Lecture 1 Flashcards
Ear diagram (picture)
How should we think of the ME?
Think of the ME like a room. It is filled with air but can flood.
What is pulsatile tinnitus?
The person is hearing blood flow (vascular system)
What are the vascular structures? Where are the vascular structures compressing the ME?
- Internal carotid artery (on the front wall of the ME)
- Jugular bulb (floor of the ME)
The vascular structures are compressing on the front and floor of the ME
What are the two muscles of the ME?
- Stapedius muscle
- Tensor tympani muscle
Where is the stapedius muscle located?
It comes from the back wall of the ME
Where is the stapedius muscle hidden?
Hidden inside a bony structure (the pyramidal eminence); however, the tendon shows up in the ME
How is the stapedius muscle involved in acoustic reflex?
The stapedius tendon is connected to the stapedius neck which pulls the stapes up and down (stiffens up the ossicular chain) = acoustic reflex
What is the biggest muscle of the ME?
The tensor tympani muscle
Where is the tensor tympani muscle located in the ME?
On a right angle (back front corner of the ME)
The angle creates leverage providing additional force
Where is the tensor tympani muscle hidden?
Hidden in the cochleariform process
What is the tensor tympani connected too and how does is it involved?
- The tensor tympani muscle is connected to the malleus which is connected to the TM (runs across the ceiling)
- When the tensor tympani contracts, it pulls the eardrum in towards the center (this stiffens the TM as well as the ossicular chain)
- The footplate of the stapes is coupled to the fluid of the cochlea, which pumps the cochlear fluid
- No idea what the tensor tympani does
Why is otoscopy important?
- For acoustic immitance measures
- Helps with interpretation of results/management decisions
- Looking at the canal, pinna, and TM visual inspection
What things can you find with otoscopy?
- PE tube
- TM perforation
- Negative pressure/retraction pocket
- Foreign objects/debris/lesions
- Occasional middle ear items visible [e.g. ossicles, RW, PET]
Tymps wont tell you this information, you need to do otoscopy
What happens to the TM with negative pressure?
It is sucked into the ME space
What can happen when negative pressure gets very robust?
A retraction pocket can happen, adhering the TM against the ossicular bones and the wall of the cochlea
What can a retraction pocket cause?
Cholesteatoma
What is a patulous ET?
The ET is open in an abnormal way
What are the otoscopic landmarks?
- External ear (pinna): shine a light on the pinna
- Debris/cerumen (EAC): look for the TM (with no obstruction you will be able to visualize the TM)
- TM: look at colour (pinkish/gray)
- Cone of light: in the lower, frontal quadrant (lets you know the TM is positioned correctly)
- Ossicles (malleus)
What does it mean if there is no cone of light?
Could be negative pressure (retraction pockets) or positive pressure (ballooned out into the OE space)
Normal TM (picture)
- Incus at the top
- Middle is the malleus
- Round window at the bottom (has a flaccid window opening which allows the wave to propagate)
Acute Otitis Media (picture)
- ME infection
- No cone of light
- Very red, inflamed TM
Severe Otitis Externa (picture)
- OE infection
- Very moist
What is otitis externa also known as?
Swimmers ear (exostoses)
Exostoses (picture)
- Cartilaginous, bony bumps grow on the skin tissue of the OE (not inflammation, it is a structural change)
- No dampness
- May be a surgical candidate
- Due to swimming in cold water
What can indicate impacted cerumen?
Very small ear canal volume and poor hearing
What are the layers of the TM?
3 layers
- Thick fibrous in the middle
- Mucous layer in the inside (ME)
- Epithelial layer on the outside (OE)
What are PE tubes?
Pressure equalization tubes or tympanostomy tubes are inserted in the lower part of the TM to let drainage out of the ME and is also an air vent (replacing the function of the ET).
What will happen if you run a tymp on someone with PE tubes?
You will get a large ear canal volume (patent measure)
What does it mean if you get a normal tymp on someone with ear tubes?
You get a non-patent measure (there is blockage somewhere)
What is immittance?
- An invented term that is derived to describe both admittance and impedance
- Admittance and impedance are looking at the same thing through opposite lenses
What is admittance?
- How much sound is going through
- Tests are actually measuring admittance
What is impedance?
How much sound is being blocked
What are the key compentents of a tymp machine?
- Air pump: pumps air to manipulate pressure
- Microphone: picking up and measuring acoustic energy
- Speaker: produces a continuous tone
When it comes to measuring acoustic immittance, what is everything based around?
EVERYTHING is based around the concept of measuring the CHANGE in response to a PURE TONE that is being delivered to the external canal.
Same ____, different ____ can create change
output, environment
When we change the ____ with the probe tone, the microphone will pick up ____.
environment, changes
Explain the tone involved with the tymp
- The tone in the ear canal is kept at the same SPL (it remains constant)
- The immittance machine makes it so when you put the tone up to your ear, it gets quieter (when the probe tip isnt in the ear, everyone in the room can hear it)
- The microphone acts as a monitor to keep the SPL constant (this allows us to measure how much of the sound is being absorbed by the ME)
Whatever voltage is require to maintain SPL is our ____
Acoustic admittance
How does the machine work in a small room?
- Putting the tip into a small syringe
- SPL will want to increase, but the voltage decreases to maintain constant SPL (60dB)
- The SPL will want to go up to 110dB, but the machine keeps the SPL constant at 60dB
- The smaller the room, the lower the admittance
How does the machine work in a large room?
- Putting the tip into a syringe 4x the size
- Because there is so much air, the SPL will be very low (30dB), so the voltage level needs to increase to 60dB to maintain constant SPL
- The bigger the room, the more admittance
What happens when the TM is at 0daPa?
- At 0, the ME becomes less stiff (admittance increases –> sound is being absorbed into the ME so overall soundi s decreasing, therefore, the machine increases SPL to maintain 60dB)
- With more admittance, sound is quieter (it is traveling through the ME, so SPL needs to increase)
What happens when the TM is at -200 or 200daPa?
- The TM is super stiff from all positive or negative pressure (admittance decreases)
- With less admittance, sound is louder (it is trapped in OE with nowhere to go so SPL needs to decrease)
What are the acoustic immittance units of measurement?
- daPa (pressure)
- ml
- mmho (admittance)
- dB
- Hz (frequency of probe tone and stimulating signal)
Acoustic immittance uses a ____Hz probe tone.
226Hz
What type of instrument measures pressure?
Manometer
How did pressure used to be measured?
mm H2O
What is the acoustic OHM?
the unit of acoustic impedance
Why is the height of the Y tymp described in ml?
Because it is useful for us (clinically helpful)
Who was the first to describe the acoustic impedance theory?
Otto Metz