Clinical and Physiological Aspects of Hearing and Balance

Question 1

How does the middle ear act as a sound amplifier?

Answer 1

The area effect of the tympanic membrane ratio of TM to stapes footplate (17:1)
Lever action of ossicular chain

Question 2

What is the function of the eustachian tube with regards to the tympanic membrane?

Answer 2

Tympanic membrane function is optimal when the middle ear pressure is the same as the atmospheric pressure. Swallowing and yawning to open eustachian tube orifice allows equalisation of pressure

Question 3

What effect does chronic dysfunction of the eustachian tube have on the ear?

Answer 3

Chronic dysfunction of eustachian tube leads to a relative negative pressure in the middle ear. This can lead to retraction of the tympanic membrane and sometimes formation of middle ear fluid- otitis media with effusion

Question 4

What happens as a sound wave passes through the cochlea?

Answer 4

As a sound wave passes through the cochlea, it causes movement of the basilar membrane which results in motion of the cilia of the inner and outer hair cells. This motion depolarises the inner hair cells which in turn sets off afferent electrical nerve impulses

Question 5

How is middle ear function and hearing assessed clinically?

Answer 5

Clinical testing
Tuning fork tests
Audiometry
Tympanometry
Objective testing

Question 6

How is hearing assessed in children?

Answer 6

Pure tone audiometry with play conditioning techniques (3-6 years)
Visual reinforcement audiometry (6 months to 3 years)
Distraction testing (6 months to 2/3 years)
Otoacoustic emissions (0-6 months)

Question 7

How is hearing loss managed?

Answer 7

Surgery of outer and middle ear
Sound amplification
Direct stimulus of cochlear nerve cells

Question 8

What clinical conditions can affect balance?

Answer 8

Benign paroxysmal positional vertigo
Vestibular neuritis
Menier’s disease
Migraine