Cranial Nerve Q&A Flashcards
A 21-year-old man is transported to the Emergency Department from the site of a motorcycle collision. He is unconscious upon arrival, and the initial neurological examination reveals a dilated left pupil. He has facial and scalp injuries, “road rash,” and a fractured femur. Three hours later he is conscious, has had a CT, and further examination reveals a loss of all voluntary movement of the left eye, a drooping left eyelid, and loss of pinprick sensation on his left forehead, in addition to the still dilated left pupil. CT revealed a skull fracture. Significant damage to structures traversing which of the following would most likely explain this man’s deficits?
(A) Infraorbitalforamen
(B) Inferior orbital fissure
(C) Supraorbitalforamen
(D) Superior orbital fissure
(E) Optic canal
The answer is D: Superior orbital ssure. This patient has damage to the abducens, trochlear, and oculomotor nerves (loss of all eye movement), a dilated pupil (loss of parasympathetics in IIIrd nerve), and the ophthalmic nerve (sensory loss over the forehead). All of these structures, plus small vessels, traverse the superior orbital fissure. The inferior orbital fissure contains the maxillary nerve which is sensory to the maxillary area of the face, the nasal mucosa, and the maxillary sinus. The supraorbital and infraorbital foramina contain cutaneous branches of the ophthalmic and maxillary nerves; this injury does not involve the supraorbital fissure, as this would exclude all nerves innervating extraocular muscles. The optic canal contains the optic nerve; this man has no visual complaints.
Which of the following cranial nerves pass through the foramen identified by the circle in the image below?
(A) Facial and abducens
(B) Hypoglossal and spinal accessory
(C) Glossopharyngeal and vagus
(D) Vagus and spinal accessory
(E) Vestibulocochlear and facial
The answer is E: Vestibulocochlear and facial.
This is a view of the medial aspect of the petrous portion of the temporal bone and immediately adjacent parts of the occipital bone on the left side of the skull. The petrooccipital fissure is the location of the inferior petrosal sinus; this groove may also be called the sulcus for the inferior petrosal sinus. The opening immediately above this fissure (and in the circle) is the internal acoustic meatus. This particular foramina is characterized by the transverse crest (seen here) and the fact that it does not open directly to the external aspect of the skull. The vestibulocochlear nerve and the facial nerve enter this opening; the former originates from sensory receptors in the petrous portion of the temporal bone, while the latter portion passes through to eventually exit the stylomastoid foramen to innervate the muscles of facial expression. The hypoglossal nerve exits through the hypoglossal canal and the accessory, vagus, and glossopharyngeal nerves exit the skull via the jugular foramen. The abducens nerve, after traversing the cavernous sinus, passes through the superior orbital
A 41-year-old man is brought to the Emergency Department from the site of a motor vehicle collision. He is conscious, has facial abrasions, a broken nose, and an apparent shoulder dislocation. CT confirms the broken nose, and reveals a fracture of the proximal humerus, and a basal skull fracture that passes through the jugular foramen. Based on these observations, which of the following cranial nerves might be damaged?
(A) III, IV, VI
(B) V (motor + sensory)
(C) VII,VIII
(D) IX, X, XII
(E) IX, X, XI
The answer is E: IX, X, XI. Cranial nerves IX (glossopharyn-
geal), X (vagus), and XI (accessory) traverse the jugular foramen.
Damage to these nerves will result in several deficits, the most
noticeable of which will be dysarthria, dysphagia, the inability
to elevate the shoulder against resistance (the shoulder may
also droop), and an inability to rotate the head to the opposite
side against resistance. Cranial nerves III (oculomotor), IV
(trochlear), and VI (abducens) pass through the superior
orbital fissure; VII (facial) and VIII (vestibulocochlear) enter
the internal acoustic meatus; the facial nerve exits the skull
via the stylomastoid foramen. The nerves arising from the
trigeminal ganglion course through the superior orbital fissure
(V —ophthalmic), the foramen rotundum (V —maxillary), 12
and foramen ovale (V3—mandibular + motor root); the XII nerve (hypoglossal) traverses the hypoglossal canal.
