7 - Ear

Question 1

Which bone of the skull contains the parts of the ear?

Answer 1

Petrous part of temporal bone

Question 2

What comprises the external ear?

Answer 2

Pinna
External auditory meatus
Lateral surface of tympanic membrane

Question 3

What is the function of the external ear?

Answer 3

Collects, transmits and focuses soundwaves onto tympanic membrane

Question 4

What causes abnormalities of the pinna?

Answer 4

Ramsey-Hunt syndrome: Shingles of facial nerve, sensory ganglia affected
Trauma: Cauliflower ear, cartilage destroyed

Question 5

Describe the process that leads to cauliflower ear

Answer 5

Pinna haemotoma - accumulation of blood between cartilage and perichondrium, which deprives the cartilage of its blood supply - necrosis
Fibrosis and asymmetrical cartilage development - cauliflower ear

Question 6

How is a pinna haematoma treated?

Answer 6

Prompt drainage
Prevent reaccumulation of blood
Re-apposition of cartilage and perichondrium

Question 7

What needs to be done when examining tympanic membrane?

Answer 7

Pull ear up and back to straighten sigmoid shape of ear

Question 8

Describe the structure of the external acoustic meatus

Answer 8

Cartilaginous outer 1/3 - full of hair and wax to prevent objects entering deeper and gets shed epithelial cells out of ear
Inner 2/3 - bony, no hairs

Question 9

How long is the external acoustic meatus?

Answer 9

2.5 cm

Question 10

What is otitis externa?

Answer 10

Inflammation of external acoustic meatus, can’t see tympanic membrane.
Caused by eczema or swimmers ear

Question 11

What causes perforation of the tympanic membrane?

Answer 11

Pus accumulation on other side of membrane, increasing pressure
Middle ear pushing against membrane - bulging secondary to otitis media

Question 12

What is the function of the middle ear?

Answer 12

Amplify vibration from tympanic membrane to cochlea via oval window - air to fluid medium

Question 13

What comprises the middle ear?

Answer 13

Ossicles - malleus, incus and stapes
Pharyngotympanic tube
Oval window

Question 14

How are the ossicles joined?

Answer 14

Synovial joints

Question 15

What is the acoustic reflex?

Answer 15

Tensor tympani (V3) and stapedius (VII) muscles contract in response to excessive vibrations to prevent damage from loud noises

Question 16

What is hyperacousis?

Answer 16

Acoustic reflex is lost due to loud noises

Question 17

What is otosclerosis?

Answer 17

Base of stapes and oval window become fused

No fluid moving in inner ear so vibrations not transmitted -deafness

Question 18

What is the function of the pharyngotympanic tube?

Answer 18

Equilibrate pressure of middle ear to atm pressure
Mucous membrane in middle ear continuously reabsorb air, causing negative pressure
Pharyngotypanic tube, via nasopharynx, allows drainage of air and mucus from middle ear

Question 19

Why are children more likely to develop a middle ear infection?

Answer 19

Pharyngotympanic tube shorter and more horizontal in children
Easier passage for infection from nasopharynx
Tube blocks easily, compromising drainage, increasing risk of middle ear infection

Question 20

What is otitis media with effusion/glue ear?

Answer 20

Build up of transudate and negative pressure in middle ear
Due to pharyngotympanic dysfunction
Tympanic membrane retracted and is straw coloured

Question 21

How is otitis media with effusion treated?

Answer 21

Most resolve spontaneously

Grommets to ventilate middle ear

Question 22

What is acute otitis media?

Answer 22

Acute middle ear infection, causes red bulging tympanic membrane

Question 23

What are the complications of acute otitis media?

Answer 23

Tympanic membrane perforation
Facial nerve/ chorda tympani damage as runs through middle ear cavity
Mastoiditis
Intracranial: Meningitis, sigmoid sinus thrombosis, brain abscess

Question 24

What is mastoiditis?

Answer 24

Mastoid swells up, turning ear foreward

Middle ear cavity communicates with mastoid antrum with mastoid air cells, route for infection

Question 25

What is cholesteatoma?

Answer 25

Sac/cyst of skin cells growing into middle ear, behind tympanic membrane Secondary to chronic ear infections Causes painless, smelly otorrhea (ear discharge) Tympanic membrane retracted due to negative pressure caused by blockage of pharyngotympanic tube

Question 26

What is the function of the inner ear?

Answer 26

Cochlea converts vibration into electrical signals, interpreted as sound Vestibular apparatus maintains sense of balance

Question 27

Describe how cochlea enables sound to be heard

Answer 27

Movements at oval window cause movement of the fluid in the cochlea Fluid waves cause stereocilia cells to move within cochlear duct Generates action potential in vestibulocochlear (VIII)

Question 28

If the cochlear is damaged, what kind of hearing loss develops?

Answer 28

Sensorineural hearing loss

Question 29

Describe the overall process of hearing

Answer 29

1 - Auricle and external auditory canal focus/funnel sound wave to tympanic membrane, which vibrates 2 - Vibration of the ossicles sets up movement in cochlear fluid 3 - Movement sensed by stereocilia in cochlear duct 4 - Movement of stereocilia trigger action potentials in vestibulocochlear (VIII) 5 - VIII sends signals to primary auditory cortex in temporal lobe

Question 30

What constitutes the vestibular apparatus?

Answer 30

Semicircular ducts Saccule Utricle

Question 31

What is the function of the vestibular apparatus?

Answer 31

To respond to position and rotation and maintain sense of balance

Question 32

What are the symptoms of vestibular apparatus disease?

Answer 32

Vertigo Hearing loss Tinatus Nystagmus (involuntary eye movement)

Question 33

What disease affect the inner ear?

Answer 33

Meniere's disease - fluid build up in labyrinth of inner ear Benign paroxysmal positional vertigo - spinning feel when turning head, calcium carbonate moving round inner ear Labyrinthitis - inflammation of inner ear, infection

Question 34

What causes conductive hearing loss?

Answer 34

``` Pathology involving external or middle ear: Wax Otitis media Glue ear Otosclerosis ```

Question 35

What causes sensorineural hearing loss?

Answer 35

``` Pathology involving inner ear or vestibulocochlear (VIII) nerve Presbyacusis (age related hearing loss) Meniere's disease Acoustic neuroma Ototoxic meds ```