Study of Binaural Squelch Effect in Unilateral Otosclerosis

Otosclerosis is one of the main causes of transmission hypoacusis. It can be treated with stapedectomy surgery.

But the understanding ability in noise has not been really studied. The Oldenburg MATRIX test is a well know test in audiology and allow to study the understanding in noise.

This study included all the patients coming in our center for stapedectomy for otosclerosis with controlateral audition under 30 decibels (dB) loss.

They will all undergo the MATRIX test in three situations: vocal material and noise from the front of the patient (S0N0 situation); vocal material from the front and noise from the bad-earing side (S0N-90 situation); vocal material from the front and noise from the good-earing side (S0N90 situation).

This might give three informations:

-Squelch effect which is the difference between Speech Reception Threshold (SRT) in S0N90 situation at 9month after surgery and before surgery.

The squelch effect is the ability of cortical discrimination to extract spatial cues and information providing from two different sources. So we considered the situation before surgery as a unilateral condition and the surgery rehabilitation as a bilateral condition.

• Head Shadow effect which is the difference between S0N90 and S0N-90 audiometry situations. The head shadow effect is the difference in the Speech Reception Threshold (SRT) due to diffraction effect of the physical sound wave.
• Binaural benefit which is the difference between S0N0 situation after and before surgery.

The binaural benefit is the SRT gain of both ear with same threshold comparing to a gap of threshold between the two ears.

The patients will also filled two questionnaires of quality of life: Abbreviated Profile of Hearing Aid Benefit (APHAB) and Speech and Spatial Questionnaire (SSQ).

The aim is to show the benefit of the surgery in otosclerosis for comprehension in noise.

Inclusion criteria

• diagnosis of otosclerosis
• controlateral audiometry under 30dB loss
• the ear to be operated with a transmission over 30dB

Exclusion criteria

• otosclerosis which has already operated on the ear studied
• other cause of transmission hypoacusis
• transmission after surgery other 30dB