11. Anatomy of the Ear Flashcards
1
Q
Give examples of possible signs or symptoms of ear disease (in general)
A
Otalgia (ear pain) Discharge Hearing loss(conductive vs sensorineural) Tinnitus Vertigo Facial nerve palsy
2
Q
What is tinnitus?
A
perception of a sound when there is no actual sound
3
Q
What is vertigo?
A
sensation of spinning
4
Q
What structures are part of the external ear?
A
- Pinna
- External auditory meatus
- Skin-lined
- lateral surface of tympanic membrane
5
Q
What contributes to the middle ear and what is it lined with? what is this cavity filled with?
A
- Air filled cavity
- Ossicles
- Lined with respiratory epithelium - columnar ciliated epithelia
- PT connects it to NP
6
Q
what seprates the external and middle ear cavity?
A
tympanic membrane
7
Q
What is the connection between the middle ear and the pharynx, and which part of the pharynx?
A
Eustachian tube (Pharyngotympanic tube) connects middle ear to the nasopharynx
8
Q
what is the function of the eusatachian tube?
A
intermittently opens to nasopharynx to allow air filled cavity to equilibrate with atmospheric pressure
9
Q
What structures are part of the inner ear?
A
- Cochlea
- Semicircular canals
- Fluid filled
10
Q
Which nerves carry general sensory innervation from the ear?
A
Branches of • Cervical spinal nerves (C2/C3) • Vagus • Trigeminal (auriculotemporal n.) • Glossopharyngeal (tympanic n.) • ...and a small contribution from CN VII
11
Q
which nerve carries special sensory from ear?
A
Special sensory (“hearing and balance”) carried in CN VIII
12
Q
Why do lots of conditions have referred pain to the ear?
A
Because many nerves carry general sensation from the ear
13
Q
otalgia with normal ear examination should be suspicion of what?
A
alternative site of pathology
• Otalgia can be non-otological or otological in origin
14
Q
Give 3 examples of non-ontological causes for otalgia.
A
- TMJ dysfunction (CN Vc)
- Diseases of oropharynx (CN IX)
- Disease of larynx and pharynx including cancers
15
Q
What is the function of the glossopharyngeal nerve in sensation of the ear?
A
The medial surface of the tympanic membrane and middle ear cavity
16
Q
What is the function of the external ear?
A
Collects, transmits and focuses sound waves onto the tympanic membrane
17
Q
What are the different causes of pinna abnormalities?
A
Congenital, inflammatory, infective, traumatic
18
Q
Give examples of 3 conditions that can affect the pinna.
A
- shingles (varicells zoster)
- perichondritis
- pinna haematoma `
19
Q
What is Ramsay Hunt syndrome?
A
Shingles of the facial nerve
- facial palsy (Bell’s palsy)
- otalgia
- red ear with vesicles on the pinna and external meatus
20
Q
What is perichondritis?
A
infection of the perichondrium - connective tissue layer overlying cartilage of pinna
- injuries e.g. ear piercings, insect bites introduce infection causing inflammation
21
Q
how does the ear appear in perichondritis and how is it treated?
A
painful, red, swollen
treated with antibiotics
22
Q
Where does blood accumulate in a pinna haematoma?
A
Between cartilage and its overlying perichondrium
23
Q
What does a pinna haematoma occur secondary to ?
A
Secondary to blunt injury to the pinna
• Common in contact sports
24
Q
What is the complication of pinna haematoma?
A
- Subperichondrial haematoma pushes the perichondrium away from the cartilage
- Hence, cartilage is stripped of its blood supply leading to necrosis
- Haematoma also increases the pressure and cause pressure necrosis
25
what may result if pinna haematoma is untreated?
Untreated, fibrosis occurs, new asymmetrical cartilage development, 'cauliflower deformity'
26
How is a pinna haematoma treated?
Drainage & prevent re-accumulation/re-apposition of
| two layers - tamponade on both sides of ear to keep perichondrium against cartilage
27
What is the length of the external acoustic meatus?
2.5 cm
28
what is the external acoustic meatus lined with?
Lined with keratinising, stratified squamous epithelium continuous onto lateral surface of tympanic membrane
29
What is the external acoustic meatus made of and what is its shape?
Cartilaginous (outer 1/3) and bony (inner 2/3)
| - has a sigmoid shape
30
What specialisations are present in the external acoustic meatus and on which part are they present?
On cartilaginous part:
| - hair, sebaceous and ceruminous glands: barrier to foreign objects
31
Which glands in the ear produce wax?
Ceruminous glands
32
what specialisation are present on bony part of external acoustic meatus?
Bony part lacks glands and hairs
33
what is the shape of external acoustic meatus?
Sigmoid shape
34
What is the self-cleaning function of the external acoustic meatus and what is it called?
