Cranial Nerve Questions
1. After Malik experiences head trauma, his doctor gently touches his eyes with a cotton swab to elicit the corneal eye blink reflex. When the doctor touches Malik’s left eye, both of his eyes blink in response. When the doctor touches Malik’s right eye, neither eye blinks. These results suggest a deficit with Malik’s:
- A. Right trigeminal nerve
- B. Right and left oculomotor nerves
- C. Right facial nerve
- D. Right and left trigeminal nerves
Show Answer
Correct answer: A
The corneal eye blink reflex tests the integrity of the trigeminal & facial nerves. The trigeminal nerve is the sensory limb of the reflex & the facial nerve controls the blinking of the eyes. The healthy response to touching one cornea would be that both eyes would blink. In Malik’s case, both facial nerves are functional as indicated by his healthy response to touching his left eye. When his right eye is touched, neither eye blinks, which suggests a problem with his right trigeminal nerve.
2. When a patient attempts to look to the left, his left eye does not move. When he looks straight ahead, his left eye deviates medially (toward his nose). What cranial nerve is likely implicated in the patient's symptoms?
- A. CN III (oculomotor)
- B. CN IV (trochlear)
- C. CN VI (abducens)
- D. CN II (optic)
Show Answer
Correct answer: C
The abducens nerve controls the lateral rectus muscle, which moves the eye laterally (i.e., to the side). When there is damage to the abducens nerve, a patient will often display an inability to move the eye laterally, and when they look straight ahead the eye will deviate medially because of the unopposed action of the medial rectus muscle (which moves the eye medially). There are a number of potential reasons for abducens nerve damage, including trauma, tumors, stroke, infections, and others.
3. A patient arrives at the hospital with several symptoms: her left eye is deviated to the side, she can't move her left eye up or down, she has double-vision, her left eyelid is drooping, and her left pupil is constantly dilated. Which cranial nerve seems to be affected?
- A. her left optic nerve (CN II)
- B. her left facial nerve (CN VII)
- C. her left oculomotor nerve (CN III)
- D. her left abducens nerve (CN VI)
Show Answer
Correct answer: C
The oculomotor nerve controls the function of four of our extraocular muscles as well as the muscle that raises the eyelid and the muscle that constricts the pupil. When the oculomotor nerve is damaged, the collection of symptoms in the question often occurs.
4. Rebecca wakes up one morning to find that she cannot move the left side of her face. Her left eye will not close, her mouth is drooping on the left side, and she can only make facial expressions with the right side of her face. She has not had a stroke, and is apparently healthy besides the symptoms she is experiencing. What cranial nerve seems to have been affected?
- A. facial nerve
- B. trigeminal nerve
- C. oculomotor nerve
- D. vagus nerve
Show Answer
Correct answer: A
The facial nerve controls the muscles of facial expression, and facial nerve dysfunction can cause the symptoms Rebecca is experiencing. When these types of symptoms occur in someone who is otherwise healthy (and thus there is no clear cause of the symptoms), the diagnosis is often Bell's palsy. Bell's palsy involves facial nerve dysfunction with an unknown origin. The symptoms typically come on rapidly, but also usually resolve on their own within several months.
5. After a stroke, a patient is asked to stick his tongue out straight. When he does, his tongue deviates to the left. This suggests damage to:
- A. his right hypoglossal nerve or nucleus
- B. his left glossopharyngeal nerve or nucleus
- C. his left hypoglossal nerve or nucleus
- D. his right glossopharyngeal nerve or nucleus
Show Answer
Correct answer: C
The hypoglossal nerve (cranial nerve XII) controls most of the muscles of the tongue. When there is damage to the hypoglossal nerve or nucleus on one side, it can cause tongue weakness and atrophy of muscles on the side of the damaged nerve/nucleus. When the patient sticks out their tongue, it will typically deviate toward the side of the damage.
6. A patient has severe glaucoma, and a doctor shines a small flashlight into the patient's right eye. Neither the patient's right nor left pupil constrict in response. When the doctor shines the flashlight into the patient's left eye, both pupils constrict. What does this response suggest?
- A. potential damage to the patient's right oculomotor nerve (CN III)
- B. potential damage to the patient's left optic nerve (CN II)
- C. potential damage to the patient's right optic nerve (CN II)
- D. potential damage to the patient's left oculomotor nerve (CN III)
Show Answer
Correct answer: C
The doctor was testing the patient's pupillary light reflex. In a healthy reflex, when a light is shone into one eye, both pupils constrict. If the light is shone into one eye and neither pupil restricts, it suggests a deficit with the sensory portion of the reflex: the optic nerve. In other words, the reflex doesn't occur because the light is not detected. If light is shone into one eye and only one pupil constricts, it suggests damage to the oculomotor nerve on the side lacking a response.
