Cranial nerve testing of the orbit

Question 1

Which nerves supply which of the extrinsic muscles of the eye?

Answer 1

Trochlear nerve (CNIV) supplies superior oblique. Abducens nerve (CNVI) supplies lateral rectus. Oculomotor nerve (CNIII) supplies the remaining 4 extrinsic eye muscles: inferior oblique, inferior rectus, superior rectus, medial rectus.

SO4, LR6, all the rest 3.

Question 2

What movement does the lateral rectus muscle of the eye control?

Answer 2

Abduction of the eye, i.e. lateral movement along horizontal plane.

Question 3

What movement does the medial rectus muscle of the eye control?

Answer 3

Adduction of the eye, i.e. medial movement along horizontal plane.

Question 4

What movements does the inferior rectus muscle of the eye control?

Answer 4

Depression, extorsion + adduction.

Question 5

What movements does the superior rectus muscle of the eye control?

Answer 5

Elevation, intorsion + adduction.

Question 6

What movements does the superior oblique muscle of the eye control?

Answer 6

Intorsion, depression + abduction.

Question 7

What movements does the inferior oblique muscle of the eye control?

Answer 7

Extorsion, elevation + abduction.

Question 8

How is the function of extrinsic muscles of the eye tested in a clinical setting?

Answer 8

Stand in front of patient + ask them to follow your finger with their eyes without moving their head

Draw a “H” with your finger to test all muscles in the eye

At the end, bring your finger directly in towards the patient’s nose. This will cause the patient to look cross-eyed + the pupils should constrict (accommodation)