Neuroanatomy & Neurophysiology Flashcards

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?

Answer: Oculomotor nerve (CN III)

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.

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

Answer: Abducens nerve (CN VI)

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

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?

Answer: Left facial nerve

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

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

Answer: Medulla oblongata

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

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

Answer: Right hypoglossal nerve

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

The corneal reflex tests which combination of cranial nerves?

Answer: CN V afferent and CN VII efferent

The ophthalmic branch of CN V senses the corneal touch and CN VII produces the blink.

A patient with a pontine lesion has pinpoint pupils. What mechanism best explains this finding?

Answer: Disruption of descending sympathetic fibers leaving parasympathetic tone unopposed

Pontine lesions interrupt descending sympathetic pathways, so parasympathetic constriction predominates and pupils become pinpoint.