494-868 (III)

Question 1

1. A facial sensory loss in an onion-skin distribution
   around the mouth would most likely
   be associated with which of the following
   lesions?
   (A) Cavernous sinus thrombosis
   (B) Cerebellopontine angle tumor
   (C) Tumor of the orbital apex
   (D) Glioma of the lateral medulla
   (E) Peripheral neuropathy including CN V-2
   and CN V-3

Answer 1

l-D. A glioma of the lateral medulla could destroy part of the spinal trigeminal nucleus and
result in a facial sensory loss in an onion-skin distribution around the mouth. Lesions involving
the peripheral divisions of CN V would correspond to the dermatomes

Question 2

2. All of the following statements concerning
   the spinal trigeminal tract are correct EXCEPT
   (A) it contains axons from the trigeminal
   ganglion
   (B) it mediates pain and temperature sensation
   (C) it is equivalent to the dorsolateral tract
   of Lissauer
   (D) it is the afferent limb of the jaw jerk
   reflex
   (E) it extends from C3 to a midpontine level

Answer 2

2-D. The afferent limb of the jaw jerk reflex, a myotatic (muscle stretch) reflex, is mediated by
the pseudounipolar neurons of the mesencephalic nucleus; the efferent limb is mediated by the
motor neurons of the trigeminal motor nucleus.

Question 3

3. All of the following statements concerning
   the ventral trigeminothalamic tract are correct
   EXCEPT
   (A) it transmits pain and temperature information
   (B) it consists of axons from the spinal
   trigeminal nucleus
   (C) it receives axons from the principal sensory
   nucleus of CN V
   (D) it projects to the contralateral ventral posteromedial
   (VPM) nucleus of the thalamus
   (E) first-order neurons are located in the
   mesencephalic nucleus

Answer 3

3-E. The mesencephalic nucleus does not contribute to the ventral trigeminothalamic tract.
The ventral trigeminothalamic tract consists of axons from the spinal trigeminal nucleus that
transmit pain and temperature information to the contralateral ventral posteromedial (VPM)
nucleus. In addition, it receives and transmits tactile discriminatory input from the principal
sensory nucleus of CN V to the VPM nucleus.

Question 4

4. The trigeminal motor nucleus innervates
   all of the following muscles EXCEPT
   (A) the tensor tympani muscle
   (B) the posterior belly of the digastric muscle
   (C) the mylohyoid muscle
   (D) the temporalis muscle
   (E) the lateral and medial pterygoid muscles

Answer 4

4-B. The posterior belly of the digastric muscle is innervated by the facial nerve (CN VII); the
anterior belly of the digastric muscle is innervated by the trigeminal nerve (CN V).

Question 5

5. An aneurysm of the cavernous sinus could
   result in all of the following EXCEPT
   (A) ptosis
   (B) anesthesia of the tongue
   (C) paralysis of the superior oblique muscle
   (D) complete internal ophthalmoplegia
   (E) diplopia

Answer 5

5-B. An aneurysm of the cavernous sinus would not involve the mandibular nerve (CN V-3),
which does not pass through the wall of the sinus. The mandibular nerve provides the sensory
innervation of the anterior two-thirds of the tongue. Involvement of the oculomotor nerve
(CN III), if complete, would result in internal ophthalmoplegia because of interruption of
preganglionic parasympathetic fibers (a fixed, dilated, unresponsive pupil).

Question 6

6. All of the following statements concerning
   trigeminal neuralgia are correct EXCEPT
   (A) it is characterized by recurrent paroxysms
   of sharp, lancinating pain
   (B) it occurs in any of the three divisions of
   the trigeminal nerve
   (C) it usually occurs in people over 50 years
   of age
   (D) it is more common in men than in women
   (E) it may result from pressure on the nerve
   from a nearby artery

Answer 6

6-D. Trigeminal neuralgia is more common in women than in men, and it occurs most often
on the right side of the face. A redundant loop of the anterior inferior cerebellar artery may
impinge on the trigeminal nerve, causing electric “chatter,” which is felt as pain. This type of
trigeminal neuralgia has been successfully treated by placing a small sponge between the
artery and the nerve. Classic idiopathic trigeminal neuralgia is treated with carbamazepine,
an anticonvulsant drug.

Question 7

7. All of the following statements concerning
   the trigeminal ganglion are correct EXCEPT
   (A) it lies in Meckel’s cave
   (B) it lies in the middle cranial fossa
   (C) it contains bipolar ganglion cells
   (D) it contains first-order neurons of the dorsal
   trigeminothalamic tract
   (E) its destruction results in abolition of the
   corneal reflex and the jaw jerk reflex

Answer 7

7-C. The trigeminal (gasserian) ganglion lies within a dural duplication, Meckel’s cave,
located in the trigeminal fossa of the petrous portion of the temporal bone in the middle cranial
fossa. It contains pseudounipolar ganglion cells similar to those found in the dorsal root ganglia.
These first-order neurons give rise to the ventral and dorsal trigeminothalamic tracts.
Destruction of the trigeminal ganglion interrupts the afferent limbs of the corneal (CN V-l)
and jaw jerk (CN V-3) reflexes. The motor root of CN V lies between the ganglion and the
petrous bone.

