Physiology/Clinical Aspects of Hearing and Balance

Question 1

What is the effect of otitis media with effusion

Answer 1

Affects movement of tympanic membrane

Causes conductive hearing loss

Question 2

What is the effect of otosclerosis?

Answer 2

The deposition of new bone where the footplate of stapes fits into oval window reduces movement of stapes footplate causing a conductive hearing loss

Question 3

What is the pathway of a pressure wave in the cochlea?

Answer 3

Up scala vestibuli from piston action of the stapes
Through helictotrema at apex
Down scala tympani
Pressure differential deflects the basilar membrane of scala media

Question 4

What is the hearing mechanism in the cochlea?

Answer 4

Footplate of stapes moves in and out oval window creates wave
Causes movement of basilar membrane and movement of inner and outer hair cells in organ of corti
Cilia of hair cells are deflected = ion channels open
Cations flow from endolymph to hair cells
Depolarisation occurs = sends impulse up cochlear nerve
Inner hair cells activate afferent nerves
Outer hair cells modify response of inner hair cells

Question 5

What is the tonotopic arrangement on the basilar membrane?

Answer 5

For every frequency = specific place on basilar membrane where the hair cells are most sensitive to that specific frequency

Question 6

What are the 2 types of tuning fork tests?

Answer 6

Weber = lateralisation
Rinne = compares loudness of perceive air to bone conduction (one ear at a time)

Question 7

What are the different types of audiometry?

Answer 7

Pure tone
Visual reinforcement
Play
Tympanometry

Question 8

What is pure tone audiometry?

Answer 8

Determines faintest tones a person can hear at selected pitches from low to high

Question 9

What is conductive hearing loss?

Answer 9

Bone conduction perception is greater than air conduction

Question 10

What types of audiometry tests are used for testing children?

Answer 10

Play audiometry

Visual reinforcement audiometry

Question 11

What is otoacoustic emission testing?

Answer 11

Sound stimulates cochlea
Outer hair cells vibrate
Vibration produces nearly inaudible sound that echoes back into middle ear
Picked up with small probe inserted into ear canal

Question 12

What is tympanometry?

Answer 12

Air pressure pushed into ear canal
Makes eardrum move back and forth
Test measures pressure within the middle ear and mobility of eardrum
Can detect fluid in middle ear, eardrum perforation or wax blocking ear canal

Question 13

How is hearing loss managed?

Answer 13

Surgery
Sound amplification (hearing aids)
Direct stimulus of cochlear nerve cells (cochlear implants)

Question 14

What is a bone anchored hearing aid?

Answer 14

An osseous integrated screw into the skull
Microphone + amplifier clipped onto abutment or attached via magnet
Sound conducts through skull to cochlea

Question 15

When is a bone anchored hearing aid used?

Answer 15

In people that cannot make use of conventional hearing aid

e.g. persistent otitis externa, external canal atresia

Question 16

What is a cochlear implant?

Answer 16

Very strong hearing aid

Electrode placed into cochlea

Question 17

When is a cochlear implant used?

Answer 17

In those with profound hearing loss

Question 18

What are the 2 otolith organs?

Answer 18

Utricle

Saccule

Question 19

What is the sensory epithelium in the otolith organs called?

Answer 19

Macula
horizontal in utricle
vertical in saccule

Question 20

What is embedded on the surface of the otolithic membrane?

Answer 20

Calcium carbonate crystals called otoliths

Question 21

What are ampullae?

Answer 21

Expanded areas at each end of the semicircular canals that contain the crista (sensory organ)

Question 22

What is the role of the crista?

Answer 22

Movement of the crista is the stimulus for the vestibulo-ocular reflex

Question 23

What is the role of the vestibulo-ocular reflex?

Answer 23

Stabilises gaze by moving eyes to compensate for head and body movement
Fixes image on retina for clear sight

Question 24

What is benign paroxysmal positional vertigo?

Answer 24

Loose otoconia move out of utricle into SC canals

When moving head, otoconia move in canal which stimulates the cristae and provokes vertigo and nystagmus

Question 25

What is the test for benign paroxysmal positional vertigo?

Answer 25

Dix-Hallpike maneouvre

Question 26

What is the treatment for benign paroxysmal positional vertigo?

Answer 26

Epley manouvre

Question 27

What are the initial presentations of vestibular neuritis?

Answer 27

Acute onset verigo
Nausea and vomiting
Rarely hearing loss
Nystagmus (if seen early enough)

Question 28

What are the potential causes of vestibular neuritis if hearing loss is present?

Answer 28

Mumps
Measules
Infectious mononucleosis

Question 29

What is meniere’s disease?

Answer 29

Rare condition
Classic triad (vertigo, hearing loss, tinnitus)

Question 30

What vertigo signs are present in meniere’s disease?

Answer 30

Unpredictable
Severe
Lasts 30 minutes - 24 hours
May ‘burn out’

Question 31

What are the hearing loss signs present in meniere’s disease?

Answer 31

Unilateral
Sensorineural
Initially recovers but with time usually develops low tone sensorineural hearing loss

Question 32

What is a common clinical condition that affects balance?

Answer 32

Migraine:
common cause of episodic vertigo
abortive treatments rarely work
lifestyle management important
prophylactic medication helpful