extraocular muscles

Question 1

what are the cranial nerves involved in extraocular movement?

Answer 1

CN III - oculomotor
CN IV - trochlear
CN VI - abducens

Question 2

what muscles do the oculomotor, trochlear and abducens CNs innervate?

Answer 2

oculomotor - everything besides the lateral rectus and superior oblique, plus the levator palpaebrae
trochlear - superior oblique (depression and intorsion)
abducens - lateral rectus (eye abduction)

Question 3

what is the common presentation for a oculomotor palsy

Answer 3

down and out (ptosis and lateral abduction)

pupil sparing is seen in diabetes, cavernous sinus or orbital apex syndrome

lesions involving the pupil suggest a ruptured subarachnoid aneurysm of the PComm and internal carotid junction

Question 4

Dipolopia is what

Answer 4

double vision due to a problem with the extraocular muscles

Question 5

Ptosis

Answer 5

is when the upper eyelid droops because of a CNIII palsy

Question 6

what is the common presentation for a trochlear nerve palsy

Answer 6

a vertical diplopia corrected with a a head tilt away from affected eye

• shear injury (long thin coarse)
• cavernous sinus, orbit problem
• aneurysm
• neoplasm
• infection
• diabetes

Question 7

what is the common presentation for a abducens nerve palsy

Answer 7

a horizontal diplopia

caused by effects of intracranial pressue, hydrocephalus and neoplasm

Question 8

horizontal eye movements are carried out by which extraocular muscles

Answer 8

lateral and medial rectus

Question 9

what nucleus coordinates conjugate horizontal eye movements

Answer 9

MLF - medial longitudinal fasiculus

Question 10

an MLF lesion will cause what condition

Answer 10

intranuclear opthalmoplegia:

no eye abduction on the ipsilateral eye, nystagmus on the contralateral eye

Question 11

cavernous sinus syndrome

Answer 11

affects
- oculomotor nerve, abducens, trochlear, V1 and V2

• causes opthalmoplegia
• fixed dilated pupil
• loss of facial sensation
• caused by pituitary adenoma
• cancers
• carotid aneursyms
• venous thrombosis
• infection, inflammatory disorders
• AV fistulas

Question 12

orbital apex syndrome

Answer 12

affects the same nerves as the cavernous sinus syndrome but includes CN2 (sometimes spares V2)

• same symptoms as the cavernous sinus syndrome but may cause visual loss and proptosis from mass effect

causes:

• neoplasia
• orbital infection
• myositis