How will the optic disc appear during fundoscopy if there is raised intracranial pressure?
Papilloedema = swelling of the optic nerve
- Optic disc = swollen with blurred margins
How will the optic disc appear during fundoscopy if there is raised intra-ocular pressure?
Optic disc cupping
What is optic disc cupping?
Increased diameter of central cup of optic nerve, due to increased intra-ocular pressue
* sign of glaucoma
What is a Meibomian cyst? How is this different to a stye?
Blocked Meibomian gland within tarsal plate
Stye = blocked sebaceous gland at base of eyelash (infected hair follicle)
Outline the consensual pupillary light reflex:
- Light shone in left eye
- Sensory afferent from L retina via CN II
- To Pretectal nucleus (brainstem)
- To BOTH L + R Edinger-Westphal nuclei
- Parasympathetic fibres hitchhike on CN III
- Innervate both sphincter pupillae
= Both L + R pupils constrict
What are the afferent and efferent nerves of the pupillary light reflex?
Afferent = CN II Efferent = CN III
Why might someone not be able to look up if they have a blow-out fracture?
Blow-out fracture = fractured floor of orbit
- Orbital fat can prolapse and ocular-muscles can become trapped
- Haematoma may form in inferior rectus
- Inferior rectus contracts in response to damage, preventing patient from looking up
Why might someone with a blow-out fracture have reduced sensation over their cheek?
- Damage to the inferior orbital branch of CN V2
- -> Emerges below orbit via infra-orbital foramen
What are the effects on lacrimation if orbicularis oculi is damaged?
- Inferior eyelid retracts, exposing cornea
- Cornea becomes dry and unprotected
- Constant corneal irritation increases lacrimal secretion
- Risk of ulceration
Which nerve stimulates the lacrimal gland?
Parasympathetic fibres associated with CN VII
-> via Greater petrosal to pteygopalatine ganglion to gland
How can thrombophlebitis of the facial veins spread into the cranial cavity?
Facial veins drain directly into internal jugular vein,
BUT have anastamoses with superior + inferior ophthalmic veins which drain into cavernous sinus
What are the afferent and efferent nerves of the corneal blink reflex?
Afferent = CN V1 (Ophthalmic) Efferent = CN VII
How is visual acuity tested?
Name the 4 parts of the temporal bone:
- Squamous part
- Petromastoid part
- Tympanic plate
- Styloid process
The external acoustic meatus lies within which part of the temporal bone?
Describe the epithelium of the external acoustic meatus:
- Cartilaginous outer 1/3rd = is lined with hairs + produces cerumen (+ dead cells = wax)
When examining the ear, how should the pinna be manipulated for ideal view of the tympanic membrane?
Child = Down + back Adult = UP, OUT + BACK
The middle and inner ear lie in which part of the temporal bone?
What is the function of the external ear?
Collect, transmits + focuses sound waves onto tympanic membrane
What is the approx. length of the external acoustic meatus?
~ 2.5 cm long
What is the approx. diameter of the tympanic membrane?
~ 1 cm
Which nerve innervates the internal surface of the tympanic membrane?
What structures does the middle ear cavity communicate with anteriorly and posteriorly?
Ant = nasopharynx via eustachian tube Post = Mastoid air cells
Why is it important for the middle ear cavity to be connected to the nasopharynx?
- Allows equalisation of air pressure between middle ear + atmosphere
- Allows drainage + ventilation
When is the Eustachian tube opened?
- opened due to pull of palate muscles
Name the ossicles:
Which ossicle is attached to the tympanic membrane?
Which ossicle articulates with the bony labyrinth of the inner ear (via oval window)?
What is the function of the ossicles?
Amplify and concentrate sound energy from eardrum to oval window
Which muscles reduce sound amplitude by resisting ossicle movement? Which nerves innervate them?
- Stapedius - CN VII
- Tensor tympani - CN V3
The membranous labyrinth of the ear sits within the bony labyrinth. Name the fluid which separates these structures:
Name the fluid contained within the membraneous labyrinth:
Which organ lies within the cochlear, and is reponsible for hearing?
Spiral organ of Corti
Describe the process of hearing:
- Sound waves are transmitted down the external ear, causing vibration of the tympanic membrane
- Vibration of the ossicles results in transmission of the sound waves to the oval window
- Causes wave motion of the endolymph within the membranous labyrinth
- Stimulates hair cells triggering AP in CN VIII > Brain