
Perilymphatic fistula	Assists in diagnosis
Intraoperative monitoring	Monitors cochlear function during surgery

Purpose of ETF Testing:

To assess whether the Eustachian tube is:

• Opening properly during swallowing or yawning 
• Allowing adequate pressure regulation
• Contributing to middle ear disorders such as otitis media, barotrauma, or Eustachian tube dysfunction
   

Methods of Testing:

1. Tympanometry-based ETF Test (Non-perforated eardrum):

• A baseline tympanogram is recorded.
• The patient performs swallowing or Valsalva maneuver (forced exhalation with the nose pinched).
• Changes in middle ear pressure are measured.
• Normal Function: Pressure in the middle ear changes in response to maneuvers.
  

2. ETF Test with Perforated Eardrum or Vent Tube:

3. Sonotubometry:

• Uses a sound source in the nose and a microphone in the ear canal.
• Sound passes through the Eustachian tube during swallowing.
  
• Presence of sound in the ear canal = patent tube.
  

4. Nasopharyngoscopy:

Interpretation:

Clinical Significance:

ETF testing helps diagnose:

• Chronic otitis media with effusion 
• Barotrauma (e.g., flying/diving problems) 
• Hearing loss due to middle ear pressure issues
• Eustachian tube dysfunction (ETD) 
• Patulous Eustachian tube (open all the time—causes autophony) 

Symptoms of ETF Dysfunction:

• Feeling of fullness or pressure in the ear 
• Hearing loss 
• Popping or crackling sounds
• Discomfort with altitude or pressure changes