What are the goals of acoustic reflex testing?

Objectively assess the middle ear muscle reflex (MEMR) pathway -can provide cross-check for audiogram when patient reliability is questionable -can be used to evaluate central pathology (e.g. VIII n. tumor, VIII n. paralysis)

How activiation of the MEMR pathway causes a change in tympanic membrane/middle ear admittance

MEMR Pathway • Involves outer ear > middle ear > inner ear > auditory brainstem > facial nerve > stapedius muscle • Is bilateral Acoustic Reflex Threshold Testing • Assesses integrity of MEMR pathway by measuring admittance during activation of the MEMR The lowest level of an elicitor required to initiate the MEMR is called the “acoustic reflex threshold”

The branches of the MEMR pathway and the conditions that we use to test them. What information is gained by testing all four branches?

Because the MEMR pathway is bilateral, four “branches” of the pathway can be tested: • When 226 Hz probe tone and MEMR elicitor are in the same ear, we call it “ipsilateral” acoustic reflex • When 226 Hz probe tone and MEMR elicitor are in opposite ears, we call it “contralateral”

How acoustic reflex thresholds are measured

. Test ipsilateral (first) and contralateral (second) conditions in one probe ear before testing the opposite ear 2. At beginning of test, ear canal pressure is held at/near 0 daPa 3. Start by presenting 500 Hz elicitor ipsilaterally and increase elicitor volume by 5 dB until (equal to or more than) > 0.02 mmho decrease in admittance is observed -the elicitor volume level that produced this change in admittance is the ART -if no ART is seen, mark “No Response” (NR) 4. Repeat ipsilaterally for 1000, 2000, and 4000 Hz 5. Repeat steps 2-4 in contralateral conditions Normal ART values fall within the range of ~70-95 dB across all frequencies