A 23-year-old woman is brought to the Emergency Department from the site of a motorcycle collision. The initial examination reveals a compound fracture of the right humerus, significant “road rash” (extremities, right side of face), and a probable broken nose. CT also shows a fractured right clavicle and a basal skull fracture transecting the structure indicated by the arrow in the image below. Which of the following deficits would most likely be seen in this woman?
(A) Dysarthria and dysphagia
(B) Loss of facial movements on left side
(C) Tongue deviates to right on protrusion
(D) Tongue deviates to the left on protrusion
(E) Unable to elevate left shoulder
The answer is D: Tongue deviates to the left on protrusion. This T2-weighted axial MRI is through the midmedullary levels and shows the left root of the hypoglossal nerve exiting between the pyramid, which is anterior to the exit, and the inferior olivary eminence, which is posterior to the exit. This nerve passes through the hypoglossal canal as it exits the skull to serve the muscles of the tongue on the same side. Damage to the hypoglossal root results in the tongue deviating to the weak side on attempted protrusion, in this case to the left. Dysarthria, dysphagia, and the inability to elevate the shoulder, especially against resistance, would be seen in damage to the vagus, glossopharyngeal, and accessory nerves, all of which share the common feature of exiting the skull via the jugular foramen.
Which of the following combinations of cranial nerves may be collectively referred to as the cranial nerves (CNs) of the pons- medulla junction?
(A) CNs III, IV, VI
(B) CNs V, VI, IX
(C) CNs XI, X, XII
(D) CNs VI, VII, VIII
(E) CNs VIII, IX, X
The answer is D: CNs VI, VII, VIII.
The abducens (VI), facial (VII), and vestibulocochlear (VIII) nerves are lined up from medial to lateral at the caudal edge of the pons where it is continuous with the rostral medulla. The oculomotor (III) and trochlear nerves exit the inferior and superior aspects of the midbrain; the trigeminal (V) nerve exits the lateral surface of the pons. The glossopharyngeal (IX), vagus (X), and accessory (XI) nerves are associated with the postolivary sulcus of the medulla; the hypoglossal (XII) nerve exits the medulla via the preolivary sulcus.
You gently touch a wisp if cotton to the left cornea of a 23-year-old man during a routine neurological examination,and the left eye blinks (direct response) and the right eye blinks (consensual response). The cell bodies of the afferent limb of this reflex are located in which of the following?
(A) Cornealepithelium
(B) Mesencephalic nucleus
(C) Principal sensory nucleus
(D) Spinal trigeminal nucleus
(E) Trigeminal ganglion
The answer is E: Trigeminal ganglion . This is the corneal reflex. The afferent endings are naked nerve endings in the cornea; their cell bodies are located in the left trigeminal ganglion, and their central processes terminate in the left spinal trigeminal nucleus, pars caudalis. The spinal nucleus of V, in turn, sends crossed ascending fibers toward the thalamus (for recognition of pain) and collaterals to the motor facial nuclei on both sides. The efferent limb of this reflex originates in the facial nuclei; the left for the direct response, and the right for the consensual response. Cell bodies in the mesencephalic nucleus are unipolar and convey proprioceptive information; these fibers do not have cell bodies in the trigeminal ganglion and are involved in the jaw-jerk reflex. The principal sensory nucleus contains the second order neurons that convey discriminative touch on the trigeminal nerve. The spinal trigeminal nucleus contains the second-order neurons for the corneal reflex pathway; the first- order cells are in the trigeminal ganglion.
A 62-year-old man visits his dentist with the complaint of gum and tooth pain. A thorough examination reveals no infection or lesion, and the man is referred to his physician. As part of the examination and evaluation, an MRI reveals an aberrant vascular loop impinging on the root of a cranial nerve as shown at the arrow in the image below. This man is most likely suffering which of the following?
