Inner Ear Pathology And Physiology

Question 1

What is the physiology of hearing in the outer and middle ear?

Answer 1

Sound enters the ear caught by the pinna, goes through the auditory canal and hits the tympanic membrane. This vibrates and sound pressure is transmitted through the ossicles, last one being the scapes.
The scapes vibrates against the membrane of ova window and transmits sound into the inner ear.

Question 2

What does the middle ear do?

Answer 2

Transforms acoustic energy from the medium of air to fluid

Question 3

What does the middle ear act as?

Answer 3

A sound amplifier

Question 4

How does the middle ear act as a sound amplifier?

Answer 4

The area effect of the tympanic membrane- ration of TM to stapes footplate is 17:1
Lever action of ossicular chain- ratio of pressure on tapes to footplate to pressure on malleus is 1.3:1

Question 5

What does otitis media cause?

Answer 5

Affects the movement of tympanic membrane. Causes conductive hearing loss

Question 6

How does small perforation affect hearing?

Answer 6

Variable effect.
Main indication for repair is recurrent infection

Question 7

How can subtotal perforation effect hearing?

Answer 7

If sensorineural function is maintained, the maximum hearing loss is in order of 60dB.
Even if whole drum is gone, some sound will go through hitting the ossicles and ova window

Question 8

What is otosclerosis

Answer 8

Deposition of new bone where footplate of scapes fits into oval window

Question 9

How does otosclerosis effect hearing?

Answer 9

Reduces movement of stapes footplate causing a conductive hearing loss

Question 10

Describe the structure of the cochlea

Answer 10

A pressure wave flows up fron the vestibule from the piston of the stapes, through the helictotrema at the apex and down the scala tympani. The pressure differential deflects the basilar membrane of the scala media

Question 11

What is the hearing mechanism of the cochlea?

Answer 11

Footplate of the stapes moves in and out of the oval window creating a traveling wave in the scala vestibule and scala tympani of the cochlea
This causes the movement of the basilar membrane and movement of the inner and outer hair cells in the organ of corti in relation to the tectorial membrane
The iliac of the hair cells are deflected and ion channel opens
Cations flow from the endolymoh into the hair cells
Depolorisation takes place and an impulse is sent up the cochlear nerve
Inner hair cells activate the afferent nerves
Outer hair cells modify the response of the inner hair cells

Question 12

What is tonotopic arrangement?

Answer 12

For every frequency there is a specific place on the basilar membrane where the hair cells are maximally sensitive to that frequency

Question 13

Where does the tonotopic arrangement continue to?

Answer 13

Through the auditory pathway up to the acoustic area of the temporal lobe

Question 14

What can be used to assess hearing?

Answer 14

Clinical testing
Tuning fork test
Audiometry
Objective testing

Question 15

What are the two different tuning fork tests?

Answer 15

Weber
Rinne

Question 16

What is Webers test?

Answer 16

Compare the two ears
Fork in middle of forehead and sound radiates to both ears.
If equal hearing on both side= sound in middle
If sound loss in one ear - in conductive, sound work be louder in affected ear
- in senseroneural hearing loss, sound louder in unaffected ear

Question 17

What is conductive hearing loss?

Answer 17

Something blocking the sound getting into the inner ear

Question 18

What is sensory neural hearing loss?

Answer 18

Issue with cochlea or cochlear nerve or both

Question 19

What is rinne test?

Answer 19

A test that compares loudness of perceived air conduction to bone conduction in one ear at a time

Question 20

In Rinnes test, what would be seen in normal hearing function?

Answer 20

Sound louder at front of ear than back

Question 21

In rinnes test, what would be heard in conductive hearing loss?

Answer 21

Louder on the bine at back than in front of ear

Question 22

What are the different types of audiometry?

Answer 22

Pure tone audiometry
Visual reinforcement audiometry
Play audiometry
Tympanometry

Question 23

What is different about tympanometry?

Answer 23

Don’t need a response from an individual

Question 24

Wha can you measure for hearing?

Answer 24

Frequency and volume

Question 25

What is pure tone audiometry?

Answer 25

Pure-tone air conduction hearing test determines the faintest tones a person can hear at selected pitches, from low to high. During this test, earphones are worn so that information can be obtained for search ear

Question 26

What is the air-bone gap?

Answer 26

Bone conduction perception is greater than air conduction perception

Question 27

What are OAEs?

Answer 27

Otoacoustic emissions are sounds given off by the inner ear when the cochlea is stimulated by a sound. When sound stimulates the cochlea, the outer hair cells vibrate. The vibration produces a nearly inaudible sound that echoes back into the middle ear. The sound can be measured with a small probe inserted into the ear canal. People with normal hearing produce emissions. Those with hearing loss greater than 25-30 dB, do not produce these very soft sounds. The OAE test is often part of a newborn hearing screening programme.

