Lecture 8

Question 1

What is the acoustic stapedius reflex?

Answer 1

When a sufficiently loud sound is presented to one ear, the stapedial muscle would be contracted in both ears simultaneously.

Question 2

What is the origin, insertion, action and nerve of the tensor tympani?

What kind of stimuli?

Answer 2

Origin: Eustachian tube
Insertion: Malleus
Action: Protects and critically damps ossicular chain
Nerve: Trigeminal

Nonacoustic stimuli

Question 3

What is the origin, insertion, action and nerve of the stapedius?

What kind of stimuli?

Answer 3

Origin: Pyramid
Insertion: Stapes
Action: Protects and critically damps ossicular chain
Nerve: Facial

Acoustic and nonacoustic stimuli

Question 4

In the acoustic stapedius test, what is the probe ear?

Answer 4

Ear containing the probe tip in which the immittance change is being monitored

Question 5

In the acoustic stapedius test, what is the stimulus ear?

Answer 5

The ear receiving the stimulus used to activate the reflex.

Question 6

In the acoustic stapedius test, what is ipsilateral (uncrossed)?

Answer 6

When the probe ear and stimulus ear are the same.

Question 7

In the acoustic stapedius test, what is contralateral (crossed)?

Example?

Answer 7

When the probe ear and stimulus ear are different.

Ex: Contralateral left = stimulus in left ear, probe tone in right ear.

Question 8

What is the acoustic reflex threshold? (ART)

Answer 8

The lowest stimulus level that produces a change in acoustic immittance (lowering the admittance/increasing the impedance)

Question 9

What is the ART dependent upon?

Answer 9

The level of the reflex-activator stimulus

Characteristics of the middle ear transmission system.

Question 10

What is considered a significant shift in the ART?

What is the maximum level you go to for ART?

Answer 10

Discernible from the baseline = 0.02 considered a significant shift.

Max level = 100dB

Question 11

Why is ART better(lower) and grows faster for ipsilateral measurement compared to contralateral measurement?

Answer 11

Reflex pass phase is over - see faster growth (change of function of intensity) - number of increases in amplitude and intensity.

Question 12

What are 2 characteristics of ART?

Answer 12

ART for broadband noise is 10-20 dB lower than for tonal stimuli.
As stimulus level increases, the magnitude of the immittance change also increases.

Question 13

What is the ART procedure? (basic)

Answer 13

Obtain reflex at level corresponding to best part of middle ear - pressure set to peak. Set reflex to this.
Select stimulus - start level at reflex obtained as normal for the age group.
Start at 85dBHL, go up by 5dB. Change from baseline, want to run higher than that by 5dB
Have to include BBN - much lower intensity to obtain reflex threshold

Question 14

What is acoustic stapedius reflex decay?

What does is depend on?

Answer 14

A decrease in the strength of stapedius contraction during continuous stimulation.

Depends on frequency: the greatest adaptation occurring for high frequency tones, less for low frequency tones, and very little for BBN.

Question 15

How is acoustic stapedius reflex decay measured?

Answer 15

Half-life: the time required for reflex magnitude to diminish to one half of its maximum value during a continuous stimulus presented for 10 seconds.

Question 16

What is considered normal and abnormal decay in the reflex decay?

Answer 16

Normal: amplitude maintained at 10 seconds
Abnormal: amplitude has decayed more than 50% of original value in first 5 second of stimulus presentation.

Question 17

What are some common pathologies related to abnormal reflex decay?

Answer 17

Meniere’s disease: fluctuation of HL at frequencies, tinnitus. Maintains amplitude but not more than 50% in first 5 sec (is considered normal). Report negative decay.

CN VII - Schwannoma: declination of more than 50% in first 5 seconds (abnormal). Report positive decay.