Functional anatomy and disorders of the ear Flashcards
What is otalgia?
pain in the ear
What is the external ear called?
pinna
contains pinned external auditory meatus and lateral surface of tympanic membrane
What is the ear canal?
external auditory meatus - it is skin lined (keratinising stratified squamous epithelium)
What is the middle ear?
A bony air filled cavity containing ossicles
What is the middle air lined with?
respiratory epithelium
What connects the middle ear to the oropharynx?
the pharyngotympanic tube
What is in the inner ear?
-cochlea and 3 semicircular fluid filled canals
What nerves carry GENERAL sensation from the ear?
- cervical spinal nerves (C2/C3)
- vagus
- trigeminal (auriculotemporal)
- glossopharyngeal (tympanic)
this has implications for referred pain e.g. something wrong with larynx or pharynx can cause ear pain
What nerve carries SPECIAL SENSORY to the ear?
vestibulocohlear nerve (CNVIII) -hearing and baalnce
What should you as a doctor be thinking if a patient comes in with otalgia but has a normal ear examination?
- alternative site of pathology
- otalgia can be non-otological or otological
What are the non-otological causes for otalgia?
- TMJ dysfunction (CNVc)
- Disease of oropharynx (CNIX)
- Disease of larynx and pharynx (cancers)
What is the role of the external ear?
collects, transmits and focuses sound waves onto the tympanic membrane
What conditions can affect the external ear?
- congenital
- inflammatory
- infective
- traumatic
What is ramsey hunt syndrome?
“shingles of the facial nerve)
-bells palsy and a painful red vesicular ear rash
What is perichondritis?
inflammation of the pinna carticlage
-after ear piecings
What is a pinna haematoma?
-the perichondrium is the lining over the cartilage that contains the blood supply to the underlying cartilage so when it is stripped away blood can accumulate between the cartilage and the perichondrium
What is the treatment for pinna haematoma?
Drainage and reaccumulation called re-apposition of the 2 layers
What happens if the pinna haematoma is untreated?
if not treated, can form a cauliflower ear as when ear tries to heal itself, it will lay down scar tissue altering the shape
-common in contact sport injuries e.g. boxing and rugby
When looking in the ear canal, how do you get the best view?
-pull ear back, up and out as the external acoustic meatus has a sigmoid shape
What do you find in the cartilaginous 1/3 of the external acoustic meatus?
hair, sebaceous glands and ceruminous glands (wax) - important as acts as a barrier to foreign objects
bony 2/3 lack these glands and hair
What is otitis externa?
inflammation of the external acoustic meatus - can involve the pinna too
- very painful
- affects hearing as air can’t reach tympanic membrane
can develop into malignant otitis externa - seen in patients who are immunocompromised - infection starts to involve the bone- not just the skin
What causes otitis external?
usually infection but can be allergy e.g. eczema
What are some tympanic membrane common abnormalities?
normal - apex points out to external ear side (only slightly)
buldging - secondary to bacterial acute otitis media (pus built up behind tympanic membrane pushing it more towards to external ear side)
otitis media with effusion - retracted and evidence of fluid within the middle ear cavity - tympanic membrane will be sucked in (due to negative pressure)
What is cholesteatoma?
- rare but should not be missed
- caused by a -ve pressure pull the pockets into the middle ear (due to blockage of the eustachian tube)
- retraction of top part of the tympanic membrane (par flaccid) forming a pocket which traps stratified squamous epithelium and keratin (becomes crusty)
What are the symptoms of cholesteatoma?
- painless
- smell otorrhea (ear discharge)
- can get hearing loss due to retracted tympanic membrane
What are the consequences on untreated cholesteatoma?
- not malignant but slowly grows and expands
- can eat away at ossicles and enter petrous bone and enter brain
NEEDS REFERAL!!
What is the middle ear?
an air filled cavity between the tympanic membrane and inner ear containing ossicles
How are ossicles connected?
via synovial joints
What are the ossicles called?
- malleus
- incus
- stapes
What do the ossicles do?
amplify and relay vibration from the TM to the oval window of the cochlea in the inner ear
-transmit vibration to waves in a fluid-medium
What muscles tamper down vibrations?
-stapedius and tensor tympani
they will contract if excessive vibration due to loud noise
What is otosclerosis?
- one of the most common causes of acquired hearing loss in young adults
- has both genetic and environmental causes but the exact cause is unknown
What happens in otosclerosis?
the ossicles are fused at articulations due to abnormal bone growth, particularly between the base plate of the staled and the oval window of the cochlear so the sound vibration aren’t transmitted effecitvely
How would a patient present with otosclerosis?
