Week 7- The ear Flashcards Preview

Head and Neck > Week 7- The ear > Flashcards

Flashcards in Week 7- The ear Deck (88):
1

What are the four parts of the temporal bone?

  • Squamous 
  • Styloid Process
  • Tympanic plate 
  • Petromastoid 

2

What part of the temporal bone is the external auditory meatus made up of? What does it do?

  • Tympanic plate 
  • It provides attachment for cartilage of the external ear 

3

What does the petromastoid part of the temporal bone contain? What do the upper and lower surfaces of it form? 

  • Contains the middle and inner ear 
  • Upper surface forms floor of:
    • Middle cranial fossa
    • Posterior cranial fossa
      • This is pierced by the internal acoustic meatus
      • Transmits the facial and vestibulocochlear nerve 
  • Lower surface is irregular:
    • contains carotid canal which carries the internal carotid artery 

4

What is the external ear made up of? What is its function?

  • The pinna/auricle and external acoustic meatus
  • It collects (pinna), transmits (external acoustic meatus) and focuses sound waves onto the tympanic membrane

5

Q image thumb

A image thumb
6

Q image thumb

A image thumb
7

The pinna is made up of a cartilagenous part and a fatty tissue part. Describe the carilagenous part

  • Cartilages arranged in a number of curved ridges which tunnel air into the external acoustic meatus
    • Helix (outer rim)
    • Anti-helix (inner fold)
    • Tragus (small flap guarding EAM)
    • Anti-tragus

8

What can congenital loss of the anti-helix cause?

'Bat ears', the ears stick out 

9

What is the fatty tissue part of the pinna?

The lobule (ear lobe)

This contains no cartilage so is easier to pierce

10

What can we use to view the tympanic memrane?

An otoscope, look down external acoustic meatus with it 

11

The external acoustic meatus is made up of cartilage and bone. Describe this

  • Cartilagenous laterally
    • outer 1/3rd 
  • Bony canal medially 
    • Inner 2/3rds 

12

What is the external acoustic meatus lined by?

  • Skin
  • This secretes cerumen (modified sebum) which protects the delicate meatal skin 

13

Describe the self cleaning function of the external acoustic meatus (ear canal)

  • Cerumen secreted by skin mixes with discarded skin cells to form wax (this occurs in the cartilagenous part)
  • This along with the arrangemen of hair cells:
    • Prevents objects entering deeper in the ear canal 
    • Aids in desquamation and skin migration out of the canal 

14

When examining the ear canal which way do we have to pull the pinna to straighten the canal?

  • Up, out and back 
  • In children pull it down and back

15

How long is the external acoustic meatus?

2.5cm 

16

The tympanic membrane is fibrous. Describe its shape and explain why we can see structures in the middle ear through it?

  • It is a shallow cone with apex pointing medially 
  • It is translucent so allows structures to be viewed
    • especially malleus (this is attached to the apex of the ear drum)

17

Q image thumb

  • Handle of malleus seen because this ossicle is in direct contact with the membrane 

A image thumb
18

The pars flaccida is the loose connective tissue of the tympanic membrane above the malleus. What is another name for it?

  • The attic as it is at the top

19

Describe the pars tensa

  • Taut surface area
  • This is the most stretched part and is the bit that vibrates when air waves hit the membrane

20

When is the cone of light seen on the tympanic membrane?

  • When viewing the membrane with an otoscope 

21

When can we sometimes find it hard to view the anatomical features of the tympanic membrane?

If there is infection just behind the membrane in the middle ear cavity 

22

What is a pinna haematoma? What can cause one?

  • The cartilage in the ear is covered in a layer of perichondrium (which is where it gets its blood supply from)
  • In a pinna haematoma the perichondruim is pulled away from the cartilage and blood collects between them
  • It is caused by blunt injury to the pinna e.g. in contact sports

23

What can pinna haematomas cause?

