BRS Gross Anatomy - 9. Cranial and Autonomic Nerves

1. A 27-year-old man came to his physician with drooping of the upper eyelid (ptosis), a dilated pupil, and a difficulty in focusing on close objects. Furthermore, he has an internal strabismus (medial deviation of the eye) and inability to look inferiorly when the eye is adducted. Which of the following is the most likely cause?

(A) Lesion in the medulla

(B) Tumor in the optic canal

(C) Thrombosis in the cavernous sinus

(D) Lesion of the olfactory nerve

(E) Fracture of the foramen spinosum

(C) Thrombosis in the cavernous sinus

Rationale:

Thrombosis in the cavernous sinus might damage all three CNs (III, IV, VI): lesion of CN III causes ptosis, a dilated pupil, and loss of accommodation; lesion of CN IV causes inability to look inferiorly when adducted; and lesion of CN VI causes the eyeball deviates medially (internal strabismus). Lesion in the medulla may damage CNs IX, X, and XII. Tumor in the optic canal injures the optic nerve and ophthalmic artery. Lesion of the olfactory nerve causes anosmia (loss of smell). Fracture of the foramen spinosum damages the middle meningeal artery.

2. A 16-year-old boy presents with double vision. Further examination reveals that he has difficulty in turning his eye inferolaterally and trouble going downstairs. Which of the following nerves is most likely damaged?

(A) Oculomotor nerve

(B) Optic nerve

(C) Ophthalmic nerve

(D) Trochlear nerve

(E) Abducens nerve

(D) Trochlear nerve

Rationale:

If the trochlear nerve is injured, the patient is unable to turn the eyeball inferolaterally and has trouble going downstairs due to paralysis of the superior oblique muscle. Lesion of the oculomotor nerve causes ptosis due to paralysis of the levator palpebrae superioris, dilation of the pupil due to paralysis of the sphincter pupillae, loss of accommodation due to paralysis of ciliary muscles, and loss of pupillary light reflex due to loss of the efferent limb of the pupillary light reflex. Lesion of the optic nerve causes blindness. Lesion of the ophthalmic nerve causes loss of cutaneous sensation on the face above the upper eyelid. Lesion of the abducens nerve causes internal strabismus in which the eyeball turns medially.

3. A 31-year-old man with a penetrating injury to the posterior triangle of the neck is unable to shrug his shoulder and turn the head to the opposite side. Which of the following nerves is most likely damaged?

(A) Trigeminal nerve

(B) Facial nerve

(C) Glossopharyngeal nerve

(D) Accessory nerve

(E) Hypoglossal nerve

(D) Accessory nerve

Rationale:

Accessory nerve passes through the posterior cervical triangle and is responsible for shrugging the shoulder and turn the head to the opposite side. The trigeminal nerve carries sensory fibers for the face and motor fibers for the muscles of mastication. The facial nerve carries motor fibers to the muscles of facial expression, secretomotor fibers to lacrimal, submandibular, sublingual, and nasal glands, and taste fibers from the anterior two-thirds of the tongue. The glossopharyngeal nerve conveys motor fibers to the stylopharyngeus muscle and taste fibers from the posterior one-third of the tongue. The hypoglossal nerve carries motor fibers for the muscles of tongue movement.

4. A 23-year-old woman suffers from a fracture of the jugular foramen by car accident. Which of the following nerves is/are most likely damaged?

(A) Cranial nerve V2

(B) Cranial nerve VI

(C) Cranial nerves VII and VIII

(D) Cranial nerves IX, X, and XI

(E) Cranial nerve XII

(D) Cranial nerves IX, X, and XI

Rationale:

The jugular foramen transmits cranial nerves, IX, X, and XI, along with the internal jugular vein. The cranial nerve V2 runs through the foramen rotundum. The cranial nerve VI passes through the superior orbital fissure. The cranial nerves VII and VIII courses through the internal auditory meatus. The cranial nerve XII passes through the hypoglossal canal.

5. A 17-year-old boy is involved in a gang fight and receives a penetrating injury to the neck. Which of the following conditions is most likely exhibited by this misadventure?