-present with gradual unilateral or bilateral conductive hearing loss
What does the eustachian tube do?
it equilibrates the pressure of the middle eat with the atmospheric pressure and allows for ventilation and drainage of mucus from the middle ear to the oropharynx
How is negative pressure in the inner ear created?
the mucous membrane of the middle ear continuously reabsorbs air in the middle ear causing the negative pressure
What is otitis media with effusion?
AKA glue ear
-not an actual infection but can predispose to it
What causes glue ear?
eustachian tube dysfunction
What happens in glue ear?
fluid and negative pressure in the middle ear
decreases the mobility of the TM and ossicles –> affects hearing
What happens if glue ear persists?
-impede speech and language deelopement and school performance
How do you solve glue ear?
grommets (typanostomy tube)
-allows equibilration of pressures and prevents build up of negative pressure
What does the TM look like with glue ear?
retracted and straw colour
What is acute otitis media?
-an acute middle ear infection common in infants and children
What are the signs and symptoms of acute otitis media?
- otalgia (infants will tug ear)
- temperature
- red and buldging TM
What causes acute otitis media?
viral aetiology
occasionally bacterial e.g. streptococcus pneumoniae or haemophilia influenzae
Why are otitis media with effusion and acute otitis media more common in children than adults?
due tot the anatomy of the pharyngotympanic (eustachian) tube
-in infants, the tube is more horizontal and is short so there is easier passage for infection from the nasopharycn to the middle ear and the tube can block more easily compomising ventilation and drainage of the middle ear which increases the risk of middle ear infections and glue ear
What are the complications of acute otitis media?
- tympanic membrane can perforate (if pressure gets too much)
- facial nerve can become involved as it has close relationship to the middle ear cavity and 2 intrapetorus branches run through the middle ear cavity (chorda tympani and stapedius nerve)
- mastoiditis and intracranial complications
What is mastoiditis?
middle ear cavity communicates with mastoid air cells providing a potential route for middle ear infections to spread into the mastoid bone
What would a patient with mastoiditis present with?
red swelling behind the ear
ear is pushed forward
What is in the inner ear?
fluid filled vestibular apparatus (or semicircular canals) and cochlea
What is the function of the inner ear?
contains structures involved in hearing and position-sense/balance
What does the cochlea do?
it converts fluid movement generated by the footplate of the stapes, via the special sensory cells stereocillia, into action potentials in CNVIII which we perceive as sound
Who do the vestibular apparatus do?
converts fluid movement generated by position and rotation of the head into action potentials in CNVIII which we perceive as position sense and balance
What can disease of the inner ear cause?
- sensorineural hearing loss
- tinnitus
- disturbances balance and vertigo
How do we hear?
1) auricle and external auditory canal focusses sound waves towards tympanic membrane which vibrates
2) Vibration of the ossicles (stapes at the oval window) sets up vibrations and movements in the cochlear flid
3) Sensed by sterocilia nerve cells in the cochlear duct (spiral organ of corti)
4) movement of the sterocilia in organ of corti trigger action potentials in the cochlear part of CN VIII
5) primary auditory cortex in the temporal lobe makes sense of the input
What are the vestibular apparatus made up of?
includes the semicicular canals, the saccule and utricle
- these are all fluid lined time containing sterocilia
- the fluid movements bend the clinical which generates the action potential
What is presbycusis?
sensorineural hearing loss associated with old age
-bilateral and grandual
What is benign paroxysmal positional vertigo?
- vertigo only
- short lived episodes triggered bey movement of head
- caused by little crystals in the ear moving (otoconia)
What is meniere’s disease?
- affects cochleae and vestibular canals
- vertigo, hearing loss and tinnitus, nausea and vomiting
- symptoms are longer lasting
- hearing may deteriorate over time
What is acute labrynthitis vs acute vestibular neuritis?
- infective cause
- hidtory of upper resp tract infection
- AL - involvement of all inner ear structures
- AVN = no hearing disturbances or tinnitus (doesn’t affect the cochlear)
What is conductive hearing loss?
pathology involving the external or middle ear e.g.
- wax
- acute otitis media
- otitis media with effusion-
- otosclerosis
What is sensorineural hearing loss?
pathology involving the inner ear structures or CN VIII e.g.
- presbycusis
- meniere’s disease
- noise related hearing loss
- acoustic neuroma
- ototoxic medications
How can hearing loss be categorised?
using webers and rinnes tests
-tuning fork tests