  • The cartilage is derived of blood leading to necrosis 
  • Also the build up of blood in the space increases pressure and can cause pressure necrosis 
  • If it is untreated this leads to fibrosis and the new cartilage develops asymetrically causing cauliflower ear

24

Describe the treatment of a pinna haematoma

  • It must be promptly drained to bring the cartilage and perichondrium back together otherwise the cartilage will die
  • Measures to prevent re-accumulation and re-apposition of the two layers are also done 

25

What conditions are there relating to the external acoustic meatus?

  • Wax build up 
  • Otitis externa 
    • inflammation of the ear canal due to infection 
    • common in primary care
    • painful 

26

What can otitis externa also be known as?

  • Swimmers ear
  • This is because it is common in swimmers due to moisture in their ears making them prone to infection

27

Describe the tympanic membrane in otitis externa

  • Hard to view due to inflammation 

A image thumb
28

Describe the treatment of otitis media

  • Antibiotic drops if infected 
  • Steroid drops if inflamed but not infected 

29

What can cause perforation of the tympanic membrane?

Q image thumb

  • Cotton buds
  • Build-up of infection in the middle ear causing a hole to be blown in the membrane 
  • It is painful 

30

What can cause bulging of the tympanic membrane?

  • Otitis media (middle ear infection)
  • The ear drum appears red and bulging and the features of the membrane are less identifiable

A image thumb
31

what is the middle ear?

  • An air filled cavity (tympanic cavity) between the tympanic membrane and the inner ear 
  • It contains the ossicles 

32

What is the role of the ossicles?

  • To amplify and concentrate vibrations from the tympanic membrane to the cochlea via the oval window 
  • The articulations between the ossicles are synovial joints they relay vibrations encountered by the tympanic membrane to the inner ear 

33

What are the 3 ossicles?

  • Remember MIS:
    • Malleus
      • handle of malleus attaches to tympanic membrane
      • Its body articulates with incus
    • Incus
      • Articulates with stapes
    • Stapes
      • Stabelised by stapedius- the nerve to this is a branch of the facial nerve
      • The foot of stapes articulates with oval window of cochlea 

34

Where are the ossicles found?

  • At the top of the tympanic cavity, they run into the epitympanic cavity 

35

Why do we need ossicles to amplify the vibrations?

  • The cochlea is full of fluid and it is harder to transmit vibrations through fluid than air so they need to be amplified 

36

As the tympanic membrane vibrates so do the ossicles. By how much do they amplify the vibrations?

By around 20 times 

37

Q image thumb

  1. Epitympanic cavity 
  2. Cochlea
  3. Oval window
  4. Pharyngotympanic tube (Eustachian tube)
  5. Stapes
  6. Tympanic cavity
  7. Incus
  8. Malleus 

38

What is the role of the pharyngotympanic (eustachian) tube?

  • Equilibration of pressure within the middle ear with that of the atmosphere as it links to the nasopharynx
  • If pressure in the middle ear is too high or too low this affects the ability of the tympanic membrane to vibrate 
  • Also important in venitlation of and drainage of mucous from the middle ear 

39

What does the eustachian tube connect to anteriorly and posteriorly?

  • Anteriorly
    • the nasopharynx
  • Posteriorly 
    • mastoid air cells 

40

What does the link of the eustachian tube with the nasopharynx allow?

Infection to spread to the middle ear from the upper respiratory tract 

41

How can middle ear infection cause mastoiditis?

  • The cavity of the mastoid antrum (prolongation of the cavity of the middle ear) extends into the mastoid process by intercommunicating air cells
  • Middle ear infection can spread via this route to cause mastoiditis 

 

42

43

Is the eustachian tube open or closed?

  • Normally closed but intermittently opened by the pull of attached muscles when you swallow 

44

What is otitis media with effusion also known as? What is it?

  • Also known as glue ear 
  • Buil-up of fluid and negative pressure in the middle ear 
  • it is NOT an infection (but otitis media is)

45

What is otitis media with effusion caused by?

