(PM3A) ENT - Ear Flashcards
What is the outer ear?
Filled with air
Composed of auricle (pinna) + auditory canal
What is the middle ear?
Air-filled
Comprises tympanic membrane (ear drum) + auditory ossicles
What are the auditory ossicles?
Chain of bones
(1) Malleus - hammer
(2) Incus - anvil
(3) Stapes - stirrup
What is the tympanic membrane?
Ear drum
What is another name for the ear drum?
Tympanic membrane
What is the Eustachian tube?
Part of middle ear
Goes into respiratory system via nasopharynx
What is the inner ear?
Labyrinth
Fluid-filled
Consists of vestibular system + cochlea
What is the vestibular system?
Part of inner ear
3 semicircular canals + the vestibule
What is the cochlea?
Spiral-shaped series of 3 tubular canals
Contains organ of Corti (sound)
Where is the organ of Corti?
Inner ear (labyrinth)
Cochlea
What is the organ of Corti?
Found in cochlea in labyrinth (inner ear)
Organ of sound
What nerves are present in the inner ear?
(1) Vestibular nerve
(2) Cochlea nerve
What is the function of the outer ear?
To direct sound waves into auditory canal
What is the function of the middle ear?
(1) Amplified by tympanic membrane (ear drum)
2) Sound waves must be converted into pressure waves in fluid in inner ear (cochlea
What is the function of the inner ear (labyrinth)?
Cochlea - controls hearing
Vestibular system - controls balance
Both function by mechanical -> electrical signal transduction
What is the cochlea?
Part of the inner ear responsible for our ability to hear
Snail-shaped
Series of 3 ducts
- (1) Scala vestibuli - filled with perilymph
- (2) Scala tympani - filled with perilymph
- (3) Scala media - filled with endolymph + organ of corti
What are the sites of auditory transduction?
Organ of Corti (sound)
Inner + outer hair cells
What is the role of the inner hair cells in the organ of Corti?
Signalling to the brain via the cochlea nerve
What is the role of the outer hair cells in the organ of Corti?
Act as amplifiers
How do the hair cells of the organ of Corti transduce sound?
Bodies of the hair cells in contact with auditory (cochlea) nerve fibres
Cilia of the hair cells in contact with tectorial membrane
How do we hear?
(1) Vibration of basilar membrane activates inner + outer hair cells (sensory receptors) - caused by bending of cilia in contact with tectorial membrane
(2) Inner hair cells are depolarised
(3) Glutamate (excitatory neurotransmitter) released to activate afferent cochlear auditory nerves
Opposing this, when inner hair cells are hyperpolarised, the afferent cochlear auditory nerves are inhibited
How do we detect different frequencies of sound?
Basilar membrane in inner ear varies in width and stiffness along its length
What are stereocilia?
Cilia of inner hair cells
Largest is known as the kinocilium
What fluid do the stereocilia bathe in?
Endolymph
What fluid do the bodies of the hair cells bathe in?
Perilymph
Describe the properties of endolymph.
High potassium
Describe the properties of perilymph.
Low potassium
What is the potential difference of endolymph?
80mV
What is the potential difference of perilymph?
0mV
How do hair cells signal?
(1) Vibration of basilar membrane causes bending of stereocilia
(2) Bending of stereocilia towards kinocilium (largest stereocilia) mechanically opens ion channels
(3) Causes influx of potassium
(4) This causes depolarisation which leads to influx of calcium ions via voltage-gated calcium channels
(5) Leads to glutamate (excitatory neurotransmitter) release
(6) Activation of afferent cochlea nerve fibres
What happens if stereocilia are bent away from the kinocilium?
(1) Closing of ion channels
(2) Leads to hair cell hyper polarisation
(3) Inhibition of afferent nerve fibres
How do the afferent cochlea nerve fibres signal to the brain?
(1) Synapses -> Brainstem
(2) Brainstem ->
- Different brain region, e.g. cortex for cochlea
- Different brain region, e.g. cerebellum and cranial nerves for vestibular system
What is the purpose of the vestibular system?
Maintenance of equilibrium/ balance
How does the vestibular system maintain equilibrium/ balance?
Detection of angular/ linear accelerations of the head
How is angular acceleration detected?
Vestibular system
Detected by semicircular canals
(1) Anterior (superior) in sagittal plane
(2) Posterior (inferior) in frontal plane
(3) Lateral (horizontal) in vertical axis
How is linear acceleration or gravity detected?
Detected by otolithic organs
(1) Utricle - horizontal
(2) Saccule - vertical
Where are the hair cells found in the semicircular canals?
In the ampullae
What is the purpose of hair cells in the vestibular system?
Detection of movement of fluid to detect angular/ linear acceleration
What happens following movement of the stereocilia in the vestibular system?
Downstream signalling to the brain of position/ movement
What is otitis externa?
Outer ear inflammation
What is otitis media?
Middle ear inflammation
What is labrynthitis?
Inner ear inflammation
What is vestibular neuronitis?
Inner ear inflammation
Is ear wax build up considered a condition?
No
What can ear wax build up cause?
Ear ache
Hearing loss
Difficulty upon examination
How can an ear wax build up be treated?
Cerumenolytic products
3-5 days of ear drops to soften
Olive/ almond oil TDS/QDS
Can use sodium bicarbonate/ chloride ear drops
Avoid tool insertion into ear
How can ear wax build up be prevented?
(1) Avoid compacting ear wax
(2) Use preventative ear drops
What are some products which can be used to treat ear wax buildup, that are not recommended by NICE?
