494-868 (II)

Question 1

1. Peripheral nerve fibers regenerate at the rate of
(A) 0.1 mm/day
(B) 3 mm/day
(C) 100 mm/day
(D) 200 mm/day
(E) 400 mm/day

Answer 1

l-B.

Peripheral nerve fibers regenerate at the rate of 3 mm/day.

Question 2

2. Fast pain has a conduction velocity of
(A) 1 m/sec
(B) 5 m/sec
(C) 15 m/sec
(D) 30 m/sec
(E) 100 m/sec

Answer 2

2-C.

Fast pain has a nerve fiber (A delta) conduction velocity of 12-30 m/sec. Slow pain has a
nerve fiber (C) conduction velocity of 0.5-2 m/sec.

Question 3

3. All of the following statements concerning neurons are correct EXCEPT
   (A) they are of neuroectodermal origin
   (B) they have lost the capacity to undergo cell division
   (C) they contain Nissl substance
   (D) they are derived from the neural tube and neural crest
   (E) bipolar neurons are the most common type of neuron

Answer 3

3-E.

Neurons are of ectodermal origin, contain Nissl substance, and have lost the capacity to undergo cell division. The neural tube and the neural crest both give rise to neurons. Multipolar neurons are the most common type. Bipolar neurons are found in the olfactory mucous membrane,in the ganglia of the vestibulocochlear nerve, and in the retina

Question 4

4. All of the following statements concerning axons are correct EXCEPT they
(A) may arise from the perikaryon
(B) may arise from a dendrite
(C) arise from the axon hillock
(D) contain rough endoplasmic reticulum
(E) transmit action potentials

Answer 4

4r-D. Axons may arise from the perikaryon or from a dendrite. They always arise from the axon hillock. Axons do not contain rough endoplasmic reticulum (Nissl substance). Axons generate and transmit action potentials

Question 5

5. All of the following statements concerning myelin are correct EXCEPT
   (A) it is produced by the microglia
   (B) it is produced by Schwann cells
   (C) it is produced by oligodendrocytes
   (D) myelinating cells of the PNS myelinate only one internode
   (E) myelinating cells of the CNS myelinate several internodes of different axons

Answer 5

5-A.

Myelin is produced by Schwann cells in the peripheral nervous system (PNS) and by oligodendrocytes in the central nervous system (CNS). Schwann cells myelinate only one internode; oligodendrocytes myelinate several internodes of different axons (up to 30). Microglial cells are the scavenger cells of the CNS; they do not produce myelin.

Question 6

6. All of the following statements concerning astrocytes are correct EXCEPT
   (A) they possess many processes
   (B) they are found in both white and gray matter
   (C) they are considered to be the scavenger cells of the CNS
   (D) they have perivascular end feet
   (E) in damaged

Answer 6

6-C.

Astrocytes have many processes and are found in the gray and white matter. They have perivascular end feet. In the damaged brain, astrocytes form glial scar tissue, known as gliosis or astrogliosis. The microglial cells are the scavenger cells of the central nervous system (CNS).

Question 7

7. All of the following statements concerning Schwann cells are correct EXCEPT
   (A) they play an important role in peripheral
   nerve regeneration
   (B) they are derived from the neural tube
   (C) they may give rise to tumors of peripheral
   nerves
   (D) one Schwann cell myelinates one internode of an axon
   (E) they are neurolemmal cells

Answer 7

7-B. Schwann cells (neurolemmal cells) play an important role in peripheral nerve regeneration.
They are derived from the neural crest. They may give rise to benign tumors called schwannomas.
Schwann cells are the myelin-forming cells of the peripheral nervous system (PNS); they myelinate only one internode of an axon.

Question 8

8. All of the following statements concerning ependymal cells are correct EXCEPT
   (A) they are derived from the neural crest
   (B) they line the central canal
   (C) they are in contact with CSF
   (D) they produce CSF
   (E) they include tanycytes and choroid plexus
   cells

Answer 8

8-A. Ependymal cells are derived from the neural tube, line the central canal and ventricles,
and are in contact with cerebrospinal fluid (CSF). Ependymal cells include choroid plexus cells,
which produce CSF. Tanycytes are modified ependymal cells found in the wall of the third ventricle.

Question 9

9. All of the following statements concerning wallerian degeneration are correct EXCEPT
   (A) it occurs in the CNS
   (B) it occurs in the PNS
   (C) it is a retrograde degeneration
   (D) it is characterized by the disappearance of axons and myelin sheaths
   (E) it is characterized by the proliferation of
   Schwann cells

Answer 9

9-C.