(A) Internal strabismus

(B) Trouble going down the stairs

(C) Constricted pupil

(D) Inability close the eye

(E) Deviation of tongue toward lesion side

(C) Constricted pupil

Rationale:

Lesion of sympathetic nerves in the cervical region results in a constricted pupil due to paralysis of the dilator pupillae. Internal strabismus is caused by a lesion of the abducens nerve. Lesion of the trochlear nerve results in difficulty going downstairs. Inability to close the eye is due to a lesion of the facial nerve. Lesion of the hypoglossal nerve causes deviation of the tongue toward the lesion side.

6. A 28-year-old woman comes to her family physician and complains of difficulty in swallowing. Further examination reveals that she has no taste sensation of the posterior one-third of her tongue and a lack of secretion of the parotid gland. Which of the following would most likely cause this condition?

(A) Fracture of the mandibular canal

(B) Section of the zygomatic nerve

(C) Glossopharyngeal nerve injury

(D) Tumor in the pituitary gland

(E) Lesion of the hypoglossal nerve

(C) Glossopharyngeal nerve injury

Rationale:

Injury to the glossopharyngeal nerve causes paralysis of the stylopharoyngeus muscle, which is involved in swallowing, no general and taste sensation of the posterior onethird of the tongue, a lack of salivary secretion from the parotid gland due to parasympathetic nerve injury, and no visceral sensation from the carotid sinus and body. Lesion of the inferior alveolar nerve in the mandibular canal results in a lack of sensation to the canine and incisor teeth and the skin over the chin. Section of the zygomatic nerve causes a lack of lacrimal secretion because it carries postganglionic parasympathetic fibers from the pterygopalatine ganglion for lacrimal secretion. Tumor in the pituitary gland may damage the optic chiasma, resulting in the bitemporal hemianopia. Lesion of the hypoglossal nerve causes deviation of the tongue toward the injured side on protrusion.

7. A 34-year-old man in a bar fight suffers a knife wound that severs the abducens nerve proximal to its entrance into the orbit. Which of the following conditions results from this injury?

(A) Ptosis of the upper eyelid

(B) Loss of the ability to dilate the pupil

(C) External strabismus (lateral deviation)

(D) Loss of visual accommodation

(E) Internal strabismus (medial deviation)

(E) Internal strabismus (medial deviation)

Rationale:

The abducens nerve (CN VI) innervates the lateral rectus muscle, which abducts the eyeball. A lesion of the abducens nerve results in internal strabismus (medial deviation) and diplopia (double vision). Ptosis of the upper eyelid is caused by lesions of the oculomotor nerve or sympathetic nerve to the levator palpebrae superioris. Inability to dilate thepupil is caused by a lesion of the sympathetic nerve to the dilator pupillae. External strabismus (lateral deviation) is caused by paralysis of the medial rectus muscle, which is innervated by the oculomotor nerve. Loss of visual accommodation is due to a lesion of parasympathetic nerve fibers to the ciliary muscle.

8. Following radical resection of a primary tongue tumor, a 72-year-old patient has lost general sensation on the anterior two-thirds of the tongue. This is probably due to injury to branches of which of the following nerves?

(A) Trigeminal nerve

(B) Facial nerve

(C) Glossopharyngeal nerve

(D) Vagus nerve

(E) Hypoglossal nerve

(A) Trigeminal nerve

Rationale:

The anterior two-thirds of the tongue is innervated by the lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V). The posterior one-third of the tongue is innervated by the glossopharyngeal nerve (CN IX) for general and taste sensations. The facial nerve supplies taste fibers to the tongue through the chorda tympani but does not supply general sensation. The vagus nerve supplies general sensation and taste sensation to the epiglottis by way of the internal laryngeal branch. The hypoglossal nerve innervates the tongue muscles.

9. A 53-year-old woman is diagnosed as having a pituitary tumor. If the tumor is large enough, she could exhibit which of the following disorders?

(A) Blindness

(B) Bitemporal (heteronymous) hemianopia

(C) Right nasal hemianopia

(D) Left homonymous hemianopia

(E) Binasal hemianopia

(B) Bitemporal (heteronymous) hemianopia

Rationale:

Lesion of the optic chiasma by a pituitary tumor results in bitemporal hemianopia resulting from loss in the nasal field of vision of both eyes. Lesion of the optic nerve causes blindness. A right perichiasmal lesion by an aneurysm of the internal carotid artery leads to right nasal hemianopia because of loss of vision in the nasal field of the right eye. Lesion of the right optic tract or optic radiation causes left homonymous hemianopia resulting from loss of the left half of the visual fields of both eyes. Aneurysms of both internal carotid arteries cause right and left perichiasmal lesions, leading to binasal hemianopia (loss of vision in the nasal fields of both eyes).

