CNS Neuroanatomy & Neurophysiology 2

Question 1

A patient has a right eye that is deviated 'down and out' with ptosis and a dilated pupil. Which cranial nerve is most likely affected?

Accepted Answer

Oculomotor nerve (CN III)

Answer

CN III palsy leaves the lateral rectus (CN VI) and superior oblique (CN IV) unopposed, producing a down-and-out eye with ptosis and mydriasis.

Question 2

Which cranial nerve has the longest intracranial course, making it vulnerable to palsy with raised intracranial pressure?

Accepted Answer

Abducens nerve (CN VI)

Answer

CN VI travels a long path over the petrous apex, so increased ICP can stretch it and cause a false localizing lateral rectus palsy.

Question 3

A patient cannot wrinkle the forehead or close the eye on the left and has a drooping left mouth corner. Where is the lesion most likely located?

Accepted Answer

Left facial nerve

Answer

Lower motor neuron facial nerve lesions cause ipsilateral weakness of the entire face, including the forehead.

Question 4

Which brainstem structure contains the nuclei of cranial nerves IX, X, XI, and XII?

Accepted Answer

Medulla oblongata

Answer

The medulla houses the nuclei for CN IX through XII, governing swallowing, phonation, and tongue movement.

Question 5

Tongue deviation toward the right on protrusion indicates a lesion of which nerve?

Accepted Answer

Right hypoglossal nerve

Answer

The intact genioglossus pushes the tongue toward the weak side, so deviation to the right indicates a right CN XII lesion.

CNS - Certified Neuro Specialist Practice Test