Wallerian degeneration is an anterograde degeneration of nerve fibers, characterized by
the disappearance of axons and myelin and by Schwann cell proliferation.

Question 10

10. All of the following statements concerning axonal transport are correct EXCEPT
    (A) fast anterograde axonal transport is 200-400 mm/day
    (B) mitochondria are transported at the rate of 5 mm/day
    (C) fast retrograde axonal transport is associated
    with microtubules and dynein
    (D) fast anterograde axonal transport is
    associated with microtubules and kinesin
    (E) slow anterograde transport is 1-6 mm/day

Answer 10

10-B.

Mitochondria are transported at the rate of 50-100 mm/day.

Question 11

11. All of the following statements concerning sensory receptors are correct EXCEPT
    (A) pain and thermal receptors utilize group lb fibers
    (B) Meissner’s corpuscles are found only in the dermal papillae of glabrous skin
    (C) Merkel’s tactile disks mediate the sensation of light touch
    (D) pacinian corpuscles are acceleration detectors
    that respond to vibration sensation
    (E) annulospiral endings project centrally via the dorsal

Answer 11

11-A.

Pain and thermal receptors utilize group A delta (fast pain) and C (slow pain) fibers. Pain and thermal sensation are mediated via the lateral spinothalamic tract.

Question 12

1. All of the following statements concerning the substantia gelatinosa are correct EXCEPT
   (A) it is found at all spinal cord levels
   (B) it is a sensory nucleus
   (C) it plays a role in mediating pain and temperature
   (D) it is homologous to the spinal trigeminal
   nucleus
   (E) it is greatly reduced in size at sacral levels

Answer 12

l-E. The substantia gelatinosa is greatly enlarged at sacral levels. It is a sensory nucleus
found at all cord levels. It mediates pain and temperature and is homologous to the spinal
trigeminal nucleus.

Question 13

2. Which statement concerning the dorsal root ganglion is FALSE?
   (A) It contains pseudounipolar neurons
   (B) It is located within the intervertebral foramen
   (C) It contains neurons of neural crest origin
   (D) It usually is missing at CI
   (E) It lies within the subarachnoid space

Answer 13

2-E. The dorsal root ganglion contains large (proprioception) and small (pain and temperature)
pseudounipolar neurons of neural crest origin and lies within the intervertebral foramen.
It usually is absent in the first cervical nerve and in the coccygeal nerve.

Question 14

3. Which statement concerning the lateral horn is FALSE?
   (A) It receives viscerosensory input
   (B) It is found at the level of the phrenic nucleus
   (C) It is coextensive with the nucleus dorsalis of Clarke
   (D) It contains a visceromotor nucleus
   (E) It corresponds to Rexed lamina VII

Answer 14

3-B.
The lateral horn extends from (C8) Tl to L3. The phrenic nucleus extends from C3 to C6. The nucleus dorsalis of Clarke is coextensive with the lateral horn and its intermediolateral nucleus or cell column. Rexed lamina VII (lamina intermedia) includes the sympathetic intermediolateral
nucleus, the parasympathetic sacral nucleus (S2-S4), and the nucleus dorsalis of Clarke.

Question 15

4. All of the following statements concerning the spinal cord are correct EXCEPT
   (A) it represents 2% of brain weight
   (B) it terminates in the adult at VL1-VL2
   (C) it lies within the subarachnoid space
   (D) it terminates in the newborn at VS2
   (E) it contains 31 pairs of spinal nerves

Answer 15

4-D.
In the newborn, the spinal cord ends at the level of the third lumbar vertebra (VL3). In the adult, the spinal cord ends at the level of the interspace between the first and second lumbar vertebrae (VL1-VL2). In the adult, the dural cul-de-sac ends at the level of the second sacral vertebra (VS2).

Question 16

5. All of the following statements concerning spinal nerves are correct EXCEPT
   (A) dorsal roots contain sensory input
   (B) ventral roots contain motor output
   (C) all spinal nerves have gray communicating
   rami
   (D) all spinal nerves have white communicating
   rami
   (E) the first cervical nerves frequently have
   no dorsal roots

Answer 16

5-D.
White communicating rami are found only at thoracolumbar levels of the spinal cord (T1-L3); they contain myelinated preganglionic sympathetic fibers and myelinated GVA fibers (from splanchnic nerves). Gray communicating rami contain unmyelinated postganglionic sympathetic
fibers and contribute to all spinal nerves. The first cervical nerve and the coccygeal nerve usually have no dorsal (sensory) roots.

