Ear Flashcards
Features of external ear
Pinna, helix, anti helix, tragus, anti tragus, external auditory meatus
Features of middle ear
Ossicles- malleus, incus, stapes
Eustachian tube
Air filled
Features of inner ear
Cochlea, semicircular canals, fluid filled
What epithelium lines the inner ear
Respiratory
What innervation is there to the external ear
C2/3, 5, 7, 9, 10
What nerve does special sensory
Vestibulocochlear
CN8
What innervation is there to middle ear
CN 9
What is the function of the external ear
Collect, transmit, focus waves onto membrane
What epithelium lines the external ear
Keratinising, stratified, squamous epithelium
How does the external ear self clean
Desquamation and skin migration laterally
Epithelial migration
Function of middle ear
Amplify and relay vibrations from membrane to oval window
What nerve innervates the muscles that tamper ossicle movement
Facial nerve to stapedius
What happens if the facial nerve is damage
Acoustic reflex dampened = loud noise
What is the role of the Eustachian tube
Equilibration of middle ear pressure with atmosphere
How is negative pressure created in middle ear
Mucous membrane constantly reabsorbs air to create negative pressure
Function of inner ear
Hearing and position sense balance
What is the vestibular apparatus
Semicircular ducts, saccule, utricle with sterocilia
What are children more prone to ear issues
Shorter and more horizontal ET. Easier for passage of infections from nasopharynx
What is important about the relation of middle ear to other structures
Close to mastoid bone and air cells, ET tube, facial nerve
All routes for middle ear infections to spread.
Can also spread intracranially as close to internal carotid, sigmoid sinus.
How are sound waves translated
Cochlea is fluid filled with stereocilia that generate AP when moved by oval window.
Wave-vibrates-ossicles-stapes on window-fluid moves-stereocilia sense-trigger AP via CN8-primary auditory cortex.
How is position and balance sensed
Head moves- causing fluid to move around vestibular apparatus- bends stereocilia - AP generated via CN8 to brain
What is pinna haematoma
Subperichondrial bleed depriving cartilage of blood supply leading to necrosis
Perichondritis
Infection involving connective tissue layer
What is otitis externa
Inflammation of external ear
Pain, itch, hearing loss, unlateral
What is risk factor of Otitis externa
Swimming
How to treat Otitis externa
Dry and antibiotics
What rare thing can otitis externa lead to
Malignant otitis externa- bacterial infection that can invade and errode
Diabetics and immunosuppressed
What is acute otitis media and how does it present
Inflammation and middle ear with bulging membrane, otalgia, red
Usually viral but can be Strep p or H. Influenzae
What is otitis media with effusion and how does it present
Glue ear
ET tube dysfunction
Retracted and fluid filled middle ear
Why hearing loss with glue ear
Hearing loss and mobility of membrane and ossicles decreased
How can you treat glue ear
Grommet
What is Cholestaetoma
Retraction of pars flaccida to form sac
Traps strat squamous cells and keratin
Proliferates
Normally secondary to ET dysfunction as neg pressure pulls in membrane
What can cholesteatoma lead to
Enzymatic bone destruction of ossicles of middle ear, inner ear and skull
What is otosclerosis and what causes it
Commonest cause of hearing loss in young
Ossicles fuse at articulations due to abnormal bone growth esp stapes and window
Gradual uni or bilateral
Genetic or environmental
What i presbycusis
Sensorineural hearing loss associated with age
Conditions that affect CN 8
What is Labrinthitis
Inflammation of nerve to ear
Acute or acute vestibular (no hearing loss)
Presents with vomiting and vertigo
Normally history of upper resp tract infection
What is Meniere’s disease
Vertigo, hearing loss and tinnitus Unilateral 30 mins to 24hrs Feeling of fullness in ear ? too much endolymph
What is benign paroxysmal positional vertigo and how is it different to Meniere’s
Short lived vertigo
Triggered by head movement
Crystal in tubes
Affects vestibular apparatus only so just vertigo no hearing loss
What does a normal membrane look like
Not retracted or bulging Pearly grey Translucent Respond to pressure changes Pars flaccida and tensa- small vs larger, lack of fibrous layer vs tough fibrous later
Webber’s test
Tuning fork on top of head
Finds origin of hearing loss and damage
Rinne’s test
Tuning fork touching ear then held next to ear
Unilateral comparison of bone to air conduction
Negative Rinne test
Can’t hear when held next to ear = conductive
Positive Rinne test
Air conduction more efficient than bone = sensorineural
If louder on affected side
Conductive
If quieter on affected side
Sensorineural
Conductive vs sensorineural hearing loss
Conductive= middle and external ear Sensorineural = inner ear and CN 8
Example of sensorineural
Presbycusis, noise related, menieres, ototoxic meds, neuroma
Example of conductive
Wac, acute otitis media, glue ear, otosclerosis
