ENT Flashcards
describe the structure and function of the outer ear
pinna; elastic cartilage part of the side of the head, some use in localising sounds
ear canal; S shaped tube, protects the eardrum from foreign bodies
describe the eustachian tube
travels forwards and downwards towards the back of the nose
keeps atmospheric and middle ear pressure the same
what is the function of the mastoid tube?
connects the mastoid air system
what are the contents of the middle ear?
malleus incus stapes two muscles; protect the inner ear from damage from loud sounds very closely related to the facial nerve
how does the middle ear act as an amplifier?
area ratio effect; the tympanic membrane is much bigger than the oval window, so small movements of the tympanic membrane cause 14x movements of the oval window
lever effect; the handle of the malleus is 1.4x bigger than the handle of the stapes
describe the cochlea
the basilar and Reissner’s membranes divide it into 3 compartments; including the scala media
contains the outer and inner hair cells which sit below the tectoral membrane
what is the function of the outer hair cells?
allow us to discriminate between speech and background noise
by maintaining the vibration of the basilar membrane for longer than if they weren’t there
how is the fluid of the cochlea arranged?
the top and bottom fluid compartments share the same fluid
this is different from the scala media
what is the oval window attached to?
the stapes
what is the function of the round window?
so that the fluid is incompressible
how does the ear produce differences in pitch?
one end of the hair cells produce high pitch sounds and the other end of the hair cells produce low pitch sounds
how does the ear produce differences in volume?
a difference in the number of hair cells stimulated
what is the function of the nose?
airway
warms, moistens and filters the air
sense of smell
what are the contents of the nasal cavity?
superior, middle and inferior turbinates
what are the main functions of the larynx?
sphincter; to stop food and fluid from getting into the chest
traps air in the chest; allowing fixation of the chest wall
allows the diaphragm to expel intra-abdominal contents
speech
name an example of direct trauma to the ear
surgical trauma in a myringotomy
fractured skull
name an example of indirect trauma to the ear
bomb explosion
slap on the ear
changes in atmospheric pressure
describe an essential perforation of the eardrum
most common perforation
the tympanic membrane is still all the way around the perforation
may be at the front, back or the bottom
less risk of ingrowth of squamous epithelium than the others; resulting in a cholesteatoma
describe a marginal perforation of the eardrum
one edge of the perforation is against the edge of the ear canal
describe an attic perforation of the eardrum
in the pars flaccida
what are the causes of tympanic membrane perforation?
trauma
infection
what are the symptoms and signs of an eardrum perforation?
asymptomatic; small
conductive hearing loss
discharge; infection
what can be seen in a healthy tympanic membrane?
lateral process of malleus
handle of malleus
light reflex
what can be seen in a tympanic membrane with acute otitis media?
lateral process of malleus
handle of malleus; red and inflamed
some redness in the attic area; often the first area to be affected
later; bulging of the tympanic membrane, cannot identify any individual landmarks
what can be seen in a tympanic membrane with glue ear/otitis media with effusion?
eardrum sucked inward
handle of the malleus is lying almost horizontally
golden-brown colour; middle bit of the ear is full of a thick, sticky effusion
describe the signs and causes of tympanosclerosis
scarring of the eardrum
white chalky patches on the surface of the tympanic membrane
no hearing loss or symptoms when confined to the tympanic membrane
previous infection
surgery; inserting ventilation into the eardrum
what are the signs of a cholesteatoma developing?
attic part of the eardrum is sucked inwards
retraction pocket
describe a large tympanic membrane perforation
sub-total perforation of the right/left tympanic membrane
cochlea can be seen
no bony junction between the process of the incus and the head of the stapes
describe cholesteatoma
untreated retraction pockets
bone in the attic area has been eroded
squamous epithelium and skin growing into the middle ear mastoid
what is the treatment of tympanic membrane perforation?
left alone for 6 months; heal spontaneously, encourage to keep it dry
surgery (tympanoplasty); episodes of recurrent infection, significant hearing loss
what are the complications of tympanoplasty?