Question 8

8. All of the following statements concerning
   the maxillary nerve are correct EXCEPT
   (A) it runs in the lateral wall of the cavernous
   sinus
   (B) it exits the cranial vault via the foramen
   rotundum
   (C) it contains only GSA fibers
   (D) it innervates the skin of the dorsum of
   the nose
   (E) it innervates the palate

Answer 8

8-D. The maxillary nerve (CN V-2) contains only GSA fibers, runs in the lateral wall of the
cavernous sinus, and exits the cranial vault via the foramen rotundum and canalis rotundus.
It innervates the palate via the palatine nerves. The dorsum of the nose is innervated by the
ophthalmic nerve (CN V-l).

Question 9

9. All of the following statements concerning
   the mesencephalic nucleus are correct EXCEPT
   (A) it projects to the cerebellum
   (B) it is located in the pons
   (C) it mediates the afferent limb of the jaw
   jerk reflex
   (D) it contains bipolar neurons
   (E) it receives input from muscle spindles

Answer 9

9-D. The mesencephalic nucleus of CN V contains pseudounipolar neurons that mediate the
afferent limb of the jaw jerk reflex. It is located in the rostral pons and in the mesencephalon
and gives rise to collaterals that project to the cerebellum via the superior cerebellar peduncle.
It receives input from muscle spindles and pressure and joint receptors.

Question 10

10. All of the following statements concerning
    the dorsal trigeminothalamic tract are
    correct EXCEPT
    (A) it is an uncrossed tract
    (B) it mediates two-point tactile discrimination
    (C) it mediates the corneal reflex
    (D) it projects to the ventral posteromedial
    (VPM) nucleus of the thalamus
    (E) its first-order neurons are found in the
    trigeminal ganglion

Answer 10

10-C. The dorsal trigeminothalamic tract mediates discriminative tactile and pressure sensation
(including two-point discrimination), is an uncrossed tract, and projects to the ventral posteromedial
(VPM) nucleus. First-order neurons are in the trigeminal ganglion, second-order
neurons lie in the principal sensory nucleus of the rostral pons, and third-order neurons are located in the VPM nucleus of the thalamus. This tract corresponds in function to the dorsal
column-medial lemniscus system. The dorsal trigeminothalamic tract does not mediate the
corneal reflex.

Question 11

11. All of the following statements concerning
    the principal sensory nucleus of CN V are
    correct EXCEPT
    (A) it projects to the ipsilateral ventral posteromedial
    (VPM) nucleus of the thalamus
    (B) it projects to the contralateral VPM
    nucleus of the thalamus
    (C) it receives input from Meissner’s and
    Pacini’s corpuscles
    (D) it is located in the medulla and pons
    (E) it is a homolog to the dorsal column
    nuclei

Answer 11

11-D. The principal sensory nucleus of CN V is located in the rostral pons at the level of the
motor trigeminal nucleus; it receives input from Meissner’s and Pacini’s corpuscles. It projects
to the ipsilateral ventral posteromedial (VPM) nucleus of the thalamus via the dorsal
trigeminothalamic tract and to the contralateral VPM nucleus of the thalamus via the ventral
trigeminothalamic tract. The principal sensory nucleus is homologous to the dorsal column
nuclei (gracile and cuneate nuclei).

Question 12

12. All of the following statements concerning
    the trigeminal nerve are correct EXCEPT
    (A) it is the nerve of the first branchial arch
    (mandibular nerve)
    (B) it contains only GSA and SVE fibers
    (C) it innervates the stapedius muscle
    (D) it innervates the dura of the anterior and
    middle cranial fossae
    (E) it mediates the afferent limb of the
    corneal reflex

Answer 12

12-C. The trigeminal nerve (CN V) is the nerve of the first branchial arch (mandibular nerve)
and contains only GSA and SVE fibers. It innervates the supratentorial dura of the anterior
and middle cranial fossae. The dura of the posterior cranial fossa is innervated by the vagal
nerve (CN X) and the second and third spinal nerves (C2 and C3), which hitchhike with the
hypoglossal nerve (CN XII). The tensor tympani muscle is innervated by the trigeminal nerve;
the stapedius muscle is innervated by the facial nerve (CN VII). The ophthalmic nerve (CN V-l)
mediates the afferent limb of the corneal reflex; the facial nerve (CN VII) mediates the efferent
limb of the corneal reflex (orbicularis oculi muscle).

