otitis media Flashcards
what is otitis media?
-infection of the middle ear
what is the middle ear?
-the space that sits between the tympanic membrane and the lateral wall of the inner ear
what is contained in the middle ear?
- auditory ossicles (malleus, incus, stapes)
- tensor tympani
- stapedius
- auditory tube/ Eustachian tube (anterior wall of middle ear)
which bone does the middle ear lie within?
-temporal bone
what is the main function of the middle ear?
-to transmit vibrations from the tympanic membrane to the inner ear via the auditory ossicles
what can the middle ear be divided into?
2 parts:
- Tympanic cavity (contains auditory ossicles: malleus, incus and stapes)
- Epitympanic recess (a space superior to the tympanic cavity which lies next to mastoid air cells. The malleus and incus partially extend into it)
describe the epitympanic recess
-a space superior to the tympanic cavity that lies beside the mastoid air cells. The malleus and incus partially extend upwards into the epitympanic recess
what is the roof of the middle ear made up of?
-thin petrous portion of the temporal bone
what is in the floor of the middle ear?
-internal jugular vein and thin layer of bone
what is in the posterior wall of the middle ear?
- this is the mastoid wall
- it consists of a bony partition that separates the ear and the mastoid air cells
what is on the anterior wall of the middle ear?
- there are two openings, one for the Eustachian tube and another for the tensor tympani muscle which attaches to the malleus
- this wall separates the middle ear from the internal carotid artery
what is on the lateral wall of the middle ear?
- tympanic membrane
- lateral wall of epitympanic recess
what is on the medial wall of the middle ear?
- oval and round windows
- facial canal containing facial nerve (innervates the stapedius muscle)
- promontory (bump formed by the first turn of the cochlear)
what nerve innervates the stapedius muscle?
CNVII (facial nerve)
what nerve innervates the tensor tympani?
CNV3 (mandibular division of trigeminal nerve) as the tensor tympani dulls noise during mastication
roles of the tensor tympani and stapedius?
- they contract in response to loud noise, protecting the inner ear by inhibiting vibrations and dulling the noise
- this is also known as the acoustic reflex
where are mastoid air cells loacted?
-in the posterior epitympanic recess within a cavity called the mastoid antrum
role of the mastoid air cells?
- they act as a buffer system for air
- they release air into the tympanic cavity when pressure is too low
what are the most common causes for otitis media?
Most common bacterial cause:
- streptococcus pneumoniae (most common)
- Haemophilus influenzae
- Moraxella catarrhalis
- staphylococcus aureus
Other:
- rhino sinusitus
- tonsilitis
how does otitis media present?
- ear pain
- may have reduced hearing
- feeling generally unwell with a fever
- may have symptoms of URTI such as cough, coryzal symptoms and sore throat
how may otitis media present on otoscopy?
-bulging red, inflamed looking ear drum
what is the treatment for otitis media?
80% will resolve in 4 days without any treatment
1st line= amoxicillin
2nd line= erythromycin