7. Anatomy Of The Ear Flashcards
What are some of the signs and symptoms of ear disease?
Otalgia (ear pain) Discharge Hearing loss Tinnitus Vertigo Facial nerve palsy
What does the external ear contain?
Pinna
External auditory meatus
Skin-lined
What does the middle ear contain?
Air filled cavity
Ossicles
Lined with respiratory epithelium
Pharyngotympanic tube connects it to nasopharynx
Where is the tympanic membrane?
Between external ear and inner ear
What does the inner ear contain?
Cochlea
Semicircular canals
Fluid filled
Which nerves carry general sensation from ear and can therefore cause referred pain?
Branches of:
- cervical spinal nerves (C2/3)
- vagus
- trigeminal
- glossopharyngeal
What should otalgia with a normal ear examination lead you to suspect?
An alternative site of pathology
E.g. TMJ dysfunction (CNVc), diseases of oropharynx (CNIX), disease of larynx and pharynx including cancers (CNIX, X)
What is the role of the external ear?
Collects, transmits and focuses sound waves onto the tympanic membrane
What are some abnormalities or conditions of the pinna?
Ramsay-hunt syndrome
Perichondritis
Pinna haematoma
What is a pinna haematoma?
Accumulation of blood between cartilage and its overlying perichondrium from blunt injury
What is the consequence of subperichondrial haematoma?
Deprives cartilage of blood supply and pressure necrosis of tissue
How do you treat pinna haematoma?
Drainage and prevent re-accumulation/re-apposition of 2 layers
What can happen if a pinna haematoma is not treated?
Fibrosis, new asymmetrical cartilage development, leads to cauliflower deformity
Roughly how long is the external acoustic meatus?
2.5cm
What is the external acoustic meatus made up of?
Cartilaginous (outer 1/3) and bony (inner 2/3) - sigmoid shape
What is inside the external acoustic meatus?
Hair, sebaceous and ceremonious glands line cartilage part, barrier to foreign objects
What does the bony part of the external acoustic meatus lack?
Glands and hairs
What do the ceremonious glands produce?
Ear wax
What is otitis externa and what are the symptoms?
Inflammation of external ear (external acoustic meatus)
Itchiness, pain, discharge, possible hearing loss
What are the most common bacterial causes of otitis externa?
Pseudomonas aeruginosa
Staphylococcus species
What is a serious complication of otitis externa?
Malignant otitis externa - potentially life-threatening, bacteria erodes through bone
How is at particular risk of developing malignant otitis externa?
Immunocompromised including diabetes
What are the common abnormalities of tympanic membrane?
Tympanosclerosis (scarring)
Bulging secondary to bacterial acute otitis media
Retracted and evidence of fluid within middle ear cavity (otitis media with effusion) - glue ear
What is a cholesteatoma?
Retraction of pars flaccida (TM) forms a sac/pocket, trapping stratified squamous epithelium and keratin
Proliferates forming cholesteatoma
What is cholesteatoma usually secondary to?
Chronic Eustachian tube dysfunction - negative pressures pull the pocket into the middle ear
What are the symptoms of cholesteatoma?
Painless, often smelly otorrhea (discharge), hearing loss
What are the possible consequences of cholesteatoma?
Not malignant but slowly grows and expands
Potentially mor serious consequences due to enzymatic bony destruction e.g. erode ossicles, mastoid/petrous bone, cochlea
What are the ossicles in the middle ear?
Malleus
Incus
Stapes
What is the role of the ossicles?
Amplify and relay vibrations from the TM to the oval window of the cochlea
What tampers the ossicles movement?
Muscles tensor tympani and stapedius
What is otosclerosis?
Acquired hearing loss
What happnes in otosclerosis?
Ossicles fused at articulations due to abnormal bone growth particularly between base plate of stapes and oval window
Sound vibrations cannot be transmitted effectively to cochlea
What do patients with otosclerosis present with?
Gradual unilateral or bilateral conductive hearing loss
What does the pharyngotympanic tube do?