infection
sensorineural hearing loss; if the ossicular chain is manipulated
dizziness
define otitis media
acute inflammation of the tympanic cavity (middle ear)
what are the causes of otitis media?
infection enters the middle ear via
eustachian tube; in a child with a URTI or head cold
pre-existing perforation
carried via the bloodstream; rare
viral; RSV, parainfluenza, adenovirus
bacterial; strep pneumonia, haemophilus influenza, moraxalla catarrhalis, strep pyogenes
what are the symptoms and signs of otitis media?
fever pain agitation/irritability discharge deafness
what is the difference between the attic and the pars tensa (the rest of the eardrum)?
attic; 2 epithelial layers
pars tensa; little fibrous layer
describe the pathogenesis of acute otitis media
infection enters the post-nasal and middle ear space via the eustachian tube
swelling of the mucosa blocks off the Eustachian tube
middle ear starts to fill with pus
attic portion bulges; tension in the eardrum
what are the consequences of acute otitis media?
resolution; infection settles, eardrum doesn’t burst, fluid may/may not be reabsorbed
perforation; tension is too great, ear will discharge (bloodstained then becomes mucopurulent), pain is relieved
what are the complications of acute otitis media?
rare
mastoiditis
facial palsy
most improve within 10-14 days; occasionally can become persistent AOM
recurrent; check diagnosis, consider myringotomy and ventilator insertion
describe otitis media with effusion (OME)/glue ear in adults
a collection of serous fluid behind the ear drum
uncommon in adults
can indicate underlying problems; allergic rhinitis, chronic Eustachian tube dysfunction
can occur after flying
must always refer to an ENT surgeon if it does not occur after flying
unilateral; may be nasopharyngeal carcinoma
what are the risk factors for developing otitis media with effusion?
eustachian tube dysfunction; URTIs which cause the mucosa to swell and blocks the tube
allergy
downs syndrome; very thick URT mucosa
cystic fibrosis; problems with RT mucosa
adenoid hypertrophy; mechanical problems
cleft palate; before repair, cannot open the eustachian tube
partly resolved ear infection; infection has settled but the fluid is still trapped in the middle ear
describe the pathogenesis of otitis media with effusion
oxygen is absorbed in the middle ear
creating a vacuum
eustachian tube is blocked; air cannot get into it
the eardrum is in-driven
irritation of the mucosal glands in the middle ear; filling up with sticky mucous
what are the symptoms and signs of otitis media with effusion?
may be asymptomatic; picked up by screening otalgia deafness speech disturbance behavioural disturbance indriven tympanic membrane dull/pink/golden colour fluid level seen
what investigations are required to diagnose otitis media with effusion?
age-appropriate hearing test; to acoustic emissions distraction test visual reinforcement audiometry brainstem evoked auditory responses audiogram; from age 4 tympanogram; appears flat
what is the management of otitis media with effusion?
leave it for 3 months; 50% resolve on their own
otovent; ear popper
persistent deafness or sore ears; surgery (grommet)
adenoidectomy; reduced the likelihood of grommets being needed to be reinserted
what are the complications of ventilator insertion?
infection; best treated with a very short course of antibiotic ear drops (particularly ototoxic)
perforation
scarring; tympanosclerosis
what are the congenital causes of sensorineural deafness?
genetic; AD, AR, X-linked, mutation
maternal infections; rubella, cytomegalovirus, toxoplasmosis, syphilis
perinatal; pre-term, low birth weight, hypoxic, toxic substance exposure, rhesus disease, blood incompatibility, jaundice
unknown; genetic mutations, undiagnosed maternal disease
what are the acquired causes of sensorineural deafness?
leisure noise
occupational noise
depends on volume, duration, individual susceptibility
trauma; surgery
describe a temporary hearing threshold shift
after being out somewhere in the evening which is noisy and then hearing a ringing
caused by the exhaustion of neurotransmitters
describe a permanent hearing threshold shift
keep being exposed to noise
permanent hearing loss
hair cells are destroyed; humans cannot regenerate hair cells
describe the hearing loss associated with noise-induced deafness
a notch in the higher frequencies
if they keep being exposed to noise; the notch will deepen and widen to affect many more frequencies
describe mumps and sensorineural deafness
most common cause of unilateral sensorineural deafness in children
describe herpes zoster oticus/ramsey hunt syndrome
reasonably common
vesicles in the concha of the ear; last for a short time
unilateral ear pain
unilateral sensorineural deafness
unilateral facial palsy
dizziness
sometimes the 9th cranial nerve is involved (glossopharyngeal); difficulty swallowing
what is the treatment of herpes zoster oticus/ramsey hunt syndrome?
