U14W1: Ear disease

Question 1

What is the function of CN7 - facial nerve?

Answer 1

GSA - skin behind the ear
SVA - taste to anterior 2/3 of tongue
GVE - parasympathetic to the lacrimal, sublingual and submandibular gland.
SVE - muscle of facial expression

Question 1

How can we differentiate between different intensities, durations and locations of sound?

Answer 1

Different patterns of action potential are generated in the sensory neurons in the spiral and vestibular ganglia.

Question 2

What is the function of CN8?

Answer 2

Special somatic afferent fibres for hearing and balance

Question 3

What is the circuitry/nuclei for the motor function of the facial nerve?

Answer 3

Corticobulbar tract
Projections from the facial motor area of the precentral gyrus to the Facial motor nucleus in the lower pons (near junction with medulla) to synapse with a LMN. **
Upper - bilateral
Lower - contralateral
LMN - not forehead sparing.

Question 4

What is the ciruitry/nuclei for the parasympathetic function of the facial nerve?

Answer 4

Originates in the superior salivatory nucleus and the lacrimal nuclei in the lower pons.
Synapse in the pterygopalatine - projections to the lacrimal gland
Synapse in the submandibular ganglion - projections to the submandibular and sublingual gland.

Question 5

What is the circuitry for the sensory element of the facial nerve? **

Answer 5

Responsible for taste from anterior 2/3 of tongue. Solitary nucleus in the brain stem, vpm nucleus of thalamus, to gustatory cortex in the insular, abd gustatory association areas in the frontal lobe.
Also porojection to amygdala and hypothalamus.

Question 6

What are the potential complications of acute otitis media?

Answer 6

1. Prolonged obstruction of e,tube and fluid accumulation in middle ear - pressure is transferred to tympanic membrane causes perforation of TM leading to discharge from ear and pain relief. In some causes pain transfers to the inner ear causing vestibular or labyrinth problems - poor balance
2. direct spread to mastoid air cells - mastoiditis or abcess.
3. Severe infection - sepsis, fevers and seuixures, intracranial invasion - meningitis, brain abscess.

Question 7

What are some risk factors for acute otitis media?

Answer 7

Tobaccos smoke - inc nasopharyngeal streptococcus pneumonia
Down syndrome - alters anatomy of e.tube
Age 6-16 months - immaute anatomy and immunity
Lack of immunizations - no memory against pathogens
Lack of breast feedings - colonisation of nasopharynx with bacteria pathogens
Day care children - overcrowding and high risk of infection spread.

Question 8

What is the key pathophysiology underpinning acute otitis media?

Answer 8

Oftens starts as URTI such as SP or RSV
Causes inflammation and edema of respiratory muscoa and up the e. tube
Obstruction of e.tube causes secretions to accumulate in the middle ear.
Negative pressure in the middle ear, pulls viruses and bacteria into it causes infection and inflammation in the middle ear
Increased pressure - otalgia and bulging TM
Cytokines - fever, fussy and poor feeding
Neutrophilic infiltrate of middle ear - cause yellow or white pus to accumulate behind TM - can discharge through perforated TM or the mastoid.

Question 9

What are the main treatments of acute otitis media?

Answer 9

Consider ENT or paediatric referall
Consider a delayed first-line antibiotic ear drops and oral - amoxicillin
Regular doses of paracetamol or ibuprofen for pain.
Advise on hygiene - avoid swimmine and fluid in ear.
Surgery if complications - tympanoplasty

Question 10

What is an audiogram?

Answer 10

Graph produce in pure tone audiometry - measures the dB and Hz of detectable sound, plot and compare to normal hearing range
Patient wears headphones in enclosed sound proof room, sound is directed to one ear at a time.
Can identify discrepancies between ears, bone conduction and air conduction,

Question 11

What is the normal hearing range in adults?

Answer 11

20dB or lower
250-8,000 Hz.

Question 12

What are the different stages of hearing loss?

Answer 12

Quietest sound heard is between
Below 20dB - norm
up to 40dB - mild
Up to 70dB - moderate
Up to 95dB - severe
Over 95dB - profound.

Question 13

What is the purpose of a CT in the diagnosis of auditory problems?

Answer 13

Used when conductive hearing loss is suspected
Used to look for structural abnormalities in the ear and surrounding structures
Identify bone or tumour abnormalities
Check for complications such as intracranial abscess or tegmen erosion.

Question 14

What clinical tests can be used to rule out neurological consequences from ear disease?

Answer 14

CT - to detect a thin tegmen.
Drain extradural abcsess - look for CSF leakage - clear fluid out of ear or MRI with gadolinium.
Risk of meningitis or intracranial abscess.