7. A doctor is testing his patient's reflexes after head trauma. The doctor touches the patient's left cornea with a cotton swab, and the left and right eyes blink simultaneously. The doctor touches the patient's right cornea with a cotton swab, and neither eye blinks. This response suggests potential damage associated with the:
- A. right facial nerve
- B. right trigeminal nerve
- C. right oculomotor nerve
- D. right optic nerve
Show Answer
Correct answer: B
The doctor is testing a reflex called the corneal reflex. In a healthy reflex, when one cornea is touched, both eyes blink at the same time. If one cornea is touched and neither eye blinks, it suggests a deficit with detecting the sensation. The trigeminal nerve is the main sensory nerve for the head, and would be responsible for detecting this sensation; thus, the deficit here would likely be with the right trigeminal nerve. The facial nerve is responsible for the motor portion of the reflex.
8. A patient presents with left shoulder weakness and difficulty lifting their left arm. Their left shoulder also is drooping compared to the right, and their left shoulder blade is protruding abnormally far from the back. The doctor determines the patient is experiencing a cranial nerve dysfunction. Which of the following cranial nerves is most likely involved?
- A. Accessory nerve (CN XI)
- B. Trochlear nerve (CN IV)
- C. Vagus nerve (CN X)
- D. Abducens nerve (CN VI)
Show Answer
Correct answer: A
The accessory nerve supplies the sternomastoid and trapezius muscle. The sternomastoid helps to turn your head to the side, as well as bend your neck down or to the side. The trapezius is involved with the movement of the neck and scapula (shoulder blade). Dysfunction of the accessory nerve often causes shoulder pain, impaired arm and shoulder movement, a drooping shoulder, and/or protrusion of the shoulder blade (winged scapula).
9. This is the longest of our cranial nerves as well as the main parasympathetic nerve of the body:
- A. Olfactory nerve (CN I)
- B. Trigeminal nerve (CN V)
- C. Vagus nerve (CN X)
- D. Hypoglossal nerve (CN XII)
Show Answer
Correct answer: C
The vagus nerve is an extremely long nerve that travels from the brainstem to the colon and has a long list of functions. One of those functions is to act as the main parasympathetic nerve of the body, providing parasympathetic innervation to organs throughout the neck, thorax, and abdomen, contributing to a variety of functions such as slowing of the heart rate.
10. Steve is playing baseball and gets hit in the middle of his forehead with an errant ball. Which branch of his trigeminal nerve would carry the pain sensation to his brain?
- A. mandibular
- B. maxillary
- C. ophthalmic
Show Answer
Correct answer: C
The trigeminal nerve is responsible for carrying touch and pain sensations from the face and head, and it has three main branches. The branch that handles sensations from the forehead is the ophthalmic branch of the trigeminal nerve.
11. This cranial nerve innervates the lateral rectus muscle to move the eye laterally, toward the side of the head:
- A. optic nerve (CN II)
- B. oculomotor nerve (CN III)
- C. trochlear nerve (CN IV)
- D. abducens nerve (CN VI)
Show Answer
Correct answer: D
The abducens nerve innervates the lateral rectus muscle to move the eye laterally.
12. This reflex can be used to test the integrity of the glossopharyngeal and vagus nerves:
- A. corneal reflex
- B. withdrawal reflex
- C. pupillary light reflex
- D. gag reflex
Show Answer
Correct answer: D
The gag reflex, also known as the pharyngeal reflex, can be used to test the integrity of the glossopharyngeal (IX) and vagus (X) nerves. The glossopharyngeal nerve is the main sensory limb of the reflex (it detects the sensation), and the vagus nerve is the primary motor limb of the reflex (it helps to contract throat muscles and expel what is in the throat).
13. Someone with damage to their accessory nerve (CN XI) would have the most trouble with which of the following activities?
- A. moving their eyes laterally (i.e., to the side)
- B. swallowing
- C. standing on one foot
- D. raising their arms above their head
Show Answer
Correct answer: D
The accessory nerve is primarily considered a motor nerve that supplies two muscles: the sternomastoid muscle and the trapezius muscle. The sternomastoid helps to turn your head to the side, as well as bend your neck down or to the side. The trapezius is involved with the movement of the neck and scapula, or shoulder blade. The trapezius is important to a variety of shoulder and arm movements, such as shrugging your shoulders or raising your arms above your head.