Desquamation (shedding) and skin migration laterally off tympanic membrane out of canal
• Epithelial migration
35
Give examples of conditions that affect the external acoustic meatus?
Otitis externa, wax and foreign bodies
36
What is otitis externa and what can it be caused by?
inflammation of external auditory canal aka "swimmer's ear"
| - usually caused by infection, although it can sometimes be due to allergy or irritation
37
What are symptoms of otitis externa?
itch, ear discharge, temporary dulled hearing and pain. Your ear may feel blocked or full.
- more commonly affects just one ear
38
How is otitis externa most commonly treated?
- Ear drops/spray, a combination of antibiotic and steroid (to reduce inflammation)
- analgesics
39
What are the risk factors for otitis externa?
```
Moisture in the ear - breeds bacteria
Humidity
Skin problems e.g. eczema
Build up of wax
Damage to skin in ear canal
```
40
What is a complication of otitis externa and what pathogen is normally responsible for it?
Malignant otitis externa
| - pseudomonas aeruginosa (gram- bacteria)
41
What is malignant otitis externa?
External ear infection that spreads to the adjacent soft tissue, cartilage and bone (osteomyelitis or erosion of the temporal bone) (not a malignancy, but still very dangerous)
42
What symptoms does malignant otitis externa cause and in which patients does it occur?
Severe ear pain and otorrhoea
| - in immunocompromised patients, including diabetes
43
What is the normal positioning of the tympanic membrane?
What is the normal positioning of the tympanic membrane?
44
What is attached to the apex of the ear drum?
Malleus, bone of the middle ear
45
How can you tell whether a tympanic membrane is left or right?
- Light cone on right for right ear and vice versa
| - malleus from the top right to middle for right ear and vice versa
46
What could cause bulging of the tympanic membrane?
Associated with bacterial acute otitis media
47
What could cause retraction of the tympanic membrane?
Fluid within the middle ear cavity (otitis media with effusion)
48
What is cholesteatoma?
Retraction of pars flaccida (TM) forms a sac/pocket
• Trapping stratified squamous epithelium and keratin (from epithelial migration)
• Proliferates forming cholesteatoma
49
What does cholesteatoma occur secondary to?
Usually secondary to chronic Eustachian Tube (ET) dysfunction
• -ve pressures pull the 'pocket' into the middle ear
• ET dysfunction means unable to equilibriate pressure in MEC so leads to increased negative pressure
50
which part of ear does cholesteatoma occur in?
develops on tympanic membrane but can extend towards middle ear cavity
51
Why is cholesteatoma serious?
Not malignant but slowly grows and expands
- Potentially more serious consequences due to enzymatic bony destruction e.g. erode ossicles, mastoid/petrous bone, cochlea
52
What are the symptoms of cholesteatoma?
Painless, often smelly otorrhoea,+/- (conductive) hearing loss
53
what is the middle ear?
Air Filled Cavity Between Tympanic Membrane and Inner Ear Containing Ossicles
54
What type of joint is between the ossicles?
Synovial joints
55
What is the function of the ossicles?
Amplify and relay vibrations from the TM to the oval window of the cochlea (inner ear)
56
What is the oval window?
The membrane that separates the middle ear from the inner ear
57
what are the 3 ossicles
malleus, incus, stapes
58
Which muscles act on the ossicles and what is their function?
Tensor tympani and stapedius
| • Contract if excessive vibration due to loud noise (protective; acoustic reflex)
59
which ossicle communicates with the oval window?
stapes
60
What is otosclerosis?
Ossicles fused at articulations due to abnormal bone growth
| • Sound vibrations cannot be transmitted effectively to cochlea
61
Where does otosclerosis most commonly occur?
Most commonly between stapes and oval window
62
What do patients with otosclerosis present with?
Gradual unilateral or bilateral conductive hearing loss
63
what cause otosclerosis?
* Both genetic and environmental causes
| * Exact cause unknown (?viral ?hereditary triggers?)
64
Why is there a negative pressure in the middle ear?
Mucous membrane of middle ear continuously reabsorbs air in middle ear causing negative pressure
65
What are 2 function of the eustachian tube?
- Allows equilibration of pressure within middle ear cavity with that of the atmosphere.
- It also allows for ventilation of and drainage of mucus from the middle ear
66
what is the early and chronic effect of dysfunction of eustachian tube?
build up of negative pressure:
early - otitis media with effusion
chronic - cholesteatoma
67
Where are mastoid air cells located and how do they communicate with the ear?
Found in the mastoid of the temporal bone, communicates with middle ear via the mastoid aditus and antrum
68
What are some conditions if the middle ear?
- otitis media with effusion (glue ear)
- acute otitis media
- complications of acute otitis media
69
What is otitis media with effusion?