Question 15

What is the use of amoxicillin in acute otitis media?

Answer 15

Clinical: delayed antibiotic prescription, recommended ear drop +/- oral, 1st line antibiotic choice. Against H.influenza, and S.pneumonia
Chem: Beta lactam ring - mimics D-Ala-D-Ala
Pharm: competitive antagonist at Transpeptidase (PBP), covalent inhibitor with serine residue
Physio: inhibit cross linking of peptidoglycan, inhibit cell wall synthesis, causes cell lysis.

Question 16

How does an ear infection cause facial paralysis?

Answer 16

THe facial nerve and the vestibulocochlear nerve are in very close proximity as they pass through the internal acoustic meatus together
Facial nerve can be found in the middle ear
- alteration in the middle ear microenvironment, such as elevated pressure, ostetitis or acute inflammation
- infections can cause inflammatory odema and ischaemia followed by neuropraxia
-direct involvement of the nerve by bacterial or viral toxins

Question 17

What is secretory otitis media and its underlying pathophysiology?

Answer 17

Fluid in the middle ear behind the ear drum without signs or symptoms of infection
The fluid can be serous or mucinous (but not purulent as it is not infected)
Often in adults or for more than 3 months in children (3m to 3yrs)
Caused by viral URTI, allergic, recurrent otitis media, barotrauma (flying.diving), eustachian tube dysfunction.

Question 18

What is a cholesteatoma and its underlying pathophysiology?

Answer 18

Is a skin lined cysts that begins at the margin of the eardum and invades the middle ear and mastoid
Abnormal collection of squamous epithelial cells in the middle ear.
1. Squamous epithelial cells originate from the outer surface of the tympanic membrane
2. Negative pressure in the middle ear caused by e.d tube dysfunction causes a pock of the tyampic membrane to retract into the middle ear
3. The sqaoumous cells of this pocket proliferate/grow into the surrounding space (bone/tissue).
4. It can damage the ossiciles causing conductive hearing loss.

Question 19

What are some complications of cholesteatoma?

Answer 19

1. Grows aggresively wih the capacity to erode bone including ossicles (conductive hearing loss)
2. Bone erosin can also lead to bony absvess (mastoiditis), labrynithtits (causing dizziness, vertigo or deafness), facial nerve palsy, meningitis or a brain abscess
3. contains bacteria can lead to recurrent infection.

Question 20

What are the general challenges that come with hearing loss?

Answer 20

Communication - frustarion, isolation, poor speach
Employement/education - performance and opportunity
Safety concerns - Fire alarms, sirens, verbal instructions
Emotional impact - anxiety, depression, low self esteem
Relationship strain

Question 21

What are some common caused of conductive hearing loss?

Answer 21

Fluid build up in middle or outer ear from infection or inflammation
Perforated tympanic membrane
Toumour
Earwax
Congenital defect
Object blockage

Question 22

What are some common causes of sensorineural hearing loss?

Answer 22

Infection - measles, mumps, meningitis
Ototoxic drugs - NSAIDs, gentamycin
Family hsitroy - congential
Ageing
Trauma (loud noise exposure)

Question 23

What is the purpose of a hearing aid and what are the three main purposes?

Answer 23

Can amplify, focus and direct sound, beneficial in noisy and quiet environments.
Contain a microphone to receive sound and convert into a digital signal, amplifier to increase strength of signal, speak to produce the amplified sound into the ear through a tiny speaker.

Question 24

What are the key differences between a hearing aid and a cochlear implant?

Answer 24

Hearing aid - amplifies sound, suitbale to mild to profound hearing loss, no surgery
Cochlear - gives ability to hear, by bypassing damaged structures and stimulating auditory nerve directly, suitable for profound hearing loss, surgery is required

Question 25

What are some different types of hearing aids?

Answer 25

Behind the ear (Most common)
Reciever in the ear
In the ear
Completely in canal
Invisible in canal
CROs (reroutes to good ear) and BiCROS (rerouts and amplifies)
Body worn hearing aids

Question 26

What is the purpsoe of a grommet?

Answer 26

Small tubes inseted into the tympaic membrane under general anaesthetic by ENT surgeon
Allows fluid to drain out of middle ear into ear canal, ventilates the middle ear cavity and equibrilates pressure in the middle and external ear
Imporves hearing, reduce frequency and severity of infection, prevent tympanic membrane complication.
Commonly used for otitis media with effusion, chronic middle ear infection, acute otits media.

Question 27

What are the risks and complications of grommet insertion?

Answer 27

usually safe
Small risks of infection, bleeding, perforation of tympanic membrane, scarring of the ear canal.
Can extuded too early or late - requires addition grommets in 1/3 cases.

