Brain stem Cerebellum DLA

Question 1

What are the major events in the development of the brainstem?

Answer 1

• In the neural tube, the alar plate sits dorsal to the sulcus limitans (SL) and is largely somatosensory in function. The basal plate is located ventral to the SL and is largely motor in function.

• Major events occur during maturation of the brainstem.
– The central canal enlarges into the fourth ventricle.
– The cerebellum develops.
– The dorsal portion of the neural tube (alar plate) rotates laterally.
– Consequently, bulbar efferent (motor) structures lie medial to the SL, and the afferent (sensory) structures sit laterally.

Question 2

How are the creation of cranial nerves dictated?

Answer 2

• Creation of the 4th ventricle shifts the alar plate from dorsal to lateral positions, dictating the nuclear organization of cranial nerves

Question 3

What are the landmarks oof the dorsal brainstem?

Answer 3

• Midbrain with superior and inferior colliculi (corpora quadrigemina) and cranial nerve IV.
• Pons with superior cerebellar peduncles (normally bridged by the superior medullary velum) and the laterally situated middle cerebellar peduncles and the sulcus limitans, which sits laterally to the facial colliculi and the more rostrally located the medial eminence.

• Rhomboid fossa.
– Rostral (pontine) rhomboid fossa.
– Caudal(medullary)rhomboid fossa.

• Lateral recesses and striae medullares of 4th ventricle (junction of medulla and pons).
• Posterior median sulcus (pontine and medullary).
• Medulla with hypoglossal and vagal trigones, obex, and gracile and cuneate tubercles

Question 4

What are the anatomical structures of the dorsal brain stem?

Answer 4

• Midbrain
– Superior colliculi
– Inferior colliculi
– CNIV

Question 5

What are the anatomical structures on the dorsal pons?

Answer 5

Pons
– Rostral 4th ventricle
– Superior and middle
cerebellar peduncles
– Facial colliculus

Question 6

What are the anatomic structures of the dorsal medulla?

Answer 6

Medulla
– Inferior cerebellar peduncle
– Obex
– Central canal
– Gracile and cuneate tubercles
– Foramen of Magendie
– Foramina of Luschka

Question 7

What are the landmarks of the ventral brainstem?

Answer 7

• Midbrain with peduncles, interpeduncular fossa, and cranial nerve III.
• Pons with basilar groove and ventral aspects of the middle cerebellar peduncles (along with cranial nerves V – VIII).
• Pontomedullary junction (between pons and medulla).
• Medulla with anterior median fissure,
pyramids, preolivary sulcus, and olives (along
with cranial nerves IX – XII)

Question 8

What are anatomic structures of the ventral midbrain?

Answer 8

• Midbrain
– Crus cerebri
– Interpeduncular fossa
– CN III

Question 9

What are the anatomic structures of the ventral pons?

Answer 9

Pons
– Basilar groove
– CNs V – VIII
– Cerebellopontine
angle

Question 10

What are the anatomic structures of the ventral medulla?

Answer 10

• Medulla
– Anterior median fissure
– Pyramids
– Olives
– CNs IX - XII

Question 11

What are the landmarks of the lateral brainstem?

Answer 11

• Cerebral peduncle (midbrain)
• Cerebellar peduncles (middle most visible)
• Medulla
     – Pyramid
     – Olive
     – Preolivary sulcus
     – Postolivary sulcus
     – Cuneate tubercle

Question 12

What are the anatomical structures of the lateral midbrain?

Answer 12

Midbrain
– Crus cerebri
– CNIV

Question 13

What are the anatomical structures of the lateral pons?

Answer 13

Pons
– CNs V, VII, VIII
– Superior and middle cerebellar peduncles
– Cerebellopontine angle

Question 14

Whaat are the anatomical structures of the lateral medulla?

Answer 14

Medulla
– Inferior cerebellar peduncle
– Foramen of Magendie
– Foramina of Luschka
– Pyramid
– Olive
– CNsIX-XIII

Question 15

Wwhat re ascending tracts in the brainstem?

Answer 15

Many tracts ascend (travel caudo-rostrally) through the brainstem, typically carrying sensory information derived from spinal or cranial nerves.
– Damage yields sensory losses.

Question 16

What are the main ascending tracts of the brainstem?

Answer 16

• Dorsal column-medial lemniscal system (with cuneate and gracile fasciculi and nuclei)
– Touch, proprioception, vibration (spinal origin)

• Spinothalamic tract (anterolateral system)
– Pain and temperature (spinal origin)

• Lateral lemniscus
– Hearing (bulbar origin)

Question 17

What are the descending tracts of the brainstem?

Answer 17

• Many tracts descend (travel rostro-caudally) through the brainstem, typically carrying motor information from the cortex
– Corticobulbar

• Terminate in the brainstem to innervate lower motor
neurons tied to cranial nerves – Corticospinal

• Pass through the brainstem to innervate lower motor neurons tied to spinal nerves
– Damage yields motor deficits (e.g., weakness

Question 18

Give examples of the main descending tracts of the brain stem

Answer 18

• Corticobulbar
– Many innervate lower motor neurons tied to cranial nerves

• Corticospinal
– Many innervate lower motor neurons tied to spinal nerves

Question 19

Summarize reticular formation

Answer 19

The reticular formation is a netlike nucleated mass of gray, occupying the core of the brainstem.

