Cranial Nerves & Brainstem — Clinical Reasoning Quiz

A patient has ptosis, a dilated pupil, and an eye positioned down and out. Which cranial nerve is most likely affected?

• CN II
• CN III
• CN IV
• CN VI
• CN VII

A patient develops vertical diplopia that is worse when walking downstairs and when looking down and to the left. Which nerve is most likely injured?

• Left CN III
• Left CN IV
• Left CN VI
• Right CN IV
• Right CN VI

A patient cannot abduct the right eye. Which muscle and cranial nerve are affected?

• Right medial rectus, CN III
• Right lateral rectus, CN VI
• Right superior oblique, CN IV
• Left lateral rectus, CN VI
• Right inferior oblique, CN III

A lesion causes loss of facial sensation in the forehead, cornea, and upper face but spares the lower face. Which division is affected?

• V1
• V2
• V3
• VII
• IX

Touching the cornea produces no blink in either eye, but facial sensation elsewhere is normal. Which afferent pathway is most likely impaired?

• CN II
• CN V1
• CN VII
• CN IX
• CN X