Extraocular Muscles & Palsies

Question 1

Causes of anisocoria:

Answer 1

IRIS PHYSIOLOGICAL*
Physiological
3rd nerve palsy
–> Cav sin, PCOM, pituitary
Horner’s
Use of cycloplegic/ mydriatic/ miotic

IRIS MECHANICAL
Traumatic mydriasis (iris concussion)
Trauma to iris
Iritis (anterior uveitis)
Acute angle closure

LIGHT PERCEPTION
Severe retinal disease
Optic neuritis/neuropathy
–> Incl. retrobulb haemor, orbital cell, GCA
–> UNCAL herniation

Question 2

CN III palsy: features

Answer 2

Levator Palpebrae
Medial rectus, Superior rectus, Inferior rectus
Inferior oblique
‘Opposite’ to CNs IV, VI
____________________

Ptosis
‘Down and out’
Fixed, dilated pupil (compressive only)

Question 3

CN III palsy: causes

Answer 3

ISCHAEMIC
- Microvascular (eg. Diabetes, HTN)

COMPRESSIVE
- Uncal herniation
- PCOM aneurysm
- Cavernous sinus thrombosis
- Pituitary tumour/ apoplexy

Other: Ophthalmoplegic migraine, demyelination, trauma, neuritis, midbrain lesion (bilat) etc.

Question 4

CN IV palsy: features

Answer 4

Superior Oblique (down + out).

____________________________
Head tilt makes eyes look normal. Other muscles can compensate for movements a lot. SUBTLE.

• Up and in (subtle)
• Head tilt (to good side)

Question 5

CN VI palsy: features

Answer 5

Lateral rectus

Question 6

Describe a relative afferent pupillary defect (RAPD) and its significance:

Answer 6

• Swinging light test.
• Usually, direct and consensual response.
• In POSITIVE RAPD: light in good eye causes normal direct + consensual constriction. Light in bad eye isn’t perceived, so both eyes dilate.

Signifies optic nerve or severe retinal problem.

A= normal
B= RAPD
C= RAPD plus fixed pupil