Lecture 13- The Middle ear

Question 1

The middle ear is a

Answer 1

• Air filled cavity.
• Between tympanic membrane and inner air
• Contains ossicles

Question 2

ossicles of the inner ear

Answer 2

•  tiny (smaller than a coin)- from lateral to medial MIS

malleus

incus

stapes

Question 3

stapes looks like a

Answer 3

stirrup

Question 4

stapes is in contact with the

Answer 4

oval window

Question 5

how do ossicles transmit information about sound waves to the inner ear

Answer 5

• vibrations from sound received on the TM
• past onto the malleus–> incus –> stapes
• Stapes looks like a stirrup
• Foot plate which communicates with the cochlear–>oval window
• Membrane will move in relation of movement to the stapes
• Transmitting vibration to waves in a fluid medium

Question 6

Ossicle movement tampered by muscles

Answer 6

tensor tympani and stapedius

Question 7

facial nerve lesion and hearing

Answer 7

• Nerve to Stapedius- facial nerve branch
  
  • Related to acoustic reflex where the stapedius contracts to dampen the vibration of the footplate of the stapes in response to very loud noises

Question 8

Otosclerosis

*

Answer 8

• One of the most common causes of acquired hearing loss in young adults
  
  • Both genetic and environmental
  • Exact cause unknown
• Ossicles fused at articulations due to abnormal bone growth particularly between base plate of stapes and oval window
  
  • Sound vibrations cannot be transmitted effectively to cochlea
• Present with gradual unilateral or bilateral conductive hearing loss

Question 9

Pharyngotympanic tube

Answer 9

equilibrates pressure of the middle ear with atmospheric pressure

Question 10

explain how the pharygotypanic tube equilibrate pressur eof the middle ear with atmospheric pressure

Answer 10

• Mucous membrane of middle ear continuously reabsorbed air in the middle air causing negative pressure
• However pharyngotympanic tube (eustachian tube) allows equilibrium of pressure within the middle ear cavity with that of the atmosphere
  
  • Also allows ventilation of and drainage if mucus from the middle ear
• If dysfunction of PT increasing build up of pressure in inner ear
  
  • E.g. causes development of cholesteatoma or otitis media with effusion

Question 11

Otitis media with effusion “glue ear” on otoscope

Answer 11

• looks retracted- loss of light reflex
• straw coloured
• evidence of fluid

Question 12

MOA of otitis media with effusion

*

Answer 12

• Not an actual infection- can predispose to infection
• Due to eustachian tube dysfunction
• Fluid and negative pressure in middle ear
  
  • Decreases mobility of TM and ossicles  affecting hearing
  • Also draws fluid from across the mucous membrane in the middle ear

Question 13

treatment of otitis media

Answer 13

• Most resolve spontaneously without Abx in 2/3 months
• If persists or impede speech and language development/ school performance
  
  • Require grommets (tympanostomy tube)
  • Act to maintain equilibration of pressure

Question 14

acute otitis media is more common in

Answer 14

infants/children

• Pharyngotympanic tube is shorter and more horizontal in infants
• easier passage for infection fromt he nasopharynx to the middle ear
• tube can block more easily, compromisisng ventilation and drainage of middle ear, icnreasing risk of middle ear ifnection and glue ear

Question 15

• Signs and symptoms of acute otitis media (middle ear infection) include

Answer 15

• Otalgia –> infants may pull or tug at ear
• Other non-specific symptoms e.g. temp
• Red +/- bulging TM and loss of normal landmarks middle ear cavity full of puss

Question 16

aetiology of acute otitis media

Answer 16

Mostly viral aetiology

Occasionally bacterial

• S. penumoniae
• H. influenza

Question 17

difference between otitis media and acute otitis media

Question 18

Complications of acute otitis media

• Tympanic membrane perforation
• Facial nerve involvement (rare)
  
  • Close relationship to middle ear cavity (via facial canal)
  • Two intrapetrous branches run through middle ear cavity *chorda typmpani and nerve to stapedius)
• Rarer but potentially life-threatening complications include
  
  • Mastoiditis
  • Intracranial complications
    
    • Meningitis
    • Sigmoid sinus thrombosis
    • Brain abscess

Question 19

mastoiditis

Answer 19

Middle ear cavity communicates via mastoid antrum with mastoid air cells

• Provides a potential route for middle ear infections to spread into the mastoid bone (mastoid air cells)
• Osteomyelitis
  
  • Red and swollen
  • Distortion of ear

Question 20

treatment for mastoiditis

Answer 20

IV antibiotics

pain relief - paracetamol (also bring temp down)

Question 21

important anatomical relations of the ear

Answer 21

Question 22

signs and symptomd of acute otitis media

Answer 22

• Otalgia –> infants may pull or tug at ear
• Other non-specific symptoms e.g. temp
• Red +/- bulging TM and loss of normal landmarks middle ear cavity full of puss
• Mostly viral aetiology
• Occasionally bacterial
  
  • S. penumoniae
  • H. influenza