Tympanometry And Stapedial Reflex Flashcards
What to do first when a patient comes with c/o of hard of hearing or hearing loss?
First examine the ear and try to localise the lesion whether it is in the external ear,middle ear,internal ear
DO NOT DO ANY TESTS BEFORE EXAMINING THE EAR
What to do in examination of a patient who c/o of hearing loss?
First examine the external ear ( pinna,eac,tympanic membrane ) . If external ear is normal then the lesion could be in middle ear or internal ear
How to find whether the lesion is in middle ear or internal ear ?
Perform TUNING FORK TESTS
This helps to identify the type of hearing loss ( CHL / SNHL)
CHL - middle ear pathology
SNHL - Inner ear pathology
FINALLY,confirm with AUDIOGRAM
What are the conditions of the Middle ear that causes conductive hearing loss despite tympanic membrane being normal?
Ossicular discontinuity
ossicular fixation
Fluid collection in middle ear
What test is done to identify the exact pathology of middle ear ?
Impedance audiometry
Impedance audiometry consists of ?
Tympanometry
Stapedial reflex
With what instrument tympanometry Is done?
A probe that has 3 openings
What does the probe do in the tympanometry?
First opening - produces sound of frequency 220-226hz
Second opening - collects the sound that is reflected back from the tympanic membrane
Third opening - changes the pressure of external auditory canal
What is the significance of collection of reflected sound ?
The main function of the middle ear is to transmit maximum sound via it
Normal middle ear - maximum transmission of sound and less sound is reflected back
Middle ear pathology - transmission is reduced and reflection is more
What is significance of changing pressure of the external auditory canal by the third opening of the probe ?
With the change in the pressure of EAC from -400 to
+ 200 we check the compliance (movement) of tympanic membrane
The pressure at which sound transmission is more is noted and is considered to be the pressure of middle ear
For proper transmission of sound , we require equal pressure on both the sides of tympanic membrane ( i.e eac and middle ear cavity )
When is the mobility / compliance of tympanic membrane is increased ?
In ossicular discontinuity
When does the mobility / compliance of tympanic membrane decrease?
Due to fixation of ossicles ( Eustachian tube normal ) and fluid in middle ear (Eustachian tube abnormal)
What is the function of Eustachian tube ?
Ventilates and maintains the pressure of the middle ear
What is indication of tympanometry?
To find the pathology of middle ear with an intact tympanic membrane
What type of test is tympanometry ?
Objective test ( patient’s cooperation not needed )
What is the graph produced by tympanometry ?
Tympanogram
What is the normal compliance ?
0.35 ml - 1.45 ml
What is the normal middle ear pressure ?
In adults = -50 to +50 mm of h2o
In children = -150 to +50 mm of h20
What the normal tympanogram curve ?
A type ( more or less the peak is in the centre of the graph)
What is Ad type of curve in tympanogram ?
In this type of curve , compliance is increased and middle ear pressure is normal
Seen in ossicular discontinuity
What is As type of curve in tympanogram?
In this type , compliance is reduced but middle ear pressure is normal
Seen in otosclerosis /tympanosclerosis
What is B type of curve in tympanogram?
Here , the compliance is reduced and pressure becomes negative
Seen in serous otitis media
What does c type of curve indicate ?
Early stage of Eustachian tube obstruction with normal compliance ( since fluid is not yet started to get collected ) and negative pressure
When is flat line seen in tympanogram?
🌟In no compliance of tympanic membrane due to excess fluid
🌟In perforation of tympanic membrane since there will be no pressure change
B type is also known as what ?
Dome shaped curve
Main aim of doing tympanometry is
To find the compliance of tympanic membrane
To find the pressure of middle ear
Middle ear pressure also indicates the status of Eustachian tube
What is Valsalva manoeuvre?
Exhalation with closed nostrils and mouth causes air to pass through Eustachian tube and causes the tympanic membrane to pop out
This popping out can be felt and as well as seen via otoscope
What is the purpose of Valsalva manoeuvre?
To check the patency of condition of eustachian tube
Contraindication of Valsalva manoeuvre
Infection of Eustachian tube / infection of throat
What is politzer test ?
Patient is asked to close one nostril and mouth
Thorough the other nostril pressure is increased via the politzer bag and causes popping out of tympanic membrane since Eustachian tube is the only passage of air and pressure
What is Toynbee manoeuvre?
Retraction of tympanic membrane occurs when sip of water is taken due to retraction of tympanic membrane due to creation of negative intratympanic membrane
What is Eustachian tube catheterisation?
Eustachian tube catheter is passed through the floor of nasal cavity into the nasopharynx
Refer marrow notes
What is frenzel manoeuvre?
Mouth and nostrils are closed and posterior part of tongue is raised by saying Ka,ka,ka
Increased pressure of air is transmitted through Eustachian tube into the middle ear
Divers use this manoeuvre to equalise middle ear pressure with the external ear
What is the best test for estimating Eustachian tube function?
Tympanometry
Other test for checking the Eustachian tube function
Valsalva manoeuvre
Politzer test
Eustachian tube catheterisation
Toynbee manoeuvre
Frenzel manoeuvre
What is stapedial reflex ?
It is a protective reflex that protects the inner ear from loud noise (70-90db)trauma
What is the centre for stapedial reflex ?
Superior olivary complex
From the superior olivary complex where does the efferent signals go?
It goes to facial nerve of both the sides and causes contraction of stapedius muscles of both the sides ultimately causing pulling back of stapes
What is the afferent and efferent of stapedial reflex ?
Afferent - 8th nerve
Efferent - 7th nerve
If stimulus of loud sound if given to say the right ear doesn’t the other ear also receive loud sound and the 8th nerve of the other side is also stimulated ?
No the other side will not get stimulated
This is because when travelling to the opposite ear around 40 db is lost in air conduction and it is not received as a loud sound in the opposite ear
But facial nerve of both the sides are stimulated since the reflex is bilateral
Stapedial reflex in middle ear defect
Not elicited
Stapedial reflex in inner ear pathology
Threshold for the reflex is decreased
Stapedial reflex in auditory pathway pathology
Initially present but later absent , this is called as STAPEDIAL DECAY
Best test for malingering
BERA
