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Brainstem 1 Flashcards

1
Q

Causes of Upper Motor Neuron Lesion (UMNL)

A
  1. Stroke
  2. Spinal Injury
  3. Brain Injury
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2
Q

Signs of Upper Motor Neurone Lesions

A
  1. Spastic Paralysis
  2. Little Muscle Wasting
  3. Babinski Sign
  4. Spasticity –> Increases & Involuntary
  5. Velocity Dependent Muscle Tone (causing resistance to movement)
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3
Q

Upper Midbrain Section

A

NB: Superior Colliculus (part of tectum) –> important in EYE MOVEMENTS

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4
Q

Importance of Substantia Nigra

A
  • Looks black on a fresh dissection
  • Shown in white here due to myelin stain (so not picked up)
  • Important in Parkinson’s Disease
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5
Q

What is found in the Lower Pons?

A
  • Bundles of Corticospinal Tract (broken up into small bundles either side)
  • Ascending Tracts
  • Middle Cerebellar Peduncle (connects pons & cerebellum)
  • 4th Ventricle
  • Cerebellum (at this level)
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6
Q

What does the branches of the basilar artery supply?

What happens if it is blocked?

What is the condition called?

A
  • Basilar Artery –> supplies the Ventral Part of the Pons
  • Some Branches of Basilar Artery –> supply only the ventral fibres –> which is where the corticospinal tract branches are found (not supply somatosensory neurones)
  • Therefore affects descending motor fibres and not ascending sensory fibres
  • Causes Locked-In Syndrome (hear & feel things but not move muscles in body)
  • Only a little bit of eye movement
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7
Q

At what point of the brainstem do the corticospinal tracts form the pyramids?

A
  • Pyramids form in the Open Medulla (uppermost part of medulla)
  • (Open Medulla because there is no central canal - it has already opened up to the 4th ventricle on the dorsal side)
  • Corticospinal tract –> comes together in the open medulla to form one bundle on either side at the front of the medulla
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8
Q

What happens if the corticospinal tract (pyramid) are damaged?

Can there be motor recovery?

A
  • Corticospinal Tract –> only tract which controls fine movements of the hand
  • There is a loss of voluntary motor control (completely for fine control of hand)
  • There can still be motor recovery but there can be motor control for all motor movements except for fine movement of the hand (always lost with pyramids)
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9
Q

Is it common for the corticospinal tract to be solely damaged?

A
  • No, it is very rare.
  • The only place where corticospinal tract damage can solely occur is at the pyramids when they are on the ventral surface of the medulla
  • Corticospinal Tract Damage –> usually comes with damage of other neurones too
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10
Q

Is the open medulla the uppermost or lowermost part of the medulla?

A
  • Uppermost Medulla –> OPEN –> because central canal is gone
  • Lowermost medulla –> CLOSED –> still has the central canal
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11
Q

What is the landmark for the open medulla (uppermost part)?

A
  • Olives
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12
Q

Where is the inferior olivary nucleus found and how is it presented?

A
  • Found in the open medulla (uppermost part)
  • Shown as a bump lateral to the pyramids
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13
Q

What is the importance of the Inferior Olivary Nucleus?

A
  • Important source of neurones/info between the BRAINSTEM (medulla) & CEREBELLUM (thus inferior peduncle)
  • This occurs ISOLATERALLY (same side)
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14
Q

Which structures are found at the open medulla (uppermost part)?

A
  1. Olives (inferior olivary nucleus)
  2. Inferior Cerebellar Peduncle
  3. Pyramids (corticospinal tract)
  4. No central canal
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15
Q

Why is the medulla described as closed?

A
  • Because it DOES have a central canal
  • This is because it has still not ‘opened up’ to the 4th ventricle
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16
Q

What is found at the closed medulla?

A
  1. Central Canal
  2. Pyramids
  3. No Olives (that is in the open)
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17
Q

At what point does the decussation of the pyramids occur?

A
  • Lowest Part of the Medulla
  • Slightly obscure due to cross over of the tracts
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18
Q

What does the rubrospinal tract do?

