Ears Flashcards
What are the components of the pinna?
Tragus & antitragus Triangular fossa Helix & antihelix Concha Lobule
Give some examples of congenital pinna deformities.
Antihelix deformity
Microfia = pinna malformation (can replace with cartilage from ribs/other ear)
Pre-auricular pit
Pre-auricular skin tag
Give some examples of acquired pinna deformities.
Trauma to elastic cartilage (note: 0% of ear damaged)
Pinna haematoma = trauma causes haematoma between cartilage and perichondrium —> hypoxia (perichondrium not in contact with cartilage) —> pressure necrosis —> “cauliflower ear” (fibrosis, pale, shrivelled outer ear)
What are the features of the external acoustic meatus?
Sigmoid, ~ 2.5cm long (therefore in order to visualise the tympanic membrane, pull the pinna to straighten the canal)
Lateral 1/3 = cartilaginous extensions of auricular cartilages (wider)
Medial 2/3 = bony tunnel through temporal bone (narrower)
Lined by skin, hair, modified sweat glands (produce cerumen)
Innervated by auriculotemporal nerve (branch of CNV3 - mandibular nerve) and auricular branch of vagus nerve (CNX)
What is earwax composed of? What is the function of earwax? What clinical conditions can be caused by earwax? ….
Earwax = cerumen + dead epithelial cells
- protects skin of ear
- cleans & lubricates external ear
- protection from water and microorganisms
- foreign bodies compacting earwax
- otitis externa = inflammation of the outer ear and external acoustic meatus —> earache
…..
What is the function of the tympanic membrane? What are the components of the tympanic membrane?
Connected to the malleus in order to transmit sound by vibration
Epithelium —> Collagen —> Mucous membrane
- only malleus visible through the membrane
- loose part of membrane superior to malleus —> pars flaccida (haphazard irregular collagen)
- taut rest of membrane —> pars tensa (regular radial collagen)
- light reflex is normal inferior to malleus (points at patient’s feet in right ear)
Give some examples of tympanic membrane-related diseases and conditions.
Tympanosclerosis = dense, white plaques present + bulging membrane (pus/fluid in middle ear)
“injection of drum” —> membrane becomes dull or red or yellow with dilated blood vessels
Retraction of membrane due to negative pressure in the middle and inner ear (caused by Eustachian tube dysfunction):
- pars flaccida first to pull inwards
- diffuse light reflex
- incus & stapes visible
- sound not conducted correctly
Cholesteatoma = necrotic mass of dead skin accumulating in retraction pocket of tympanic membrane —> production of lytic enzymes —> erosion of middle ear structures & bone —> hearing loss
Perforation:
- trauma/otitis media (pressure necrosis)
- usually heal spontaneously unless the rupture is large
What are the components of the middle ear?
Tympanic cavity (immediately adjacent to tympanic membrane) Epitympanic recess (superior) Ossicles (synovial joints): malleus, incus, stapes Oval window (medial to foot of stapes)
Communicates with:
- Anterior: nasopharynx via Eustachian tube/pharyngotympanic/auditory tube
- Posterior: mastoid area
What are the contents of the tympanic cavity?
- oval window —> stapes
- mastoid antrum contains mastoid cells (air-filled spaces)
- chorda tympani nerve (branch of CNVII)
- round window (allows movement of fluid within inner ear)
- tympanic branch of glossophayrngeal nerve (CNIX)
- Eustachian/pharyngotympanic tube
- branch from carotid plexus
- tensor tympani
What is otitis media?
Bacterial/viral infection of the middle ear cavity
Causative organisms: pneumococcus, Strep., Haemophilus (nasal bacteria)
Acute:
- painful, bulging, red ear drum with pus in middle ear
- occasionally causes perforation & discharge
- usually heals itself
With effusion (“glue ear”):
- thick effusion accumulates behind ear drum (exudate not absorbed)
- prevents aeration to equilibrate pressure (secondary to prolonged negative pressure) —> retracted tympanic membrane & conductive hearing loss
Complications:
Acute suppuration and back pressure into the mastoid cavity (mucous membrane continuous; pus fills mastoid air cells —> loss of reservoir for rapid aeration of the ear)
—> mastoiditis
—> protruding mastoid causes loss of crease behind ear
—> intracranial infection (meningitis, cerebral abscesses)
What are the features of the Eustachian tube?
