Functional anatomy and disorders of the Ear Flashcards
What symptoms and signs can be indicative of ear disease?
- Otalgia (ear pain)
- Discharge
- Hearing loss
- Tinnitus
- Vertigo
- Facial nerve palsy
Identify the External, Middle and Inner Ear and describe the features of each
- External (blue): consists of the pinna, external auditory meatus which is skin lined
- Middle (pink): air filled cavity, ossicles, lined with respiratory epithelium , Pharyngotympanic tube connects middle earto oropharynx
- Inner (green): Consists of cochlea and semicircular canals, fluid filled
Identify which nerves carry general sensation from the ear (touch, temperature and pain) and the areas that are supplied by each
- Cervical spinal nerves (C2/ C3) - most of the pinna and down the neck, area of the scalp behind the ear
- Vagus nerve- lateral surface of tympanic membrane, external acoustic meatus, pharynx and larynx, conchae
- Trigeminal (auroculotemporal branch)- lateral surface of tympanic membrane, external acoustic meatus, scalp in area of temples, TMJ, pre-auricular and tragus
- Glossopharyngeal (tympanic branch)- posterior tongue, tonsils and pharynx, middle ear, medial tympanic membrain, mastoid air cells
- Small contribution from facial nerve
Which nerve provides special sensory (hearing and balance) to the ear?
Vestibulocochlear CN VIII
If someone has Otalgia (ear pain) with normal ear examination what kind of things should you suspect?
Otalgia may be from an alterative site of origin, including:
- TMJ dysfunction (CN Vc)
- Diseases of the oropharynx (CN IX)
- Disease of the larynx and pharynx including cancer
What is the function of the external ear?
Collects, transmits and focuses sound waves onto the tympanic membrane
A patient presents with facial nerve palsy and a painful, red ear with vesicles.
What condition is this?
Ramsey- Hunt Syndrome
Which is shingles of the the facial nerve
What is perichondritis of the ear?
Inflammation of the cartilage of the pinna
What is a pinna haematoma?
An accumulation of blood between the cartilage and its overlying pericondrium of the ear
Occurs secondary to blunt trauma- common in contact sports
What are the consequences of a pinna haematoma? How would you treat to prevent this happening?
The subperichondrial hameatoma deprives cartilage of blood supply causing pressure necrosis
If untreated will cause fibrosis → cauliflower ear
Treatment: Drain the blood and apply cotton rolls to the ear to push the perichondrium back onto the cartilage of the ear
What are some of the features of the external acoustic meatus?
- Sigmoid shape
- Carilaginous outer (1/3) and bony inner (2/3)
- Lined with keratinising, stratified squamous epithelium that continues onto the lateral surface of the tympanic membrane
- Cartilage lined with hair, sebaceous and ceruminous glands which produce ear wax
- No glands or hairs on the bony part
What is the purpose of epithelial migration in the external acoustic meatus?
Desquamation and skin migrate laterally off the tympanic membrane out of the canal as a self cleaning function
What common conditions involve the external acoustic meatus?
- Wax
- Foreign bodies
- Otisis externa
What is a rare but serious complication of otitis externa infection?
Who is more at risk of developing this?
Malignant otitis externa
Infection (usually P.aeruginosa) spreads to the bone causing necrosis
Potentially life threatening
Immunocompromised patients (inc. diabetics) more at risk
This tympanic membrane is bulging outwards, what could have cause this?
secondary to a bacteral acute otitis media
This tympanic membrane is retracted with evidence of fluid in the middle ear cavity. What could have cause this?
Otitis media with effusion
Positive pressure in the middle ear sucks in the tympanic membrane
What is cholesteatoma?
How is it formed?
An abnormal, non cancerous growth of the middle ear
Usually secondary to a chronic eustacian tube dysfunction where the negative pressure pulls the typmanic membrane into a pocket in the middle ear, trapping stratified squamous epithelium and keratin which proliferate to give cholesteatoma
What are some of the symptoms of cholesteatoma?
- Painless
- often smelly otorrhea (ear discharge)
- +/- hearing loss
What is a more serious consequence of cholesteatoma?
Cholesteatoma can grown and expand, potentially causing erosion of the ossicles, mastoid/ petrous bone and the chochlea
Which bones make up the ossicles?
- Malleus
- Incus
- Stapes
What are the functions of the ossicles?
- Ossicles are connected via synovial joints
- They amplify and relay vibrations from typanic membrane to the oval window of the cochlea by transmitting vibration waves in a fluid medium
Which two muscles tamper the movement of the ossicles?
