CHAPTER 9

Question 1

1. A 40-year-old female librarian is brought to
   the emergency department. Neurological ex-
   amination reveals the following: blood pres-
   sure 160/90 mm of Hg, numbness on the right
   side of her lower face, no weakness in upper or
   lower extremities, tongue deviates to right side
   on protrusion, uvula deviates to the left side
   when patient says “Ah”. The lesion causing
   these symptoms is found in which of the fol-
   lowing loci?
   (A) Anterior limb of internal capsule
   (B) Genu of internal capsule, left side
   (C) Claustrum
   (D) Paracentral lobule, right side
   (E) Posterior limb internal capsule

Answer 1

1-B. A lesion of the genu of the internal capsule destroys corticobulbar fibers. The facial nucleus
receives bilateral corticobulbar input, the upper face division receives bilateral input, and the
lower face division receives only contralateral input. The hypoglossal nucleus receives only con-
tralateral corticobulbar input. When the tongue is protruded, it deviates to the weak side due to
the unopposed activity of the intact genioglossus muscle. The uvula deviates to the intact side
when the patient says “Ah”. The muscles of the uvula and palatal arches are innerverted by the
vagal nerve (CN X).

Question 2

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

Answer 2

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

Question 3

3. 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 3

3-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 4

4. 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 vestibu-
   lar nuclei
   (D) it contains the inferior olivary nucleus
   (E) it contains the nucleus ambiguus

Answer 4

4-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 decus-
sation 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 nu-
cleus, a cerebellar relay nucleus, is the most prominent nucleus of the medulla. The nucleus am-
biguus is found in the medulla; it gives rise to special visceral efferent (SVE) fibers of CN IX, CN
X, and CN XI. The facial nucleus is found in the caudal pontine tegmentum.

Question 5

5. All of the following statements concerning
   the hypoglossal nucleus are correct EXCEPT
   (A) it gives rise to special visceral efferent
   (SVE) fibers
   (B) it has axons that exit the medulla be-
   tween 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 5

5-A. The hypoglossal nucleus of CN XII gives rise to general somatic efferent (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 6

6. 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 nu-
   cleus of CN V
   (C) it is located in the rostral pontine tegmen-
   tum
   (D) it receives bilateral input from corticobul-
   bar fibers
   (E) it gives rise to special visceral efferent
   (SVE) fibers

Answer 6

6-A. The motor nucleus of the trigeminal nerve (CN V) is a component of the special visceral ef-
ferent (SVE) cell column, lies medial to the principal sensory nucleus of CN V, is found in the ros-
tral 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 7

7. All of the following statements concerning
   the trochlear nerve are correct EXCEPT
   (A) it has its nucleus in the midbrain tegmen-
   tum
   (B) it exits the brainstem caudal to the infe-
   rior 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 7

7-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 brain-
stem from the dorsal surface. It innervates the superior oblique muscle, which depresses, intorts,
and abducts the eyeball.

Question 8

8. All of the following statements concerning
   the oculomotor nuclear complex are correct
   EXCEPT
   (A) stimulation of its parasympathetic com-
   ponent results in mydriasis
   (B) damage to its general somatic efferent
   (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 8

8-A. Stimulation of the parasympathetic component results in miosis (sphincter pupillae mus-
cle). Preganglionic parasympathetic fibers synapse in the ciliary ganglion. The oculomotor nu-
clear 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 se-
vere ptosis, a dilated pupil paralysis of the medial, superior, and inferior recti muscles and paral-
ysis of the inferior oblique and the levator palpebrae muscles. The paralytic eye “looks down and
out.”

Question 9

9. Decussation of the superior cerebellar pe-
   duncle

The response options for items 9—16 are the
same. You will be required to select one answer
for each item in the set.
(A) Midbrain, at level of superior colliculus
(B) Midbrain, at level of inferior colliculus
(C) Tegmentum of pons
(D) Base of pons
(E) Lateral medulla
(F) Medial medulla
Match the following structures with the appro-priate brainstem division.