  • A eustachian tube deformity meaning it stays closed all the time 
  • This causes a decrease in pressure as cells in the middle ear reabsorb air--> negative pressure in the middle ear 
  • Watery or sticky fluid collects in the middle ear- this stagnant fluid predisposes to infection 
  • The tympanic membrane is sucked towards the middle ear and the membran and ossicles can't virbate properly
  • Causes problems with hearing (not painful) 

46

How can the problems with hearing caused by otitis media with effusion present?

  • Can be quite subtle e.g. drop in school performance or TV on really loud 

47

How is otitis media with effusion treated?

  • Most resolve spontaneously in 2-3months but if they persist then may require grommets 

48

What is otitis media?

An acute middle ear infection 

49

Why is otitis media more common in infants/children than adults?

  • Due to shorter and more horizontal Eustachian tube in children
    • easier passage for infection from nasopharynx to middle ear
    • Tube can block more easily, compromising ventilation and drainage of the middle ear, increasing the risk of middle ear infection 

50

What are the symptoms/signs of otitis media?

  • Otalgia (ear pain)
  • Non-specific symptoms e.g. temperature
  • Red +/- bulging tympanic membrane and loss of normal landmarks 

51

What can otalgia often present like in children?

  • If they are unable to verbalise the pain, they often pull/tug on their ear 

52

Complications of otitis media are rare as it is normally treated with antibiotics before these can arise. What possible complications could there be?

  • Tympanic membrane perforation 
  • Facial nerve involvement (as it runs through petrous bone)
  • Rarer but potentially life-threatening complications:
    • Meningitis 
    • Sigmoid sinus thrombosis 
    • Brain abscess 

53

What are important anatomical relations to the ear?

  • Internal carotid artery
  • Eustachian tube
  • Sigmoid sinus 
  • Mastoid cells 
  • Facial nerve 

54

Mastoid air cells communicate with the epitympanic cavity and so provide a potential route for middle ear infection to spread to mastoid air cells. Describe the appearance of mastoiditis

  • The ear becomes pushed forwards and the mastoid area appears red and swollen
  • Should be referred straight to hospital where it may need draining and IV antibiotics will be required

55

Describe the relationship of the facial nerve with the middle ear. 

  • Facial nerve runs through facial canal and is separated from middle ear cavity by a v thin bony partition
    • Due to proximity, infection in middle ear can cause lesion of the facial nerve 
  • Chorda tympani branch runs into middle ear cavity and can be involved in infection of middle ear. Provides taste to the anterior 2/3rd of the tongue and runs over inner surface of tympanic membrane

56

What is cholesteatoma?

  • v rare
  • Negative pressure in the middle ear due to blockage of eustachian tube causes retraction pocket as top of tympanic membrane is pulled backwards (in the attic)
  • The pocket cuases cells to get stuck and so there is proliferation and invasion of epithelial skin cells (not cancerous)
  • These cells can invade through bones of the ossicles and cochlea into the brain and cranial cavity 

57

What symptoms can cholesteatoma cause?

  • Anything from painless otorrhea to more serious neurological complications

58

What is cholesteatoma normally secondary to? When viewed with an otoscope, what is seen?

  • Chronic/recurring ear infection and blockage of Eustachian tube 
  • Viewing with an otoscope shows crusting in the attic of the tympanic membrane
  • Patient should be referred to ENT

59

What is the inner ear also known as, what is it made up of?

  • Also known as labyrinth- bony (petrous temporal bone) and membranous parts 
  • Consists of: 
    • Vestibular apparatus (to do with balance)
      • Vestibule 
        • Saccule and utricle
      • Semicircular canals and ducts
    • Cochlea and spiral organ of Corti (to do with hearing)

60

What does the membranous labyrinth of the middle ear contain?

  • Fluid called endolymph

61

What separates the bony and membranous labyrinth?

  • A fluid called perilymph 

62

What do the 3 semi-circular canals of the vestibular apparatus respond to?

