ENT 1 Flashcards
what is the outer ear consisted of?
The outer ear is air-filled
Composed of auricle (Pinna) and the auditory canal
what does the middle of the ear consist of?
The middle ear is air-filled and consists of the tympanic membrane (eardrum) and a chain of bones (auditory ossicles) called the malleus, incus, and stapes (hammer, anvil and stirrup)
-and eusthachian tube
what does the inner ear consist of
The inner ear (labyrinth) is fluid-filled and consists of the vestibular system (three semicircular canals and the vestibule) and the cochlea (a spiral-shaped series of 3 tubular canals containing the organ of Corti / organ of sound)
what is the ear physiology and how does it effect hearing
The outer ear functions to direct sound waves into the auditory canal
Sound waves travelling through air amplified by tympanic membrane
Sound waves transmitted from air-filled middle ear must be converted into pressure waves in fluid in inner ear (cochlea)
Cochlea controls hearing whilst vestibular system controls balance – both work by mechanical to electrical signal transduction
The Organ of Corti contains inner and outer hair cells, which are the sites of auditory transduction
Inner hair cells are responsible for signalling to the brain via the cochlea nerve, outer hair cells act as amplifiers
The bodies of the hair cells are in contact with auditory nerve fibres, and the cilia of the hair cells are in contact with the tectorial membrane
Vibration of basilar membrane activates inner and outer hair cells (sensory receptors) by causing bending of stereocilia (next slide)
When inner hair cells are depolarized, excitatory neurotransmitter (glutamate) is released to activate afferent cochlear auditory nerves
When inner hair cells are hyperpolarized, afferent cochlear auditory nerves are inhibited (next slide – also true for hair cells in vestibular system - later)
what does cochlea consist of?
The cochlea consists of a series of ducts called the scala vestibuli, scala tympani and scala media
Scala vestibuli and tympani are filled with perilymph, whilst scala media filled with endolymph, and which contains the organ of corti
what is the Hair cell function
Hair cells have stereocilia (left) – largest known as kinocilium (vestibular system)
Hair cells typical resting membrane potential more depolarized than neuron (from ~-45/-50mV to -60/-65mV)
High potential difference between endolymph (+80mV) + perilymph (0mV)
Bending stereocilia towards the largest stereocilium / kinocilium mechanically opens ion channels causing influx of K+
This causes hair cell depolarization that leads to influx of Ca2+ via Voltage-gated calcium channels (VGCC)
This leads to neurotransmitter release (glutamate, shown in white) and activation of the afferent nerve fibres
Bending the stereocilia backward away from the largest stereocilium /kinocilium closes the ion channels, leading to hair cell hyperpolarization and inhibition of the afferent nerve fibres
Activation leads to signals to the brain (synapses to nuclei in brainstem then from there to other brain regions such as cortex (e.g. auditory cortex for cochlea hair cells), cerebellum and cranial nerves (vestibular) – see later
Afferent and efferent connections. Different for inner and outer hair cells of cochlea
what is the vestibular system used for
The vestibular system is used to maintain equilibrium or balance by detecting angular and linear accelerations of the head
- Angular acceleration is detected by semicircular canals
- Linear acceleration & gravity is detected by the otolithic organs (utricle (horizontal) and saccule (vertical) acceleration)
what does the movement of stereocilia cause?
Semicircular canals and otolithic organs have specialized epithelium with hair cells that function much as described for cochlea
Movement of stereocilia leads to downstream signalling to the brain with information on position and movement
what are possible conditions of the ear?
Ear wax build up (not infection/condition)
Outer ear inflammation (otitis externa): conductive hearing loss
Middle ear inflammation (otitis media): conductive hearing loss
Inner ear inflammation (labryinthitis and vestibular neuronitis/neuritis): sensorineural hearing loss causing inner ear dizziness
what are the common drugs used in the management of ear disorders?
