MCQ – 87828

In a patient  with facial nerve palsy on the right side, Stapedial reflex will be absent on:

A.	Right side
B.	Left side
C.	Both sides
D.	Not absent

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Correct Answer � A Explanation

Ans: a,  Right side

• Facial nerve forms the efferent of stapedial reflex, so in facial nerve palsy of the right side, the stapedial reflex is absent on right side only.

ACOUSTIC REFLEX/STAPEDIAL REFLEX:

•  It is based on the fact that a loud sound, 70-100 dB above the threshold of hearing of a particular ear, causes bilateral contraction of the stapedial muscles which can be detected by tympanometry. 

• Tone can be delivered to one ear and the reflex picked from the same or the contralateral ear. 

The reflex arc involved is: 

• Ipsilateral: CN VIII → ventral cochlear nucleus → CN VII nucleus ipsilateral stapedius muscle. 

Contralateral: CN VIII → ventral cochlear nucleus → contralateral medial superior olivary nucleus → contralateral CN VII nucleus → contralateral stapedius muscle.

Causes of Absent Stapedial Reflex:

Afferent pathway:

Middle ear diseases

   – Otosclerosis 

   – Ossicular discontinuity 

   – Atelectasis

Cochlea/VIII nerve/ superior olivary complex lesion

   – Severe SNHL 

   – Acoustic neuroma 

   – Multiple sclerosis

EFFERENT PATHWAY:

 VII nerve diseases :

    – Facial palsy 

   – Ramsay Hunt syndrome

Stapedius muscle involvement 

   – Post Stapedectomy 

   – Myasthenia gravis.