10. A patient can move his eyeballs normally and see distant objects clearly but cannot focus on near objects. This condition may indicate damage to which of the following structures?

(A) Ciliary ganglion and oculomotor nerve

(B) Oculomotor nerve and long ciliary nerve

(C) Short ciliary nerves and ciliary ganglion

(D) Superior cervical ganglion and long ciliary nerve

(E) Oculomotor, trochlear, and abducens nerves

(C) Short ciliary nerves and ciliary ganglion

Rationale:

Damage to the parasympathetic ciliary ganglion and parasympathetic fibers in the short ciliary nerve impairs the ability to focus on close objects (accommodation). Because the patient can move his eyeballs normally, the oculomotor nerve is not damaged even if this nerve contains preganglionic parasympathetic fibers. The patient is able to see distant objects clearly because the long ciliary nerve also carries sympathetic fibers to the dilator pupillae. The ability to move the eyeball normally indicates that the oculomotor, trochlear, and abducens nerves are intact.

11. A 32-year-old woman has hoarseness in her voice, and her uvula is deviated to the left on phonation. Which of the following nerve is most likely damaged?

(A) Right trigeminal nerve

(B) Left trigeminal nerve

(C) Right vagus nerve

(D) Left vagus nerve

(E) Left glosopharyngeal nerve

(C) Right vagus nerve

Rationale:

The vagus nerve innervates the musculus uvulae. A lesion of the vagus nerve causes deviation of the uvula toward the opposite side of the injury. Because her uvula deviates to the left on phonation, the right vagus nerve is damaged. Hoarseness is caused by a paralysis of the laryngeal muscles resulting from damage to skeletal motor fibers in the recurrent laryngeal branch of the vagus nerve.

12. Following a penetrated injury in the submandibular triangle, the tongue of a 45-yearold patient deviates to the left on protrusion. Which of the following nerves is injured?

(A) Right lingual nerve

(B) Left lingual nerve

(C) Right hypoglossal nerve

(D) Left hypoglossal nerve

(E) Left glossopharyngeal nerve

(D) Left hypoglossal nerve

Rationale:

A lesion of the hypoglossal nerve causes deviation of the tongue toward the injured side on protrusion. The lingual and glossopharyngeal nerves do not supply the tongue muscles.

13. A 47-year-old man cannot move his eyeball laterally. Which of the following conditions would cause such a clinical sign?

(A) Tumor of the pituitary gland

(B) Occlusion of the posterior cerebral artery

(C) Infection in the maxillary sinus

(D) Infection in the cavernous sinus

(E) Tumor in the anterior cranial fossa

(D) Infection in the cavernous sinus

Rationale:

The abducens nerve, which innervates the lateral rectus muscle, runs through the middle of the cavernous sinus. The other conditions listed do not injure the abducens nerve. A tumor in the pituitary gland may injure the optic chiasma, causing bitemporal hemianopsia.

14. A young boy with a tooth abscess from a longstanding infection suffers damage of the lingual nerve as it enters the oral cavity. Which of the following structures contain cell bodies of injured nerve fibers?

(A) Geniculate and otic ganglia

(B) Trigeminal and submandibular ganglia

(C) Trigeminal and dorsal root ganglia

(D) Geniculate and trigeminal ganglia

(E) Geniculate and pterygopalatine ganglia

(D) Geniculate and trigeminal ganglia

Rationale:

The lingual nerve is joined by the chorda tympani in the infratemporal fossa. Therefore, the lingual nerve contains GSA fibers whose cell bodies are located in the trigeminal ganglion and SSA or taste fibers that have cell bodies located in the geniculate ganglion. In addition, the lingual nerve carries parasympathetic preganglionic GVE fibers that originated from the chorda tympani; the cell bodies are located in the superior salivatory nucleus in the pons. The chorda tympani and lingual nerves contain no fibers from the otic, submandibular, pterygopalatine, or dorsal root ganglia.

15. A knife wound has severed the oculomotor nerve in a 45-year-old man. Which of the following conditions will occur because of this injury?

