The Ear

Question 1

Describe the external ear cavity. (4)

Answer 1

The pinna, external auditory meatus, ear canal and lateral surface of the tympanic membrane.

Question 2

Describe the middle ear cavity. (5)

Answer 2

The ossicles (malleus, incus and stapes), the Eustachian tube and the medial surface of the tympanic membrane.

Question 3

Describe the inner ear cavity. (3)

Answer 3

The cochlear and vestibular apparatus (vestibule and semicircular canals).

Question 4

Describe the nerves that carry general sensation to the ear. (5)

Answer 4

C2/C3 spinal
Vagus
Trigeminal (auriculotemporal nerve)
Glossopharyngeal (tympanic nerve)
(Small bit of facial).

Question 5

List some common signs and symptoms of ear pathology. (6)

Answer 5

Otalgia, discharge, hearing loss (conductive or sensorineural), tinnitus, vertigo, facial nerve palsy.

Question 6

Explain how otalgia can be a sign of non-ear pathology. (4)

Answer 6

Can be a sign of referred pain from larynx, pharynx or TMJ.

They share innervation with one of the nerves that supplies general sensory to the ear, so it refers the pain there.

Question 7

What is the purpose of the external ear? (1)

Answer 7

Collect and focus sound waves onto the tympanic membrane.

Question 8

Describe 4 pinna abnormalities.

Answer 8

Facial nerve palsy - can cause shingles f the facial nerve in Ramsay Hunt Syndrome.
Chondritis
Pinna haematoma - blunt constant to pinna leads to haematoma between avascular cartilage and vascular perichondrium.
Cauliflower deformity

Question 9

Describe the external acoustic meatus. (4)

Answer 9

Lined with keratinised stratified squamous epithelium that continues onto the lateral surface of the tympanic membrane.
Cartilaginous outer 1/3 and bony inner 2/3 (through temporal bone) in a sigmoid shape, so pull the pinna up and out to visualise tympanic membrane.

Question 10

Describe otitis external. (4)

Answer 10

Infection of the external ear meaning tympanic membrane invisible.
Often pseudomonas or staph.
Presents with pain hearing loss and discharge.
Treated with abx.

Question 11

Apart from otitis externa, describe 3 pathologies of the outer ear.

Answer 11

Was build up
Perforation of the tympanic membrane
Bulging tympanic membrane secondary to otitis media.

Question 12

Describe the middle ear cavity. (6)

Answer 12

Air filled cavity containing ossicles connected by synovial joints. Vibrations of sound on tympanic membrane > malleus > incus > stapes > oval window of the cochlear.

Question 13

Describe the stapedius muscle. (3)

Answer 13

Acts to dampen the movement of the stapes on the oval window to stop damage, called the protective acoustic reflex.
Innervated by the facial nerve, so facial nerve palsy gives hyperacusis.

Question 14

Describe the Eustachian tube. (3)

Answer 14

It is a tube that connects the middle ear to the nasopharyngeal that acts to equilibreate the pressure difference that occurs when the mucus membranes of the middle ear reabsorb air.

Question 15

Explain why babies can pass infections of the nasopharynx to the middle ear. (1)

Answer 15

The Eustachian tube of babies is much shorter and more horizontal, meaning that infection is more likely to spread.

Question 16

Describe otosclerosis. (4)

Answer 16

A disease of unknown cause that causes fusion of the ossicles that is the leading cause of gradual onset conductive hearing loss in the young.

Question 17

Describe cholesteatoma (4)

Answer 17

A sac of trapped epithelial cells that proliferate and erode through bone, often secondary to Eustachian tube dysfunction. Not malignant, painless, often smelly otorrhoea.

Question 18

Describe glue ear. (6)

Answer 18

Otitis media with effusion
A build up of fluid and negative pressure in the middle ear due to Eustachian tube dysfunction. Can resolve on its own, can need grommets. Tympanic membrane is straw coloured and retracted.