(A) Facialtic
(B) Geniculate neuralgia
(C) Glossopharyngealneuralgia
(D) Sphenopalatineneuralgia
(E) Trigeminal neuralgia
The answer is E: Trigeminal neuralgia. Neuralgia, also called neurodynia, is a severe lancinating and/or searing pain that may have trigger zones (areas where stroking or touching will initiate pain); the painful sensations in neuralgia are related to the distribution of sensory branches of a particular cranial nerve and are paroxysmal. In this image, the superior cerebellar artery loops over the root of the trigeminal nerve. This is a likely cause of trigeminal neuralgia, which is a sudden-onset pain that may arise from a trigger zone, frequently located at the angle of the mouth. The V2 (about 20% of cases), V3 (about 17%), and V2 + V3 (40+%) divisions of the trigeminal nerve are commonly involved. There are medical and surgical treatments for trigeminal neuralgia. Facial tic is the sudden involuntary contraction of facial muscles; geniculate neuralgia is pain from deep and superficial areas of the ear mediated by the facial nerve. Sudden severe pain from the throat or palate (swallowing may be a trigger) is glossopharyngeal neuralgia; similar pain from the area of the nose, maxillary teeth, ears, and sinuses signals sphenopalatine neuralgia.
A 43-year-old man presents with swelling and pain on the left side underneath the body of the mandible. The examination reveals a subcutaneous oval mass about 2 cm × 4 cm that is painful when palpated. In addition, when this man attempts to protrude his tongue, it deviates to the left. Which of the following is most likely paralyzed to produce this deficit?
(A) Genioglossusmuscle
(B) Hyoglossus muscle
(C) Intrinsic tongue muscles
(D) Palatoglossusmuscle
(E) Styloglossus muscle
The answer is A: Genioglossus muscle. The genioglossus muscle has its origin from the superior genial (mental) spine and fans out to enter the base of the tongue. Each genioglossus muscle, when it contracts, pulls that side of the tongue toward the midline; when they contract together, the tongue protrudes symmetrically (straight) out of the mouth. When one genioglossus muscle is weak or paralyzed, the opposite pulls toward the midline and the tongue will deviate to the weak side. The styloglossus and palatoglossus muscles draw the tongue upward (elevate) and slightly backward, and the hypoglossus muscle depresses (pulls downward) the tongue. The intrinsic tongue muscles consist of longitudinal, transverse, and vertical fascicles. These muscles change the shape of the tongue, and are very important for speech.
A 62-year-old woman presents with deficits indicative of cranial nerve involvement. The results of a T2-weighted MRI reveal a lesion, represented by the circle in the given image, damaging the cranial nerve traversing the circle. Which of the following would you most likely expect to see if light was shined in the woman’s right eye?
(A) Blindness in the right eye
(B) Right homonymous hemianopia
(C) Inability to abduct right eye
(D) Loss of the consensual pupillary reflex
(E) Loss of the direct pupillary reflex
The answer is E: Loss of the direct pupillary re ex. The oculomotor nerve is clearly seen in this axial MRI almost from its site of origin at the oculomotor sulcus of the midbrain to the point where it enters the orbit. A lesion of the right oculomotor nerve interrupts the efferent limb of the pupillary light reflex pathway (the direct response is lost); the afferent limb is conveyed by the optic nerve. A light stimulus to the right eye is received at the pretectal nucleus which projects to both Edinger-Westphal nuclei bilaterally. However, the lesion of the right oculomotor nerve interrupts the parasympathetic fibers on that side, but the left efferent limb is not affected. The black spot located medially adjacent to the nerve, just anterior to the midbrain, is the P1 segment of the posterior cerebral artery. Since this is not a lesion of the optic nerve, the woman is not blind in the right eye nor does she have a hemianopia. Only lesions of optic structures caudal to the optic chiasm will produce a hemianopia involving the opposite halves of both visual fields.
A 60-year-old man presents to his family physician with what he calls a “problem seeing.” The examination reveals that his vision is normal, but his right eye is deviated slightly inward, and does not abduct on attempted gaze to the right. There are no other findings. Which of the following is the most likely location of this lesion in this patient?
(A) Abducens nucleus on the left
(B) Abducens nucleus on the right
(C) Abducens root in the basilar pons on the right
(D) Abducnes root on the right
(E) Abducens root on the left
The answer is D: Abducens root on the right. The only deficit experienced by this patient is the diplopia (his “problem seeing”) resulting from the inward deviation of his right eye; this would be exaggerated by attempted lateral gaze to the right. This indicates a right abducens root lesion: a right lateral rectus paralysis only. A lesion of the right abducens nucleus would result in right lateral rectus paralysis plus a paralysis of the left medial rectus. This is due to the fact that an abducens nucleus lesion will affect internuclear neurons, located within the right abducens nucleus, that project to medial rectus motor neurons on the left via the medial longitudinal fasciculus. In a similar manner, a lesion of the abducens root in the basilar pons on the right will result in a right lateral rectus paralysis plus a left hemiparesis due to involvement of the immediately adjacent corticospinal fibers. Lesions on the left are on the wrong side.
