4.2 Sound And Hearing

Question 1

Within which bone of the skull do we find the ear?

Answer 1

The petrous part of the temporal bone

Question 2

What is a pinna haematoma?

Answer 2

Secondary to trauma of the pinna
Blood accumulates between the perichondrium and cartilage and causes pressure necrosis of the cartilage
Requires immediate drainage

Question 3

What can pinna haematoma lead to if untreated?

Answer 3

Cauliflower ear

Due to necrosis of some cartilage so fibrosis and new asymmetrical cartilage development

Question 4

What is the function of the ossicles in the middle ear?

Answer 4

To amplify sound vibrations from the tympanic membrane to the cochlea via the oval window

(Stapes connects to the oval window which causes endolymph in the inner ear to vibrate)

Question 5

What are the nerve cells of the cochlear duct called?

Answer 5

Spiral organ of Corti

Question 6

What ion does endolymph have a high concentration of outside?

Answer 6

K+

Question 7

What channels open when stereocilia of INR hair cells in the ear bend?

Answer 7

K+ channels open

K+ influx generates an AP which can be transmitted down efferent spinal ganglia neurones to the cochlear nerve and to the cerebral cortex where it is interpreted

Question 8

What are some causes of conductive hearing loss?

Answer 8

Due to a blocked EAM e.g. with wax
Ruptured tympanic membrane
Otitis media (fluid accumulation)
Otosclerosis

Question 9

What are some causes of sensorineural hearing loss?

Answer 9

Hair cell destruction of death
Age related
Spinal ganglion damage e.g. acoustic neuroma

Question 10

How will the findings of Rinne and Weber’s test differ depending on if the hearing loss is conductive or sensorineural?

Answer 10

Weber’s:
px will hear sound louder in deaf ear if conductive loss (sound will lateralise to bad ear), but will hear sound louder in normal ear if sensorineural loss

Rinnes:
If px can hear best when tuning fork is in the air, there is no conductive hearing loss (air should be louder than bone)
If px can hear best when fork is on mastoid bone, bone conduction is better than air condition which indicates conductive hearing loss

Question 11

How would you carry out Rinne and Weber’s examination to test hearing?

Answer 11

512 hz tuning fork
Weber’s: Hit against table and placed in centre of forehead, ask where sound is heard loudest (sound will lateralise to bad ear if conductive loss)

Rinnes: hit against table and place on mastoid process and then place about 1cm from external auditory meatus, and ask where loudest (should be louder through air unless conductive loss)