Antibiotics (neomycin, flucloxacillin, amoxicillin, clarithromycin, erythromycin – see also Autumn term PM2A2)
Anti-histamines (cinnarizine, cyclizine, promethazine teoclate – see also Autumn term PM3A)
Anaesthetics (lidocaine – see also Autumn term PM3B)
Analgesics (paracetamol, ibuprofen – see also Autumn term PM3B),
Anti-fungals (clotrimazole – see also Autumn term PM3A)
Anti-infectives (clioquinol)
Anti-inflammatories (corticosteroids – dexamethasone, flumetasone; NSAID – phenazone [also analgesic and anti-pyretic] – see also Autumn term PM3A)
Astringents and acids (aluminium acetate and acetic acid)
Cerumenolytic agents (olive oil, almond oil, sodium bicarb, sodium chloride, arachis oil, urea hydrogen peroxide)
D2 receptor antagonists (prochlorperazine – see also Spring term PM3B)
how is the ears examined?
Otoscopes used to examine ear canal and tympanic membrane
Usually monocular
Can visualise e.g., bulging or perforation of tympanic membrane
what is the symptoms, diagnosis, treatment and advice for ear wax(outer year)
Symptoms: Impacted ear wax can cause: earache, hearing loss (common), discomfort, tinnitus, itchiness etc. and make examination of ear difficult
Diagnosis: By examination of ears with otoscope
If need to remove:
Cerumenolytic products act by softening ear wax (cerumen)
Usually 3-5 days of ear drops as first option (soften, help remove)
Simple remedies – olive or almond oil 3-4x daily; sodium bicarbonate (5%) or sodium chloride (0.9%) ear drops (off-label use)
If unsuccessful can try irrigation (drops and irrigation can be repeated)
Don’t insert anything else into ear to remove (e.g. cotton buds)
Other commercial options but not in NICE guidelines: Urea Hydrogen Peroxide 5% w/w
Regular use of drops can prevent build-up
- which bacteria/fugus causes otitis externa
2.what are the signs and symptoms
3.what is the diagnosis
4.what is the treatment options (acute) - what are the cautions
- Inflammatory disease typically caused by:
Bacteria (**P. aeruginosa & S. aureus most common, others e.g. S. epidermidis, P. mirabilis) or
Fungal (Candida and Aspergillus) infection.
- Signs: red, swollen ear canal, cellulitis, erythema of tympanic membrane
Symptoms: pain or tenderness tragus/pinna (can be jaw pain), itching (canal), discharge, hearing loss (less common)
- Diagnosis: on signs (2+) & symptoms (1+)
- Treatment - Self-care advice: For all cases, if necessary remove ear wax, keep clean and dry
Acute otitis externa
Often mild and self-limiting. Any pain can be treated with simple analgesia (paracetamol or ibuprofen)
Analgesia for pain (paracetamol/ibuprofen), rarely requires oral antibiotics
Consider OTC 2% acetic acid solution (e.g. EarCalm® spray) anti-fungal + anti-bacterial action
Other preparations such as astringent aluminium acetate (8% or 13% drops)
Anti-inflammatory corticosteroid ear drops (0.5% prednisolone sodium phosphate (less potent) or 0.1% betamethasone sodium phosphate)
Anti-infective: can use clioquinol (antifungal and antiprotozoal)
- In combination with flumetasone pivalate
Topical antibiotics may be considered: can use 7-14 days topical antibiotic with/wo topical corticosteroid:
- e.g. Gentamicin drops 0.3% (Genticin®)
- neomycin sulfate +/- dexamethasone (such as Otomize® spray – also has 2% acetic acid POM)
Anti-fungals: can use 1% clotrimazole solution
- cautions
If there is a perforated eardrum, aminoglycoside antibiotics (e.g. gentamicin and neomycin) are contra-indicated (can cause ototoxicity), although some specialists do use with caution
what is chronic otitis externa
signs and symptoms
treatment depending on cause
Chronic otitis externa
Signs: conductive hearing loss; dry scaly skin or red moist skin in ear canal; fluffy debris, hyphae, dots of black debris in the ear canal if fungal
Symptoms: constant itching in ear
If fungal infection suspected: topical antifungal e.g., clotrimazole 1% solution; OTC acetic acid 2% drops or spray (off label); corticosteroid + clioquinol drops (see previous slide)
If bacterial infection suspected: treat as acute otitis externa
If no signs infection: topical corticosteroid (see previous slide for examples)
what is the treatment for systemic otitis externa infection
- If systemic/infection spread beyond ear canal (cellulitis), may prescribe oral antibiotics, e.g., 7-d oral flucloxacillin (or clarithromycin if can’t have penicillin)