Question 17

6. All of the following statements concerning the cauda equina are correct EXCEPT
   (A) it contains motor fibers
   (B) it contains sensory fibers
   (C) it is found in the subarachnoid space
   (D) it is derived from the pia
   (E) it is found below the first lumbar vertebra

Answer 17

6-D.
The cauda equina consists of lumbosacral nerve roots that descend below the level of the conus medullaris, within the subarachnoid space, to exit through their respective intervertebral or sacral foramina. Dorsad roots contain sensory fibers; ventral roots contain motor fibers. The cauda equina syndrome affects the lumbosacral nerve roots, producing both sensory and motor symptoms.

Question 18

7. All of the following statements concerning the myotatic reflex are correct EXCEPT
   (A) it is a monosynaptic and ipsilateral reflex
   (B) it is a muscle stretch reflex
   (C) it includes a muscle spindle
   (D) it includes a ventral horn motor neuron
   (E) the cell body of afferent nerve fiber is
   found in the dorsal horn

Answer 18

7-E. The myotatic reflex is a monosynaptic and ipsilateral muscle stretch reflex (MSR; incorrectly
called a deep tendon reflex). The afferent limb consists of a muscle spindle (receptor) and
a la fiber (axon) of a dorsal root ganglion neuron; the efferent limb consists of the axon of a
ventral horn alpha motor neuron and the innervated striated muscle fibers (effector). The
quadriceps (patellar) and triceps surae (ankle) muscle stretch reflexes are examples of
myotatic reflexes.

Question 19

1. The ability to recognize an unseen familiar object placed in the hand depends on the integrity of which pathway?
(A) Spinospinal tract
(B) Dorsal column
(C) Dorsal spinocerebellar tract
(D) Spino-olivary tract
(E) Spinothalamic tract

Answer 19

l-B. The ability to recognize the form and texture of an unseen familiar object is called
stereognosis. This is an important function of the dorsal column-medial lemniscus system.

Question 20

2. All of the following statements concerning the corticospinal tracts are correct EXCEPT
   (A) they arise from lamina V of the cerebral
   cortex
   (B) they arise from upper motor neurons (UMNs)
   (C) they descend through the anterior limb of the internal capsule
   (D) they undergo a 90% decussation in the caudal medulla
   (E) they descend through the base of the pons

Answer 20

2-C.
The corticospinal tracts arise from UMNs found in lamina V of the cerebral cortex. They descend through the posterior limb of the internal capsule, the middle third of the crus cerebri (basis pedunculi) of the midbrain, and the base of the pons and constitute the medullary pyramids. 90% of the corticospinal fibers decussate in the caudal medulla as the pyramidal decussation.

Question 21

3. All of the following statements concerning the dorsal spinocerebellar tract are correct
   EXCEPT
   (A) it is an uncrossed tract
   (B) it enters the cerebellum via the superior
   cerebellar peduncle
   (C) it subserves unconscious proprioception
   (D) it terminates in the cerebellar vermis
   (E) it receives input from muscle spindles
   and Golgi tendon organs

Answer 21

3-B. The uncrossed dorsal spinocerebellar tract enters the cerebellum via the inferior cerebellar
peduncle and terminates in the cerebellar vermis. It receives input from muscle spindles
and Golgi tendon organs and subserves unconscious proprioception.

Question 22

4. Which statement concerning the rubrospinal tract is FALSE?
   (A) It lies ventral to the lateral corticospinal
   tract in the spinal cord
   (B) It arises from the red nucleus of the midbrain
   (C) It is an upper motor neuron (UMN) tract
   (D) It is a crossed tract
   (E) It plays a role in the control of extensor
   tone

Answer 22

4-E. The rubrospinal tract, an upper motor neuron (UMN) tract, originates in the red nucleus
of the midbrain, crosses in the ventral tegmental decussation of the midbrain, traverses the
tegmentum of the pons and medulla, and terminates in the ventral horn of the spinal cord. In
the spinal cord, the tract lies in the lateral funiculus ventral to the lateral corticospinal tract.
It plays a role in regulating flexor tone.

Question 23

5. Destruction of the ventral horn results in all of the following deficits EXCEPT
   (A) loss of muscle stretch reflexes (MSRs)
   (B) loss of muscle bulk
   (C) flaccid paralysis
   (D) Babinski’s sign
   (E) loss of superficial abdominal reflexes

Answer 23

5-D. Destruction of ventral horn motor neurons results in a lower motor neuron (LMN) lesion
and is characterized by flaccid paralysis, muscle atrophy (loss of muscle bulk), and areflexia
(loss of muscle stretch and superficial abdominal reflexes). Babinski’s sign is not seen in LMN
disease.