A 45-year-old woman presents to her otolaryngologist for throat pain. The examination reveals that the woman experi- ences lancinating pain in the posterior oral cavity (pharynx, base of tongue, ear) when swallowing or coughing. MRI reveals no overt pathology. The physician suspects that this patient is most likely suffering which of the following?
(A) Alternatinghemianesthesia
(B) Glossopharyngeal neuralgia
(C) Polyps of the vocal folds
(D) Trigeminalneuralgia
(E) Wallenberg syndrome
The answer is B: Glossopharyngeal neuralgia. Severe pain following stimulation of the posterior aspects of the oral cavity, such as when swallowing, is related to the distribution of sensory branches of cranial nerve IX to this area, and is called glossopharyngeal neuralgia. The causes are largely unknown, although multiple sclerosis or aberrant vascular loops pressing the IXth root are possibilities. Alternating hemianesthesia is a sensory loss on one side of the body and on the opposite side of the face; this, along with dysarthria, dysphagia, and ataxia, are components of the Wallenberg (posterior inferior cerebellar artery [PICA] or lateral medullary) syndrome. Trigeminal neuralgia is a severe excruciating pain originating from the face usually from the vicinity of the corner of the mouth (V2, V3) that is usually set off by a variety of actions (chewing, shaving, putting on lipstick, brushing teeth, even wind on the face). Essentially it is a pain that is identical to that of glossopharyngeal neuralgia, but of a different distribution. Polyps cause discomfort, coughing, and hoarseness, but not extreme, sudden, and unpredictable pain.
A 23-year-old man is transported from the site of a motorcycle collision to the Emergency Department. He is conscious, has a broken femur, extensive skin damage on his upper extremity, and facial and scalp lacerations. The examination reveals that the man has difficulty swallowing, loss of sensation on the pharyngeal wall, hoarseness, and weakness of the trapezius muscle. CT reveals a basal skull fracture. This fracture went through which of the following foramina to produce these deficits?
(A) Foramenovale
(B) Foramen rotundum
(C) Hypoglossalcanal
(D) Jugularforamen
(E) Superior orbital fissure
The answer is D: Jugular foramen. The collection of sym- ptoms experienced by this man clearly indicate damage to the glossopharyngeal, vagus, and accessory nerves. All three of these nerves traverse the jugular foramen and can be injured by trauma to this foramen. In fact, there are several syndromes of the jugular foramen. The foramen ovale contains the mandibular nerve and the trigeminal motor root; the maxillary nerve traverses the foramen rotundum. The superior orbital fissure contains the ophthalmic, abducens, oculomotor, and trochlear nerves, while the hypoglossal canal contains the nerve after which it is named. It should be remembered that all of these openings in the skull base also transmit small blood vessels.
A 32-year-old man is brought to the Emergency Department from the site of a motor vehicle collision. He is unconscious, has significant facial abrasions, possible broken nose, and an apparent dislocated hip. CT also shows a basal skull fracture that passes through the foramen indicated at the arrow in the image below. Assuming that the structure, or structures, traversing this opening are damaged, which of the following deficits would most likely be seen?
(A) Deafness
(B) Dysarthria, dysphagia
(C) Loss of sensation on the forehead
(D) Loss of sensation over the maxillary area
(E) Loss of sensation over the mandibular area
The answer is E: Loss of sensation over the mandibular area. The arrow is pointing to the foramen ovale which transmits the maxillary division of the trigeminal nerve, fibers comprising the trigeminal motor root, and the accessory meningeal artery. Damage to the contents of this foramen would result in a loss of pain and thermal sense over the mandibular region, a comparable sensory loss inside the oral cavity including the mandibular teeth, and weakness of the masticatory muscles; all of this would be on the right side. Deafness in one ear would require involvement of the internal acoustic meatus, and dysarthria (difficulty speaking) and dysphagia (difficulty swallowing) would be seen if a basal skull fracture involved the jugular foramen. The ophthalamic division of the trigeminal nerve traverses the superior orbital fissure, then passes through the supraorbital foramen (there may be more than one, in which case they are foramina) to fan out over the forehead. If the supraorbital foramen, or foramina, are not completely formed, this may appear as, and be called, a notch. The maxillary division of the trigeminal nerve traverses the foramen rotundum and exits on the maxillary region of the face via the infraorbital foramen; this nerve is also sensory to the maxillary teeth and palate.
