Tag: Acoustic reflex

Acoustic reflex

Acoustic reflex


ACOUSTIC REFLEX(STAPEDIAL REFLEX)

  • This reflex 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 pathway involved in the acoustic reflex is complex and can involve the ossicular chain (malleus, incus and stapes), the cochlea (organ of hearing), the auditory nerve, brain stem, facial nerve and other components.
  • Stapedial reflex is mediated by 7th and 8th Cranial Nerves.
  • Stapedial reflex is a protective reflex against loud sounds.
  • Stapedius muscle is supplied by VII nerve (facial nerve).
  • Lesions of facial nerve lead to loss of stapedial reflex and hyperacusis or phonophobia i.e. intolerance to loud sounds
  • As the stapedius muscle is innervated by the facial nerve,it can be used to locate the injury on the nerve.
  • If the injury is distal to the stapedius muscle, the reflex is still functional.

ACOUSTIC REFLEX THRESHOLD

  • The acoustic reflex threshold (ART) is the sound pressure level (SPL) from which a sound stimuli with a given frequency will trigger the acoustic reflex.
  • Individuals with normal hearing have an acoustic reflex threshold (ART) around 70-100 dB .
  • People with conductive hearing loss(-i.e. bad transmission in the middle ear) have a higher acoustic reflex threshold.

RESULTS OF ACOUSTIC REFLEX THRESHOLD IN DIFFERENT PATHOLOGIES

Bilateral normal ART results. 

Cochlear pathology/VIII nerve pathology right ear

Facial nerve pathology, right side

Mild middle ear pathology, right ear

Severe middle ear pathology, right ear

Small intra-axial brainstem pathology (small)

Larger intra-axial brainstem pathology

ACOUSTIC REFLEX DECAY TESTING

  • The acoustic reflex decay test is used to assess the integrity of CN VIII.
  • Using a stimulus of either 500 or 1000 Hz, a contralateral continuous tone is presented for 10 seconds at a stimulus level 10 dB above the acoustic reflex threshold for that stimulus frequency in that ear.
  • This suprathreshold acoustic reflex then is recorded over the 10-second stimulation period.
  • If the amplitude of the recorded deflection on the screen decreases by 50% or more within 10 seconds, the test is considered positive.
  • Positive findings on this test may suggest a retrocochlear lesion (eg, vestibular schwannoma, acoustic neuroma).
Exam Question
 
  • Stapedial reflex is a protective reflex against loud sounds.
  • Stapedial reflex is mediated by 7th and 8th Cranial Nerves.
  • Acoustic/Stapedial reflex decay test is positive in lesion of Eighth nerve
Don’t Forget to Solve all the previous Year Question asked on Acoustic reflex

Acoustic reflex

Acoustic reflex

Q. 1

A 31 year old female patient complaints of bilateral impairment of hearing for the past 5 years. On examination, tympanic membrane is normal and audiogram shows a bilateral conductive deafness. Impedance audiometry shows normal curve and acoustic reflexes are absent. All of the following constitute part of its treatment, EXCEPT:

 A

Gentamicin

 B

Hearing aid

 C

Stapedectomy

 D

Sodium fluoride

Q. 1

A 31 year old female patient complaints of bilateral impairment of hearing for the past 5 years. On examination, tympanic membrane is normal and audiogram shows a bilateral conductive deafness. Impedance audiometry shows normal curve and acoustic reflexes are absent. All of the following constitute part of its treatment, EXCEPT:

 A

Gentamicin

 B

Hearing aid

 C

Stapedectomy

 D

Sodium fluoride

Ans. A

Explanation:

The patient is showing features of otosclerosis.

It is a condition due to new spongy bone formation.

About 50% of the cases may have a positive family history and deafness starts between the age of 20-30 years.

Non surgical treatment of otosclerosis includes use of hearing aid and sodium fluoride.

Use of high doses of sodium fluoride is thought to increase the remineralization of otospongotic foci.

It has been reported to stabilize progressive inner ear hearing loss and tinnitus. Surgical treatment of choice is stapedectomy.
 

Q. 2

A patient has brought to the outpatient department complaining of loss of hearing since some months. His relative is telling that he is going to so many doctors and his hearing complaints are not settling down. After examination you are suspecting malingering in this patient. You decide to proceed with further tests. 

Assertion: To find malingers, acoustic reflex test is helpful

Reason: A person who feigns total deafness and does not give any response on pure tone audiometry but shows a positive stapedial reflex is a malingerer.

 A

Both Assertion and Reason are true, and Reason is the correct explanation for Assertion

 B

Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion

 C

Assertion is true, but Reason is false

 D

Assertion is false, but Reason is true

Q. 2

A patient has brought to the outpatient department complaining of loss of hearing since some months. His relative is telling that he is going to so many doctors and his hearing complaints are not settling down. After examination you are suspecting malingering in this patient. You decide to proceed with further tests. 

Assertion: To find malingers, acoustic reflex test is helpful

Reason: A person who feigns total deafness and does not give any response on pure tone audiometry but shows a positive stapedial reflex is a malingerer.

 A

Both Assertion and Reason are true, and Reason is the correct explanation for Assertion

 B

Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion

 C

Assertion is true, but Reason is false

 D

Assertion is false, but Reason is true

Ans. A

Explanation:

Acoustic reflex (stapedial reflex) 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.


