Lecture 11 - Anatomy of the ear Flashcards
Symptoms and signs of ear disease
Otalgia - ear pain Tinnitus Discharge Vertigo Hearing loss Facial nerve palsy
2 types of hearing loss
Conductive - external and middle ear
Sensorineural - inner ear
External ear structures
Pinna and auricle
External auditory meatus - skin lined ear canal
Lateral tympanic membrane
Middle ear structures
Air filled cavity lined with resporatory epithelium
Ossicles
- The pharyngotympanic tube connects it to the oropharynx
Inner ear structures
Cochlear
Semicircular canals
- Fluid filled
Mastoiditis
Mastoid process contains mastoid air cells that communicates with the middle ear cavity via the mastoid antrum.
Potential route of infection spread from the middle ear to the mastoid air cells
Auricle
Cartilaginous
Covered in skin
Includes ear lobe
Covered in ridges - direct sound waves and guard the external acoustic meatus
Helix
Outer rim of auricle
Tragus
Small flap of auricle
External acoustic meatus
Laterally: Cartilaginous
(1/3rd) Contains hair, cerumen and sebaceous glands
Medially: Bony canal formed by the tympanic plate (2/3rd)
Most medially: fibrous tympanic membrane - ear drum
Lined by skin secreting cerumen (modified sebum) for protection
Sigmoid shape
Ear wax
Discarded skin and cerumen
Self cleaning - desquamation and skin migration laterally off the TM out of the canal
Ossicles
Malleus
Stapes
Incus
Amplify and transmit vibrations to oval window of cochlear
Eustachian tube (pharyngotympanic)
Connects the middle ear to the oropharynx and equalises pressure with the atmosphere.
Ventilates and drains mucus from the middle ear.
Potential route for infection spread from the oropharynx to the middle ear
Eustachian tube innervation
Innervated by the Glosspharyngeal nerve - an feel general sensation and pain
Lining of the eustachian tube
Lined with pseudostratified columnar epithelium
How does the eustachian tube open
Usually closed but intermittently opened by pull of muscles when swallowing and yawning
Special sensory nerve for hearing and balance
CN VIII - vestibulocochlear
Innervation of the ear
Branches of:
C2/C3:
- Pinna
Vagus nerve:
- Lateral tympanic membrane
- External acoustic meatus
- Concha
Trigeminal auriculotemporal nerve (Vc):
- Lateral tympanic membrane
- External acoustic meatus
- Part of tragus
Glosspharyngeal nerve (tympanic nerve):
- Mastoid air cells
- Middle ear
- Medial tympanic membrane
Facial nerve (nervus intermedius) :
- Lateral TM
- EAM
- Concha
Why do you get ear pain in pharyngitis?
Referred pain due to glossopharyngeal nerve
Otalgia with normal ear examination
Can have a non- ontological cause e.g.
TMJ dysfunction - CN Vc
Oropharynx disease - CN IX
Larynx/pharynx disease - CN X
Function of the external ear
Collects, transmits and focuses sound waves onto the TM
Pinna abnormalities
Ramsey Hunt syndrome - Varicella Zoster with facial nerve palsy
Pinna haematoma
Perichondritis
Varicella zoster
Vesicular rash in ear - shingles
Pinna haematoma
Accumulaton of blood between the cartilage and overlying perichondrium secondary to blunt injury to pinna
- deprives cartilage of blood supply thus necrosis can occur
How to treat a pinna haematoma
Tamponade eitehr side of the ear so layers are together quickly
Untreated can cause fibrosis and new assymetrical carilage formation
Cauliflower deformity
Untreated pinna haematoma can cause fibrosis and new assymetrical cartilage formation
Lining of the external acoustic meatus
Keratinisising stratified squamous epithelium continuous onto the lateral TM
Common abnormalities of the external acoustic meatus
Wax/foreign body blockage
Otitis externa
Malignant otitis externa
NOT cancer
Excruciating pain
Deep pain involving bone
In diabetics and immunocompromised
Otits externa presentation
Pain
Discharge
Narrow EAM
Associated with asthma and infection
Normal tympmanic membrane
Apex points medially
Bacterial acute otitis media
Bulging of TM towards external ear
Due to high pressure
Puss and inner ear infection
Otitis media with effusion
Retracted TM and evidence of fluid within middle ear cavity due to negative pressure
Bubbles
Cholesteatoma
Tretraction of pars flaccida TM forms a sac
Traps stratified squamous epithelium and keratin
Proliferated forming a cholesteatoma
Usually secondary to chronic ET dysfunction which creates negative pressure
Cholesteatoma presentation
Painless Crusting of pars flaccida Smelly otorrhea \+/- hearing loss NOT malignant
Serious consequence of cholesteatoma
Ezymatic bony destruction of ossicles, mastoid, petrous bone and cochlear
How are the ossicles connected
Via synovial joints
What muscles tamper ossicle vibration
Stapedius
Tensor tympani
Otosclerosis
Genetic and environmental cause
Idiopathic
Ossicles fuse at articulations due to abnormal bone growth (particularly between the stapes and oval window)
Vibrations cannot be properly transmitted to the cochlea
Gradual unilateral or bilateral conductive hearing loss
What causes negative pressure in the middle ear?