(1) Urea hydrogen Peroxide 5%
(2) Arachis oil
What is otitis externa commonly caused by?
(1) Bacteria - e.g. P. aeruginosa/ S. aureus
(2) Fungi - e.g. Candida/ Aspergillus
What are some symptoms of otitis externa?
Red + swollen
Scaly skin
Swelling (with central pus?) + pressure
Painful + itchy
Hearing loss
What self-care advice can be given for localised otitis externa?
Keep clean + dry
Analgesia
Local heat
Usually self-limiting
What treatment is available for acute diffuse otitis externa?
Acute diffuse:
(1) Corticosteroid ear drops/ astringents/ 2% acetic acid solution
(2) Topical antibiotics, e.g. neomycin sulfate
(3) Topical antifungal, e.g. 1% clotrimazole solution
(4) Anti-infective, e.g. clioquinol
What is the treatment if otitis externa has spread beyond ear canal?
Regard as cellulitis
Oral flucloxacillin
(clarithromycin if penicillin intolerant)
What is the treatment for chronic diffuse otitis externa?
Fungal: Anti-fungal agent, e.g. clotrimazole 1% solution
If ear drum (tympanic membrane) is perforated, aminoglycoside antibiotics (gentamicin + neomycin) are contraindicated
Why are aminoglycoside antibiotics contraindicated in otitis externa with perforation of the ear drum (tympanic membrane)?
Can cause ototoxicity (hearing/ balance problems)
What is contraindicated if a patient presenting with otitis externa has a perforated ear drum (tympanic membrane)?
Aminoglycoside antibiotics
e.g. gentamicin/ neomycin
Name some examples of aminoglycoside antibiotics.
(1) Neomycin
(2) Gentamicin
What causes otitis media?
Eustachian tube become inflamed/ blocked, traps fluid in middle ear
Common in young children
Common following viral respiratory tract infection
Typically caused by viruses
What are some symptoms of otitis media?
(1) Sudden onset of otalgia (ear ache)
(2) Fever
(3) Hearing loss
(4) Vomiting/ discharge when more severe
What is the considerations for treatment for otitis media?
Usually self-limiting (3-7 days)
(1) Analgesia
(2) Antibiotics often not needed
(3) Can give backup Rx for worsening of symptoms
(4) ABx considered when patient is systemically unwell or high risk of complications or <2yrs old
What is the first line treatment for otitis media?
5-7 days oral amoxicillin
Clarithromycin/ erythromycin if amoxicillin not tolerated (penicillin allergy)
Erythromycin is preferred alternative
What often defines chronic otitis media?
(1) Perforated ear drum - tympanic membrane
(2) Referral to ENT specialist
What is the treatment for chronic otitis media?
Antibiotic ear drops, e.g. topical quinolones
Refer to ENT specialist
What is labrynthitis?
Inflammation of inner ear (labyrinth)
What vestibular neuritis?
Inflammation of vestibular nerve
What are some conditions of the inner ear?
(1) Vestibular neuritis
(2) Labyrinthitis
What causes inner ear infections?
Commonly viral infections
Can be linked with stress + ototoxicity
Rarely bacterial infection
What are some symptoms of inner ear conditions?
(1) Dizziness/ vertigo
(2) Balance disorder
(3) Tinnitus
(4) Hearing loss (labyrinthitis ONLY)
What is the treatment for inner ear conditions?
Self-care + rest
Prochloperazine for vertigo + nausea
Antihistamines, e.g. cinnarizine/ cyclizine
Corticosteroids for inflammation (not recommended by NICE)
Antivirals usually not recommended
Antibiotics IF bacterial
What is normally not recommended for inner ear condition treatment?
(1) Corticosteroids
(2) Antivirals
(3) Benzodiazepines
What is hearing loss?
Temporary/ permanent
Can be mild/ moderate/ severe/ profound
One/ both ears
Either sensorineural/ conductive
What is sensorineural hearing loss?
Damage to hair cells of cochlea/ auditory nerve
Permanent
Hair cells cannot regenerate
What is conductive hearing loss?
Inhibition of sound transmission from outer to inner ear
e.g. blockage
Permanent/ temporary
What are some different causes of hearing loss?
(1) Genetic
(2) Noise-induced (loud noises damage hair cells)
(3) Age-related (gradual damage to hair cells)
(4) Otosclerosis (bony growths in ear, conductive loss)
What are some causes of sudden hearing loss?
(1) Ototoxic drugs (damage inner ear)
(2) Infections (e.g. viral Rubella, measles, mumps, or bacterial meningitis
(3) Trauma/ injury (infection/ noise)
(4) Meniere’s disease (changes in fluid pressure in inner ear - endolymph)
Name some drugs associated with ototoxicity.
(1) Analgesics/ antipyretics - not so severe
(2) Aminoglycosides (neomycin in particular)
(3) Macrolide ABx - may be reversible
(4) Glycopeptide ABx - not so severe
(5) Antineoplastics (cisplatin in particular)
(6) Loop diuretics (furosemide)
What are hearing aids?
Behind ear/ in ear/ in canal
Used for conductive/ sensorineural hearing loss
Amplifies sounds to aid hearing
What are ear implants?
Bone-anchored hearing aids, e.g. cochlea implants, auditory brainstem implants, middle ear implants
What are cochlea implants?
For more severe sensorineural hearing loss (damage/ loss of hair cells)
For more profound deafness
Directly stimulate cochlea nerve
Bypass damaged upstream signalling to nerve