Q. 3

Regarding stapedial reflex, which of the following is true:

 A

It helps to enhance the sound conduction in middle ear

 B

It is a protective reflex against loud sound

 C

It helps in masking the sound waves

 D

It is unilateral reflex

Q. 3

Regarding stapedial reflex, which of the following is true:

 A

It helps to enhance the sound conduction in middle ear

 B

It is a protective reflex against loud sound

 C

It helps in masking the sound waves

 D

It is unilateral reflex

Ans. B

Explanation:

Ans. is b i.e. It is a protective reflex against loud sounds 

 Stapedius muscle helps to dampen very loud sound and thus prevents noise trauma to the inner ear. It is supplied by VII nerve (facial nerve). Lesions of facial nerve lead to loss of stapedial reflex and hyperacusis or phonophobia i.e. intolerance to loud sounds. For more details see chapter – physiology of hearing and assessment of hearing loss of the guide Stapedial reflex = Acoustic reflex



Q. 4

Stapedial reflex is mediated by:

 A

V and VII nerves

 B

V and VIII nerves

 C

VII and VI nerves

 D

VII and VIII nerves

Q. 4

Stapedial reflex is mediated by:

 A

V and VII nerves

 B

V and VIII nerves

 C

VII and VI nerves

 D

VII and VIII nerves

Ans. D

Explanation:

 

It is based on the fact that a loud sound of 70-100 dB above the threshold of hearing of particular ear, causes bilateral contraction of the stapedial muscle which can be detected by tympanometry.This can be seen both in the stimulating ear (ipsilateral ear) and in the non stimulating ear (contralateral ear).


Q. 5

A 31 year old female patient complains of bilateral impairment of hearing for the 5 year. On examination, tympanic membrane is normal and audiogram shows a bilateral conductive deafness. Impedance audiometry shows As type of curve and acoustic reflexes are absent. All constitute part of treatment, except:

 A

Hearing aid

 B

Stapedectomy

 C

Sodium fluoride

 D

Gentamicin

Q. 5

A 31 year old female patient complains of bilateral impairment of hearing for the 5 year. On examination, tympanic membrane is normal and audiogram shows a bilateral conductive deafness. Impedance audiometry shows As type of curve and acoustic reflexes are absent. All constitute part of treatment, except:

 A

Hearing aid

 B

Stapedectomy

 C

Sodium fluoride

 D

Gentamicin

Ans. D

Explanation:

 

Gentamicin is used to treat Meniere’s disease.



Q. 6

Acoustic/Stapedial reflex decay test is positive inlesion of:          

 A

Cerebellum

 B

Midbrain

 C

Eighth nerve

 D

Auditory cortex

Q. 6

Acoustic/Stapedial reflex decay test is positive inlesion of:          

 A

Cerebellum

 B

Midbrain

 C

Eighth nerve

 D

Auditory cortex

Ans. C

Explanation:

Q. 7

All are tests for vestibular function EXCEPT:

 A

Galvanic stimulation

 B

Fistula test

 C

Acoustic reflex

 D

Cold caloric test

Q. 7

All are tests for vestibular function EXCEPT:

 A

Galvanic stimulation

 B

Fistula test

 C

Acoustic reflex

 D

Cold caloric test

Ans. C

Explanation:

 

The acoustic reflex/ Stapedius reflex/ Attenuation reflex/ Auditory reflex

  • It is an involuntary muscle contraction that occurs in the middle ear in response to high-intensity sound stimuli
  • When presented with a high-intensity sound stimulus, the stapedius and tensor tympani muscles of the ossicles contract.
  • The stapedius stiffens the ossicular chain by pulling the stapes (stirrup) of the middle ear away from the oval window of the cochlea and the tensor tympani muscle stiffens the ossicular chain by loading the eardrum when it pulls the malleus (hammer) in toward the middle ear.
  • The reflex decreases the transmission of vibrational energy to the cochlea, where it is converted into electrical impulses to be processed by the brain.
  • The acoustic reflex normally occurs only at relatively high intensities; activation for quieter sounds can indicate ear dysfunction.
  • The pathway involved in the acoustic reflex is complex and can involve the ossicular chain (malleus, incus and stapes), the cochlea (organ of hearing), the auditory nerve, brain stem, facial nerve and other components.

Q. 8

A 31 year old female patient complains of bilateral impairment of hearing for the past 5 years. On examination, tympanic membrane is normal and audiogram shows a bilateral conductive deafness. Acoustic reflexes are absent. All constitute part of treatment EXCEPT:       

 A

Hearing aid

 B

Stapectomy

 C

Sodium fluoride

 D

Gentamycin

Q. 8

A 31 year old female patient complains of bilateral impairment of hearing for the past 5 years. On examination, tympanic membrane is normal and audiogram shows a bilateral conductive deafness. Acoustic reflexes are absent. All constitute part of treatment EXCEPT:       

 A

Hearing aid

 B

Stapectomy

 C

Sodium fluoride

 D

Gentamycin

Ans. D

Explanation:

 

There is no medical treatment that cures otosclerosis.

Sodium fluoride has been tried to hasten the maturity of active focus and arrest further cochlear loss, but controversies exist and this treatment is NOT recommended generally



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