Session 7 - functional anatomy and disorders of the ear Flashcards
what is otalgia
ear pain. pain that originates within the ear is primary otalgia; pain that originates outside the ear is referred otalgia.
Typical sources of primary otalgia are external otitis, otitis media, mastoiditis, and auricular infections
wihtin which bone of the skull do we find parts of the ear
petrous part of the temporal bone
what parts make up the external ear
what is its function
pinna
external auditory meatus
lateral surface of tympanic membrane
collects, transmits, and focuses sound waves onto the tympanic membrane
how does cauliflower ear occur
secondary to blunt injury to the pinns
accumulation of blood between cartilage and perichondrium
deprives the cartilage of its blood supply + pressure necrosis of
tissue
Prompt drainage of blood, measures to prevent re-accumulation and re-apposition of two layers are necessary
Untreated or poorly treated leads to fibrosis and new
asymmetrical cartilage development- ‘cauliflower
deformity’ of the ear
why can ear infection affect the facial nerve and cause facial palsy
the facial nerve travels through the internal auditory meatus
what is ramsey-hunt sydrome
is a herpes zoster oticus
where you get unilateral facial palsy
caused by the reactivation of the varicella zoster virus from the geniculate nucleus (nucleus if the facial nerve)
in what way does the ear have to be positioned to examine it
straighten it by pulling it back and up as it has a sigmoid shape
where are the gland that produce wax and hair found
outer part of ear canal (cartilaginous)
how long is the external acoustic meatus
2.5cm
what is ottitis externa
Inflammation of the external acoustic meatus usually caused by infection, sometimes due to allergy or irritation
Give ear drops/ steroids if infection
Swimmers ear- lots of water in ear predispose to this
More commonly seen in people with eczema
how do you get a perforated tympanic membrane
Pressure has built up on the inside
Which can cause the tympanic membrane to perforate
Pus and exudate can leak out
Usually resolves itself
can also be due to poking the ear with things
why might you get bulging of the tympanic membrane secondary to ottitis media
bulging due to increased pressure with the build up of immune cells
what is the middle ear
and which bones are found here
tympanic cavity - the air filled cavity between the tympanic membrane and the inner ear
three ossicles- incus, malleus and stapes
what do the ossicles do
Connected via synovial joints and relay vibrations from the tympanic membrane to the oval window of the cochlea (inner ear)
Transmitting vibration from an air medium to a fluid-medium
what protects the ear from very loud noises
Movement is ‘tampered’ by two muscles tensor tympani and stapedius (faical nerve)
Muscles contract automatically if potentially excessive vibration due to loudnoise (protective; acoustic reflex)
what is otosclerosis
Ossicles can become fused at articulations, in particular between base plate of stapes and oval window (otosclerosis)
Sound vibrations cannot be transmitted
Causes deafness
Patients develop gradual hearing loss
why might you get hyperacusis
Can get hyperacoustis if they have facial nerve damage- lose ability to dampen loud noise
as the stapedius muscle which contracts when there is loud noise is innervated by the facial nerve
why do we get a negative pressure in the middle ear
Mucous membrane of middle ear continuously reabsorbs air in middle ear causing negative pressure
what is the function of the eustachian tube
Pharyngotympanic tube (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
what is glue ear
otitis media with effusion
not an infection
Build up of fluid and negative pressure in middle ear due to Eustachian tube dysfunction: can predispose to infection
Decreases mobility of TM and ossicles- affecting hearing
Most resolve spontaneously in 2-3 months.. but some may persist
if glue ear persists what has to be done
Require grommets (tympanostomy tube) to ventilate middle ear and equilibrate pressure
why do we get the formation of a transudate in glue ear
cannot equilibrirate pressure in middle ear
negative pressure draws fluid out of mucosa
how does the tympanic membrane look in glue ear
retracted and straw coloured
because of the negative pressure pulling the membrane towards the middle ear cavity
can also see a build up of fluid behind membrane giving straw colour
what is acute otitis media
Acute middle ear infection
More common in infants, Otalgia (infants may pull or tug at the ear)
non-specific symptoms e.g. temperature
Red +/- bulging TM and loss of normal landmarks
why are children more likely to get an ear infection
Pharyngotympanic tube is shorter and more horizontal in infants
In infants therefore 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
what are some complications of Acute Otitis Media
Tympanic membrane perforation
Facial nerve involvement
Rarer but potentially life-threatening complications include
– Mastoiditis
– Intracranial complications
• Meningitis
• Sigmoid sinus thrombosis
• Brain abscesshow can you get meningitis from an ear infection
the middle ear cavity communicates with air filled cavities in the mastoid process via mastoid antrum (mastoid air cells)
if infection spreads into mastoid air cells it spread into venous structures close by or the brain itself causing meningitis
what is mastoiditis and how does it present
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)
Infection in mastoid air cells has pushed the ear forward
Ear needs to be drained
which branch of the facial nerve runs through the middle ear cavity
chorda tympani
what is a cholesteatoma
Abnormal skin growth (sac or cyst of skin cells) growing into into middle ear, behind the tympanic membrane - ear drum retracted due to negative pressure
Rare, but should not be missed!