Equilibrates pressure of middle ear with atmospheric pressure
How does the pharyngotympanic tube equilibrate pressure?
Mucous membrane of middle ear continuously reasons air in middle ear causing negative pressure
Pharyngotympanic tube allows equilibration of pressure within middle ear cavity with that of atmosphere
Allows for ventilation of and drainage of mucus from middle ear
What is otitis media with effusion?
Glue ear
Fluid and negative pressure in middle ear - decreases mobility of TM and ossicles, affecting hearing
Due to Eustachian tube dysfunction
How do you get rid of otitis media with effusion?
Most resolve spontaneously in 2-3 months
,at persist and/or impede speech and language development/school performance - requires grommets
What is acute otitis media?
Acute middle ear infection
What are the signs and symptoms of acute otitis media?
Otalgia
Other non-specific symptoms e.g. temperature
Red/bulging TM and loss of normal landmarks
What are the bacterial (occasional) causes of acute otitis media?
Streptococcus pneumoniae
Haemophilus influenzae
What usually causes acute otitis media?
Usually viral
Why are children more susceptible to ear problems?
Pharyngotympanic tube is shorter and more horizontal in infants
Therefore, easier passage for infection from nasopharynx to middle ear
Tube can block more easily (adenoids), compromising ventilation and drainage of middle ear, increasing risk of infection/glue ear
What are some complications of acute otitis media?
Tympanic membrane perforation
Facial nerve involvement (rare)
Rarer but potentially life-threatening: mastoiditis, intracranial complications (meningitis, sigmoid sinus thrombosis, brain abscess)
What is mastoiditis?
Infection that affect mastoid bone
Swollen and red behind ear, possible ear pushed forward
Why can mastoiditis occur?
Middle ear cavity communicates via mastoid antrum with mastoid air cells
Provides a potential route for middle ear infections to spread into the mastoid bone
What does the inner ear consist of?
Vestibular apparatus and cochlea
What is the inner ear involved in?
Hearing and position-sense/balance
What happens in the cochlea?
Fluid movement (generated by footplate of stapes) Converted into action potentials (in CNVIII) -> perceived as sound
What happens in the vestibular apparatus?
Fluid movement (generated by position and rotation of head) Converted into action potentials (in CNVIII) -> perceived as position sense and balance
What do inner ear pathology present with?
Hearing loss (sensorineural)
Tinnitus
Disturbances of balance and vertigo
What is the cochlea?
Fluid-filled tube with specialise hair cells that generate action potentials when moved
What causes movement of fluid in cochlear duct?
Movements at the oval window
What do the waves of fluid cause in the cochlea?
Movement of special sensory cells (stereocilia)
Which generate action potentials via CNVIII
What is the vestibular apparatus?
Fluid-filled tubes with specialised hai cells that generate action potentials when moved
What does the vestibular apparatus include?
Semicircular ducts
Saccule
Utricle
How does the vestibular apparatus work?
Moving position or road action of head, moves fluid
Bends stereocilia
Generate actions potentials via CNVIII
What is presbycusis?
Sensorineural hearing loss associated with old age
Bilateral and gradual
Affects cochlea or vestibular apparatus
What is benign paroxysmal positional vertigo?
Vertigo only
Short lived episodes, triggered by movement of head
Affects vestibular apparatus
What are the diagnostic tests/treatments for benign paroxysmal positional vertigo?
Dix-hallpike
Epley manoeuvres
What is Ménière’s disease?
Vertigo, hearing loss and tinnitus
Affects both cochlea and vestibular apparatus
May describe aural fullness, nausea and vomiting
Symptoms longer lasting
Recovery in between
Hearing may deteriorate over time
What is acute labrynthitis?
History of upper respiratory tract infection
Affects both cochlea and vestibular apparatus
Involvement of all inner ear structures, associated with hearing loss/tinnitus, vomiting and vertigo
What is acute vestibular neuronitis?
History of upper respiratory tract infection
Affects both cochlea and vestibular apparatus
Usually no earring disturbance or tinnitus
Sudden onset of vomiting and severe vertigo
