Lecture 11 - Anatomy of the ear Flashcards

1
Q

Symptoms and signs of ear disease

A
Otalgia - ear pain 
Tinnitus
Discharge
Vertigo 
Hearing loss
Facial nerve palsy
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2
Q

2 types of hearing loss

A

Conductive - external and middle ear

Sensorineural - inner ear

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3
Q

External ear structures

A

Pinna and auricle
External auditory meatus - skin lined ear canal
Lateral tympanic membrane

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4
Q

Middle ear structures

A

Air filled cavity lined with resporatory epithelium
Ossicles

  • The pharyngotympanic tube connects it to the oropharynx
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5
Q

Inner ear structures

A

Cochlear
Semicircular canals

  • Fluid filled
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6
Q

Mastoiditis

A

Mastoid process contains mastoid air cells that communicates with the middle ear cavity via the mastoid antrum.

Potential route of infection spread from the middle ear to the mastoid air cells

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7
Q

Auricle

A

Cartilaginous
Covered in skin
Includes ear lobe
Covered in ridges - direct sound waves and guard the external acoustic meatus

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8
Q

Helix

A

Outer rim of auricle

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9
Q

Tragus

A

Small flap of auricle

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10
Q

External acoustic meatus

A

Laterally: Cartilaginous
(1/3rd) Contains hair, cerumen and sebaceous glands

Medially: Bony canal formed by the tympanic plate (2/3rd)

Most medially: fibrous tympanic membrane - ear drum

Lined by skin secreting cerumen (modified sebum) for protection

Sigmoid shape

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11
Q

Ear wax

A

Discarded skin and cerumen

Self cleaning - desquamation and skin migration laterally off the TM out of the canal

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12
Q

Ossicles

A

Malleus
Stapes
Incus

Amplify and transmit vibrations to oval window of cochlear

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13
Q

Eustachian tube (pharyngotympanic)

A

Connects the middle ear to the oropharynx and equalises pressure with the atmosphere.

Ventilates and drains mucus from the middle ear.

Potential route for infection spread from the oropharynx to the middle ear

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14
Q

Eustachian tube innervation

A

Innervated by the Glosspharyngeal nerve - an feel general sensation and pain

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15
Q

Lining of the eustachian tube

A

Lined with pseudostratified columnar epithelium

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16
Q

How does the eustachian tube open

A

Usually closed but intermittently opened by pull of muscles when swallowing and yawning

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17
Q

Special sensory nerve for hearing and balance

A

CN VIII - vestibulocochlear

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18
Q

Innervation of the ear

A

Branches of:

C2/C3:
- Pinna

Vagus nerve:

  • Lateral tympanic membrane
  • External acoustic meatus
  • Concha

Trigeminal auriculotemporal nerve (Vc):

  • Lateral tympanic membrane
  • External acoustic meatus
  • Part of tragus

Glosspharyngeal nerve (tympanic nerve):

  • Mastoid air cells
  • Middle ear
  • Medial tympanic membrane

Facial nerve (nervus intermedius) :

  • Lateral TM
  • EAM
  • Concha
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19
Q

Why do you get ear pain in pharyngitis?

A

Referred pain due to glossopharyngeal nerve

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20
Q

Otalgia with normal ear examination

A

Can have a non- ontological cause e.g.

TMJ dysfunction - CN Vc
Oropharynx disease - CN IX
Larynx/pharynx disease - CN X

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21
Q

Function of the external ear

A

Collects, transmits and focuses sound waves onto the TM

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22
Q

Pinna abnormalities

A

Ramsey Hunt syndrome - Varicella Zoster with facial nerve palsy

Pinna haematoma

Perichondritis

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23
Q

Varicella zoster

A

Vesicular rash in ear - shingles

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24
Q

Pinna haematoma

A

Accumulaton of blood between the cartilage and overlying perichondrium secondary to blunt injury to pinna

