Extraocular Muscle Palsy Flashcards
What are the 7 extraocular muscles?
Superior rectus
Inferior rectus
Medial rectus
Lateral rectus
Superior oblique
Inferior oblique
Levator palpebrae superioris
What are the functions of the rectus muscles?
Superior rectus - elevation of orbit
Inferior rectus - depression of orbit
Medial rectus - adduction of orbit
Lateral rectus - abduction of orbit
What are the functions of the oblique muscles?
Superior oblique
- intorsion (medial rotation)
- depression
Inferior oblique
- extorsion (lateral rotation)
- elevation
What is the function of the levator palpebrae superoris?
Elevates upper eyelid
What is the acronym which can be used to remember the innervations of the extraocular muscles?
LR6 SO4 AO4
Lateral rectus - CN VI (abducent)
Superior oblique - CN IV (trochlear)
All others - CN III (oculomotor)
What muscle(s) does CN VI innervate?
Lateral rectus
What muscle(s) does CN IV innervate?
Superior oblique
What muscle(s) does CN III innervate?
“All others”
Superior rectus Inferior rectus Medial rectus Inferior oblique Levator palpebrae superioris
How does CN VI palsy present?
Diplopia (horizontal)
Loss of abduction
Distant vision loss (abduction occurs when looking in distance)
How does CN IV palsy present?
Diplopia (vertical)
Loss of depression when eye adducted
Head tilt (compensatory mechanism for loss of intorsion)
Difficulty looking down (loss of depression)
Of CN III, IV and VI, which nerve is most prone to traumatic damage and why?
CN IV
Is thin and has longest intracranial course
How does CN III palsy present
Diplopia (diagonal)
Exotropia (from unopposed lateral rectus)
Hypotropia (from unopoosed superior rectus)
^^looking down and out^^
Ptosis (levator palpebrae superioris palsy)
Dilated pupil (sphincter pupillae palsy)
Sudden onset diplopia with mydriasis suggests palsy of which cranial nerve?
CN III
Diplolpia from exotropia and hypotropia
Mydriasis from sphincter pupillae muscle palsy
Of CN III, IV and VI, which nerve is most likely to be damaged by an aneurysm?
CN III
close proximity to posterior communicating artery
Sudden onset diplopia and headache suggests palsy of which cranial nerve?
CN III
Diplolpia from exotropia and hypotropia
Headache from aneurysm