A 56-year-old woman complains of persistent headache that seems to be largely refractory to OTC medications. The examination reveals that these headaches are frontal and sometimes centered in the orbit. To test one aspect of visual system function, a light shined in both eyes results in a normal pupillary light reflex in both eyes. The efferent limb of this reflex is conveyed by which of the following?
(A) Abducensnerve
(B) Facial nerve
(C) Medial longitudinal fasciculus
(D) Oculomotor nerve
(E) Optic nerve
The answer is D: Oculomotor nerve. The afferent limb of the papillary light reflex is via the optic nerve, to the pretectal nucleus, and bilaterally to the Edinger-Westphal (EW) nucleus. The efferent limb originates in the EW nucleus, travels via the oculomotor nerve to the ciliary ganglion, and from this structure to the sphincter muscle of the pupil. The abducens nerve innervates the ipsilateral lateral rectus muscle; the facial nerve innervates the muscles of facial expression and other targets. The medial longitudinal fasciculus contains, among other fibers, abducens interneurons involved in the internuclear ophthalmoplegia pathway.
The cranial nerve indicated by the arrow in the image below contains sensory and motor fibers. Which of the following is the target of the motor fibers conveyed by this nerve?
(A) Mylohyoidmuscle
(B) Orbicularis oculi
(C) Pharyngealmusculature
(D) Stylopharyngeusmuscle
(E) Vocalis muscle
The answer is D: Stylopharyngeus muscle. The plane of this image is immediately caudal to the medulla-pons junction (note the large size of the restiform body) and is at the level of the cerebellopontine angle (note the obvious appearance of the flocculus on the left side). Consequently, at this location the cranial nerve in the image is the most rostral nerve exiting the postolivary sulcus: cranial nerve IX. The glossopharyngeal nerve exits from the postolivary sulcus rostral to the root of the vagus nerve; consequently, of these two nerves, it is the one closest to the medulla-pons junction. The stylopharyngeus muscle is the only muscle innervated by the glossopharyngeal nerve. This muscle originates from the 2nd pharyngeal arch, has a Special Visceral Efferent functional component, and is part of the efferent limb of the gag reflex. The mylohyoid muscle is innervated by the trigeminal nerve, and the orbicularis oculi by the facial nerve. The pharyngeal musculature and the vocalis muscle are innervated by the vagus nerve.
Which of the following structures contains neurons whose axons end in terminal ganglia (sometimes, these may be called intramural ganglia)?
(A) A
(B) B
(C) C
(D) D
(E) E
The answer is D (Dorsal motor nucleus of the vagus nerve).
This plane of section is through mid-to-rostral portions of the hypoglossal nucleus (choice E); and, in the section, the laterally adjacent dorsal motor nucleus (D) and the solitary nucleus (A) are clearly seen. The dorsal motor vagal nucleus (and other parasympathetic nuclei) appears very light in myelin-stained sections due to the fact that these preganglionic fibers are very lightly myelinated. The preganglionic parasympathetic fibers arising from this nucleus distribute, via branches of the vagus nerve, to terminal ganglia located in thoracic and abdominal viscera. From the terminal ganglia, short postganglionic fibers distribute to smooth muscle and glandular epithelium in the target organs. The inferior (B) and medial (C) vestibular nuclei function in balance, equilibrium, and regulation of eye movement, while the hypoglossal nucleus (E) serves the motor function to the ipsilateral side of the tongue. The solitary nucleus (A) is the visceral center (general and special visceral sensation) of the brainstem.