A
  • Controls voluntary movement
  • Controlled from the cerebral cortex (therefore voluntary)
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19
Q

What is the pathway of the rubrospinal tract?

A
  • Motor Control occurs here via the Red Nucleus
  • Neurones from the Red Nucleus (midbrain) –> go down the rubrspinal tract –> to indirectly control motor neurones/interneurones (which lead to motor anyway)
  • Partially intermingles with the corticospinal tract
    *
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20
Q

Where is the Red Nucleus found in the brainstem?

A
  • Midbrain
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21
Q

Describe the 2 different pathways of the rubrospinal tract & corticospinal tract?

  • Where do they start?
  • Where in the brainstem do they synapse?
  • Where is there decussation?
  • Where in the spinal cord are they located?
A
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22
Q

What does the somatosensory system do?

A
  • Allows you to feel precisely localised sensations?
  • Cerebral Cortex –> is where you ‘perceive’ anything
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23
Q

Describe the general route of a somatosensory pathway?

A
  1. Peripheral afferents from peripheral receptor
  2. Peripheral neurones synapses at the same level as ascending sensory neurone
  3. Neurone goes up sensory tract to the cerebral cortex (decussation varies)
  4. Cerebral cortex perceives somatosensation
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24
Q

Are the motor & sensory control/sensations contralateral?

A
  • Yes
  • One cerebral cortex will control & sense the contralateral side
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25
Q

Where are the peripheral sensory neurones located?

  • Cell Body
  • Dendrites
  • Axons
A
  • Cell Body –> in the DORSAL ROOT GANGLIA
  • Dendrites –> go out to the peripery (skin / bone etc.)
  • Axons –> goes into the CNS
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26
Q

What is the minimum number of neurones in the pathway between the peripheral receptor & cerebral cortex?

A
  • 3

There is a minimum of 3 neurones between cerebral cortex & sensory receptor

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27
Q

Where are the cell bodies of primary afferent nerve fibres found?

A
  • Dorsal Root Ganglia
  • Cranial nerve Sensory Ganglia
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28
Q

What is the peripheral nerve classification for muscle physiologists?

Which side is smallest?

A
  • Peripheral Nerves classified from 1-4
  • 4 is the smallest
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29
Q

What is the skin peripheral nerve classification for skin physiologists?

Which side is smallest?

A
  • From A to C
  • C –> is smallest
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30
Q

Describe Class 4 & C-Fibres

A
  • Unmyelinated
  • Small Diameters
  • Small Cell Bodies
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31
Q

Describe A-betas

A
  • Large
  • Myelinated Neurone
  • Large Somas
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32
Q

Describe C-Fibres.

Which somatosensation do they usually convey?

Where do these fibres usually end in the spinal cord?

Where do they come from?

A
  • Finest Diameter
  • Majority of C-Fibres are Nociceptive Fibres
  • Usually end in superficial dorsal grey horn (lamina 1 & 2)
  • Come from the Skin or Muscles
  • They particularly terminate in Lamina 2 (lamina gelatinosa)
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33
Q

Pathology of neurone types

A
  • Occasionally during pathology the cerebral cortex interpretation of neurones changes
  • Chemoreceptors can be interpreted as pain or touch etc.
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34
Q

Where do 1alpha afferents usually come from?

  • What are they important for?
A
  • Muscle Spindles (stretch reflex)
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35
Q

How is the intensity of stimuli coded?

A
  • Frequency of action potentials
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36
Q

How are peripheral axons classified?

Is this linked to function?

A
  • Peripheral axons are classified according to size
  • Size is related to function
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37
Q

The functions of the following are …

  • C-Fibres …
  • 1a Afferents …
  • Abeta Afferents …
A
  • C-Fibres –> PAIN
  • 1a Afferents –> STRETCH RECEPTOR INFO (muscle spindles to spinal cord)
  • A-beta Afferents --> mechanoreceptors from skin)
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38
Q

Describe 1a Afferents.

