6 - outer, middle and inner ear

what is auricular haematoma

collection of blood underneath perichondrium of ear

what causes auricular haematoma

trauma

treatment of auricular haematoma

incision and drainage

pressure dressing to prevent reaccumulation

antibiotics to prevent infection of cartilage

common complication of auricular haematoma

cauliflower ear - necrosis of cartilage leading to deformity

foreign body removal times

- button batteries

within HOURS - can cause permanent damage through corrosion

foreign body removal times

- organic

within DAYS - will cause infection

foreign body removal times

- inorganic

within DAYS

how are foreign bodies removed from ear

appropriate instrument removal

sometimes under general anaesthetic if cannot get it out

define otitis externa

inflammation of the external ear canal

presentation of otitis externa

ear pain

discharge

itching

hearing loss

management of otitis externa

antibiotic/steroid ear drops

suction for discharge

antibiotics for infection - amoxicillin

steroids for inflammation - prednisolone

prevention of otitis externa

no water or cotton buds

- OE is often called swimmers ear and results from improper drying of ears

define malignant otitis externa

osteomyelitis of temporal bone

-not malignant in cancer sense but malignant in the fact it can spread through skull base and cause serious morbidity or mortality

who is most at risk for malignant otitis externa

elderly diabetics

presentation of malignant otitis externa

severe pain in elderly diabetic

granulations in external auditory meatus

+/- cranial nerve palsies

management of malignant otitis externa

ciprofloxacin long term

what is the causative agent of malignant otitis externa

Pseudomonas aeruginosa

what is otitis media

infection of the middle ear

what is a complication of otitis media

untreated and recurring otitis media may result in a perforated eardrum

presentation of otitis media

redness, swelling, bulging, of tympanic membrane

fluid and or pus trapped under eardrum - glue ear

management of otitis media

observation for 3 months

if not resolving or recurring

- otovent

- grommet

what is acute supparative OM

pus in middle ear

presentation of acute supparative OM

otalgia +/- ottorhoea

- increasing ear pain followed by discharge when eardrum bursts and resolution of pain

management of acute supparative OM

conservative - observation

- antibiotics ONLY IF INFECTED

what is tympanosclerosis

calcification in tympanic membrane +/- middle ear

what causes tympanosclerosis

-chronic ear infections

-trauma to tympanic membrane

otoscope findings in tympanosclerosis

white patches on tympanic membrane

management of tympanosclerosis

observation

symptoms of tympanosclerosis

asymptomatic but can sometimes affect hearing

what are the 2 types of chronic supparative OM

perforated tympanic membrane

cholesteatoma

- both lead to long term discharge from ear

what is cholesteatoma

benign cyst in the mastoid cavity

complications of chronic supparative OM

complete hearing loss

CN VII palsy

meningitis

brain abscess

causes of perforated tympanic membrane

infection

trauma

grommet

presentation of perforated tympanic membrane

recurrent infections +/- hearing loss

management of perforated tympanic membrane

water precautions +/- myringoplasty

pathophysiology of cholesteatoma

2 types of

- eustachian tube dysfunction

-impaired skin migration

presentation of cholesteatoma

1. Drainage with foul odor

2. Fullness or pressure in ear

3. Hearing loss

4. Ache behind ear at night

5. Dizziness

6. Muscle weakness on ipsilateral face

management of cholesteatoma

refer to ENT

mastoidectomy - drill into mastoid bone to remove

what is otosclerosis

conductive hearing loss + normal tympanic membrane

pathology of otosclerosis

fixation of stapes by extra bone

management of otosclerosis

hearing aid

stapedectomy

what is the external ear made of and it’s overall function

auricle (pinna)

external acoustic meatus (ear canal)

tympanic membrane (eardrum)

to collect, amplify and transmit sound waves to the middle ear

what is the auricle made of and what’s it’s function?

elastic cartilage

collects and directs sound into the ear canal

external acoustic meatus

ear canal - 2.5cm long tube leading to the eardrum

outer 1/3 cartilaginous with glands (produces earwax)

inner 2/3 bony

conducts sound to tympanic membrane

tympanic membrane

eardrum - thin membrane separating external and middle ear

vibrates in response to sound waves

epithelial lining of external ear canal and middle ear

external ear canal:

• outer 1/3 keratinised stratified squamous epithelium

• inner 2/3 also lined with keratinized stratified squamous epithelium, but thinner and more tightly attached to bone. 

middle ear:

simple cuboidal to columnar epithelium, becomes ciliated pseudostratified columnar with goblet cells near the eustachian tube

structure and function of tympanic membrane

layers:

• outer layer : keratinised stratified squamous epithelium

• middle layer: fibrous connective tissue (provides strength)

• inner layer: simple cuboidal or columnar epithelium

internal auditory meatus

A short canal in the petrous part of the temporal bone. 

