Acoustic Reflex (AR) and Tone decay (TDT)

Acoustic Reflex (AR) types
Advantage and disadvantag
and Tone decay (TDT)

1. Acoustic reflex and tone decay

2. Introduction: Acoustic reflex also called Acoustic stapedius Reflex Measurement. Acoustic stapedius Reflex Measurement have become a standard component of the clinical test battery : 1- to cross – check behavioral results 2- in conjunction with other test results, to differentiate among middle ear, cochlear retocochlear and even non-auditory sites of lesion ( e.g., superior semicircular canal dehiscence )

3.   The Acoustic Reflex usually elicited at intensity level between 70 and 90 to 100 dB HL Acoustic reflex is measured using Imittance meter  It enables the examiner to present a signal to one ear and detect a decrease in TM compliance in either that ear ( Ipsi -lateral acoustic reflex ) or the opposite ear ( contra- lateral acoustic reflex) Acoustic Reflex measurement

4. Types Ipsilateral and contralateral The ear with the probe assembly is called the probe ear, and the ear receiving the stimulus sound is called the stimulus ear.

5. Contralateral or crossed acoustic reflex testing involves presenting the stimulus to one ear and monitoring the acoustic immittance in the opposite (probe) ear.

6. Ipsilateral (uncrossed) acoustic reflex testing involves stimulating the probe ear, which is also the ear in which the acoustic immittance is being measured.

7. How to name the ear: Because the stimulus ear and the probe ear are the same with ipsilateral testing, there is no question about which ear and reflex pathways are being tested. However, with contralateral reflexes, “ right contralateral ” indicates that the stimulus is in the right ear and the probe is in the left ear “ left contralateral ” means that the stimulus is in the left ear and the probe is in the right ear “ right ipsilateral ” means that the stimulus and probe are in the right ear “ left ipsilateral ” means that the stimulus and probe are in the left ear

8. Advantage of contralateral reflex: 1- It is able to assess the crossed pathway ( detect the axial tumors) 2- Less susceptible to artifact ( stimulus in one ear and response in the middle ear) 3- Could be elicited at higher intensities ( due to less susceptible to artifact ) 4- More data about

9. Advantage of ipsilateral reflex: 1- More sensitive to ME pathology 2- Assess each ear independently 3- Could be done without headset 4- Avoid the problem of collapsed ear canal

10. tone decay

11.  Normally stapedius muscle gradually relaxed between contraction as response to intense sound because it is constantly stimulated  This relaxation between the contractions is known as “ Acoustic Reflex Decay “  Acoustic reflex Decay is normal at high frequencies However, significant amount of decay at low frequencies is seen in patients with auditory nerve or brain stem lesions

12. Procedure : Reflex decay is measured by presenting a sustained tone at 10 dB above ART or (90 to 105) test completed either by the end of the 10 seconds or when the reflex original amplitude reduced (decayed) to the half , whichever occur first  Test usually administered at 500 and 1000 Hz because for unknown reasons, some subjects with normal hearing are showing Reflex decay at 2000 and 4000 Hz Test better to be done contra-laterally to save time and comparison between both pathway is good to isolate lesions in ascending viruses descending tract

13. Results interpretation  Decay is present or abnormal ( the Reflex amplitude reduced to half of its original amplitude within 5 seconds >>> usually seen in patients with 8th nerve lesions like tumors  Decay present or abnormal at higher frequencies >>>>>>> cochlear lesions  Decay absent at low frequencies ( 500 and 1000 Hz) >>>>> normal or cochlear pathology

14. Graphs for interpretation

15. Thanks for your attention Any questions? Done by : Eatedal Alqahtani