Question 24

6. All of the following tracts decussate in the ventral white commissure EXCEPT the
(A) lateral spinothalamic tract
(B) ventral spinocerebellar tract
(C) ventral corticospinal tract
(D) dorsal spinocerebellar tract
(E) ventral spinothalamic tract

Answer 24

6-D. The dorsal spinocerebellar tract is an uncrossed tract.

Question 25

7. The corticospinal tracts receive contributions
from all of the following areas EXCEPT
(A) prefrontal cortex
(B) premotor cortex
(C) motor cortex
(D) somatesthetic cortex
(E) paracentral lobule

Answer 25

7-A. The corticospinal (pyramidal) tracts receive contributions from the premotor (area 6),
motor (area 4), and the sensory or somatesthetic (areas 3, 1, and 2) cortices. They receive
approximately one-third of their axons from each of these cortical areas. The paracentral lobule
represents a continuation of the motor and somatesthetic cortices onto the medial aspect of
the hemisphere. The prefrontal cortex lies rostral to the premotor cortex.

Question 26

8. All of the following statements concerning
   the lateral spinothalamic tract are correct
   EXCEPT
   (A) it projects collaterals to the reticular formation
   (B) it projects to intralaminar nuclei of the
   thalamus
   (C) it projects to the ventral posteromedial
   (VPM) nucleus of the thalamus
   (D) it mediates pain and temperature
   (E) its cells of origin are in the dorsal horn

Answer 26

8-C. The lateral spinothalamic tract mediates pain and temperature sensation and projects to
the reticular formation of the brainstem and to the ventral posterolateral (VPL) and intralaminar
nuclei of the thalamus. First-order neurons are in the dorsal root ganglion, second-order
neurons (cells of origin) are in the dorsal horn, and third-order neurons lie in the VPL nucleus
of the thalamus.

Question 27

9. All of the following statements concerning
   the dorsal column-medial lemniscus pathway
   are correct EXCEPT
   (A) it has second-order neurons in the
   medulla
   (B) it receives input from Pacini’s and Meissner’s
   corpuscles
   (C) it decussates in the spinal cord
   (D) it mediates kinesthetic sensation
   (E) it mediates vibration sensation

Answer 27

9-C. The uncrossed dorsal columns consist of the fasciculus gracilis and the fasciculus cuneatus
and mediate tactile discrimination, form recognition, vibration, movement, and joint and
muscle sensation (proprioception). They receive input from tactile receptors (Pacini’s and
Meissner’s corpuscles), muscle spindles, joint receptors, and Golgi tendon organs. The dorsal
column-medial lemniscus pathway decussates in the caudal medulla (decussation of the
medial lemniscus). First-order neurons are in the dorsal root ganglion; second-order neurons
are in the gracile and cuneate nuclei of the medulla; and third-order neurons are in the VPL
nucleus of the thalamus.

Question 28

4. All of the following statements concerning
   amyotrophic lateral sclerosis (ALS) are correct
   EXCEPT
   (A) it is associated with upper motor neuron
   (UMN) lesions
   (B) it is associated with lower motor neuron
   (LMN) lesions
   (C) it results in sensory deficits
   (D) its onset usually occurs between 50 and
   70 years of age
   (E) it results in muscle weakness

Answer 28

4-C. Amyotrophic lateral sclerosis (ALS) is a motor system disease and does not involve sensory
systems. Onset is usually after the age of 50 years. ALS affects the corticospinal and corticobulbar
tracts [upper motor neuron (UMN) lesion] and the ventral horn cells of the spinal cord and
their cranial nerve equivalents in the brainstem [lower motor neuron (LMN) lesion].

Question 29

5. All of the following statements concerning
   syringomyelia are correct EXCEPT it
   (A) is a central cavitation of the spinal cord
   (B) usually is found at lumbosacral levels
   (C) usually includes a lower motor neuron
   (LMN) lesion
   (D) usually results in a bilateral loss of pain
   and temperature sensation
   (E) may result in Horner’s syndrome

Answer 29

5-B. Syringomyelia is a central cavitation of the cervical spinal cord and is of unknown etiology.
Expansion of the syrinx typically affects the ventral white commissure, interrupting the decussating
fibers of the spinothalamic tracts and resulting in a bilateral loss of pain and temperature
sensation at the level of involvement. Lateral extension involves one or both of the ventral horns
and results in a lower motor neuron (LMN) lesion with muscle wasting and flaccid paralysis.
Caudal extension to (C8) T1-T2 may involve the lateral horn (ciliospinal center of Budge) and
produce Horner’s syndrome.