(A) Constricted pupil

(B) Abduction of the eyeball

(C) Complete ptosis

(D) Impaired lacrimal secretion

(E) Paralysis of the ciliary muscle

(E) Paralysis of the ciliary muscle

Rationale:

The oculomotor nerve carries parasympathetic fibers to the ciliary and sphincter pupillae ciliary muscles; thus, a lesion of the oculomotor nerve leads to ciliary muscle paralysis and a dilated pupil. The abducens nerve supplies the lateral rectus, which is an abductor of the eye. The levator palpebrae superioris inserts on the tarsal plate in the upper eyelid, which is innervated by sympathetic fibers. Thus, a lesion of the oculomotor nerve does not cause complete ptosis. The secretomotor fibers for lacrimal secretion come through the pterygopalatine ganglion. Thus, severance of the oculomotor nerve has no effect on lacrimal secretion.

16. A 20-year-old guard at the gate of the Royal King’s palace blinks his eyes when a strong wind hits the cornea of his eye. The afferent fibers of the corneal reflex arc are carried by which of the following nerves?

(A) Optic nerve

(B) Lacrimal nerve

(C) Nasociliary nerve

(D) Zygomatic nerve

(E) Oculomotor nerve

(C) Nasociliary nerve

Rationale:

The afferent limb of the corneal reflex arc is the nasociliary nerve, and its efferent limb is the facial nerve. The other nerves are not involved in the reflex arc. The opening of the eye is conducted by the oculomotor nerve, but it is not a part of the corneal reflex.

17. A 71-year-old man suffers from a known benign tumor in the pterygoid canal. Which of the following nerve fibers could be injured by this condition?

(A) Postganglionic parasympathetic fibers

(B) Taste fibers from the epiglottis

(C) General somatic afferent (GSA) fibers

(D) Preganglionic sympathetic fibers

(E) General visceral afferent (GVA) fibers

(E) General visceral afferent (GVA) fibers

Rationale:

The nerve of the pterygoid canal (Vidian nerve) contains taste SVA fibers from the palate, GVA fibers, postganglionic sympathetic fibers, and preganglionic parasympathetic fibers.

18. A 22-year-old patient has dryness of the corneal surface of his eye because of a lack of tears. Which of the following nerves may be damaged?

(A) Proximal portion of the lacrimal nerve

(B) Zygomatic branch of the facial nerve

(C) Lesser petrosal nerve

(D) Greater petrosal nerve

(E) Deep petrosal nerve

(D) Greater petrosal nerve

Rationale:

The secretomotor fibers to the lacrimal gland are parasympathetic fibers that run in the facial, greater petrosal, Vidian (nerve of the pterygoid canal), maxillary, zygomatic (of maxillary), zygomaticotemporal, and lacrimal (terminal portion) nerves. The lesser petrosal nerve carries secretomotor (preganglionic parasympathetic) fibers to the parotid gland. The deep petrosal nerve contains postganglionic sympathetic fibers. The zygomatic branch of the facial nerve supplies the facial muscles.

19. A 31-year-old hockey player is hit in the head by a puck. His radiogram shows a fracture of the foramen rotundum. Which of the following nerves would be damaged by this event?

(A) Ophthalmic nerve

(B) Mandibular nerve

(C) Maxillary nerve

(D) Optic nerve

(E) Trochlear nerve

(C) Maxillary nerve

Rationale:

The maxillary nerve runs through the foramen rotundum; the ophthalmic nerve runs through the supraorbital fissure; the mandibular nerve passes through the foramen ovale; the optic nerve runs through the optic canal; and the trochlear nerve passes through the superior orbital fissure.

20. Muscles derived from the second (hyoid) pharyngeal arch are innervated by which of the following cranial nerves?

(A) Trigeminal nerve

(B) Facial nerve

(C) Glossopharyngeal nerve

(D) Vagus nerve

(E) Accessory nerve

(B) Facial nerve

Rationale:

Muscles derived from the second (hyoid) pharyngeal arch are innervated by the facial nerve. Muscles derived from the first (mandibular) pharyngeal arch are innervated by the mandibular division of the trigeminal nerve. A muscle derived from the third pharyngeal arch is innervated by the glossopharyngeal nerve. Muscles derived from the fourth and sixth pharyngeal arches are innervated by the vagus nerve. Muscles of myotome origin that shrug shoulder and turn head are innervated by the accessory nerve