Question 13

13. All of the following lesions could interrupt
    the corneal reflex EXCEPT
    (A) occlusion of the anterior inferior cerebellar
    artery (AICA)
    (B) occlusion of the posterior inferior cerebellar
    artery (PICA)
    (C) an acoustic neuroma
    (D) an aneurysm of the cavernous sinus
    (E) destruction of the principal sensory
    nucleus of CN V

Answer 13

13-E. The principal sensory nucleus of CN V mediates tactile discriminatory sense and position
sense, homologous to the gracile and cuneate nuclei. The anterior and posterior inferior
cerebellar arteries (AICA and PICA, respectively) both interrupt the afferent corneal pathway
as may an aneurysm of the cavernous sinus. An acoustic neuroma interrupts the efferent limb
of the corneal reflex (CN VII).

Question 14

14. All of the following statements concerning
    the corneal reflex are correct EXCEPT
    (A) it is a bisynaptic reflex
    (B) it is abolished ipsilaterally by transection
    of the facial nerve
    (C) it is abolished by a transection of the
    spinal trigeminal tract made within its
    caudal medullary extent
    (D) it is mediated via axons found in the
    spinal trigeminal tract
    (E) it is mediated via axons arising from the
    spinal trigeminal nucleus

Answer 14

14-C. The afferent corneal reflex pathway is as follows: First-order neurons of the ophthalmic
nerve (CN V-l) are found in the trigeminal ganglion. Their axons enter the pons and descend
in the spinal trigeminal tract. They enter the spinal trigeminal nucleus in its rostral portion
and synapse on second-order neurons, which project to the ipsilateral and contralateral facial
nuclei. Axons from third-order neurons in the facial nuclei innervate the orbicularis oculi muscles
bilaterally (directly and consensually). Trigeminal tractotomy at caudal levels produces
facial anesthesia without interruption of the corneal reflex.

Question 15

1. All of the following statements concerning
   conduction deafness are correct EXCEPT
   (A) the sound of a vibrating tuning fork
   placed on the vertex is heard best in the
   deaf ear
   (B) it may be the result of an acoustic neuroma
   (C) it may be the result of otosclerosis
   (D) it may be the result of otitis media
   (E) it may be the result of wax in the external
   auditory meatus

Answer 15

l-B. Conduction deafness is produced by interruption of the passage of sound waves through
the external or middle ear. An acoustic neuroma is a tumor of the vestibulocochlear nerve
located in the internal auditory meatus or in the cerebellopontine angle of the posterior cerebral
fossa. This tumor causes unilateral nerve deafness. In conduction deafness, a vibrating
tuning fork placed on the vertex of the skull would be heard best in the deaf ear; this is the
Weber test.

Question 16

2. All of the following statements concerning
   nerve deafness are correct EXCEPT
   (A) in patients with partial nerve deafness,
   air conduction is better than bone conduction
   (B) it may result from a middle ear infection
   (C) it may result from a tumor in the internal
   auditory meatus
   (D) it may result from toxins and drugs
   (E) it may result from degenerative disease
   of the organ of Corti

Answer 16

2-B. Sensorineural, or nerve, deafness results from damage to the organ of Corti, the cochlear
nerve, or the central neural pathway. Middle ear infection (otitis media) results in conduction
deafness. In patients with partial nerve deafness, air conduction is better than bone conduction.

Question 17

3. The auditory pathway includes all of the
following structures EXCEPT the
(A) trapezoid body
(B) nucleus of the inferior colliculus
(C) inferior olivary nucleus
(D) lateral lemniscus
(E) medial geniculate body

Answer 17

3-C. The inferior olivary nucleus is a cerebellar relay nucleus found in the medulla. The superior
olivary nucleus is an important way station in the auditory pathway; it is found in the
pons at the level of the facial nucleus.

Question 18

4. All of the following statements concerning
   the auditory system are correct EXCEPT
   (A) the membranous labyrinth is irrigated by
   a branch of the anterior inferior cerebellar
   artery
   (B) it is characterized by multiple decussations
   at all levels
   (C) it is characterized by pitch localization at
   all levels
   (D) it detects sound frequencies from 20 Hz
   to 50 kHz
   (E) it can discriminate intensity changes
   between 1 dB and 2 dB

Answer 18

4-D. The auditory system detects sound frequencies from 20 Hz to 20,000 Hz. The membranous
labyrinth is perfused by the labyrinthine artery; this is usually a branch of the anterior
inferior cerebellar artery (in 85% of patients) but, in some cases, it is a direct branch of the
basilar artery (in 15%).

