Acoustic reflex is lost in case of

ACOUSTIC REFLEX is the contraction of the stapedius muscle causing a change in impedance.The minimum sound intensity required to produce stapedial reflex is called stapedial reflex threshold(S). Reflexes are bilateral and can be measured on the ipsilateral and contralateral side. For ipsilateral the reflex is measured in the ear in which the tone is given while for contralateral the reflex is tested in the ear opposite to which the tone is given. Normally,the reflex occurs about 70-90 dB above the patient's threshold. ref:Hazarika 3rd edition,page no.63