Causes painless, often smelly otorrhea (ear discharge) +/- hearing loss
But also potentially more serious neurological complications
Usually secondary to chronic ET dysfunction or chronic/recurring ear
infections
Not malignant but slowly grows and expands, eroding into structures e.g. ossicles, mastoid bone, cochlea
what is the function of the cochlea
the cochlea converts vibrations into an electrical signal (action potential) that is perceived as sound
it is a fluid filled tube
Movements at the oval
window set up movements of the fluid in the cochlea.
Waves of fluid cause
movement of special sensory cells (stereocilia) within the cochlear duct which generate action potentials in CN VIII - vestibulocochlear nerve
what does the vestibular apparatus do
maintains our sense of position and balance
what is sensorineural hearing loss
pathology involving the inner ear structures or CNVIII
A sensorineural hearing loss is defined as damage to the hair cells in the cochlea (this is the sensory hearing organ) or damage to the neural pathways of hearing (nerves).
how do we hear
Auricle and external auditory canal focuses and funnels sound waves towards tympanic membrane which vibrates
Vibration of the ossicles (stapes at the oval window) sets up vibrations/movement in
cochlear fluid
Sensed by stereocilia (nerve cells) in the cochlear duct (part called the spiral organ of Corti)
Movement of the stereocilia in organ of Corti trigger action potentials in cochlear part of CN VIII
Primary auditory cortex (make sense of the input)
what is the vestibular apparatus
Vestibular apparatus includes the semicircular ducts, the saccule and
utricle: these are a fluid filled series of channels and sacs that respond to position and rotation and maintain our sense of balance
what is menineres disease
This is a disorder of the inner ear caused by a change in fluid volume in the labyrinth
symtoms include vertigo tinnitus and fluctuating hearing loss
acute attacks
what is Benign paroxysmal positional vertigo
causes short episodes of intense dizziness (vertigo) when you move your head in certain directions. Vertigo is the sensation that you or your surroundings are moving. Benign paroxysmal positional vertigo is thought to be caused by tiny solid fragments (otoconia) in the inner ear labyrinth
what is labyrinthitis
an inner ear infection which cause the labyrinth to become inflamed affecting your hearing and balance
symptoms include vertigo
feeling or being sick
some hearing loss
which tests are performed to differentiate between sensorineural and conductive hearing loss
Rhine’s test and Weber’s test
how do you perform a rhines (conduction)test
tap tunning fork, get it to ring and place the base of the tinning fork over mastoid
and then pace it in front of ear
and ask the patient which was louder
in a normal ear should be loudest when placed in front of ear as conduction in air should be greater than conduction in bone
in sensorineural loss it will also be louder in air than bone
but in conductive hearing loss the sound will be louder in bone than air as ambient noise is blocks the sound in air but the bone still conducts
how do you perform a weber’s (localisation) test
ring tuning fork
place base of tuning fork on midline of head
see which ear the sound is louder in
if the sound is the same in both ears it is normal
if the sound is louder in the normal ear it is senorineural hearing loss
if it is louder in the affected ear it is conductive hearing loss
What are some causes of sensorineural hearing loss
presbyacusis - old age
meniere’s disease
acoustic neuroma
ototoxic medications
what are some causes of conductive hearing loss
pathology involving the external or middle ear wax otitis media glue ear otosclerosis