Question 19

5. All of the following statements concerning
   the tympanic cavity are correct EXCEPT
   (A) it contains the chorda tympani
   (B) it contains parasympathetic input to the
   submandibular and sublingual glands
   (C) it contains two striated muscles
   (D) it communicates with the nasopharynx
   (E) it receives sensory innervation by the
   vagal nerve

Answer 19

5-E. The tympanic cavity contains the chorda tympani (of CN VII), which supplies taste to the
anterior two-thirds of the tongue. The chorda tympani also contains parasympathetic input to
the submandibular and sublingual glands. It contains two striated muscles, the tensor tympani
(innervated by CN V) and the stapedius (innervated by CN VII). It communicates, via the
auditory tube, with the nasopharynx. The tympanic branch of the glossopharyngeal nerve (CN
IX) innervates the mucosa of the middle ear.

Question 20

6. All of the following statements concerning
   the organ of Corti are correct EXCEPT
   (A) it receives input from the brainstem
   (B) it is innervated by bipolar neurons of the
   spiral ganglion
   (C) it contains mechanoreceptors
   (D) it contains inner and outer hair cells
   (E) it is a structure of the middle ear

Answer 20

6-E. The organ of Corti, an inner ear structure, lies within the cochlear duct. It contains the
peripheral receptor cells of the auditory system, the inner and outer hair cells. Hair cells are
mechanoreceptors, receive input from the brainstem via the efferent cochlear bundle, and are
innervated by bipolar neurons of the spiral ganglion (of CN VIII).

Question 21

7. All of the following statements concerning
   the basilar membrane are correct EXCEPT
   (A) it separates the cochlear duct from the
   scala tympani
   (B) it has a pitch localization along its length
   (C) it is in contact with endolymph
   (D) it gives rise to the tectorial membrane
   (E) its destruction at the apex of the cochlea
   results in a hearing loss in the low frequency
   range

Answer 21

7-D. The basilar membrane supports the organ of Corti, separates the cochlear duct from the
scala tympani, and is in contact with both endolymph and perilymph. The basilar membrane
has a pitch localization along its length; high frequencies are registered at the base of the
cochlea, low frequencies at the apex. The tectorial membrane is a projection of the spiral limbus
that overlies the hair cells of the organ of Corti.

Question 22

8. All of the following statements concerning
   the hair cells of the organ of Corti are correct
   EXCEPT
   (A) they are mechanoreceptors
   (B) they project centrally to the cochlear
   nuclei
   (C) they are stimulated by vibrations of the
   basilar membrane
   (D) they are derived from the otic placode of
   the rhombencephalon
   (E) they contain stereocilia that are embedded
   in the tectorial membrane

Answer 22

8-B. The hair cells of the spiral ganglion of Corti are mechanoreceptors. Vibrations of the
basilar membrane force the stereocilia (microvilli) of the hair cells against the overlying tectorial
membrane; this shearing force is the adequate stimulus. Hair cells stimulate the afferent
bipolar neurons of the spiral ganglion, which project centrally to the cochlear nuclei of the
brainstem. The inner ear is derived from the otic placode of the rhombencephalon.

Question 23

9. All of the following nuclei receive binaural
input EXCEPT
(A) cochlear nuclei
(B) medial geniculate body
(C) nucleus of inferior colliculus
(D) nuclei of lateral lemniscus
(E) superior olivary nucleus

Answer 23

9-A. The cochlear nuclei do not receive input from both ears; destruction of the cochlear nuclei
results in ipsilateral nerve deafness.

Question 24

10. All of the following agents can cause
nerve deafness EXCEPT
(A) cytomegalovirus
(B) marijuana
(C) rubella
(D) streptomycin
(E) syphilis

Answer 24

10-B. There is no evidence to date that marijuana is a human teratogen.

Question 25

1. Tilting the head forward would maximally
   stimulate the hair cells in the
   (A) crista ampullaris of the anterior semicircular
   duct
   (B) crista ampullaris of the lateral semicircular
   duct
   (C) crista ampullaris of the posterior semicircular
   duct
   (Dj macula of the utricle
   (E) macula of the saccule

Answer 25

l-D. Tilting the head forward would maximally stimulate the hair cells in the utricle. Tilting
the head to the side would maximally stimulate the hair cells in the saccule. Utricle and saccule
both respond to linear acceleration and the force of gravity.

Question 26

2. A comatose patient’s head is elevated 30°
   from the horizontal. Cold water is injected
   into the left external auditory meatus. If the
   brainstem is intact, which one of the following
   ocular reflexes would you see?
   (A) Horizontal nystagmus to the left
   (B) Vertical upper nystagmus
   (C) Horizontal nystagmus to the right
   (D) Deviation of the eyes to the left
   (E) Deviation of the eyes to the right

Answer 26

2-D. Nystagmus is not seen in comatose patients. The patient’s eyes will deviate toward the
side of cold water injection.

Question 27

3. All of the following statements concerning
   decerebrate rigidity are correct EXCEPT
   (A) it results from a lesion transecting the
   brainstem between the superior and inferior
   colliculi
   (B) it is considered to be alpha rigidity
   (C) it is characterized by opisthotonos with
   arms and legs extended and adducted
   (D) it can be abolished by dorsal root rhizotomy
   (E) it can be abolished by section of the
   vestibular nerve

Answer 27

3-B. Classic decerebrate (posturing) rigidity is considered to be gamma rigidity. Alpha rigidity
is seen when the anterior cerebellum of a decerebrate preparation is infarcted.