14. Which combination of cranial nerves is primarily responsible for carrying taste sensations from the tongue?
- A. III (oculomotor) and VI (abducens)
- B. V (trigeminal) and X (vagus)
- C. XI (spinal accessory) and XII (hypoglossal)
- D. VII (facial) and IX (glossopharyngeal)
Show Answer
Correct answer: D
The facial nerve carries taste sensations from the anterior 2/3 of the tongue, and the glossopharyngeal nerve carries taste sensations from the posterior 1/3 of the tongue. The vagus nerve also carries some taste sensations, but primarily from the epiglottis and throat.
15. Damage to this cranial nerve often causes ptosis, or a drooping of the upper eyelid:
- A. Optic (CN II)
- B. Oculomotor (CN III)
- C. Trochlear (CN IV)
- D. Abducens (CN VI)
Show Answer
Correct answer: B
The oculomotor nerve controls four of the six extraocular muscles (muscles that control movement of the eye), but it also supplies the levator palpebrae superioris---the muscle that elevates the eyelid. Thus, damage to the oculomotor nerve often causes drooping of the eyelid (ptosis), as well as deviation of the eye to the side and several other symptoms.
16. Which cranial nerve is responsible for controlling most of the muscles of your tongue?
- A. Facial nerve (CN VII)
- B. Glossopharyngeal nerve (CN IX)
- C. Vagus nerve (CN X)
- D. Hypoglossal nerve (CN XII)
Show Answer
Correct answer: D
The hypoglossal nerve is a motor nerve that controls all of the muscles of the tongue (except for one, the palatoglossus, which is controlled by the vagus nerve). Healthy function of the hypoglossal nerve is thus critical for things like eating, swallowing, and speaking.
17. To test the corneal blink reflex, a doctor touches a patient's left eye with a wisp of cotton. When this is done, the patient's left eye blinks but the right eye does not. What is a likely explanation?
- A. there is damage to the patient's left trigeminal nerve
- B. there is damage to the patient's right trigeminal nerve
- C. there is damage to the patient's right facial nerve
- D. there is damage to the patient's left facial nerve
Show Answer
Correct answer: C
The corneal reflex involves sensory input from the ophthalmic branch of the trigeminal nerve (CN V) and motor output via the facial nerve (CN VII), which causes blinking. Since the left eye blinks, the sensory portion (left CN V) is functioning properly. The failure of the right eye to blink suggests that the right facial nerve (CN VII) is not carrying out the motor response.
18. A physician shines a light into a patient's right eye, and neither the right nor the left pupil constricts. When light is shined into the patient's left eye, both pupils constrict. Which of the following structures is most likely damaged?
- A. right optic nerve
- B. right oculomotor nerve
- C. left optic nerve
- D. left oculomotor nerve
Show Answer
Correct answer: A
The sensory limb of the pupillary light reflex is the optic nerve (CN II). If light shined into one eye fails to cause constriction in either eye, it suggests a problem with the sensory input—in this case, the right optic nerve. The motor (efferent) pathways are still intact, as the pupils can constrict when the other eye is stimulated.
19. Which of the following cranial nerves carries the majority of all the parasympathetic fibers in the body?
- A. Trigeminal nerve (CN V)
- B. Glossopharyngeal nerve (CN IX)
- C. Vagus nerve (CN X)
- D. Accessory nerve (CN XI)
Show Answer
Correct answer: C
The vagus nerve (cranial nerve X) carries over 75% of all parasympathetic fibers in the body. It innervates organs in the thorax and abdomen, including the heart, lungs, and digestive tract, making it the main parasympathetic nerve of the body.
20. A patient presents with their right eye deviated laterally (i.e., to the side). They also are unable to move their right eye up and down. They are experiencing diplopia (double-vision) and have a slight drooping of the eyelid on the right side. Which cranial nerve has likely been affected?
- A. Optic nerve (CN II)
- B. Oculomotor nerve (CN III)
- C. Trochlear nerve (CN IV)
- D. Abducens nerve (CN VI)
Show Answer
Correct answer: B
The oculomotor nerve innervates most of the extraocular muscles (superior rectus, inferior rectus, medial rectus, inferior oblique), as well as the levator palpebrae superioris (which elevates the eyelid). CN III damage often leads to lateral deviation of the eye, impaired vertical movements, diplopia, and ptosis (drooping of the eyelid).
21. Bell's palsy is characterized by facial weakness or paralysis and results from dysfunction of which cranial nerve?
- A. CN III
- B. CN VII
- C. CN X
- D. CN XI
Show Answer
Correct answer: B
Bell’s palsy is a disorder that results from the dysfunction of cranial nerve VII, the facial nerve. It involves weakness or paralysis, typically on one side of the face. The cause of Bell's palsy is not clear, and Bell’s palsy is only diagnosed when there is not another identifiable cause of the facial paralysis (e.g., Lyme disease, trauma).