Mucous membrane of the middle ear reabsorbs air
Otitis media with effusion
- glue ear
- can predispose to infection
- due to ET dysfunction
- fluid and negative pressure in middle ear decreases mobility of TM and ossicles
Complications of otitis media with effusion
Affects hearing but may resolve spontaneously in most children
If persists and impedes speech and language development, requires grommets to maintain equilibration of pressure
Acute otitis media presentation
Middle ear infection
Common in infants
- otalgia
- temperature
- red +/- bulging TM
Causes of acute otitis media
Viral aetiology
bacterial:
- strep pneumoniae
- Haemophilus influenzae
Why is acute otitis media seen in infants most commonly?
Infants have a shorter and more horizontal eustachian tube
- easier passage of infection
- tube can block more easily, compromising ventilation and drainage
Complications of acute otitis media
- TM perforation due to pressure
- Facial nerve involvement due to nerve to stapedius and chorda tympani running through the middle ear cavity
- Mastoiditis
Intracranial:
- Meningitis
- sigmoid sinus thrombosis
- brain abscess
Cochlea
Endolymph filled tubes with specialised hair cells that generate APs when moved
Converts fluid movement in the cochlear duct (due to stapes vibrations on the oval window) into action potential via CN VIII cochlear part. Perceived as sound.
Movement of special sensory steriocilia into APs
Scala vestibuli
Scala media
Scala tympani
Separated by membranes
Vestibular apparatus
Semicircular canals
Saccule
Utricle
(contain steriocilia)
Semicircular canals convert fluid movement generated by position and rotation of head into action potentials in CN VIII by steriocilia movement perceived as position and balance
Inner ear disease complications
Hearing loss
Tinnitus
Vertigo
How do we hear>
- Auricle focuses and directs sound waves into the external auditory canal.
- The waves are transmitted to the typmanic membrane and it vibrates.
- The ossicles vibrate in the middle ear.
- The stapes transmits the vibrations to the oval window of the inner ear.
- The vibrations are transmitted to the cochlear duct where movement of fluid is converted to APs by the steriociliar cells in the spiral organ of Corti
- APS in the cochlear part of CN VIII are sent to the primary auditory cortex in the temporal lobe.
Presbycusis
Sensorineural loss of hearing associated with old age (natural)
Bilateral and gradual
Benign paroxysmal positional vertigo
- Vertigo only
- Short episodes (seconds)
- Triggered by movement of head
Dix - Hallpike manoeuvre
Diagnosis benign paroxysmal positional vertigo
When lowering a patients head suddenly, they get involuntary eye movements (nystagmus)
Epley manoeuvres
Dix- Hallpike manoeuvre but turn 90 degress when lying down. Feel dizzy
Meniere’s disease
Vertigo, tinnutis and hearing loss usually unilateral
- Nausea and vomiting
- Longer lasting symptoms (30mins - 24 hours)
- Recurrent episodes
- hearing may deteriorate over time
Acute labrynthitis
History of upper resp tract infection
Caused by virus affecting the inner ear
- all inner ear structures affected
- associated with hearing loss, tinnitus, vertigo and vomiting
Acute vestibular neuronitis
Usually don’t get hearing loss or tinnitus
Sudden onset vomiting and severe vertigo lasting days
Causes of conductive hearing loss
Wax/ Foreign object
Acute otitis media
Otitis media with effusion
Otosclerosis
Sensorineural hearing loss causes
Presbyacusis Noise- related hearing loss Meniere's disease Ototoxic medications Acoustic neuroma
Weber’s test
- Place tune fork on top of head in midline
- Vibrations send sound through bone to the cochlea equally on both sides
External ambient noises mask fork input
If conductive - will hear sound louder on affected side
If sensorineural - Will hear sound louder on normal sound
Rinne’s test
Sound conducted through air (external and middle ear) is louder than through bone
- Place fork on mastoid process therefore vibrations directly to inner ear
- Place fork in front of the external acoustic meatus (normal pathway of sound)
- ve result - sound will be heard louder when at mastoid process due to conductive pathology
High pitched loud sounds
High amplitude and frequency sounds waves