Question 28

4. A patient sitting erect with his head
   inclined 30° forward was rotated to the right
   10 turns in 20 seconds, after which he was
   suddenly stopped. All of the following signs
   and symptoms will be experienced EXCEPT
   (A) the patient would have a vertical nystagmus
   (B) the fast phase of the nystagmus would be
   to the left
   (C) the slow phase of the nystagmus would
   be to the right
   (D) the patient would past-point to the right
   (E) the patient would experience a sensation
   of turning to the left

Answer 28

4-A. Forward 30° inclination of the erect head would result in maximal stimulation of the
cristae ampullares of the lateral (horizontal) semicircular ducts. Rotation of this plane would
result in horizontal nystagmus.

Question 29

5. All of the following statements concerning
   endolymph are correct EXCEPT
   (A) it is found in the helicotrema
   (B) it is found in the utricle
   (C) it is found in the semicircular ducts
   (D) it is secreted by the stria vascularis
   (E) it is absorbed by the endolymphatic sac

Answer 29

5-A. The helicotrema is a space at the apex of the cochlea through which the scala vestibuli
and the scala tympani communicate.

Question 30

6. Which of the following statements concerning
   caloric induced nystagmus is FALSE?
   (A) Cold-water irrigation of the left ear results
   in nystagmus to the right (fast phase)
   (B) Cold-water irrigation of the left ear
   results in past-pointing to the left
   (C) Caloric testing permits the evaluation of
   the individual semicircular ducts
   (D) Caloric testing is contraindicated in
   comatose patients
   (E) Hot-water irrigation results in the reverse
   reactions

Answer 30

6-D. One of the advantages of caloric stimulation is that it can be used safely in all states of
consciousness. Caloric testing enables the examiner to evaluate the individual semicircular
canals separately. Past-pointing and falling is to the side of irrigation. Remember the
mnemonic for calorics: COWS = Cold, Opposite; Warm, Same.

Question 31

7. Which of the following statements concerning
the semicircular ducts is FALSE?
(A) They are three in number
(B) They contain endolymph
(C) They contain hair cells
(D) They are found within the vestibule
(E) They comprise the kinetic labyrinth

Answer 31

7-D. The three semicircular (membranous) ducts lie within the three semicircular (osseus)
canals of the petrous part of the temporal bone. They contain endolymph and have hair cells
within the cristae ampullares. The kinetic labyrinth consists of the semicircular ducts; the static
labyrinth consists of the utricle and saccule. The vestibule is a central cavity of the inner
ear that contains the saccule and the utricle.

Question 32

8. All of the following statements concerning
   the hair cells of the vestibular apparatus are
   correct EXCEPT
   (A) hair cells contain one kinocilium and
   many stereocilia (microvilli)
   (B) hair cells of the semicircular ducts are
   stimulated by perilymphatic flow
   (C) hair cells are innervated by bipolar cells
   found in the internal auditory meatus
   (D) hair cells are found in the cristae ampullares
   (E) hair cells are found in the maculae of the
   saccule and utricle

Answer 32

8-B. The hair cells of the vestibular apparatus contain one kinocilium and many stereocilia
(microvilli). Hair cells of the semicircular ducts are stimulated by endolymphatic flow (not perilymphatic
flow); they are innervated by bipolar cells found in the fundus of the internal auditory
meatus. Hair cells are found in the cristae ampullares and in the maculae of the utricle
and saccule.

Question 33

9. All of the following statements concerning
   the static labyrinth are correct EXCEPT
   (A) it responds to linear acceleration
   (B) it responds to the pull of gravity
   (C) it lies within the vestibule of the bony
   labyrinth
   (D) it includes the macula of the utricle
   (E) it is tested clinically by caloric stimulation

Answer 33

9-E. The static labyrinth consists of the utricle and saccule, which are found in the vestibule
of the bony labyrinth. The hair cells of the maculae of the utricle and saccule respond to linear
acceleration and deceleration and gravitational pull. Introduction of warm or cold water into
the external auditory meatus stimulates the hair cells of the semicircular ducts (i.e., the
kinetic labyrinth).

Question 34

10. All of the following statements concerning
    the vestibular ganglion are correct
    EXCEPT
    (A) it lies within the bony modiolus
    (B) it innervates the hair cells of the cristae
    ampullares
    (C) it innervates the hair cells of the utricle
    and saccule
    (D) it contains bipolar ganglion cells
    (E) it projects directly to the cerebellar cortex

Answer 34

10-A. The vestibular ganglion of Scarpa lies in the fundus of the internal auditory meatus. It
contains bipolar neurons that innervate the hair cells of the cristae ampullares and the maculae
of the utricle and the sacculus. Bipolar neurons project centrally to the vestibular nuclei of
the brainstem and the flocculonodular lobe of the cerebellum. The spiral (cochlear) ganglion of
the cochlear nerve lies in the modiolus of the petrosal bone.

