The Ear

Question 1

Which bone is the ear situated around and what are its 4 parts?

Answer 1

The temporal bone houses many of the structures of the ear as well as constituting a large proportion of the lateral side of the skull. It is split into 4 parts: squamous, petromastoid, tympanic plate and styloid process.

Question 2

What parts of the temporal bone are the middle and inner ear in? Which nerves pass through here?

Answer 2

The petromastoid part contains the middle and inner ear. It is pierced by the internal acoustic meatus transmitting the facial and vestibulocochlear cranial nerves.

Question 3

What is the mastoid process?

Answer 3

The mastoid process is a large landmark to which several muscles are attached. The mastoid antrum communicates into this process by mastoid air cells. Middle ear infections can spread by this route to cause mastoiditis.

Question 4

What kind of symptoms can ear problems present with?

Answer 4

Symptoms of Diseases involving the ear: pain, discharge, hearing loss, tinnitus, vertigo and facial palsy.

Question 5

What makes up the external ear?

Answer 5

The External Ear containing the pinna (auricle), external auditory meatus and lateral surfaces of the tympanic membrane.

Question 6

Describe the pinna?

Answer 6

The pinna is made of cartilage, skin and fatty tissue, it’s function is to collect transmit and focus sound waves onto the tympanic membrane. The outer elastic cartilages are arranged in curved ridges the outer being the helix, the anti-helix, the tragus a small flap guarding the external acoustic meatus and an anti-tragus opposite it covering the concha, (ear lobe is manly fat and is called the lobule).

Question 7

What is Ramsay hunt syndrome?

Answer 7

Ramsay hunt syndrome – shingles of the facial nerve causing drooping of one side of the face and vesicles in the ipsilateral ear.

Question 8

What is a pinna haematoma?

Answer 8

A pinna haematoma occurs secondary to blunt injury and is common in contact sports, causing an accumulation of blood between cartilages and perichondrium. This deprives the cartilage of its blood supply and causes pressure necrosis of the tissue. Treatment includes: prompt drainage, measure to prevent re-accumulation and re-apposition of the two layers are necessary. If left untreated it causes fibrosis and new asymmetrical cartilage development also known as cauliflower ear (complication not a diagnosis).

Question 9

What is the external acoustic meatus?

Answer 9

The external acoustic meatus is the ear canal.
This is a skin‐lined cul‐de‐sac. Sigmoid shape: need to pull ear up and back to straighten when examining. A cartilaginous (outer 1/3) and bony part (inner 2/3). Self‐cleaning function, to keep it clear. Arrangement of hairs and production of wax (cartilaginous part). Prevent objects entering deeper into ear canal. Also, aid in desquamation and skin migration out of canal

Question 10

Why might there be excess wax?

Answer 10

Otitis Externa infection and inflammation of the ear canal – known as swimmer’s ear

Question 11

Describe the structure you might see on a tympanic membrane with an otoscope?

Answer 11

In the middle the handle of the malleus should be visible. To the left of this is the parsa tensa which is the tauntest part of the tympanic membrane. Above the malleus is the pars flaccida or the attic which is the least taunt part of the membrane. A cone of light from the otoscope being used can also be seen and this poitn down towards the feet.

Question 12

What makes up the middle ear?

Answer 12

The Middle Ear containing the Ossicles and air filled cavity. The Ossicles include the malleus, incus and the stapes. Malleus is in contact with the tympanic membrane and incus which itself is in contact with the stapes. These articulations are synovial. They function to amplify vibrations from the tympanic membrane to the cochlea via the oval window.

Question 13

What is the stapedius muscle?

Answer 13

The stapedius muscle is innervated by a branch of the facial nerve and dampens the stapes when we know a loud noise is coming.

Question 14

Where in the middle ear are the Ossicles located?

Answer 14

Right at the top in the epitympanic cavity is where the Ossicles are.

Question 15

What is the function of the Eustachian tube?

Answer 15

The middle ear is connected to the nasopharynx by the eustachian tube or pharyngotympanic tube which equilibrates pressure within the middle ear with the atmosphere and is also important in ventilation of and drainage of mucus from the middle ear. It is normally closed but opens when you swallow by the pull of the palate muscles.

Question 16

What is otitis media with effusion?

Answer 16

Otitis media with effusion (glue ear) – Not an actual infection just a build-up of fluid and negative pressure in middle ear – Due to Eustachian tube dysfunction and cells in middle air absorbing air. Can predispose to infection. Decreases mobility of TM and Ossicles affecting hearing – Most resolve spontaneously in 2‐3 months but some may persist requiring grommets (small ventilator tube through the tympanic membrane.

Question 17

What is otitis media?

Answer 17

Acute middle ear infection that is more common in infants and children than in adults. Otalgia (infants may pull or tug at the ear) and other non‐specific symptoms e.g. temperature, red +/‐ bulging TM and loss of normal landmarks. It is more common in children because the Eustachian tube is more horizontal allowing easier passage of infection from the nasopharynx and is easier to block due to its size.