  • They are in 3 different planes, perpendicular to each other
  • They respond to position and rotation of the head and maintain our balance

63

What do the utricle and saccule of the vestibular apparatus respond to?

  • Contain receptors which repsond to rotational acceleration and static pull of gravity (the canals don't respond to gravity)

64

What can problems with the vestibular apparatus lead to?

  • Meniere's Disease
  • Benign Paroxysmal Positional vertigo

Vertigo is a symptom of both of these 

65

What is Meniere's Disease? Including who it is most common in, symptoms and treatment 

  • Caused by abnormal amounts of endolymph in the labyrinth causing swelling. This causes abnormal signals to be sent to the brain and so vertigo and sickness
  • Occurs normally between 40-60
  • Normally comes in attacks:
    • Dulled hearing, tinnitus, vertigo, ear pressure, sensitvity to loud sounds 
  • Often begins in one ear 
  • Hearing loss and tinnitus 
  • Vertigo (symptom) can be treated but the condition cannot be cured 

66

What is benign paroxysmal positional vertigo?

  • Calcium carbonate crystal are normally embedded in the gel in the utricle. These are dislodged and migrate into one/more of the semi-circular canals
  • The fluid in these canals doesn't normally repsond to gravity but the crystals do causing movement of the fluid when it would normally be still 
  • This sends signals to the brain that the head is moving when it isn't; this contradicts signals from the eyes and causes vertigo 

67

What is the role of the cochlea?

  • It converts vibrations into an electrical signal (action potential) which is perceived as sound
  • It is the oran of hearing 

68

What is the cochlea made up of?

  • The cochlear duct which contains the spiral organ of Corti
  • It is a fluid filled, spiral tube 

69

What does vibration of the stapes cause?

  • Movement of the oval window causing movement in the fluid in the cochlea
  • This movement is sensed by sensory cells in the spiral organ of corti in the cochlear ducts
  • The movement of receptors here triggers action potentials in CNVIII (vestibulocochlear nerve)
  • These signals are sent to the brain and perceived as sound

70

If you suspect pathology or infection of one ear which ear should be inspected first?

The normal ear 

71

Where should blood vessels be visible on the tympanic membrane?

Round the perimeter

72

What might dense, white plaques on the tympanic membrane be due to?

Tympanosclerosis

73

How is the ear tested?

  • First examine ear from front
  • Then examiner sits next to the patient on the side of the ear that is being examined 
  • Begin with inspection and palpation of the skin adjacent to the pinna, the mastoid process and the pinna itself 
  • Then use an otoscope and speculum inspect the auditory canal
  • Complete the ear exam with 'bedside' hearing tests such as Weber and Rinne then if needed refer for formal audiometry testing 

74

What is an acoustic neuroma?

  • Rare, slow growing benign tumour arising from Schwann cells of the vestibular nerve
  • Often arises in the internal auditory meatus where it compresses nerves running through the space
  • Typical symptoms are unilateral hearing loss, tinnitus and problems with balance 

75

What causes conductive and sensorineural hearing loss?

  • Conductive hearing loss is from pathology affecting the external ear or middle ear
    • e.g. otitis externa, otitis media, otosclerosis
  • Sensorineural hearing loss is secondary to pathology affecting the inner ear or CN VIII where it enters the brainstem (including the nuclei in the brainstem) 

76

Describe the function of Webers and Rinnes tests

  • Sensorimotor vs conductive loss= Rinnes 
    • Tuning fork in front of the ear in the air 
    • Then behind th ear against the mastoid process
    • If the sound is louder on bone then conductive loss
    • If the sound is louder in air then sensorimotor 
    • (if both ears normal then louder in air)
  • Localisation= Webers
    • If the loss is conductive then sounds louder in the affected ear 
    • If the loss is sensorimotor then sounds louder in the normal ear 
    • (if both ears normal then sounds the same in both)

77

If someone has an acoustic neuroma why are they likely to experience tingling on their face?