Middle ear effusion without acute inflammation
| - not an infection but can predispose to infections
70
Why does OME occur and what symptom does this lead to?
Due to Eustachian tube dysfunction
• Fluid and negative pressure in middle ear
• Decreases mobility of TM and ossicles, affecting
hearing
71
how does eustachian tube dysfunction lead to otitis media with effusion?
eustachian tube unable to equilibrate pressure and so there is increased negative pressure in the middle ear cavity due to air being absorbed by mucous membranes. the negative pressure draws fluid across mucous membrane into MEC and retracts the tympanic membrane - sucked more towards MEC
72
What is the treatment for OME?
Most resolve spontaneously in 2-3 months
| - persistence can be treated with a grommet
73
How do grommets work?
Act to maintain equilibration of pressures, opening between external and middle ear
74
How does the tympanic membrane appear in an OME?
Retracted and straw coloured (due to fluid visible behind it)
- may have air bubble due to fluid in normally air filled cavity
75
What is the problem with excess wax or foreign bodies in the external acoustic meatus?
It can impact in the external auditory meatus which can block sound waves and lead to a loss of hearing
76
Describe how a cholesteatoma forms and develops
- Eustachian tube dysfunction causes chronic increased negative pressures in the middle ear
- This retracts the pars flaccida, forming a sac/pocket
- Prevents epithelial migration, hence epithelia and keratin becomes trapped and proliferates to form a cholesteatoma
- It slowly grows and expands
- Serious consequences as it may erode the bone through enzymes and affect the inner ear and even the brain
77
How does the pharyngotympanic tube open?
In swallowing/yawning, the palate muscles open it
78
What is the acoustic reflex?
contraction of the stapedius and tensor tympani muscles to dampen loud noises/excessive vibrations of the ossicles
79
How is sound relayed to the inner ear from the middle ear?
Vibrations amplified & relayed from the tympanic membrane, along the ossicles to the oval window of the cochlea
80
Why must vibrations be amplified between the middle and inner ear?
Vibrations are transmitted into a fluid medium
| If not amplified, they will not get conveyed
81
What is acute otitis media and who is it more common in?
Acute middle ear infection
| - More common in infants/ children than in adultsc
82
What are the Signs and symptoms of acute otitis media?
- Otalgia (infants may pull or tug at the ear)
- Other non-specific symptoms e.g. temperature
- Red +/- bulging TM and loss of normal landmarks
83
What type of pathogen most commonly causes acute otitis media?
Mostly viral aetiology
• Occasionally bacterial... causes
- Streptococcus pneumoniae
- Haemophilus influenzae
84
why does the TM bulge in acute otitis media?
build up of pus and inflammatory exudate increases pressure causing TM to bulge
85
Why are middle ear infections more common in infants?
Eustachian/pharynotympanic tube shorter and more horizontal in infants
• Easier passage for infection from the nasopharynx to the middle ear
• Tube can block more easily, compromising ventilation and drainage of middle ear, increasing risk of middle ear infection and "glue ear"
86
why do children with enlarged adenoids present with frequent middle ear problems?
location wher ET connects to nasopharynx is adenoids and if enlarged, may obstruct the ET
87
What are the complications of acute otitis media?
TM perforation (most common)
Facial nerve involvement (rare)
• Rarer but potentially life-threatening complications include
- Mastoiditis
- Intracranial complications: Meningitis, Sigmoid sinus thrombosis, Brain abscess
88
Why can TM perforation occur in AOM?
Build up of pressure from pus production
Patient will present with hearing problems with an intense build of pain, followed by sudden relief and discharge
Can heal itself in time
89
Why can there be facial nerve involvement in AOM?
- Close relationship to middle ear cavity (via facial canal)
| - Two intrapetrous branches run through middle ear cavity (chorda tympani, n to stapedius)
90
What is mastoiditis and how does it occur?
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)
- can lead to Osteomyelitis of the mastoid portion of the temporal bone
91
Signs of mastoiditis?
Redness, swelling and tenderness behind the ear
| Ear turned forwards
92
How is mastoiditis managed?
Quick recognition and referral to hospital
IV antibiotics
Possibly surgery - draining middle ear and/or removing part of the mastoid bone
93
What contributes to the inner ear and what are these structures filled with ?
Vestibular apparatus and cochlea: fluid filled tubes
94
What are the cochlea and vestibular apparatus responsible for?
Sound and position-sense/balance respectively
95
What do diseases of the inner ear present with?
One of or combination of
- Hearing loss (sensorineural)
- Tinnitus
- Disturbances balance and vertigo
96
how is sound perceived?
• Cochlea
– fluid movement (generated by footplate of stapes)
– Converted into action potentials (in CN VIII) --> perceived as sound
97
how is balance perceived>?