Question 30

6. All of the following statements concerning subacute combined degeneration are correct EXCEPT it
   (A) causes demyelination of the dorsal
   columns
   (B) causes demyelination of spinocerebellar tracts
   (C) is associated with pernicious anemia
   (D) is characterized by pyramidal tract signs
   (E) is characterized by lower motor neuron (LMN) symptoms

Answer 30

6-E. Subacute combined degeneration, associated with pernicious anemia, results in demyelination
of the dorsal columns (the fasciculus gracilis more often than the fasciculus cuneatus), the
spinocerebellar tracts, and the lateral corticospinal tracts. Lower motor neurons (LMNs) are not
involved.

Question 31

7. Hemisection of the spinal cord at Tl on the left side results in all of the following signs or symptoms EXCEPT
   (A) plantar response flexor on the left side
   (B) loss of vibration sensation in the left leg
   (C) leg dystaxia on the right side
   (D) exaggerated knee jerk reflex on the left side
   (E) normal pain and temperature sensation on the left side

Answer 31

7-A. Hemisection of the spinal cord is known as Brown-Sequard syndrome. Transection of the
left lateral corticospinal tract would result in an extensor plantar response on the left side
(Babinski’s sign). Leg dystaxia on the right side results from interruption of the crossed ventral
spinocerebellar tract.

Question 32

8. Upper motor neuron (UMN) lesions can be found in all of the following clinical syndromes
EXCEPT
(A) amyotrophic lateral sclerosis (ALS)
(B) subacute combined degeneration
(C) syringomyelia
(D) cauda equina syndrome
(E) ventral spinal artery occlusion

Answer 32

8-D. Upper motor neuron (UMN) lesions by definition are lesions in which the corticospinal or
corticobulbar tracts have been damaged. Amyotrophic lateral sclerosis (ALS), subacute combined
degeneration, syringomyelia (with extension into the lateral funiculus), and ventral spinal artery
occlusion all cause UMN lesions with spastic paresis. The cauda equina lies external to the
spinal cord; lesions of this structure do not cause UMN lesions.

Question 33

9. Lower motor neuron (LMN) lesions result in all of the following deficits or signs EXCEPT
(A) loss of muscle stretch reflexes
(B) loss of superficial reflexes
(C) fasciculations
(D) muscle wasting
(E) plantar reflex extensor

Answer 33

-E. Lower motor neuron (LMN) lesions result from destruction of ventral horn (or cranial
nerve) motor neurons or transection of their axons. LMN lesions interrupt the final common
pathway to skeletal muscles; they result in flaccid paralysis and atrophy (muscle wasting) and a
loss of all reflex action (areflexia). Fasciculations (visible muscle twitching) and fibrillations (seen
on an electromyogram) are signs of LMN disease. Babinski’s sign, an extensor plantar reflex, is
not seen in LMN lesions.

Question 34

10. All of the following statements concerning poliomyelitis are correct EXCEPT
    (A) it is a viral infection
    (B) it is a lower motor neuron (LMN) disease
    (C) it affects dorsal root ganglion cells
    (D) it affects motor cranial nerve nuclei and
    ventral horn motor neurons
    (E) it results in hypotonia

Answer 34

10-C. Poliomyelitis is an acute inflammatory viral infection affecting lower motor neurons
(LMNs) in the spinal cord and brainstem (bulbar paralysis) and results in flaccid paralysis, muscle
atrophy, and areflexia. There is a loss of muscle tone (atonia). The poliovirus does not attack
the sensory neurons of the dorsal root ganglia.

Question 35

11. All of the following statements concerning upper motor neuron (UMN) lesions are correct EXCEPT
    (A) they are found above the pyramidal decussation
    (B) they result in the presence of Babinski’ssign
    (C) they result in the absence of the knee jerk reflex
    (D) they are commonly caused by cerebrovascular accidents
    (E) they frequently involve the internal capsule

Answer 35

11-C. Upper motor neuron (UMN) lesions result from destruction of cortical neurons (or their
axons) that give rise to the corticospinal and corticobulbar tracts. UMNs are found in the cerebral
cortex and in the brainstem. UMN lesions result in spastic paralysis (hyperreflexia, hypertonia,
clasp-knife phenomenon, clonus, muscle weakness, and Babinski’s sign). UMN lesions are
commonly caused by cerebrovascular accidents and frequently damage the internal capsule.