Question 35

11. All of the following statements concerning
    the vestibular nuclei are correct EXCEPT
    (A) they are three in number
    (B) they receive input from the fastigial
    nuclei
    (C) they project to the MLF
    (D) they project to the nuclei of the extraocular
    muscles
    (E) they are found in the medulla and pons

Answer 35

11-A. There are four vestibular nuclei: lateral, medial, inferior, and superior. They receive
input from the fastigial nuclei via the uncinate fasciculus and the juxtarestiform body.
Vestibulocerebellar fibers project to the nodulus, flocculus, and uvula but not to the fastigial
nucleus. They project via the MLF to the ocular motor nuclei (of CN III, CN IV, and CN VI).
Vestibular nuclei are found in the medulla and pons.

Question 36

12. All of the following statements concerning
    the lateral vestibulospinal tract are correct
    EXCEPT
    (A) it arises from the lateral vestibular nucleus
    (B) it is located in the ventral funiculus of the
    spinal cord
    (C) it is found at all spinal cord levels
    (D) it facilitates extensor muscle tone in antigravity
    muscles
    (E) it is a crossed pathway

Answer 36

12-E. The lateral vestibulospinal tract arises from the ipsilateral lateral vestibular nucleus of
Deiters, located in the lateral pontine tegmentum, and descends to all spinal cord levels in the
ventral funiculus. It facilitates extensor muscle tone in the antigravity muscles. It is an
uncrossed tract.

Question 37

13. All of the following statements concerning
    the MLF are correct EXCEPT
    (A) it is located in the midbrain
    (B) it is located in the spinal cord
    (C) it contains vestibulo-oculomotor fibers
    (D) it mediates adduction in lateral conjugate
    gaze on command
    (E) transection results in paralysis of convergence

Answer 37

13-E. Transection of the MLF results in a medial rectus palsy on attempted lateral gaze; convergence
remains intact. The MLF extends from the spinal cord to the rostral midbrain; it contains
vestibulo-oculomotor fibers that mediate eye movements in response to head and neck
posture. It carries fibers to the medial rectus subnucleus from the pontine lateral conjugate
gaze center.

Question 38

14. All of the following statements concerning
    vestibular nystagmus are correct EXCEPT
    (A) it is named after the fast component
    (B) it has a slow component that is opposite
    the direction of rotation
    (C) it may be horizontal, vertical, or rotatory
    (D) it is frequently associated with nausea
    and vertigo
    (E) it results in nystagmus to the same side
    with ice-water irrigation of the external
    auditory meatus

Answer 38

14-E. Nystagmus is named after the fast component; the slow component is opposite the
direction of rotation, thus maintaining visual fixation. Nystagmus may be horizontal, vertical,
or rotatory and is frequently associated with nausea, vomiting, and vertigo. Irrigation of the
external auditory meatus (with the head tilted back 60°) with ice water results in nystagmus to
the opposite side. Remember the mnemonic COWS = Cold, Opposite; Warm, Same.

Question 39

15. All of the following statements concerning
    the primary vestibular cortex are correct
    EXCEPT
    (A) it receives input from the ventral posteroinferior
    (VPI) nucleus
    (B) it receives input from the ventral posterolateral
    (VPL) nucleus
    (C) it is located in areas 2 and 3
    (D) it is located in the somesthetic cortex
    (E) it is located in the paracentral lobule

Answer 39

15-E. The primary vestibular cortex (areas 2v and 3a) is located in the postcentral gyrus, the
somesthetic cortex of the parietal lobe. The vestibular cortex receives input from the ventral
posteroinferior (VPI), ventral posterolateral (VPL), and the ventral lateral nuclei of the thalamus.
The paracentral lobule is a continuation of the motor and sensory strips onto the medial
surface of the hemisphere; it receives no vestibular input.

Question 40

1. The cavernous sinus contains all of the following
structures EXCEPT the
(A) ophthalmic nerve
(B) mandibular nerve
(C) abducent and trochlear nerves
(D) postganglionic sympathetic fibers
(E) preganglionic parasympathetic fibers

Answer 40

l-B. The mandibular nerve (CN V-3) does not pass through the cavernous sinus; it exits the
skull via the foramen ovale.

Question 41

2. Parasympathetic fibers are found in all of
the following cranial nerves EXCEPT the
(A) oculomotor nerve
(B) trigeminal nerve
(C) facial nerve
(D) glossopharyngeal nerve
(E) vagal nerve

Answer 41

2-B. The trigeminal nerve (CN V) contains only special visceral efferent (SVE) and general
somatic afferent (GSA) fibers.

