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 the 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 the horizontal plane.

Question 4

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

Answer 4

Depression, extorsion and adduction.

Question 5

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

Answer 5

Elevation, intorsion and adduction.

Question 6

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

Answer 6

Intorsion, depression and abduction.

Question 7

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

Answer 7

Extorsion, elevation and abduction.

Question 8

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

Answer 8

Stand in front of the patient. Ask them to follow your finger with their eyes while keeping their head in one position Using your finger, trace an imaginary “H” or rectangular shape in front of them, making sure that your finger moves far enough out and up so that you’re able to see all appropriate eye movements (i.e. lateral and up, lateral down, medial down, medial up). At the end, bring your finger directly in towards the patient’s nose. This will cause the patient to look cross-eyed and the pupils should constrict- accommodation.