Question 36

12. All of the following neurologic deficits are associated with transection of the lateral corticospinal tract EXCEPT
    (A) it results in ipsilateral spastic paresis below the lesion
    (B) it results in ipsilateral loss of vibration sensation below the lesion
    (C) it results in an ipsilateral extensor plantar reflex
    (D) it results in an ipsilateral hyperreflexia below the lesion
    (E) it results in a loss of superficial abdominal cremasteric reflexes

Answer 36

12-B. Transection of the lateral corticospinal tract results in an upper motor neuron (UMN)
lesion. The deficits are ipsilateral and caudal to the lesion. Plantar stimulation results in extension
of the great toe and abduction of the other toes—this is Babinski’s sign. Loss of vibration
sensation results from interruption of the dorsal column-medial lemniscus system.

Question 37

13. All of the following statements concerning Horner’s syndrome are correct EXCEPT
    (A) it is seen in spinal cord lesions above Tl
    (B) it is ipsilateral to the lesion
    (C) it results from interruption of descending autonomic pathways
    (D) it results in mydriasis and mild ptosis
    (E) it results in facial hemianhidrosis

Answer 37

13-D. Interruption of descending autonomic pathways found in the lateral funiculi of the spinal
cord result in Horner’s syndrome. Horner’s syndrome is ipsilateral to the lesion and consists of
miosis, ptosis, facial hemianhidrosis, and apparent enophthalmos.

Question 38

14. Ventral spinal artery occlusion results in all of the following deficits EXCEPT
    (A) areflexia at the level of the lesion
    (B) loss of vibration and position sensation below the lesion
    (C) bilateral loss of pain and temperature sensation below the lesion
    (D) bilateral spastic paralysis below the lesion
    (E) urinary incontinence

Answer 38

14-B. The ventral (anterior) spinal artery irrigates the ventral two-thirds of the spinal cord including the ventral horns, the corticospinal tracts, and the spinothalamic tracts. Lower motor
neuron (LMN) deficits (flaccid paralysis and areflexia) are seen only at the level of infarction.
Bilateral destruction of the lateral spinothalamic tracts results in bilateral loss of pain and temperature
sensation caudal to the lesion. Vibration and position sensation are not affected because
the dorsal columns are intact. Bilateral lesions of the anterior quadrants of the lateral funiculi
interrupt corticosacral fibers that control bladder function (urinary incontinence).

Question 39

15. All of the following statements concerning cauda equina syndrome are correct EXCEPT
    (A) its signs are frequently unilateral
    (B) it may result from a herniated disk
    (C) it classically involves spinal roots L3-Co
    (D) it may result in profound motor deficits
    (E) it may result in Babinski’s sign

Answer 39

15-E. Pure cauda equina syndrome involves the descending dorsal and ventral roots, classically spinal roots L3-S5. A herniated nucleus pulposus compressing the spinal roots may cause sensory
and/or motor deficits, urinary and fecal incontinence, and impotence. Disk prolapse usually
occurs unilaterally, producing symptoms on the ipsilateral side. Profound motor deficits may be
seen. Babinski’s sign is seen in upper motor neuron (UMN) lesions, not in lower motor neuron
(LMN) lesions.

Question 40

16. All of the following statements concerning intervertebral disk herniation are correct EXCEPT
    (A) it results from prolapse of the nucleus pulposus through a defective annulus fibrosus into the vertebral canal
    (B) it may involve the cauda equina
    (C) it usually involves a single nerve root
    (D) it most frequently appears in the L4-L5 interspace
    (E) it usually results in urinary incontinence

Answer 40

16-E. Intervertebral disk herniation results from the prolapse of the nucleus pulposus through a
defective annulus fibrosus into the vertebral canal. In 90% of cases, it appears at the L4r-L5 or
the L5-S1 interspace. In 10% of cases, it appears at the cervical region, usually at the C5-C6 or
C6-C7 interspace. Intervertebral disk herniation may involve the cauda equina; usually it
involves a single nerve root. Urinary incontinence is not seen with unilateral root lesions.

Question 41

17. All of the following statements concerning conus medullaris syndrome are correct EXCEPT
    (A) plantar reflexes are usually extensor
    (B) it involves spinal segments S3-Co
    (C) it may result in perianogenital sensory loss
    (D) it may result in a paralytic bladder
    (E) it may result in impotence

Answer 41

17-A. Conus medullaris syndrome involves spinal segments S3—Co and results in perianogenital
sensory loss, a paralytic bladder, and impotence. The plantar reflex is flexor (no Babinski’s sign).
Also, epiconus syndrome is found at segments L4-S2; this syndrome is characterized by considerable
motor disability and an absent Achilles tendon reflex, in addition to urinary incontinence.

