Week 2 - H - Ophthamology 7 - CN III,IV,VI palsies, INO &visual field defects Flashcards
What muscles of the eye are supplied by the oculomotor nerve? (try name 7)
Superior rectus Inferior rectus Medial rectus Inferior oblique Levator palpebrae superioris
What are the features of an oculomotor nerve palsy?
The eye points down and out There is a ptosis (due to the LPS not being supplied - drooping eyelid) There is also a dilated pupil
What are the causes of oculomotor nerve palsy?
Microvascular eg diabetes Tumour If painful - anuerysm
Which muscle of the eye has the main function to abduct, depress and internally rotate the eye? What is the end eye position?
This is the superior oblique muscle Moves the eye down and out
What nerve supplies the superior oblique muscle? WHat does it look like if there is a palsy of this nerve?
Supplied by trochlear nerve. If CN IV palsy Then head is tilted, the eye points up and in and also a vertical diplopia
Which way does the head tilt in a fourth nerve palsy?
To compensate for the double-vision resulting from the weakness of the superior oblique, patients characteristically tilt their head down and to the side opposite the affected muscle ie if Right SO palsy, patients head will tilt left
What is the most common cause of fourth nerve palsies?
Congenital trauma
Blunt nerve trauma can cause a bilateral trochlear nerve palsy What happens here as presentation?
Will cause depressed chin
What muscle causes abduction of the eye? What nerve supplies it? What does palsy if this nerve present like?
Lateral rectus supplied by the abducent nerve Palsy presents like eye is unable to look laterally and eyes will be medially deviated, horizontal diplopia
What type of squint is the one seen in abudcent nerve palsies?
This would be an esotropic squint (convergent squint)
What is the main cause of sixth nerve palsies? and therefore what is ususally also seen on fundoscopy?
Raised intracranial pressure Therefore may seen papilloedema on fundsocopy
Which cranial nerve palsy is common in diabetic retinopathy - a microvascular complication of diabetes? (all three can have palsies due to it remember)
This would be cranial nerve VI palsy
Why is cranial nerve VI palsy more likely to be affected by an increase intracranial pressure?
This is because it has to curve around the petrous part of temporal bone therefore raised ICP may cause it to push down on this
Why are the pupils involved in oculomotor nerve palsies?
The parasympathetics run on the outside of the nerve and therefore if there is something pressing on the nerve it will also affect this
Eyes need to be able to work at the same time Eg look left involves the left eye using the abducent nerve and the right eye using the oculomotor nerve The nerves are therefore connected by pathways What are these pathways known as?
Known as inter-nuclear pathways