Answer 9

9-B. The decussation of the superior cerebellar peduncle is diagnostic of midbrain division at
the level of the inferior colliculus.

Question 10

10. Inferior olivary nucleus

The response options for items 9—16 are the
same. You will be required to select one answer
for each item in the set.
(A) Midbrain, at level of superior colliculus
(B) Midbrain, at level of inferior colliculus
(C) Tegmentum of pons
(D) Base of pons
(E) Lateral medulla
(F) Medial medulla
Match the following structures with the appro-priate brainstem division.

Answer 10

10-E. The inferior olivary nucleus, a cerebellar relay nucleus, is the most prominent nucleus in
the lateral medulla.

Question 11

11. Nucleus ambiguus

The response options for items 9—16 are the
same. You will be required to select one answer
for each item in the set.
(A) Midbrain, at level of superior colliculus
(B) Midbrain, at level of inferior colliculus
(C) Tegmentum of pons
(D) Base of pons
(E) Lateral medulla
(F) Medial medulla
Match the following structures with the appro-priate brainstem division.

Answer 11

11-E. The nucleus ambiguus is found in the lateral medulla; it gives rise to the special visceral
efferent (SVE) components of cranial nerves IX, X, and XL

Question 12

12. Abducent nucleus

The response options for items 9—16 are the
same. You will be required to select one answer
for each item in the set.
(A) Midbrain, at level of superior colliculus
(B) Midbrain, at level of inferior colliculus
(C) Tegmentum of pons
(D) Base of pons
(E) Lateral medulla
(F) Medial medulla
Match the following structures with the appro-priate brainstem division.

Answer 12

12-C. The abducent nucleus (CN VI) is located in the dorsomedial tegmentum of the pons. All
brainstem cranial nerve nuclei are found in the tegmentum.

Question 13

13. Facial nucleus

The response options for items 9—16 are the
same. You will be required to select one answer
for each item in the set.
(A) Midbrain, at level of superior colliculus
(B) Midbrain, at level of inferior colliculus
(C) Tegmentum of pons
(D) Base of pons
(E) Lateral medulla
(F) Medial medulla
Match the following structures with the appro-priate brainstem division.

Answer 13

13-C. The facial nucleus (CN VII) is located in the lateral tegmentum of the pons.

Question 14

14. Oculomotor nucleus

The response options for items 9—16 are the
same. You will be required to select one answer
for each item in the set.
(A) Midbrain, at level of superior colliculus
(B) Midbrain, at level of inferior colliculus
(C) Tegmentum of pons
(D) Base of pons
(E) Lateral medulla
(F) Medial medulla
Match the following structures with the appro-priate brainstem division.

Answer 14

14-A. The oculomotor nucleus (CN III) lies in the dorsomedial tegmentum of the midbrain at
the level of the superior colliculus; it lies medial to the medial longitudinal fasciculus.

Question 15

15. Red nucleus

The response options for items 9—16 are the
same. You will be required to select one answer
for each item in the set.
(A) Midbrain, at level of superior colliculus
(B) Midbrain, at level of inferior colliculus
(C) Tegmentum of pons
(D) Base of pons
(E) Lateral medulla
(F) Medial medulla
Match the following structures with the appro-priate brainstem division.

Answer 15

15-A. The red nucleus is diagnostic of midbrain division at the level of the superior colliculus;
it lies between the oculomotor nucleus (CN III) and the substantia nigra.

Question 16

16. Trochlear nucleus

The response options for items 9—16 are the
same. You will be required to select one answer
for each item in the set.
(A) Midbrain, at level of superior colliculus
(B) Midbrain, at level of inferior colliculus
(C) Tegmentum of pons
(D) Base of pons
(E) Lateral medulla
(F) Medial medulla
Match the following structures with the appro-priate brainstem division.

Answer 16

16-B. The trochlear nerve (CN IV) is located in the dorsomedial tegmentum of the midbrain at
the level of the inferior colliculus.