Question 42

1. Which one of the following nuclei does not project to the cerebellum?
(A) Lateral reticular nucleus
(B) Arcuate nucleus
(C) Inferior olivary nucleus
(D) Accessory (lateral) cuneate nucleus
(E) Nucleus ambiguus

Answer 42

l-E. The nucleus ambiguus is a SVE cell column that gives rise to the motor components of
CN IX, CN X, and CN XI. The nucleus ambiguus also contains GVE (parasympathetic) neurons
with axons that innervate the heart via the vagal nerve.

Question 43

2. Decussation of the superior cerebellar peduncles occurs in which area of the brain?
(A) Rostral midbrain
(B) Caudal midbrain
(C) Rostral pons
(D) Caudal pons
(E) Cerebellum

Answer 43

2-B. Decussation of the superior cerebellar peduncles occurs in the caudal midbrain tegmentum
at the level of the inferior colliculus.

Question 44

3. The cerebral aqueduct is found in which part of the brain?
(A) Telencephalon
(B) Diencephalon
(C) Mesencephalon
(D) Metencephalon
(E) Myelencephalon

Answer 44

3-C. The cerebral aqueduct is found in the mesencephalon; it connects the third ventricle to
the fourth ventricle.

Question 45

4. The base of the pons contains all of the following
   nuclei and fibers EXCEPT the
   (A) cerebellar relay nuclei
   (B) arcuate nuclei
   (C) corticospinal fibers
   (D) corticobulbar fibers
   (E) exiting fibers of the abducent nucleus

Answer 45

4-B. The base of the pons contains corticospinal, corticobulbar, and corticopontine fibers and
pontine nuclei (cerebellar relay nuclei). Exiting intra-axial abducent fibers of CN VI pass
through the corticospinal fibers in the base of the pons. Arcuate nuclei are displaced pontine
nuclei found in the pyramids.

Question 46

5. All of the following statements concerning the trapezoid body are correct EXCEPT
   (A) it is found in the ventral pontine tegmentum
   (B) it contains the medial longitudinal fasciculus
   (MLF)
   (C) it contains the medial lemniscus
   (D) it contains aberrant corticobulbar fibers
   (E) it contains auditory fibers

Answer 46

5-B. The trapezoid body contains auditory fibers from the cochlear and superior olivary
nuclei, the medial lemniscus, and corticobulbar fibers. Exiting intra-axial abducent fibers pass
through the trapezoid body. The medial longitudinal fasciculus (MLF) lies dorsal to this structure.

Question 47

6. All of the following statements concerning the spinal trigeminal nucleus are correct EXCEPT
   (A) it is a homolog of the substantia gelatinosa
   (B) it gives rise to the dorsal trigeminothalamic tract
   (C) it receives input from free nerve endings
   (D) it projects to the contralateral ventral posteromedial nucleus of the thalamus
   (E) it is

Answer 47

6-B. The spinal trigeminal nucleus of CN V extends from C3 to the caudal pole of the principal
sensory nucleus of the trigeminal nerve. It is considered a homolog of the substantia gelatinosa.
It lies in the lateral medulla and lateral pontine tegmentum and gives rise to the crossed
ventral trigeminothalamic tract. The dorsal trigeminothalamic tract arises from the principal
sensory nucleus of CN V.

Question 48

7. All of the following statements concerning the medulla oblongata are correct EXCEPT
   (A) it extends from the pyramidal decussation to the inferior pontine sulcus
   (B) it contains the facial nucleus
   (C) it contains the medial and inferior vestibular nuclei
   (D) it contains the inferior olivary nucleus
   (E) it contains the nucleus ambiguus

Answer 48

7-B. On its ventral aspect, the medulla extends from the pyramidal decussation to the inferior
pontine sulcus (pontobulbar sulcus); on its dorsal aspect, it extends from the pyramidal decussation
to the striae medullares of the rhomboid fossa. The medial and inferior vestibular nuclei
are found in the medulla and extend into the caudal pontine tegmentum. The inferior olivary
nucleus, a cerebellar relay nucleus, is the most prominent nucleus of the medulla. The nucleus
ambiguus is found in the medulla; it gives rise to SVE fibers of CN IX, CN X, and CN XI. The
facial nucleus is found in the caudal pontine tegmentum

Question 49

8. All of the following statements concerning the hypoglossal nucleus are correct EXCEPT
   (A) it gives rise to SVE fibers
   (B) it has axons that exit the medulla between the olive and the pyramid
   (C) it lies dorsal to the medial longitudinal fasciculus (MLF)
   (D) it innervates the intrinsic musculature of the tongue
   (E) its intra-axial root fibers lie adjacent to the medial lemniscus

Answer 49

8-A. The hypoglossal nucleus of CN XII gives rise to GSE fibers. The hypoglossal nucleus lies
dorsal to the medial longitudinal fasciculus (MLF), gives rise to fibers that exit the medulla in
the preolivary sulcus, and innervates the intrinsic and extrinsic muscles of the tongue (except
the palatoglossus muscle, which is innervated by CN X). Intra-axial root fibers lie between the
medial lemniscus and the inferior olivary nucleus.