Question 42

3. The superior orbital fissure contains all of
the following structures EXCEPT the
(A) ophthalmic veins
(B) ophthalmic nerve
(C) trochlear nerve
(D) abducent nerve
(E) optic nerve

Answer 42

3-E. The optic nerve (CN II) enters the skull via the optic canal. The optic canal also contains
the ophthalmic artery.

Question 43

4. Transection of the left oculomotor nerve
   results in all of the following conditions
   EXCEPT
   (A) diplopia when attempting to adduct the
   left eye
   (B) a fixed dilated pupil on the left side
   (C) no consensual reaction when light is
   shone in the left eye
   (D) a normal bilateral corneal reflex
   (E) a left eye that “looks down and out”

Answer 43

4r-C. Transection of the oculomotor nerve (CN III) does not interrupt the afferent limb of the
pupillary reflex, which is bilateral. Light shone into the left eye results in constriction of the
contralateral pupil, the consensual reaction.

Question 44

5. A glioma destroying the right trochlear
   nucleus would result in all of the following
   conditions EXCEPT
   (A) extorsion of the affected eye
   (B) diplopia when looking down
   (C) a head tilt
   (D) paralysis of the right superior oblique
   muscle
   (E) unaffected pupillary light reflexes

Answer 44

5-D. The right trochlear nucleus of CN IV projects to the left superior oblique muscle.
Diplopia occurs when an image falls on disparate parts of the retina. The pupillary light reflex
is mediated by the parasympathetic fibers of the oculomotor nerve.

Question 45

6. All of the following statements concerning
   the vestibulocochlear nerve are correct
   EXCEPT
   (A) it exits the brainstem in the cerebellopontine
   angle
   (B) the vestibular ganglion is located in the
   internal auditory meatus
   (C) irritative lesions cause tinnitus and nystagmus
   (D) destructive lesions cause unilateral deafness
   (E) it is a special visceral afferent (SVA)
   nerve

Answer 45

6-E. The vestibulocochlear nerve (CN VTII) is classified as a special somatic afferent (SSA)
nerve, as is the optic nerve (CN II).

Question 46

7. All of the following statements concerning
   the vagal nerve are correct EXCEPT
   (A) its dorsal motor nucleus lies in the
   medulla
   (B) it contains parasympathetic fibers from
   the nucleus ambiguus
   (C) it emerges from the postolivary sulcus
   (D) it exits the skull via the foramen magnum
   (E) it innervates the levator veli palatini
   muscle

Answer 46

7-D. The vagal nerve (CN X) emerges from the brainstem in the postolivary sulcus of the
medulla and exits the skull via the jugular foramen with CN LX and CN XI. It contains preganglionic
parasympathetic fibers from the nucleus ambiguus that project to the cardiac ganglia of
the heart. The vagal nerve innervates the levator veli palatini muscle, which raises and
retracts the soft palate. The dorsal motor nucleus of the vagal nerve lies in the medulla.

Question 47

8. All of the following statements concerning
   the geniculate ganglion are correct EXCEPT
   (A) it is found within the temporal bone
   (B) it receives taste fibers from the anterior
   two-thirds of the tongue
   (C) it gives rise to the greater petrosal nerve
   (D) it contains postganglionic parasympathetic
   neurons
   (E) it contains sensory neurons that innervate
   the outer ear

Answer 47

8-D. The geniculate ganglion contains all of the first-order sensory neurons of the facial nerve
(CN VII) [general somatic afferent (GSA) and special visceral afferent (SVA)]. It is found
within the temporal bone and gives rise to the greater petrosal nerve. Sensory neurons in the
geniculate ganglion innervate taste buds from the anterior two-thirds of the tongue. Taste
fibers from the posterior third of the tongue belong to the glossopharyngeal nerve (CN LX).
Pseudounipolar ganglion cells of the geniculate ganglion innervate part of the outer ear.

Question 48

9. All of the following statements concerning
   the olfactory nerve are correct EXCEPT
   (A) it projects directly to the forebrain
   (B) it synapses with mitral cells
   (C) its cells of origin are found in the nasal
   mucosa
   (D) it is a special somatic afferent (SSA) nerve
   (E) it enters the skull via the cribriform
   plate of the ethmoid bone

Answer 48

9-D. The olfactory nerve (CN I), a special visceral afferent (SVA) nerve, consists of the
unmyelinated axons of bipolar neurons found in the olfactory epithelium of the upper nasal
cavity. There are 25 million neurosensory cells on each side. These axons synapse with mitral
cells in the olfactory bulb, a rhinencephalic structure of the forebrain. Mitral cells project
directly via the olfactory tract to the primary olfactory cortex of the uncus.