  • At late stages the expansion of the neuroma can cause compression of structures in the cerebellopontine angle (space between cerebellum and pons) and posterior cranial fossa
    • This compresses the trigeminal nerve so causing sensory signs in the face 
  • The facial nerve is also in the internal auditory meatus so can be compressed causing facial weakness 

78

What functions are carried by the facial nerve?

  • Muscles of facial expression 
  • Stapedius muscle in middle ear 
  • Parasympathetic to lacrimal and salivary gland in the floor of the mouth 
  • Taste to anterior 2/3rds of the tongue
  • Sensory information to a small part of the external auditory meatus 

79

Which facial expressions do we ask the patient to do to test the facial nerve?

  • Smile 
  • Show teeth 
  • Raise eyebrows
  • Frown 
  • Squeeze eyes shut (doctor tries to open them)
  • Blow out cheeks and hold (doctor pushes on each cheek) 

80

Why might a patient with a facial nerve lesion complain of sensitivity to loud sounds? What is this called?

  • Hyperacousis 
  • Because nerve to stapedius may be damaged 
  • This normally innervates stapedius muscle which stabilises stapes and dampens vibrations at the oval window. 
  • If it is paralysed/weakened then there is a greater degree of vibration in response to sound so patient reports hyperacousis 

81

What are two reasons why a patient's eye might be at risk after a facial nerve lesion? How is this managed?

  • It innervates obicularis oculi so if paralysed then eye can't close
    • Less protection against foreign bodies
    • Less sweeping of secretions and so conjunctiva and cornea can dry out 
  • If lesion is before greater petrosal nerve has branched then secretomotor function of lacrimal gland is affected making the eye dry
  • Management
    • Use of an eye patch and artificial tears till facial nerve function recovers

82

How do you test the corneal reflex?

  • Whisp of cotton wool is gently touched against the edge of the cornea (not conjunctiva) while patient turns their eye to one side
  • This should immediately close both eyelids 

83

What is the sensory nerve supply to the external ear and tympanic membrane?

  • The pinna/auricle
    • Anterior to acoustic meatus:
      • Auriculotemporal nerve (CN V3)
    • Back of ear and helix/anti helix and lobe
      • Greater auricular nerve (C2/3)
  • Tympanic membrane 
    • External surface
      • Auriculotemporal nerve
      • Small bit from auricular branch of vagus nerve 
    • Internal surface 
      • Glossopharyngeal nerve 

Also a v small contribution from the facial nerve, which branches after it has exited the stylomastoid foramen- this helps explain vesicles affecting the ear seen in Ramsay Hunt syndrome

84

Why do patients with a sore throat sometimes complain of ear pain?

  • Infection can spread from the back of the throat and nasopharynx into middle ear via Eustachian tube causing otitis media 
  • Also shared sensory innervation of oropharynx and inner surface of tympanic membrane and middle ear cavity (glossopharyngeal)

85

Why might a child with recurrent ear infections benefit from an adenoidectomy?

  • Adenoids/pharyngeal tonsils are in nasopharynx, close to Eustachian tube opening (in children but not adults)
  • If they are large then can obstruct nasal passage and compress opening of eustachian tube stopping it from draining and ventilating the middle ear
  • Dysfunction of the eustachian tube secondary to this can lead to recurrent ear infections and/or development of otitis media with effusion
  • Removal of adenoids leads to restored function of eustachian tube

86

If someone presents with difficulty moving the left side of their face, a dry left eye and an altered sense of taste, where is it likely that there has been a lesion of the facial nerve?

  • Internal auditory meatus 
  • As there is motor, sensory and autonomic function loss 

87

What is the round window?

  • It is another window between the middle ear and the cochlear of the inner ear that is covered in a membrane 
  • Basically when the oval window vibrates due to movement of the stapes the round window membrane moves out to allow movement of fluid in the cochlea 

A image thumb
88