Lecture 13- The external ear

Question 1

the pinna

Answer 1

cartilaginous covered with skin and fatty tissue

Question 2

how long is the external auditory meatus

Answer 2

2.5cm- ends at the lateral surface of the TM

Question 3

function of external ear

Answer 3

Collects, transmits and focuses sound waves onto the tympanic membrane causing the tympanic membrane to vibrate

Question 4

Pinna (auricle) abnormalities

Answer 4

• Congenital
• Inflammatory
• Infective
• Traumatic

Question 5

infective causes of pinna abnormalities

Answer 5

ramsey hunt syndrome

perichondritis

Question 6

• E.g. Ramsey hunt syndrome
  *

Answer 6

Unilateral face droop and red ear with vesicles

Question 7

• Perichondritis

Answer 7

• Layer which coats the cartilage and provides blood supply
• Causes by infection introduced by ear piercings/ insect bites
• Needs ABx

Question 8

traumatic cuase of pinna abnormality

Answer 8

pinna haematoma

Question 9

pinna haematoma

Answer 9

• Pinna haematoma- accumulation of blood between the cartilage and its overlying perichondrium from blunt injury
  
  • Common in contact sport
  • Subperichondrial haematoma deprive cartilage of blood supply, increase in blood build up = increased pressure= necrosis of tissue

Question 10

treatment of pinna haematoma

Answer 10

• Drainage and prevent re-accumulation/re-apposition of two layers
• Untreated fibrosis, new asymmetrical cartilage development cauliflower deformity)

Question 11

shape of the external acoustic meatus

Answer 11

sigmoid shape

Question 12

EAM lined with

Answer 12

• Lined with keratinising, stratified squamous epithelium continuous onto lateral surface of tympanic membrane

Question 13

embryology of EAM

Answer 13

from cleft of the 1st and second pharyngeal arches lined with ectoderm

Question 14

make up of the EAM

Answer 14

• Cartilaginous outer 1/3
  
  • Hair
  • Sebaceous
  • Ceruminous glands (wax glands lined cartilage part)
    
    • Barrier for foreign objects
• And bony inner 2/3 (petrous bone)

Question 15

special function of EAM

Answer 15

self cleaning

Question 16

how is the eam self cleaning

Answer 16

• Epithelial migration
• Surface of the skin moves laterally from the tympanic membrane towards the ear canal

Question 17

nromal typanic membrane features when using otoscope

Answer 17

• Corn of light (light reflex)–> how light reflects off tympanic membrane off the otoscope
• Large extent of tympanic membrane = pars tensa and par flaccida
• Can see attachment of the manubrium of the malleus

Question 18

Common condition involving external acoustic meatus

Answer 18

• wax/ foreign body
• otitis externa

Question 19

Otitis externa

Answer 19

Inflammation of the external ear esp EAM

• Known as swimmer ear

Question 20

presentation of otitis externa

Answer 20

• Presents with ear pain and itchiness
• Discharge

Question 21

• Rare complication of otitis externa=

Answer 21

• malignant otitis externa
  
  • Rare and very serious–> potential life threatening esp in immunocompromised e.g. diabetics

Question 22

Tympanic membrane common abnormalities

• Disease can affect the tympanic membrane itself
  *

Answer 22

• E.g. tympanosclerosis
  
  • Scarring other tympanic membrane

Question 23

Tympanic membrane common abnormalities

Can also be affected by disease happening in the middle ear e.g.

Answer 23

acute otitis media

Question 24

acute otitis media

Answer 24

• Building secondary to bacterial acute otitis media
• Infections usually viral

Question 25

• Acute otitis media with effusion (glue ear)

Answer 25

• Underlying problem is not infection
• Causes the tympanic membrane to become retracted –> sucked into the middle ear cavity
• Increasing negative air pressure
  
  • dysfucntion of the eustachian tube –> meaning liquid is not replaced when the mucus membrane absorbed air–> equilibrium lost–> negative air pressure
  • reduced TM movement- reduced ossicle meovemnt -> decreased hearing
• May see presence of fluid within middle ear via air bubbles

Question 26

why does acute otitis media predisopose to acute ear infections

Answer 26

• by nature of shorter and more horizontal ET
• stagnant liquid

Question 27

• another TM dysfunction- Cholesteatoma

Answer 27

• Cholesteatoma
  
  • Rare- should not be missed
  • Not a tumour or related to cholesterol
  • If chronically increased negative ear pressure in the middle ear – the pars flaccida will start to retract forms a sac/pocket
  • Trapping stratified squamous epithelium and keratin  collecting in the retraction pocket
  • Proliferates forming cholesteatoma

Question 29

cholesteatoma usually secondary to

Answer 29

secondary to chronic eustachian tube (ET) dysfunction

Question 30

• Symptoms of cholesteatoma:

Answer 30

painless, often smelly otorrhea (ear discharge) +/- hearing loss

Question 31

cholesteatoma is potentially serious… why

Answer 31

• not malignant but slowly grows and expands
  
  • Can erode ossicles, mastoid/petrous bone, cochlea via enzymatic action

Question 32

outline how a cholesteotoma is formed

Answer 32

1. eardrum is sucked inwards due to negative pressure caused by blockage of ET
2. early cholesteatoma cyst forms in the small pocked - skin cells collect
3. cholesteatoma grows- at first it is more liekly frow into (erode) and destroy structures in the middle iear
4. in time may grow and erose into and damage structures in the inner ear or even erode into the bone fo the enarby skull and into the brain