Question 19

Explain how grommets can help in glue ear. (2)

Answer 19

They act to equilibriate the pressure between the atmosphere and the middle ear. They do not drain the fluid.

Question 20

Describe acute otitis media and it’s complications. (8)

Answer 20

An acute middle ear infection commonly in children associated with strep throat (strep pneumoniae).
Presents with otalgia, infective symptoms, red tympanic membrane with possible bulging.
Complications include perforation, facial nerve involvement, mastoiditis, intracranial complications (meningitis, sigmoid sinus thrombosis, brain abscess).

Question 21

Describe mastoiditis. (3)

Answer 21

An infection of the mastoid air cells that has spread via the mastoid antrum from the middle ear.

Question 22

Describe the cochlea. (4)

Answer 22

Vibration is detected by the displacement of fluid in the tubes from the oval window into the round window. This moves stereocilia which generates an action potential in the vestibulocochlear nerve.

Question 23

Describe the vestibular apparatus. (6)

Answer 23

It includes the 3 semi-circular ducts (one in each plane), the saccule and the utricle, which are fluid filled sacs containing stereocilia which bend as the head moves position. This generates and action potential in the vestibulocochlear nerve, which helps us to perceive and maintain balance.

Question 24

Describe benign paroxysmal positional vertigo. (4)

Answer 24

Most common cause of vertigo. Comes in second long spurts resulting from moving the head because crystals have formed in the semicircular canals which dislodge on movement, but continue to form ripples after movement ceases. Hearing unaffected.

Question 25

Describe Meniere’s Disease. (3)

Answer 25

Vestibular and cochlear symptoms - hearing loss, vertigo and tinnitus in longer bursts. Ducts of inner ear are abnormally full of fluid.

Question 26

Describe labrynthitis. (2)

Answer 26

Acute onset hearing loss, tinnitus and persistent vertigo due to inner ear infection.

Question 27

Describe the pathway that explains how we hear. (7)

Answer 27

Pinna and external acoustic meatus focus and funnel sound waves to the tympanic membrane, which vibrates.
Vibration of the ossicles (stapes at the oval window) sets up movement in the cochlear fluid.
Sensed by stereocilia in the cochlear duct.
Triggers action potential in the vestibulocochlear nerve.
Primary auditory cortex of the temporal lobe makes sense of the input.

Question 28

Define conductive hearing loss. (2)

Answer 28

Pathology affecting the external or middle ear eg wax, acute otitis media. Problem with the vibrations getting through to the inner ear.

Question 29

Define sensorineural hearing loss. (2)

Answer 29

Pathology involving the inner ear or cranial nerve VIII eg presbyacusis, noise-related, acoustic neuroma.

Question 30

Name and explain some causes of sensorineural hearing loss. (4)

Answer 30

Presbyacusis - age related degeneration of the cochlea.
Noise-related - excessive vibrations cause damage to the cochlear.
Meniere’s - cochlea too full of fluid.
Acoustic neuroma - benign tumour of the vestibulocochlear nerve.

Question 31

What is the frequency of the tuning fork used for Weber’s and Rinne’s tests?

Answer 31

512Hz

Question 32

Describes Weber’s test. (5)

Answer 32

Place vibrating fork on centre of forehead. Ask which ear is loudest.
Normal - equal
Conductive - louder in affected ear
Sensorineural - louder in unaffected ear.

Question 33

Describe Rinne’s test. (5)

Answer 33

Hold vibrating fork in front of pinna. 
Hold vibrating fork against mastoid process. 
Normal - air louder than bone
Sensorineural - air louder than bone. 
Conductive - bone louder than air.

Question 34

Describe the two options if the Weber’s test is louder on the right. (2)

Answer 34

Abnormal Rinne’s (bone louder) on right - conductive hearing loss on the right
Normal Rinne’s (air louder) on right - sensorineural hearing loss on the left.