aciclovir
steroids
what are the trauma-related causes of sensorineural deafness?
surgical bacterial viral tumour drugs; aminoglycoside antibiotics vascular; thrombus degeneration; presbyacusis
describe bacterial causes of sensorineural deafness
acute otitis media might spread to the inner ear; very rare complication
more likely in chronic otitis media; cholesteatoma
describe tumour causes of sensorineural deafness
vestibular schwannoma/acoustic neuroma
presents with unilateral sensorineural deafness in adults
diagnose with MRI; must be excluded in unilateral sensorineural deafness
what is the treatment of vestibular schwannomas?
small/asymptomatic; observed
bigger/starting to cause trouble; removal
benign tumours
what is the treatment of vascular deafness?
carbogen; a mixture of carbon dioxide and oxygen
very powerful vasodilator
what is the treatment of sensorineural deafness?
prevention genetic counselling noise protection hearing aid cochlear implant
what are the contents of the facial nerve?
motor fibres; muscles of facial expession
parasympathetic fibres; lacrimal and submandibular glands
special sense; taste to the anterior 2/3s of the tongue
ordinary sensation; skin of the external ear
what are the causes of facial nerve palsy?
congenital; rare
acquired; trauma, infection, tumour, vascular (brain stem vascular accident), idiopathic
how can trauma cause a facial nerve palsy?
temporal bone trauma;
longitudinal fractures; middle ear and mastoid damage, no cochlear damage
transverse fractures; fracture band can run straight through the facial nerve
immediate onset after trauma; direct facial nerve damage, requires surgical exploration repair
gradual onset; due to bleeding, oedema or other form of pressure, no urgent treatment required
facial surgery
describe the infective causes of facial nerve palsy
viral;
ramsey hunt; caused by herpes zoster which has involved into the 7th, 8th and sometimes 9th CN
pain, vesicles on the concha, facial palsy, sensorineural deafness, dizziness, often short-lived
treatment; acyclovir and steroid combination
bacterial;
very rare complication of acute otitis media in children
cholesteatoma; a form of chronic suppurative otitis media
how can a tumour cause a facial nerve palsy?
vestibular schwannoma; presents with sensorineural deafness and facial palsy
investigations; MRI, requires excision if its causing symptoms
parotid gland tumour; if it presents with facial palsy it is malignant
describe the idiopathic causes of facial nerve palsy
Bell’s palsy;
diagnosis of exclusion
accounts for 70-80% of facial palsies
worse prognosis and require treatment if complete palsy present
treatment; acyclovir, steroid (reduce the oedema around the facial nerve and restore function)
describe the input section of the vestibular system
eyes
vestibular apparatus; gives you information about movement
proprioceptors; stretch receptors in muscles and joints that detect how you are working
touch and pressure receptors in the skin
describe the output section of the vestibular system
cerebral cortex; tells the higher centres what’s going on
muscles; adjust
describe the peripheral vestibular system
made up of a central box; utricle and saccule
attached to the semicircular canals
fluid is made in the cochlea and reabsorbed in the CSF through the endolymphatic sac
describe the semicircular canal
ampulla houses the sensory apparatus made up of hair cells detects movement embedded in cupula; jelly like substance contains otoliths; tiny stones
what is the function of the vestibular system?
semicircular canal; detect rotatory or angular acceleration and deceleration
utricle and saccule; detect linear acceleration and deceleration, respond to gravity
describe the examination of a patient with reduced balance
rombergs test extended rombergs test unterbergers test nystagmus finger-nose test dysdiadochokinesis cranial nerve examination peripheral nerve; sensation, motor, reflexes