Hearing & Balance Flashcards

1
Q

What is the function of the middle ear?

A

Amplifying and converting sound from acoustic energy in an air medium to a liquid medium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does the middle ear amplify sound? [2]

A

= A high area effect ratio from tympanic membrane to stapes footplate (17:1) - So a small vibration of the membrane results in a large vibration of the stapes footplate

= The lever action of the ossicular chain also results in a pressure on the stapes footplate 1.3x that on the malleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

List some common pathologies of the middle ear [5]

A
  • Otitis Media +/- effusion
  • Perforation (small, subtotal or total)
  • Eroded Incus. Often occurs with chronic middle ear infections or vasculitis
  • Otosclerosis. Bone deposition in ligaments preventing movement of the oval window
  • Fibrosis of ossicles to middle ear walls preventing movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How does the inner ear contribute to hearing? (in detail) [4]

A

1) Stapes pushes pressure waves into perilymph of Scala Vestibuli
2) Pressure waves travel round through the Scala Vestibuli to Scala Tympani
3) Waves stimulate the basilar membrane triggering pressure waves in the endolymph of the scala media
4) Stimulates cochlear hair cells triggering action potential in nerve fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what happens if there’s damage to the cochlear hair cells?

A

Damage to them (particularly the inner ones) will lead to hearing loss and distortion of sounds.
This is known as sensorineural hearing loss

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What types of tests do we have for assessing hearing? [4]

A
  • Clinical tests e.g. Whispered hearing test
  • Tuning Fork Tests E.g. Rinne & Weber
  • Audiometry
  • Objective Testing E.g. Otoacoustic Emissions (OAEs)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does the Rinne test work?

A

Tuning Fork placed next to ear then against the mastoid process.
Ask the patient to tell you which is louder, the Air Conduction or the Bone Conduction.
Louder through the bone indicates conductive hearing loss in that ear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How does the Weber test work?

A

Tuning fork placed on middle of forehead.

  • Normal or bilateral hearing loss would show as audible sound even between the two ears.
  • The sound would be louder in an ear with conductive hearing loss as the sound is bounced back by the obsturction.
  • It would be quieter in an ear with sensorineural hearing loss.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the types of audiometry? [4]

A

Pure Tone Audiometry:
- Determines the faintest sound someone can hear at various frequencies

Visual Reinforcement Audiometry

Tympanometry:

  • Measures ear drum mobility by pushing air into the canal to bounce it back & forth.
  • Shows if the ear is stiff, loose or perforated.

Play Audiometry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is an Otoacoustic Emission? [5]

A

The sound given off by the inner ear when the cochlea is stimulated:

Sound stimulates Cochlea

  • -> Outer hair cells vibrate
  • -> Produce nearly inaudible sound
  • -> Echoes back into middle ear
  • -> Small probe in External ear canal measures it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How are Otoacoustic Emissions used as an objective test for hearing loss? [3]

A

It detects outer ear blockage, middle ear fluid and outer hair cell damage

  • Those with hearing loss >25-30dB dont make these sounds
  • Also used in Newborn Hearing Screening Programs because you need a response from the patient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe noise induced hearing loss

A

Loud noises damage the cilia, starting at the high frequency end of the cochlea.
So a louder volume is required to hear sounds at that frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe Presbycusis?

A

Its the most common form of sensorineural hearing loss.

Occurs due to aging of the auditory system

It occurs gradually, starting at the high frequency end of the spectrum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does conductive hearing loss appear on a graph of audiometry?

A

Hearing via bone conduction would be around normal

But Hearing by air conduction would be lost across the frequencies.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do we manage hearing loss? [4]

A

Surgery

Sound amplification:

  • Hearing aids
  • Middle ear implants

Cochlear implants to directly stimulate cochlear nerve cells

In the future –> Intracochlear Modification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What part of the inner ear is covered in cilia just like the cochlea?

A

The vestibular Apparatus!

17
Q

Describe the structure of the vestibular apparatus?

A

Contains an ant., lateral and post. semi-circular canal.

Also two otolith organs, the Utricle and saccule

18
Q

What is the function of the semi-circular canals in the vestibular apparatus of the inner ear?

A

They detect angular acceleration.
When you tilt your head the canal moves and the inertia of the fluid causes it to move round the canal in the opposite direction, this movement stimulates the cilia triggering depolarisation.

19
Q

What is the vestibulo-ocular reflex?

A

It stabilizes your gaze allowing you to focus the image on your retina even as your head moves.

Basically the vestibular apparatus tell us about movement of the head and the eyes compensate by moving in the opposite direction at the same rate as the head turns, so it feels like your eyes arnt moving at all

20
Q

What systems are involved in regulating balance? [3]

A

Input:

  • Visual
  • Vestibular (rotation & gravity)
  • Proprioceptive (pressure)

Signals sent to the CNS (specifically the cerebral cortex, brainstem & Cerebellum)

Output:

  • Vestibulo-ocular reflex
  • Postural Control
21
Q

List some inner ear pathologies that can affect balance?

A
  • Benign Paroxysmal Positional Vertigo
  • Vestibular Neuritis (Commonly reactivation of a previous viral infection)
  • Meniere’s Disease
22
Q

What is meniere’s disease?

A

Excess endolymph in the ear canals results in excessive stimulation on movement of the head.
It can also effect hearing

23
Q

What non-inner ear pathologies commonly affect balance?

A

MIGRAINES

These can be paroxysmal or visually evoked.

24
Q

DDX vestibular neuritis and labyrinthitis [2]

A

Vestibular neuritis is used to define cases in which only the vestibular nerve is involved [1], hence there is no hearing impairment; Labyrinthitis is used when both the vestibular nerve and the labyrinth are involved, usually resulting in both vertigo and hearing impairment. [1]

25
Q
Otosclerosis
Inheritance pattern, gender epi
Pathology
Onset
Worsened by [3]
Other symptoms [2]
A

AD with incomplete penetrance, F:M 2:1
Vascular spongy bone replaces normal lamellar bone esp around oval window
Onset: early adult life
Worsened by: pregnancy, menstruation, menopause
Tinnitus, mild transient vertigo

26
Q

Otosclerosis
Type of hearing loss?
Sign?
Tx [4]

A

Conductive hearing loss
Schwartz’s sign - pink tinge to drum
Tx:
- Hearing aid or surgery to replace adherent stapes with implant
- Fluoride may inhibit sclerotic progression
- Microdrill and CO2 laser stapedotomy
- Cochlear implant

27
Q

Unilateral sensorineural deafness > main differential?

[13]

A

Think ACOUSTIC NEUROMA

  • Get expert ENT help
  • ANA
  • INR
  • Blood glucose
  • Cholesterol
  • ESR
  • FBC, LFT
  • Viral titres
  • Audiology
  • CXR, Mantoux
  • MRI
  • Biopsy of LN, nasopharyngeal for malignancy or TB culture
  • Imaging: galodinium MRI, CT
  • High dose steroids