A 43-year-old welder is brought to the Emergency Department following an accident at a construction site. The EMS personnel indicate that the man fell about 30 feet from a scaffolding onto a concrete surface. The examination reveals broken limb bones and head injuries with bleeding from the mouth and nose; the man is unconscious. CT reveals a basal skull fracture passing through the foramen, indicated by the arrow in the image below, which damaged the structures traversing this opening. When he regains consciousness, which of the following deficits would be the most immediate clinical concern?
(A) Apnea
(B) Deafness in left ear
(C) Dysphagia
(D) Masticatoryparalysis
(E) Tongue paralysis
The answer is C: Dysphagia. The left jugular foramen is identified by the arrow. This foramen transmits the glossopharyngeal, vagus, and accessory cranial nerves. In addition, it contains two small arteries and the continuations of the inferior petrosal sinus and the sigmoid sinus with the internal jugular vein. Injury to these cranial nerves at this location will result in hoarseness, dysphagia, dysarthria, increased heart rate, sensory losses (minor) representing the peripheral branches of IX and X, and weakness of the trapezius and sternocleidomastoid muscles. Of these, the most immediate concern will be dysphagia or difficulty swallowing. With the laryngeal and pharyngeal muscles on the left side paralyzed, including the vocalis on the left, there is the real danger of swallowed solids or fluids entering the trachea (held open by cartilaginous rings and with the vocal folds not closing completely) and resulting in aspiration pneumonia. Apnea is not a feature of syndromes of the jugular foramen, and this patient will not be deaf in his left ear since the auditory meatus, internal or external, is not involved. Masticatory weakness would be present in damage to the foramen ovale, and tongue paralysis would result from damage to the hypoglossal canal; neither is damaged in this case.
Which of the following receives projections from the nucleus indicated at the arrow in the image below?
(A) Ciliaryganglion
(B) Otic ganglion
(C) Sphenopalatineganglion
(D) Submandibular ganglion
(E) Terminal ganglia
The answer is B: Otic ganglion. The inferior salivatory nucleus, as indicated in this image, is located immediately medial to the rostral portions of the solitary tract and nucleus. The parasympathetic preganglionic fibers that originate from this nucleus travel on the glossopharyngeal nerve and, via the tympanic nerve and lesser petrosal nerve, end in the otic ganglion. Postganglionic fibers from the otic ganglion innervate the parotid gland. The ciliary ganglion receives preganglionic fibers, via the oculomotor nerve, from the Edinger-Westphal nucleus which, in turn, projects to the sphincter pupillae muscle of the eye. The sphenopalatine and submandibular ganglia receive preganglionic parasympathetic input that originates from the superior salivatory nucleus and travels on the facial nerve. These ganglia serve the lacrimal gland and the submandibular and sublingual salivary glands, respectively. Terminal ganglia receive parasympathetic preganglionic input from the dorsal motor vagal nucleus (obviously via the vagus nerve) and send their postganglionic fibers to the thoracic and abdominal viscera.
Which of the following cranial nerves, or major branches of cranial nerves, is located in the opening indicated by the arrow in the image below?
(A) Abducensnerve
(B) Mandibular nerve
(C) Maxillarynerve
(D) Ophthalmicnerve
(E) Trochlear nerve
The answer is C: Maxillary nerve. The overall opening indicated by the arrow is the inferior orbital fissure. The maxillary nerve leaves the trigeminal ganglion between the ophthalmic and mandibular branches of the ganglion, traverses the inferior orbital fissure and infraorbital groove, to exit onto the face from the infraorbital foramen (as the infraorbital nerve) to serve the maxillary part of the face and lateral aspect of the nose. The infraorbital groove and foramen are clearly seen in this image. The maxillary nerve is sensory to the maxillary sinus, portions of the palate, maxillary teeth and gums, and the maxillary area of the face. The abducens and trochlear nerves, and the ophthalmic nerve, a major branch of the trigeminal nerve, all pass through the cavernous sinus, then exit the cranial cavity by passing through the superior orbital fissure. The mandibular nerve arises from the lateral part of the trigeminal ganglion, exits the skull via the foramen ovale, and is sensory to the mandibular teeth and gums, tongue, and the mandibular area of the face. The motor fibers of the trigeminal nerve also travel with the mandibular nerve.