Tensor Tympani and Strapedius
Contract if there is excessive vibration due to loud noise - known as the acoustic refex
Otosclerosis is one of the most common causes of aquired hearing loss in young adults, explain what it is
Otosclerosis = fused ossicles at articulations due to abnormal bone growth (particularly between base plate of stapes and oval window)
Therefore sound vibrations cannot be transmitted effectively to the cochlea
Both genetic and environmental causes. Present with granual, unilater/ bilateral conductive hearing loss
What is the function of the Pharyngotypmanic Tube (Eustacian Tube)
Explain how it does this
Equilibriates pressure of the middle ear with atmospheric pressure
How:
- mucous membrane of middle ear continually reabsorbs air in the middle ear causing negative pressure
- ET allows eliquilibrium with atmospheric pressure, stopping pressure getting too negative
- ET also allows for ventilation and drainage of mucus from the middle ear
What is ‘glue ear’
Not an infection! → otitis media with effusion due to eustacian tube dysfunction
A build up of negative pressure and fluid in the middle eat cause a retracted, straw coloured tympanic membrane
Decreases mobility of TM and ossicles affecting hearing
How long does it take for glue ear to resolve and what measures can you take if it doesn’t?
Usually resolves spontaneously 2-3 months
Doesn’t resolve may require grommets (tympanostomy tube)- a tube that equilibrates pressures
secondary function … drains fluid from middle ear
Which microorganisms cause acute otitis media?
Mostly viral
Bacterial causes occasionally:
- Streptococcus pneumoniae
- Haemophilus influenzae
Why is it easier for infants to get middle ear infections?
Infancts have a shorter, more horizontal eustacian tube
This makes it easier for infection from the nasopharynx to spread to the middle ear
Tube can block more easily, compromise ventialtion and drainage increasing risk of glue ear
What complications can arise as a consequence of acute otitis media?
- Tympanic membrane perforation
- Facial nerve involvement - due to close relationship with middle ear (chorda tympani and nerve to strapedius run through middle ear)
Rarer but potentially life threatining complications:
- mastoiditis
- intracranial: meningitis, sigmoid sinus thrombosis or brain abscess
A young girl with a recent history of fever, runny nose and acute otitis media. She presents with a swollen, red area behind the ear and it is pushed forward.
What is the diagnosis and explain how this happens with reference to the ear anatomy?
Mastoiditis
The middle ear cavity comminicates with mastoid air cells via the mastoid antrum. This provides a potential route for middle ear infectios to spread to mastoid air cells in the bone
What are the 2 structures of the inner ear and what is the function of each?
Cochlea: Conch shaped fluid tube → converts fluid movement from footplate of stapes into action potentials in vestibulocochlear nerve → percieved as sound
Vestibular apparatus: Fluid filled tube converts fluid movement from head rotations into action potentials in vestibulocohlear nerve → percieved as sense & balance
How can diseases of the inner ear present?
One, or a combination of:
- Hearing loss (sensorineural)
- Tinnitus
- Disturbances in balance and vertigo
Explain how the cochlea generates action potentials
- Movements of the stapes on the oval window set up movement of fluids in the cochlea duct
- Waves of fluid cause movement of stereocilia (special sensory hair cells) that generate AP in CN VIII
Explain the step-by-step process of how we hear (5)
- Auricle and external auditory canal focus & funnel sound waves towards the tympanic membrane which vibrates
- Vibration of the ossicles (stapes at oval window) sets up vibrations of cochlear fluid
- Stereocilia in cochlear duct sense fluid movement (part of the spiral organ of Corti)
- Stereocilia in organ of Corti triggers action potentials in the cochlear part of CN VIII
- Action potentials on CN VIII sensed by the primary auditory cortex in the temporal lobe
How do the semicircular canals transmit information on balance?
Vestibular apparatus made up of semicircular ducts, the saccule and utricle which are all fluid filled tubes
Fluid moves depending on position or rotation of the head
Fluid bends stereocilia which generates action potentials via vestibular part of CN VIII
Percieved and maintain our sense of balance
What is presbycusis?
Natural, age- related sensorineural hearing loss
Usually bilateral and gradual
What is Benign Paroxysmal Positonal Vertigo?
Tiny, solid fragments (octonia) that get lodged in the innear ear labrynth (semi-circular canals)
Causes short episodes of intense dizziness when moving the head in certain positions
What is Meniere’s Disease?
Vertigo, hearing loss and tinnitus (typical unilateral)
- Describe ‘aural fullness’ and nausea and vomiting
- Symptoms last 30mins-24 hrs
- Reccurrent episodes, hearing may deteriorate over time
What is acute labrynthitis?
A history of upper respiratory tract infection
Hearing loss/ tinnitus, vomiting and vertigo
Involves all inner ear structures
What is Acute Vestibular Necrotitis?
A history of upper respiratory tract infection
Sudden onset of vomiting and sever vertigo in recent days
has no hearing disturbance or tinnitus
Explain the Weber’s and Rinne’s hearing tests
What are some of the causes of conductive hearing loss?
- Wax
- Acute Otitis media
- Otitis media with effusion
- Otoscerosis
What are some of the causes of sensorineual hearing loss?
Pathologies involving the inner ear or vestibulocochlear nerve
- Presbyacusis
- Noise- related hearing loss
- Meniere’s Disease
- Ototoxic medications
- Acoustic neuroma