Question 50

9. All of the following statements concerning the abducent nucleus are correct EXCEPT
   (A) it is found in the pontine tegmentum
   (B) it underlies the facial colliculus
   (C) it exits the brainstem at the superior pontine sulcus
   (D) it gives rise to fibers that traverse the cavernous sinus
   (E) it gives rise to fibers that traverse the corticospinal tracts

Answer 50

9-C.
The abducent nucleus of CN VI underlies the facial colliculus in the caudal pontine tegmentum. It gives rise to GSE fibers that innervate the lateral rectus muscle. It exits the brainstem at the inferior pontine sulcus (pontobulbar sulcus). Exiting abducent fibers pass through the corticospinal tracts, which traverse the base of the pons.

Question 51

10. All of the following statements concerning the motor nucleus of the trigeminal nerve are correct EXCEPT
    (A) it plays a role in the corneal reflex
    (B) it lies medial to the principal sensory nucleus of CN V
    (C) it is located in the rostral pontine tegmentum
    (D) it receives bilateral input from corticobulbar fibers
    (E) it gives rise to SVE fibers

Answer 51

10-A. The motor nucleus of the trigeminal nerve (CN V) is a component of the SVE cell column,
lies medial to the principal sensory nucleus of CN V, is found in the rostral pontine
tegmentum, and receives bilateral corticobulbar input. The afferent limb of the corneal reflex
is the ophthalmic nerve (CN V-l); the efferent limb is the facial nerve (CN VII), which innervates
the orbicularis oculi muscle.

Question 52

11. All of the following statements concerning the trochlear nerve are correct EXCEPT
    (A) it has its nucleus in the midbrain tegmentum
    (B) it exits the brainstem caudal to the inferior colliculus
    (C) it decussates in the superior medullary velum
    (D) it innervates a muscle that depresses the globe
    (E) it innervates a muscle that extorts the globe

Answer 52

11-E.
The trochlear nerve (CN IV) has its nucleus in the midbrain tegmentum at the level of the inferior colliculus. It decussates in the superior medullary velum and exits the brainstem lateral to the frenulum of the superior medullary velum. It is the only cranial nerve to exit the brainstem from the dorsal surface. It innervates the superior oblique muscle, which depresses, intorts, and abducts the eyeball.

Question 53

12. All of the following statements concerning the locus ceruleus are correct EXCEPT
    (A) its neurons contain melanin
    (B) its neurons contain dopamine
    (C) it is located in the pons and midbrain
    (D) it projects to the spinal cord
    (E) it projects to the cerebral cortex

Answer 53

12-B. The locus ceruleus is a pigmented (melanin-containing) nucleus found in the rostral pontine tegmentum that extends into the midbrain. Its cells contain catecholamines (noradrenaline). It projects to all parts of the central nervous system (CNS), including the cerebral cortex and the spinal cord. Dopamine is found in the substantia nigra of the midbrain.

Question 54

13. All of the following statements concerning the oculomotor nuclear complex are correct EXCEPT
    (A) stimulation of its parasympathetic component results in mydriasis
    (B) damage to its GSE fibers results in severe ptosis
    (C) it is found in the midbrain at the level of the superior colliculus
    (D) its preganglionic parasympathetic fibers
    synapse in the ciliary ganglion
    (E) its exiting GSE fibers pass through the crus cerebri

Answer 54

13-A. Stimulation of the parasympathetic component results in miosis (sphincter pupillae
muscle). Preganglionic parasympathetic fibers synapse in the ciliary ganglion. The oculomotor
nuclear complex is found in the midbrain at the level of the red nucleus and the superior colliculus.
Exiting oculomotor fibers pass through the crus cerebri. Transection of these fibers
results in severe ptosis, a dilated pupil, paralysis of the medial, superior, and inferior recti
muscles and paralysis of the inferior oblique and the levator palpebrae muscles. The paralytic
eye “looks down and out.”