Eustachian tube/pharyngotympanic tube/auditory tube
Lateral 1/3 = bony
Medial 2/3 = cartilaginous (adult)
- usually closed; intermittently pulled open by palate muscles whilst swallowing
- children: tube shorter and more horizontal (therefore more prone to otitis media from infections of nasal cavity)
What is mastoiditis?
Presence of air-filled spaces provide ideal medium for infection
Infection can spread to bone —> osteomyelitis —> middle cranial fossa —> breach of cranial vault —> meningitis
Drainage of pus required (avoid facial nerve)
What is the purpose of the air-filled spaces in the mastoid antrum?
- helps equilibrate pressure of tympanic cavity with pressure outside of ear
- storage of oxygenated air
What are the ossicles? What muscles are present and what function do they serve?
Ossicles: form osseous chain, 90 degrees to each other to transmit sound, develop from branchial arches
- MALLEUS = articulates with tympanic membrane, incus, & tensor tympani
- INCUS = no muscle attachment, articulates with malleus and stapes
- STAPES = articulates with stapedius, incus, and oval window (opening into cochlea)
Tensor tympani = contracts to pull handle of malleus medially, slowing sound (supplied by CNV3 - mandibular nerve)
Stapedius (origin is pyramidal entrance) = contracts to pull stapes posteriorly, preventing excessive oscillation which would damage the cochlea
These muscles are sound absorbers - prevent pressurisation causing pain from loud sounds
What are the components of the internal ear? What is the function of these components?
Cochlea = hearing
Vestibular labyrinth = balance
(interplay between vestibular end organ, vision, & sensation)
- 2 fluid-filled sacs: utricle & saccule (one for up-down acceleration, one for forwards-backwards acceleration)
- 3 fluid-filled cylinders: information on orientation due to movement of fluid over organelles
What are the types of rotational vertigo?
Based on history of attacks of vertigo
Secs-mins = benign paroxysmal positional vertigo
= due to displacement of otolith —> endolymph moves and otolith crystals move too —> artificial feeling of keeping moving
Mins-hrs = Ménière’s disease
= due to endolymphatic hydrops —> extra fluid causes increased pressure in vestibular system
24hrs+ = labyrinthine failure
Random + other symptoms = vertiginous migraine
What are some of the causes of vertigo?
True rotational
VERTIGO
- Vascular
- Epilepsy
- Receiving treatment
- Tumours/Trauma/Thyroid
- Infection
- Glial (MS)
- Ocular
Give some examples of causes of otalgia.
Ear pain
- otitis externa & otitis media
- referred pain from teeth, pharynx, cervical spine (ipsilateral ear) (inflammation/trauma/neoplasms of trigeminal, facial glossopharyngeal, vagus cranial nerves + cervical nerves C2 & C3)
What can pruritis of the ear indicate?
Itching
Caused by primary disorder of external ear or discharge from the middle ear
What can otorrhoea indicate?
Discharge from ear
Generally indicates infection
Bloody discharge associated with leakage of CSF (skull fracture)
What are the components of the external ear?
Pinna/auricle
External auditory canal/acoustic meatus
Tympanic membrane
What is the sensory innervation of the auricle & tympanic membrane?
External ear:
- greater auricular nerve (C2 & C3)
- lesser occipital nerve
- auricular branch of CNX
- auriculotemporal nerve (CNV3)
Tympanic membrane:
- external surface = auriculotemporal nerve (CNV3) & auricular branch of vagus (CNX)
- internal surface = tympanic branch of glossopharyngeal nerve (CNIX)
How can infection spread from the middle ear?
- to mastoid cells (pos. to mastoid antrum)
- to epitympanic recess (ant. to mastoid antrum)
- to sigmoid venous plexus (dural sinus) (ant. to mastoid antrum)
What are the three branches of the facial nerve given off in the petrous temporal bone, and what is their significance?
Greater petrosal nerve (PS) = supplies lacrimal & nasal glands
Stapedial nerve = motor control of stapedius (reduces movement of stapes & prevents damage to inner ear by loud noises)
Chorda tympani = taste to anterior 2/3 of tongue & parasymp. fibres to submandibular & sublingual salivary glands