Question 28

What is a mastoidectomy?

Answer 28

Surgical removal of infected mastoid air cell connected to the middle ear space.

Question 29

What is a mastoid tympanoplasty?

Answer 29

Repair of the tympanic membrane (using a graft of patient fascie or cartilage or manufactured graf) and middle ear structures through the mastoid bone.
Can improve symptoms and treat ear infection
Recommended in chronic otitis media with perforation, cholesteatoma or complicated ear infection
80-90% show good results.

Question 30

What is a myringotomy?

Answer 30

A surgery performed on yout tympanic membrane
A tiny incision in created to allow fluid to drain from middle ear
Usually takes four weeks to reheal incision.

Question 31

What is the sue of abscess drainage in ear infection?

Answer 31

Tend to combine myringotomy/grommet insertion with simple mastoidectomy or abscess drainage via microsuction.
Area is often flushed with saline if appropriate to remove any debris/remaining bacteria from the ear.
A temporarily drain may be left to allow for continued drainage or fluid and prevent re-accumulation of pus.

Question 32

What is the surgical approach for tympanoplasty?

Answer 32

Typically done under general anaesthetic, sometimes a CT scan is request to help plan the surgery.
Can be transcanal using an endoscope - typically to repair small holes of the anterior portion of the eardrum, incision posterior to ear to receive graft material.
Can be postauricular - curved incision posterior to the auricle, gives view of entire tympanic membrane.
Both can then by underlay - graft is placed under existing ear drum, held in place by gel foam sponges which eventually dissolve, used as scaffold by remaining membrane to grow.
O overlay approach - whole existing ear drum is remove, graft secured to ear canal to replace whole TP, ear canal used graft as scaffold, also sues soluble foam secureses.

Question 33

What is the difference between conductive and sensorineural hearing loss?

Answer 33

Conductive - damage to outer/middle ear, lack of conduction of sound to cochlea
Sensorineural - loss due to defect in sensory hair cell detection within the cochlear or neural detection by primary sensory neruons located in spiral ganglion, so info not projected down cochlear nerve, damage to inner ear strcutres.

Question 34

How is human behaviour affected by neurological auditory deficits?

Answer 34

Social - difficult understanding and communicating, can become isolating, stigma, bullying
Physical - speech development, understanding of language (harder to learn to read)
Learning difficulties - social development, physical play, cognitive understanding of words.language

Question 35

How do learning difficulties or autism affect diagnosis or treatment of hearing difficulties?

Answer 35

Hearing impairement - misdiangosed as autism originally due to knock on effects on social and congivitve development. Slower to receive treatment. Share social isolation, slower speech development
Hearing problems more common in learning difficulties such as down syndrome - facial antomy alteration, eustachina tube dysfunction.
Children harder to communicate symptoms, pain, more distressed by healthcare environment.

Question 36

What is the prevalence and demographic distribution of ear infections?

Answer 36

AOM - most common in children under 2yrs old, most common reasons for children to consult in primary care
COM - in children and sults, more common in allergies, cleft palate or et tube dysfunction

Demographics - children under 5yrs (shorter and more horizontal E,tube), 5/6 kids have had at least one ear infection before they reach preschool.
More common in disadvantaged communities - less access to healthcare services

Question 37

Describe the embryology of the face and how this relates to the complex facial innervation.
Relate to the ear.

Answer 37

The face grows and develops from the pharyngeal arches in the embryonic head.
Cranial nerves innervate these arches and are ‘carried with’ the tissues as they migrate during the morphogenesis of the face.
The ear develops from the 1st and 2nd pharyngeal arch which is innervated by CN5 and CN8 respectively.

Question 38

What ear structures develop from the relevant germ layers?

Answer 38

Ectoderm - external auditory meatus and neurons inside otic capsule (via otic placode)
Neural crest (from ectoderm) - ossciles of the middle ear.
Mesoderm -otic capsule (bony labrinth around inner ear)
Endoderm - eustachian tube

Question 39

What is the function of the medulla?

Answer 39

Responsible for vital functions and reflexive actions (vomiting, swallowing, coughing and sneezing)
Some cranial nerves exit the brainstem at this level.

Question 40

What is the function of the pons?

Answer 40

Cranial nerve nuclei
Head and face sensations
Motor control of eyes, face and mouth
Hearing
Equilibrium
Autonomic functions such as saliva production

Question 41

What is the function of the midbrain?

Answer 41

Superior and inferior colliculi (visual adn auditory processing
Ventral tegmental area
Substangia Niagra - motivation and reward, major dopamine producing areas.