  • deprives cartilage of blood supply thus necrosis can occur
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25
How to treat a pinna haematoma
Tamponade eitehr side of the ear so layers are together quickly Untreated can cause fibrosis and new assymetrical carilage formation
26
Cauliflower deformity
Untreated pinna haematoma can cause fibrosis and new assymetrical cartilage formation
27
Lining of the external acoustic meatus
Keratinisising stratified squamous epithelium continuous onto the lateral TM
28
Common abnormalities of the external acoustic meatus
Wax/foreign body blockage | Otitis externa
29
Malignant otitis externa
NOT cancer Excruciating pain Deep pain involving bone In diabetics and immunocompromised
30
Otits externa presentation
Pain Discharge Narrow EAM Associated with asthma and infection
31
Normal tympmanic membrane
Apex points medially
32
Bacterial acute otitis media
Bulging of TM towards external ear Due to high pressure Puss and inner ear infection
33
Otitis media with effusion
Retracted TM and evidence of fluid within middle ear cavity due to negative pressure Bubbles
34
Cholesteatoma
Tretraction of pars flaccida TM forms a sac Traps stratified squamous epithelium and keratin Proliferated forming a cholesteatoma Usually secondary to chronic ET dysfunction which creates negative pressure
35
Cholesteatoma presentation
``` Painless Crusting of pars flaccida Smelly otorrhea +/- hearing loss NOT malignant ```
36
Serious consequence of cholesteatoma
Ezymatic bony destruction of ossicles, mastoid, petrous bone and cochlear
37
How are the ossicles connected
Via synovial joints
38
What muscles tamper ossicle vibration
Stapedius | Tensor tympani
39
Otosclerosis
Genetic and environmental cause Idiopathic Ossicles fuse at articulations due to abnormal bone growth (particularly between the stapes and oval window) Vibrations cannot be properly transmitted to the cochlea Gradual unilateral or bilateral conductive hearing loss
40
What causes negative pressure in the middle ear?
Mucous membrane of the middle ear reabsorbs air
41
Otitis media with effusion
- glue ear - can predispose to infection - due to ET dysfunction - fluid and negative pressure in middle ear decreases mobility of TM and ossicles
42
Complications of otitis media with effusion
Affects hearing but may resolve spontaneously in most children If persists and impedes speech and language development, requires grommets to maintain equilibration of pressure
43
Acute otitis media presentation
Middle ear infection Common in infants - otalgia - temperature - red +/- bulging TM
44
Causes of acute otitis media
Viral aetiology bacterial: - strep pneumoniae - Haemophilus influenzae
45
Why is acute otitis media seen in infants most commonly?
Infants have a shorter and more horizontal eustachian tube - easier passage of infection - tube can block more easily, compromising ventilation and drainage
46
Complications of acute otitis media
- TM perforation due to pressure - Facial nerve involvement due to nerve to stapedius and chorda tympani running through the middle ear cavity - Mastoiditis Intracranial: - Meningitis - sigmoid sinus thrombosis - brain abscess
47
Cochlea
Endolymph filled tubes with specialised hair cells that generate APs when moved Converts fluid movement in the cochlear duct (due to stapes vibrations on the oval window) into action potential via CN VIII cochlear part. Perceived as sound. Movement of special sensory steriocilia into APs Scala vestibuli Scala media Scala tympani Separated by membranes
48
Vestibular apparatus
Semicircular canals Saccule Utricle (contain steriocilia) Semicircular canals convert fluid movement generated by position and rotation of head into action potentials in CN VIII by steriocilia movement perceived as position and balance
49
Inner ear disease complications
Hearing loss Tinnitus Vertigo
50
How do we hear>
1. Auricle focuses and directs sound waves into the external auditory canal. 2. The waves are transmitted to the typmanic membrane and it vibrates. 3. The ossicles vibrate in the middle ear. 4. The stapes transmits the vibrations to the oval window of the inner ear. 5. The vibrations are transmitted to the cochlear duct where movement of fluid is converted to APs by the steriociliar cells in the spiral organ of Corti 6. APS in the cochlear part of CN VIII are sent to the primary auditory cortex in the temporal lobe.
51
Presbycusis
Sensorineural loss of hearing associated with old age (natural) Bilateral and gradual
52
Benign paroxysmal positional vertigo
- Vertigo only - Short episodes (seconds) - Triggered by movement of head
53
Dix - Hallpike manoeuvre
Diagnosis benign paroxysmal positional vertigo When lowering a patients head suddenly, they get involuntary eye movements (nystagmus)
54
Epley manoeuvres
Dix- Hallpike manoeuvre but turn 90 degress when lying down. Feel dizzy
55
Meniere's disease
Vertigo, tinnutis and hearing loss usually unilateral - Nausea and vomiting - Longer lasting symptoms (30mins - 24 hours) - Recurrent episodes - hearing may deteriorate over time
56
Acute labrynthitis
History of upper resp tract infection Caused by virus affecting the inner ear - all inner ear structures affected - associated with hearing loss, tinnitus, vertigo and vomiting
57
Acute vestibular neuronitis
Usually don't get hearing loss or tinnitus Sudden onset vomiting and severe vertigo lasting days
58
Causes of conductive hearing loss
Wax/ Foreign object Acute otitis media Otitis media with effusion Otosclerosis
59
Sensorineural hearing loss causes
``` Presbyacusis Noise- related hearing loss Meniere's disease Ototoxic medications Acoustic neuroma ```
60
Weber's test
1. Place tune fork on top of head in midline 2. Vibrations send sound through bone to the cochlea equally on both sides External ambient noises mask fork input If conductive - will hear sound louder on affected side If sensorineural - Will hear sound louder on normal sound
61
Rinne's test
Sound conducted through air (external and middle ear) is louder than through bone 1. Place fork on mastoid process therefore vibrations directly to inner ear 2. Place fork in front of the external acoustic meatus (normal pathway of sound) - ve result - sound will be heard louder when at mastoid process due to conductive pathology
62
High pitched loud sounds
High amplitude and frequency sounds waves