Transmits cranial nerves VII (facial) and VIII (vestibulocochlear), and labyrinthine vessels. 

Leads from the posterior cranial fossa to the inner ear. 

ossicular chain (middle ear bones)

Three small bones that transmit sound from the tympanic membrane to the inner ear: 

Malleus (hammer) – Attached to the tympanic membrane. 

Incus (anvil) – Connects malleus to stapes. 

Stapes (stirrup) – Base (footplate) fits into the oval window of the cochlea. 

transmission of sound across middle ear

Sound waves hit the tympanic membrane, causing it to vibrate. 

Vibrations are passed through the ossicles (malleus → incus → stapes). 

Stapes footplate pushes on the oval window, transmitting vibrations into the fluid-filled cochlea (inner ear), where they are converted into nerve impulses. 

physiology of hearing - inner ear 1

footplate of stapes moves in and out of oval window creating a travelling wave in the scala vestibuli and scala tympani of the cochlea

causes movement of the basilar membrane and movement of inner and outer hair cells in the organ of corti in relation to the tectorial membrane

physiology of hearing - inner ear 2

cilia of the hair cells are deflected and ion channels open

cations flow from the endolymph into the hair cells

depolarisation takes place and an impulse is sent up the cochlear nerve

inner hair cells activate the afferent nerves

outer hair cells modify the response of the inner hair cells

physiology of the inner ear - 3

For every frequency there is a specific place on the basilar membrane where the hair cells are maximally sensitive to that frequency.  This is known as a tonotopic arrangement.

importance of eustachian tube in middle ear function

equalises air pressure - during swallowing or yawning, allows pressure to be equal on both sides preventing damage to the eardrrum ensuring it can vibrate properly for hearing

drains fluid

protects ear from pathogens

inter connection of middle ear, mastoid air cell system and post nasal space (nasopharynx)

interconnected systems that rely on each other for air pressure regulation and the transmission of air

The postnasal space (nasopharynx) connects to the middle ear via the Eustachian tube which allows for pressure equalisation. The middle ear is connected posteriorly to the mastoid air cells, a network of air-filled cavities, through a bony passage called the aditus. The mastoid air cells are thought to act as a gas reserve for the middle ear, further helping to stabilize its pressure 

the course of facial nerve in the middle ear cavity and its importance to the surgeon

The facial nerve runs through the middle ear, traveling posterosuperior to the oval window, then inferiorly along the medial and posterior walls of the tympanic cavity before exiting downward in the mastoid.

Its importance to surgeons is that this nerve is vital for facial expression and other function

bony anatomy of the inner ear and function of the parts

Labryinth - the complex, fluid-filled system of channels in the inner ear responsible for hearing and balance 

Cochlea – controls hearing 

Vestibular system – controls balance 

bony labrynth, membranous labrynth, perilymph

• The bony labyrinth encloses the membranous labyrinth, which is a system of connected fluid-filled sacs and tubes. 

• The space between the bony and membranous labyrinths is filled with a fluid called perilymph. 

• The membranous labyrinth itself contains another fluid, endolymph, which plays a crucial role in transmitting sound and balance information. 

intra-cranial relations of the middle ear and mastoid system

This connection means that infections can spread from the middle ear to the mastoid air cells and, in severe cases, to the cranial cavity itself, leading to serious complications like meningitis or brain abscesses. The system is also adjacent to important nerves, including the facial nerve (CN VII) and the vestibulocochlear nerve (CN VIII), which are at risk during an infection. 

basic principles of pure tone audiometry and tympanometry

pure tone audiometry measures hearing sensitivity by presenting pure tones of varying frequencies and volumes to determine the softest sound a person can hear at each frequency

 tympanometry measures middle ear function by testing the movement of the eardrum and its compliance with changes in air pressure

neural pathway of hearing

The neural pathway of hearing begins with sound waves causing vibrations that travel from the outer ear to the inner ear's cochlea, where they are converted into electrical signals by hair cells.

These signals are sent via the cochlear nerve to the brainstem, which processes them in the cochlear nucleus.

The pathway continues through the midbrain (inferior colliculus) and thalamus (medial geniculate nucleus) before finally reaching the auditory cortex in the temporal lobe, where sound is consciously perceived.