Question 49

10. All of the following statements concerning
    the optic nerve are correct EXCEPT
    (A) it enters the skull via the superior orbital
    fissure
    (B) it is the afferent limb of the pupillary
    light reflex
    (C) there is no regeneration after injury
    (D) it lies within the subarachnoid space
    (E) its axons are myelinated by oligodendrocytes

Answer 49

10-A. The optic nerve (CN II) enters the skull via the optic canal of the sphenoid bone (the
ophthalmic artery is also found in the optic canal). Efferent retinal fibers are the afferent limb
of the pupillary light reflex. The efferent limb is the oculomotor nerve (CN III). The optic nerve
is invested with meninges and lies in the subarachnoid space. The optic nerve is a tract of the
central nervous system (CNS) and not a peripheral nerve. There is no regeneration after transection.
The axons of the optic nerve are myelinated by oligodendrocytes; peripheral nerve
axons are myelinated by Schwann cells.

Question 50

11. All of the following statements concerning
    the oculomotor nerve are correct EXCEPT
    (A) it originates in the rostral midbrain
    (B) it traverses the cavernous sinus
    (C) it exits the cranial vault via the superior
    orbital fissure
    (D) it has a sympathetic component
    (E) transection results in ptosis

Answer 50

11-D. The oculomotor nucleus is found in the rostral midbrain at the level of the superior colliculus.
Ptosis results after transection of the fibers to the levator palpebrae muscle. The oculomotor
nerve (CN III) traverses the wall of the cavernous sinus with CN IV, CN VI, CN V-l,
and CN V-2. The oculomotor nerve has a general visceral efferent (GVE) parasympathetic component,
which arises from the Edinger-Westphal nucleus. CN III exits the cranium via the
superior orbital fissure.

Question 51

12. All of the following statements concerning
    the accessory nerve are correct EXCEPT
    (A) it exits the skull via the jugular foramen
    (B) it contains fibers from the nucleus
    ambiguus
    (C) it contains fibers from the dorsal motor
    nucleus
    (D) it contains fibers from cervical spinal
    cord levels
    (E) it innervates two muscles of branchiomeric
    origin

Answer 51

12-C. The accessory (spinal) nerve (CN XI) exits the skull via the jugular foramen (with CN
LX and CN X). The spinal part of the spinal accessory nerve enters the skull via the foramen
magnum. CN XI contains SVE fibers from the nucleus ambiguus that innervate intrinsic muscles
of the larynx; CN XI contains special visceral efferent (SVE) fibers from the cervical spinal
cord that innervate two muscles of branchiomeric origin, the trapezius and the sternocleidomastoid.
The dorsal motor nucleus is the general visceral efferent (GVE) nucleus of the vagal
nerve (CN X).

Question 52

13. All of the following statements concerning
    the facial nerve are correct EXCEPT
    (A) it innervates the lacrimal gland
    (B) it innervates the stapedius muscle
    (C) it innervates the posterior belly of the
    digastric muscle
    (D) it provides the efferent limb for the
    corneal reflex
    (E) it projects to the otic ganglion

Answer 52

13-E. The facial nerve (CN VII) provides the preganglionic parasympathetic innervation for
the lacrimal, sublingual, and submandibular glands and innervates the stapedius muscle of
the tympanic cavity and the posterior belly of the digastric muscle. The otic ganglion receives
preganglionic parasympathetic input from the glossopharyngeal nerve (CN LX) and projects
postganglionic parasympathetic fibers to the parotid gland.

Question 53

14. All of the following statements concerning
    the trigeminal nerve are correct EXCEPT
    (A) it contains special visceral efferent (SVE)
    and general somatic afferent (GSA) fibers
    (B) it innervates the tensor tympani muscle
    (C) it innervates the anterior belly of the
    digastric muscle
    (D) it innervates the supratentorial dura
    (E) it innervates the skin over the angle of
    the jaw

Answer 53

14-E. The trigeminal nerve (CN V) [general somatic afferent (GSA) and special visceral efferent
(SVE)] innervates the tensor tympani muscle and the anterior belly of the digastric muscle.
It innervates the supratentorial dura. The skin over the angle of the jaw and the scalp of the
back of the head are innervated by the second and third cervical nerves.

Question 54

15. Transection of the glossopharyngeal
    nerve results in all of the following deficits
    EXCEPT
    (A) loss of the gag reflex
    (B) loss of neurons in the superior salivatory
    nucleus
    (C) loss of taste and pain sensation from the
    posterior third of the tongue
    (D) loss of the carotid sinus reflex
    (E) loss of neurons in the nucleus ambiguus

Answer 54

15-B. Transection of the glossopharyngeal nerve (CN IX) results in degeneration of neurons in
the rostral part of the nucleus ambiguus and in the inferior salivatory nucleus, loss of the gag
reflex, loss of sensation from the tonsillar bed, loss of taste and pain sensation from the posterior
third of the tongue, and loss of the carotid sinus reflex. The superior salivatory nucleus is
a general visceral efferent (GVE) nucleus of CN VH.