NB2-3.1 - Brainstem and Cerebellum DLAs

Question 1

Describe the development of the brainstem beginning with the neural tube.

Answer 1

1. The neural tube has an alar and basal plate situated doraslly and ventrally, respectively, on either side of the neural cavity. The alar and basal plates are separated by the sulcus limitans (refer to image).
2. The rostral neural tube cavity will begin to expand laterally to form the 4th ventricle
3. This expansion pushes the alar plates laterally while bringing the basal plates in medially (refer to image)

Question 2

Answer 2

Question 3

What symptoms would you expect to see if damage were to occur to the superior or inferior colliculi?

Answer 3

Superior Colliculi Damage - malfunctions in behavior associated with visual stimuli

Inferior Colliculi Damage - malfunctions in behavior associated with auditory stimuli

Question 4

What is the facial colliculus and what symptoms would be expected if it were damaged

Answer 4

The motor fibers from CN7 (facial) make a loop over the CN6 (abducens) making the visible bump that is the facial coliculus. Damage to this area usually presents with difficulty controlling facial expressions and certain eye movements

Question 5

What is the obex? In which structure is it located?

Answer 5

The obex is the caudal part of the fourth ventricle where it narrows down to become the central canal. This occurs within the medulla.

Question 6

Where are the foramina of luschka found? Where is the foramen of magendie?

Answer 6

On the dorsal surface of the pontine-medullary junction, lateral to the midsagittal line

The foramen of magendie is on the dorsal surface of the medulla in the midline

Question 7

Answer 7

Question 8

Where is the interpeduncular fossa and what does it contain?

Answer 8

It is the space between the crus cerebri and it contains CN3, CN4, and part of the circle of willis

Question 9

What is the basilar groove and what does it contain? What does this groove become?

Answer 9

It is a groove along the midline of the ventral surface of the pons and it contains the basilar artery

This groove continues caudally and becomes known as the anterior median fissure when it hits the medulla

Question 10

What is the clinical significance of the cerebellopontine angle?

Answer 10

It is a hot spot for tumerous development, most popularly for vestibular schwannoma

Question 11

Where are the olives and their associated sulci located? What are the clinical significances of these structures?

Answer 11

Lateral to the rostral medullary pyramids are the preolivary sulci, the olives themselves, and then the post olivary sulci.

The preolivary sulcus contains the nerve roots for CN12 so damage to this area would cause tongue weakness

The postolivary sulcus contains the nerve roots for CNs 9-11

Question 12

Answer 12

Question 13

What is the main purpose of the middle cerebellar peduncle?

Answer 13

It contains fibers that allow the cerebellum to communicate with the pons

Question 14

Answer 14

Question 15

List the major tracts ascending through the brainstem and their functions.

Answer 15

• The lateral lemnicus connects the accessory olivary nucleus to the inferior colliculi
• The trigeminal lemniscus carries fibers from CN5 through the brainstem to the thalamus
• The medial lemniscus connects the gracile and cuneate nuclei to the thalamus
• Spinothalamic Tract (anterolateral system) carries pain and temperature somatosensations from the spine to the thalamus
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Question 16

What symptoms would you expect if the lateral lemniscus was damaged and why?

Answer 16

You’d expect auditory recognition issues because the lateral lemniscus carries fibers from CN8

Question 17

What symptoms would you expect if the trigeminal lemniscus was damaged?

Answer 17

Issues with facial sensations

Question 18

What symptoms would you expect if the medial lemniscus was damaged?

Answer 18

You’d expect sensory defecits from different parts of the body depending on which aspect of it was damaged.

Question 19

Describe the dorsal column-medial lemniscal system and what information it carries.

Answer 19

This system carries somatosensory information up the dorsal column of the spinal cord. The medial portions of the dorsal column are known as the gracile fasciculi and their fibers will synapse at the gracile nucleus in the medulla. The lateral portions of the dorsal column are known as the cuneate fasciculi and their fibers synapse at the cuneate nucleus in the medulla.

Both sets of fibers then run up to the thalamus in the medial lemniscus tract

Question 20

What symptoms would you expect if the anterolateral system was damaged?

Answer 20

Issues with the sensation of pain and temperature

Question 21

List the major tracts descending through the brainstem and their functions.

Answer 21

• Corticobulbar tract connects the cortex to motor nuclei (usually for cranial nerves) in the pons and medulla
• Corticospinal tract connects the cortex to motor nuclei in the ventral horn of the spinal cord
• Rubrospinal tract connects the midbrain to the cervical spinal cord
• Vestibulospinal tract connects fibers associated with CN8 to the spinal cord
• Reticulospinal system connects fibers associated with the reticular formation of the pons/medulla to the spinal cord
• Connects nuclei in the superior colliculus (tectum) to the spinal cord

Question 22

Answer 22

Question 23

What is the reticular formation?

Answer 23

It is a net-like distribution of grey matter extending up from the spinal grey matter through the brainstem and all the way up to the midbrain. This network of nuclei is referred to as the reticular formation

Question 24

What are the various functions of the reticular formation?

Answer 24

1. Arousal (staying awake)
2. CVS control
3. Vascular tone
4. Breathing
5. Swallowing
6. Vomiting

Question 25

Does the basilar artery run along the dorsal or ventral surface of the pons?

Answer 25

Dorsal

Question 26

List the arterial branches that arise from the segment between the PCAs and the vertebral arteries.

Answer 26

Beginning Caudally

1. Posterior Inferior Cerebellar Artery (PICA)
2. Anterior Spinal Artery (ASA)
3. Anterior Inferior Cerebellar Artery (AICA)
4. Pontine Arteries
5. Superior Cerebellar Arteries (SCA)

Question 27

What does the PICA supply?

Answer 27

Lateral and Dorsal aspects of the medulla

Ventral and Dorsal aspects of the cerebellum

Question 28

What does the AICA supply?

Answer 28

The anterior and inferior portions of the cerebellum and brainstem structures it passes along the way

Question 29

What is the labrynthine artery, where does it come from, and what does it do?

Answer 29

It is a branch of the AICA that follows CN7 to supply the inner ear

Question 30

What are the pontine arteries, where do they come from, and what do they do?

Answer 30

The pontine arteries are small branches off the basilar artery between the AICAs and SCAs that supply the pons.

Question 31

What does the SCA supply?

Answer 31

Superior aspects of the pons and cerebellum. Sometimes inferior aspects of the midbrain

Question 32

Which arteries supply the bulk of the midbrain?

Answer 32

The PCAs

Question 33

Label image, say what the structure is and say from what direction we are viewing it in this image?

Answer 33

Looking at it from the superior aspect

Question 34

Answer 34

Question 35

Answer 35

Question 36

What is the clinical significance of the tonsils of the cerebellum?

Answer 36

When the brain herniates through the foramen magnum the tonsils get stuck. This is called tonsilar herniation.