22. To test a patient’s corneal reflex, a doctor touches the patient’s right cornea with a piece of cotton. What response indicates a healthy corneal reflex?
- A. neither eye blinks
- B. only the patient's right eye blinks
- C. only the patient's left eye blinks
- D. both eyes blink
Show Answer
Correct answer: D
The corneal reflex is used clinically to test the integrity of the trigeminal and facial nerves and related structures, typically by touching the cornea with a piece of cotton. The healthy response to touching one cornea would be that both eyes would blink, but damage to the trigeminal or facial nerves or other related structures may cause a deficit in the reflex.
23. The neurons of the olfactory nerve (cranial nerve I) travel between which two structures?
- A. Olfactory bulb and piriform cortex
- B. Olfactory bulb and amygdala
- C. Olfactory epithelium and olfactory bulb
- D. Olfactory epithelium and optic chiasm
Show Answer
Correct answer: C
The sensory neurons of the olfactory nerve originate in the olfactory epithelium of the nasal cavity. Their axons pass through the cribriform plate of the ethmoid bone and synapse in the olfactory bulb, where second-order neurons carry the information deeper into the brain.
24. Which cranial nerve is primarily responsible for controlling the muscles of mastication (chewing)?
- A. facial nerve (CN VII)
- B. trigeminal nerve (CN V)
- C. glossopharyngeal nerve (CN IX)
- D. hypoglossal nerve (CN XII)
Show Answer
Correct answer: B
The mandibular branch of the trigeminal nerve innervates the muscles that move the jaw for chewing.
25. Which two cranial nerves are primarily responsible for carrying taste sensations from the tongue to the brain?
- A. glossopharyngeal (CN IX) & hypoglossal (CN XII)
- B. facial (CN VII) & glossopharyngeal (CN IX)
- C. Vagus (CN X) & hypoglossal (CN XII)
- D. Accessory (CN XI) & hypoglossal (CN XII)
Show Answer
Correct answer: B
Taste information from the anterior two-thirds of the tongue is carried by the facial nerve (CN VII), while the glossopharyngeal nerve (CN IX) carries taste from the posterior one-third of the tongue.
26. Which cranial nerve is primarily responsible for carrying visual information from the retina to the rest of the brain?
- A. CN II - optic nerve
- B. CN III - oculomotor nerve
- C. CN IV - trochlear nerve
- D. CN VI - abducens nerve
Show Answer
Correct answer: A
The optic nerve is a sensory nerve responsible for transmitting information about vision to the brain.
27. After head trauma, a patient has damage to his right hypoglossal nerve. When he sticks out his tongue, which side is it likely to deviate toward?
- A. right
- B. left
- C. neither; it won't deviate at all
Show Answer
Correct answer: A
If the hypoglossal nerve on only one side is damaged and the patient is asked to protrude his or her tongue, the tongue will typically deviate toward the side of the damaged nerve.
28. A patient presents with her right eye deviated laterally (toward the side of her head), a drooping right eyelid, and an inability to move her right eye up or down. Which cranial nerve has likely been impacted in this patient?
- A. right facial nerve
- B. left abducens nerve
- C. right oculomotor nerve
- D. left trochlear nerve
Show Answer
Correct answer: C
These symptoms are a clear sign of oculomotor nerve palsy, which involves lateral deviation of the eye, ptosis (drooping of the eyelid), impaired vertical movement of the affected eye, mydriasis (constantly dilated pupil), and diplopia (double vision).
29. A woman awakens one morning with weakness on one side of her face. Her eyelid and corner of her mouth droop on the affected side. Her physician diagnoses Bell’s palsy. Which cranial nerve is involved?
- A. III
- B. V
- C. VII
- D. X
Show Answer
Correct answer: C
Bell’s palsy is a disorder that results from the dysfunction of cranial nerve VII, the facial nerve. The most common symptom is rapidly developing weakness on one side of the face.
30. When a flashlight is shined into a patient’s right eye, neither pupil constricts. However, when the light is shined into the left eye, both pupils constrict normally. Based on these findings, which cranial nerve is most likely impaired?
- A. the right oculomotor nerve
- B. the left optic nerve
- C. the left oculomotor nerve
- D. the right optic nerve
Show Answer
Correct answer: D
If light is shined into the right eye and neither pupil constricts, it suggests a deficit in sensory input and may indicate damage to the right optic nerve.