• Vestibular apparatus
– fluid movement (generated by position and rotation of head)
– Converted into action potentials (in CN VIII) --> perceived as position sense and balance
98
What is the cochlea?
Fluid-filled tube with specialised hair cells that generate action potentials when moved
99
How is movement of fluid caused in the cochlea?
movements at the oval window due to vibrations of the ossicles, set up movements of fluid in the cochlea duct
100
what happens in cochlea when the fluid vibrates?
vibrations in the cochlear fluid is sensed by stereo cilia (nerve cells) in the duct. Movement of stereo cilia trigger action potentials in the cochlear part of the CNVIII, primary auditory cortex makes sense of the input.
101
where is the cochlea housed?
in petrous part of temporal bone
102
In which part of the cochlear duct do stereocilia sense vibrations of the fluid?
Part called spiral organ of corti
103
How do we hear?
- Auricle and external auditory canal focusses and funnels sound waves towards the tympanic membrane
- Vibrations of the TM are amplified and relayed along the ossicles (stapes) towards the oval window
- This causes movement in cochlear fluid, which is sensed by stereocilia
- Movement of stereocilia generates action potentials in the cochlear part of CN VIII
- Action potentials are taken to the primary auditory cortex in the temporal lobe
- This is perceived as sound
104
What is the vestibular apparatus?
fluid filled tubes contaning specialised hair cells that generate action potentials when moved.
105
What does the vestibular apparatus consist of?
Semicircular ducts, the saccule and utricle
106
How does the vestibular apparatus perceive and maintain balance?
fluid movements due to moving position or rotation of the head, bend stereocilia which generate action potentials via CNVIII
107
What do the stereocilia in the utricle and saccule respond to?
Rotational acceleration and static pull of gravity
108
What do the stereocilia in the semicircular ducts respond to?
Rotational acceleration in 3 different planes
109
Give 5 examples of conditions that can affect the inner ear.
Presbycusis, benign paroxysmal positional vertigo, Meniere's disease, acute labrynthitis, acute vestibular neuronitis
110
What is presbycusis?
sensorineural hearing loss that occurs with aging - age related changes in cochlea
- bilateral and gradual
111
What is sensoineural hearing loss?
Hearing loss arising from conditions affecting the cochlea or vestibulocochlear nerve (inner ear)
112
How can presbycusis be managed?
Hearing aids
113
What is benign paroxysmal positional vertigo?
- only affect vestibular apparatus
– Vertigo only
– Short-lived episodes (seconds); triggered by movement of head e.g. turning over in bed, bending down
114
What causes the symptoms in BPPV?
Calcium carbonate crystals form in the tubes of the vestibular apparatus
These can dislodge and cause movement of fluid
Fluid moves stereocilia and generate action potentials - giving perception of rotation - moving despite being still
115
How is BPPV diagnosed?
Dix-Hallpike manoeuvre
| Turn head from 45 degrees right or left, to the other side, while moving from sitting to supine
116
How is BPPV treated?
Epley maneuver
117
which inner ear conditions cause only affect cochlea?
presbycusis
118
which inner ear conditions affect only vestibular apparatus?
BPPV
119
which inner ear conditions affect cochlea and vestibular apparatus?
meniere's disease
acute labrynthitis
acute vestibular neuritis
120
What is Meniere's disease and what are the symptoms?
- sudden attacks of vertigo, hearing loss and tinnitus
- may describe aural fullness, nausea and vomiting
- symptoms longer lasting (30 mins, up to 24 hrs)
- recurrent episodes, with recovery in between
- hearing may deteriorate over time
121
What are acute labrynthitis and acute vestibular neuronitis associated with and what is the difference between the?
History of upper respiratory tract infections
- AL: involvement of all inner ear structures (hearing loss, tinnitus, vertigo, vomiting)
- AVN: no hearing disturbances or tinnitus (sudden onset vomiting and severe vertigo lasting days)
122
What are the tuning fork tests?
Weber's (forehead) and Rinne's (mastoid for bone conduction and external ear for air conduction)
123
How do conductive and sensorineural hearing loss affect air and bone conduction (Rinne's tuning fork test)?
- conductive: BC is better than AC
| - sensorineural: Ac is better than BC (which is normal)
124
What are the findings of a Weber's tuning fork test in conductive and sensorineural hearing loss?
Conductive: lateralises towards ear with pathology
Sensorineural: lateralises away from ear with pathology
125
Give examples of conditions that cause conductive hearing loss.
Pathology involving external or middle ear:
| Wax, foreign body, AOM, OME, otosclerosis
126
Give examples of conditions that cause sensorineural hearing loss.
Pathology involving the inner ear structures or CNVIII:
presbycusis, meniere's, ototoxic medication, acoustic neuroma
noise related hearing loss
127
what is acoustic neuroma?
benign tumour on vestibular component of vestibulocochlear nerve
