Brainstem part II: The Pons

Question 1

what does the Pons contain?

Answer 1

• Cranial nerve nuclei for V, VI, VII, and VIII.
• The ‘base’ of the pons.
• The ‘tegmentum’ of the pons.
• Ascending and descending tracts (lemnisci, etc).
• Pontine nuclei.
• MLF, reticular formation

Question 2

Why is the Pons is more complicated than midbrain?

Answer 2

1. More cranial nerves
2. Cerebellar connections (peduncles) very important here.
3. Cortical inputs to cerebellum pass through the pons.

Question 3

what do we find in the Rostral pons?

Answer 3

1. Mesencephalic nucleus is part of CN V
2. Medial longitudinal fasciculus connects CN’s III, IV, VI and VIII
3. Superior cerebellar peduncle connects midbrain with cerebellum

Question 4

What is this part of the pons?

Answer 4

the rostral pons

Question 5

identify the parts of the rostral pons

Answer 5

Question 6

what part of the pons is this?

Answer 6

rostral pons

Question 7

identify the rostral pons parts

Answer 7

Question 8

What are the pontine nuclei and tranverse pontine fibers?

What is another name for this?

what is it for?

Answer 8

• Cortical axons going to the cerebellum first synapse ipsilaterally on pontine nuclei.
• Axons of pontine nuclei cross to the other side; they are then called the tranverse pontine fibers
• Tranverse pontine fibers enter the cerebellum via the middle cerebellar peduncle

Corticopontocerebellar pathway: is the means

by which the cortex sends its ‘blueprint’ for movement to the cerebellum.

Question 9

what level of the pons is this?

Answer 9

Mid Pons

Question 10

identify the parts of the mid pons

Answer 10

Question 11

what part of the pons is this?

Answer 11

mid pons

Question 12

identify the parts of the mid pons

Answer 12

Question 13

what landmarks can tell us we are at the level of the caudal pons?

Answer 13

Note position of CN VI and VII.

Question 14

what level of the pons is this?

Answer 14

caudal pons

Question 15

identify the parts of the pons

Answer 15

Question 16

identify the parts of the caudal pons

Answer 16

Question 17

The facial colliculus is formed by what?

Answer 17

the motor axons of CN VII; they ‘wrap’ around the nuclei of CN VI before exiting the pons. This creates a ‘bulge’ in the wall of the 4th ventricle

Question 18

How is the medial lemniscus located in the pons compared to the midbrain?

Answer 18

more medially located

Question 19

name the vascular supply to the pons

Answer 19

Question 20

what syndrome will we have if area A is damaged?

what syndrome will we have if area B is damaged?

Answer 20

A: Medial Inferior Pontine Syndrome

B: Lateral Inferior Pontine Syndrome

Question 21

What is another name for Foville Syndrome?

Why does it happen?

Answer 21

Medial Inferior Pontine Syndrome

Results from occlusion of branches of the basilar artery.

Question 22

what symptoms will we see in Foville’s?

mention why we see such symptoms?

Answer 22

Symptoms:

1. Ipsilateral medial deviation of eye: Due to damage to lateral rectus muscle (CN VI).
2. Contralateral weakness of lower face: Damage to corticobulbar tracts.
3. Contralaleral hemiparesis of trunk and limbs: Damage to corticospinal tracts.
4. Bilateral limb and gait ataxia: Damage to pontine nuclei on one side, pontine fibers on the other side.
5. Contralateral loss of discriminative touch, propriception, and vibration sense: Damage to dorsal column system.
6. May include VII if lesion is big enough.

Question 23

why does Lateral Inferior Pontine Syndrome happen?

What is another name for this syndrome?

Answer 23

Results from occlusion of the AICA

AICA syndrome

Question 24

What symptoms do we see in AICA syndrome?

why do these happen?

Answer 24

Symptoms:

1. Ipsilateral facial nerve paralysis. - Damage to Facial Nerve (VII)
2. Loss of taste from anterior 2/3 of tongue. -Damage to Facial Nerve (VII)
3. Loss of corneal and stapedial reflexes. - Damage to Facial Nerve (VII)
4. Unilateral central nerve deafness. - Damage to Cochlear Nerve (VIII)
5. Nystagmus, nausea, vomiting, and vertigo. - Damage to Vestibular Nerve (VIII)
6. Ipsilateral loss of pain and temp (face). - Damage to Spinal Trigeminal Nerve and Tract
7. Ipsilateral limb and gait ataxia. - Damage to Cerebellar Peduncles
8. Contralateral loss of pain and temp (body). - Damage to Spinothalamic Tracts
9. Ipsilateral Horner’s syndrome. - Damage to Descending Sympathetic Tract

Question 25

why does Lateral Superior Pontine Syndrome happen?

Answer 25

occlusion of the superior cerebellar artery

Question 26

what symptoms do we see in Lateral Superior Pontine Syndrome?

Answer 26

1. Ipsilateral limb and trunk ataxia. - Damage to Middle and Inferior Cerebellar Peduncles
2. Ataxia, dysmetria, and intention tremor. - Damage to Part of Cerebellum
3. Contralateral loss of pain and temp (body). - Damage to Spinothalamic and Spinotrigeminal Tracts
4. Ispilateral pain and temperature sense (head). - Damage to Descending Sympathetic Tract
5. Ipsilateral Horner’s syndrome. - Damage to Descending Sympathetic Tract
6. Contralateral loss of proprioception, vibration and discriminative touch from lower extremities and trunk. - Damage to Medial Lemniscus

Question 27

What is ‘Locked-in’ syndrome?

Why does it happen?

how does the patient communicate?

Answer 27

• quadriplegia, and paralysis of lower cranial nerves.
• infarction at base of pons affecting the corticospinal and corticobulbar tracts
• can only communicate by blinking, or moving their eyes vertically.

Question 28

what is Central Pontine Myelinolysis?

what other reason can result in this syndrome?

Answer 28

• Demyelination of central pons in patients being treated for hyponatremia (low sodium), treatment is too rapid, or the patient’s tissue has adapted to the hypotonicity, resulting in demyelination (bilateral).
• during alcohol withdrawal.

Question 29

name the arteries supplying the different parts of the pons

Answer 29

Question 30

can locked in syndrome patients feel even though they are paralized?

Answer 30

yes