Question 18

What complciations are there of otitis media?

Answer 18

Complications of otitis media
Tympanic membrane perforation, facial nerve involvement, rarer but potentially life‐threatening complications include: Mastoiditis, Intracranial complications, Meningitis, Sigmoid sinus thrombosis and brain abscess.

Question 19

What is mastoiditis?

Answer 19

Mastoid air cells communicate with middle ear cavity as they are involved in helping to equilibrate middle ear pressures. Provides a potential route for middle ear infections to spread into the mastoid bone (mastoid air cells). Behind the ear will be swollen and the affected ear will be pushed forward.

Question 20

Which nerve is closely associated with the ear?

Answer 20

Facial nerve, in particular chorda tympani branch, runs through middle ear cavity. Facial nerve may be involved in pathology involving the middle ear. Chorda tympani branch runs over the tympanic membrane and provides taste.

Question 21

What is cholesteatoma?

Answer 21

Rare, but should not be missed. Painless otorrhea to more serious neurological complications. Usually secondary to chronic/recurring ear infections and blockage of ET – Creates a sucking, negative pressure, drawing eardrum inwards – Can lead to small pocket forming. Skin cells get trapped, collect and continue to grow in this small pocket within middle ear. Not malignant but slowly grows and expands, eroding into structures e.g. Ossicles, mastoid bone and cochlea.

Question 22

What makes up the inner ear?

Answer 22

The Inner Ear also known as the labyrinth containing the vestibular apparatus and cochlea – a series of channels hollowed out of the petrous temporal bone. The cochlea converts sound vibration into an electrical signal (action potential) which is perceived as sound. The vestibular apparatus is involved in maintaining our sense of position and balance.

Question 23

What is the function of the cochlea?

Answer 23

The cochlea is our organ of hearing. It is fluid filled tube. Movements at the oval window set up movements of the fluid in the cochlea. Waves of fluid cause movement of special sensory cells within the cochlear duct which fire action potentials.

Question 24

What is sensorineural hearing loss?

Answer 24

Sensorineural hearing loss i.e. the problem is with the facial nerve or the inner ear.

Question 25

How do we hear sounds after they’ve reached the tympanic membrane?

Answer 25

Vibration of the Ossicles (stapes at the oval window) sets up vibrations/movement in cochlear fluid. This is sensed by nerve cells in the cochlear duct (part called the spiral organ of Corti). This movement of these receptors in organ of Corti trigger action potentials in CN VIII and then are interpreted in the Brain.

Question 26

What is the vestibular apparatus?

Answer 26

Vestibular apparatus includes three semi-circular canals, the saccule and utricle: these are a fluid filled series of channels and sacs that respond to position and rotation and maintain our balance.

Question 27

What is meniere’s disease and benign paroxysmal positional vertigo?

Answer 27

Meniere’s Disease
Feelings of the world spinning (vertigo) and tinnitus. Genetic and environmentally linked

Benign Paroxysmal Positional Vertigo
Repeated brief periods of vertigo and feelings of spinning when moving head.

Question 28

What is the only normal sensory contribution the facial nerve has and why is this useful to us as clinicians?

Answer 28

Facial nerve has a small contribution to the external ear hence why in ramsay hunt syndrome there are vesicles present in the ear.

Question 29

Describe the path of the facial nerve from pons to its terminal branches

Answer 29

Enters through the internal acoustic meatus into the petrous bone passing very close to the inner ear cavity. Before entering close to the middle ear there is the geniculate ganglion and then the greater petrosal nerve branches off to the lacrimal glands and nasal/oral mucosal glands. In the middle ear the branch to stapedius is given off. Before leaving through the stylomastoid foramen the chorda tympani branch carrying the parasympathetic to submadibular and sub lingual branches off. After passing through the stylomastoid foramen the facial nerve passes through the parotid gland and then branches into its 5 terminal branches

Question 30

Describe Rinne’s and Weber’s tests and what their findings would be in sensorineural and conductive hearing loss.

Answer 30

Weber’s Test
Hold tuning fork in middle of forehead. If localisation to the unaffected ear then sensorineural problem with affected ear and if localisation to the affected ear then there is coductive problem with the affected ear.

Rinne’s Test
Put tuning fork on mastoid process then adjacent to ear canal and see which is louder.
Normally air conduction should be better than bone conduction. In conductive hearing loss bone will be better than air and in sensineural air will still be better than conductive.

Question 31

What is the geniculate ganglion?

Answer 31

Also the geniculate ganglion is simple the cell bodies of the sensory neurones to the tongue.

Question 32

Describe sensory innervation to the External Ear

Answer 32

Upper 2/3 of pinna = auriculotemporal nerve (from mandibular nerve)
Concha of auricle = auricular branch of the vagus
Lower 1/3 of pinna and posterior aspect = greater auricular nerve (from cervical plexus C2)
Inferior and posterior walls of ear canal = auricular branch of the vagus
Anterior and superior walls of ear canal = auriculotemporal nerve (from mandibular nerve)

These last two continue onto the tympanic membrane