Question 28

What is tympanometry?

Answer 28

Assists in the detection of fluid in the middle ear, perforation of the eardrum, or wax blocking the ear canal. Tympanometry pushes air pressure into the ear canal, making the eardrum move back and forth. The test measures the pressure within the middle ear and the mobility of the eardrum. Graphs are created, called tympanograms.

Question 29

What can tympanometry reveal?

Answer 29

Stiff eardrum Hole in the eardrum Eardrum that moves too much

Question 30

What is the management of hearing loss?

Answer 30

Surgery Sound amplification Direct stimulus of cochlear nerve cells

Question 31

What is a bone anchored hearing aid?

Answer 31

Osseous integrated screw into the skull Microphone and amplifier clip onto an abutment or attached by magnet Sound conducts through skull to cochlea

Question 32

What sensorineural threshold does BAHA require?

Answer 32

5dB or better

Question 33

Who uses BAHA?

Answer 33

Used by those whose anatomy makes use of conventional aid difficult e.g. persistent otitis externa, external canal atresia

Question 34

What is a cochlear implant?

Answer 34

A very strong hearing aid Electrode placed inside cochlea

Question 35

Who uses a cochlear implant?

Answer 35

Those were profound hearing loss

Question 36

What is the balance part of the inner ear?

Answer 36

The vestibule

Question 37

What is the vestibule made up of?

Answer 37

2 otilist organs -uricle -saccule 3 semicircular canals -connect to uricle Blind ending part -endolymphatic sac

Question 38

What is the sensory epithelium in cochlea?

Answer 38

Organ of corti

Question 39

What is the sensory epithelium in otolith organs?

Answer 39

Macula

Question 40

What are the ampullae of semi-circular canals?

Answer 40

Expanded areas at each end of the semicircular canals. They contain the sensory organ- the crista

Question 41

What does the movement of crista cause?

Answer 41

Stimulus for the vestibulo-ocular reflex

Question 42

What does the vestibulo-ocular reflex cause?

Answer 42

Stabilises gaze by moving eyes in order to compensate for head and body movement, this fixes images on retina for clear sight

Question 43

What would a disorder in VOR cause?

Answer 43

Dizziness and vestibular problems

Question 44

What 3 main systems regulate balance?

Answer 44

Inner ear Vision Feet, hips, knees and ankles

Question 45

What’s does the inner ear help with in balance?

Answer 45

Rotation and gravity

Question 46

What does feet, hips, knees and angles help with in balance?

Answer 46

Pressure and Proprioception

Question 47

What happens if one balance system stop working?

Answer 47

It is manageable

Question 48

What happen if more than 1 balance system stops working?

Answer 48

There is a problem

Question 49

What are clinical conditions of inner ear that affect balance?

Answer 49

Benign paroxysmal postional vertigo Vestibular neuritis Ménière’s disease

Question 50

What happens in benign paroxysmal postional vertigo?

Answer 50

Loose otoconia move out of the uricle, into semicircular canals, most commonly the posterior When moving te head, the otoconia move into the canal, stimulate the cristae and provoke vertigo and nystagmus

Question 51

What is the test for BPPV?

Answer 51

Dix - hallpike maneouvre

Question 52

What is the treatment for BPPV?

Answer 52

Epley maneouvre

Question 53

What is the initial clinical presentation of vestibular neuritis?

Answer 53

Acute onset of vertigo - nausea and vomiting Rarely hearing loss nystagmus present if seen early enough

Question 54

What does the hitological evidence of vestibular neuritis show?

Answer 54

Viral damage of vestibular nerve rather than sensory cell labyrinth

Question 55

What may be the cause of hearing loss in vestibular neuritis?

Answer 55

Mumps, measles or infectious mononucleosis may be responsible

Question 56

What is the classic triad of Ménière’s disease?

Answer 56

Vertigo Hearing loss- unilateral Tinnitus

Question 57

What is the pathophysiology of Ménière’s disease?

Answer 57

Endolymohatic hydrops - unknown cause or effect - endolymph produced by stria vascularis Hydrops drug to malabsorption of endolymph in endolymphatic duct and sac

Question 58

what is the vertigo like in Ménière’s disease?

Answer 58

Unpredictable Severe Last 30mins - 24 hours May burn out

Question 59

What is hearing loss like in Ménière’s disease?

Answer 59

Unilaterlat at first Sensorineural in nature Initially removes With time usually develop low tone sensorineural hearing loss

Question 60

What is a common clinical condition affecting balance?

Answer 60

Migraine

Question 61

What do migraines cause?

Answer 61

Episodic vertigo

Question 62

How are migraines managed ?

Answer 62

Lifestyle management and propohylacic medication