• The reticular nuclei support a vast array of diverse functions.
– Eye movements
– Yawning
– Sleeping

Question 20

What are reticular in the brainstem?

Answer 20

• Net-like distribution of grey matter extending from the spinal gray matter through the brainstem

Question 21

What do vertebral arteries and posterior spinal arteries?

Answer 21

• The vertebral arteries and related branches supply the brainstem and cerebellum.
• The vertebral arteries supply the ventral medulla, following the pyramids rostrally.
• The posterior spinal arteries emerge laterally, either directly or from the posterior inferior cerebellar artery. These spinal arteries travel dorsally to supply the tubercles and the dorsal columns (eventually exiting the skull through the foramen magnum).

Question 22

What do anterior spinal arteries and posterior inferior cerebellar arteries?

Answer 22

• The anterior spinal arteries travel medially to unify, thereafter supplying the pyramids and other midline structures before also exiting the skull.
• The posterior inferior cerebellar arteries travel laterally, supplying the medullary cranial nerves en route to the dorsal medulla, inferior cerebellar peduncle, fourth ventricle, and cerebellar vermis and hemisphere

Question 23

How are the basilar artery formed, and what does the anterior inferior cerebellar arteries supply?

Answer 23

• The vertebral arteries unify to form the basilar artery, commonly near the pontomedullary junction (near the roots of cranial nerve VI).
• The anterior inferior cerebellar arteries emerge laterally from the basilar artery, often directly or indirectly (via the labyrinthine artery) supplying cranial nerves VII and VIII and the middle cerebellar peduncle en route to the fourth ventricle and the cerebellar hemisphere

Question 24

What are the variations of the basilar artery?

Answer 24

• The basilar artery may also emit the labyrinthine artery but invariably emits a succession of long and short transversely oriented pontine arteries that supply the core and lateral aspects of the pons.

Question 25

What does the superior cerebelar arteries supply?

Answer 25

• The superior cerebellar arteries arise from the rostral basilar artery. As they venture laterally and dorsally, they supply the caudal midbrain (including the inferior colliculus and cranial nerve IV) and the rostral pons (including the superior cerebellar peduncle). These arteries supply both the cerebellar vermis and hemispheres

Question 26

Where does the posterior cerebral arteries emerge and follow?

Answer 26

• The posterior cerebral arteries emerge just rostral to and follow the mesencephalic course of the superior cerebellar arteries. Along with their branches, they supply cranial nerve III, the crus cerebri, the remaining tegmentum, and the tectum (along with the choroid plexus of the Fourth and lateral ventricles, much of the diencephalon [including the thalamus], and the medial and
inferior portions of the posterior cerebru

Question 26

Where does the posterior cerebral arteries emerge and follow?

Answer 26

• The posterior cerebral arteries emerge just rostral to and follow the mesencephalic course of the superior cerebellar arteries. Along with their branches, they supply cranial nerve III, the crus cerebri, the remaining tegmentum, and the tectum (along with the choroid plexus of the Fourth and lateral ventricles, much of the diencephalon [including the thalamus], and the medial and
inferior portions of the posterior cerebru

Question 27

Summarize the blood supply of the brainstem from a ventral view

Answer 27

• Vertebral
• Spinal
   – Posterior
   – Anterior
• PICA
• Basilar
• AICA
• Labrynthine
• Pontine
• SCA
• Posterior Cerebral

Question 28

What is the significance of particular zones in the brainstem?

Answer 28

Particular zones of the brainstem (as evidenced in transverse sections) are preferentially fed by penetrating branches of specific subarachnoid arteries)
– Occlusion can result in characteristic infarctions with stereotyped destruction of specific nuclei and tracts, thereby yielding the expression of vascular brainstem syndromes

      • Some specific vascular brainstem syndromes will be discussed at later points in the course.
             – Memorization of specific bulbar vascular distributions is therefore not warranted at this juncture.

Question 29

What are the surface structures of the cerebellum?

Answer 29

-The cerebellum is a hemispheric structure that also has a midline insertion called the vermis (worm). The paravermis is transitionary between the vermis and the hemispheres.

• The cerebellum has three lobes.
– Anterior
– Posterior
– Flocculonodular

Question 30

Whhat are the main cerebellum fissures?

Answer 30

• The cerebellum has fissures. All can serve as landmarks, but not all have any particular functional significance.
– primary fissure
– horizontal fissure
– dorsolateral fissure

Question 31

What are the cerebellar peduncles?

Answer 31

• The cerebellum stands on the brainstem using three pairs of feet (peduncles)
– superior cerebellar peduncles
– middle cerebellar peduncles
– inferior cerebellar peduncles (restiform bodies)

Question 32

What is the vermis/paravermis?

Answer 32

Some of the most visible midline cerebellar structures are configured like parts of the mouth.
– Lingula (at the front)
– Uvula (at the back
– Tonsil (one on either side of the uvula)

• The tonsils can herniate through the foramen magnum,
leading to compression of the caudal brainstem