  • Are they large or small?
  • What do they innervate?
  • Are they myelinated?
  • Where do their axons end?
A
  • Large somatosensory fibres which are myelinated
  • Innervate the muscle spindles
  • Cell bodies found in the dorsal root ganglia
  • Axons end in the spinal cord –> they synapse directly with motor neurone in ventral horn
  • They form a mono-synaptic reflex or with one interneurone inbetween
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39
Q

What is the general pattern of somatosensory (ascending tracts)?

  • What is the minimum number of sensory neurones?
  • Can there be more?
  • What are these neurones called?
A
  • Minimum Number of Sensory Neurones on the pathway to the cerebral cortex is 3
  • Yes, there are probably more in the pathway but there will always be at least 3
  • Primary Sensory Neurones (1)
  • Second Order Neurones (2)
  • Thalamic / Third Order Afferent Neurones (3)
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40
Q

What do primary sensory neurones do?

  • Where is the cell body found?
  • Where does the axon terminate?
  • What types of neurones could these be?
A
  • These carry signals from the receptor to the CNS
  • Cell Bodies –> found in the DRG or CRANIAL NERVE SENSORY GANGLIA
  • Central Processes of their Axons terminate on the same side of the CNS
  • These include C-fibres & A-beta fibres
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41
Q

What do second order neurones do?

  • Where is the cell body found?
  • Where does the axon terminate?
A
  • Found on the same side of the CNS as peripheral receptor
  • Axons cross the midline to reach the thalamus (terminate here)
  • Cell Body –> is on the same side of the CNS as sensation
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42
Q

What do thalamic neurones (third afferent) neurones do?

  • Where is the cell body found?
A
  • These send information from thalamus to somatosensory cortex
  • Thalamus –> essentially a somatosensory cortex relay
  • Cell body is found in the thalamus
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43
Q

Which sensory modalities are carried by the spinothalamic tract?

A
  • Pain (nociception)
  • Temperature
  • Touch (non-discriminative touch)
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44
Q

What are the 2 somatosensory pathways in the spinal cord?

A
  • Spinothalamic Tract
  • Dorsal Column/Medial Lemniscus System
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45
Q

Where are (pain) collaterals given off to the reticular formation during ascent to the thalamus?

  • Why is it important?
A
  • Many CNS neurones have axons with terminals in more than 1 nucleus
  • Nociception –> response to burns / cuts / noxious stimuli
  • Collaterals to Brainstem Reticular Formation is important to keep you alert
  • Reticular Formation keeps you alert (against threat)
  • This allows us to respond to pain/threat
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46
Q

What does the reticular formation do?

A
  • Keeps you awake/alert
  • Other things

NB: Pain fibres send collaterals to the reticular formation

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47
Q

What are the 2 types of pain fibres?

A
  • C-fibres (slow)
  • A-delta (fast)
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48
Q

Why is the thalamus important in the context of communication with the cortices?

A
  • Acts as a translational communication centre
  • Works between almost everywhere and the cerebral cortex
  • Any information going to the cerebral cortex has to go via the thalamus
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49
Q

Describe the general pathway of the spinothalamic tract

A
  • Afferent neurones terminate on the same side as the receptor
  • Second Order Neurone –> crosses the midline (at the same level) –> then goes up the spinothalamic tract
  • Ends at the Thalamus where it synapses with Third Order neurone
  • It then relays information from the thalamus to cortex
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50
Q

What are the sensory modalities of the dorsal column / medial lemniscus system.

A
  • 2-Point Discrimination
  • Conscious Propioception
  • Vibration Sense
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51
Q

What is the main difference between the dorsal column / medial lemniscus pathway and the spinothalamic tract?

A
  • First Synapse –> for the spinothalamic tract occurs at the same level
  • Cross over also occurs at the same level
  • First Synapse –> for dorsal column / medial lemniscus pathway –> occurs in the Medulla
  • Occurs in the Medulla in the Dorsal Column Nucleus
  • Cross over occurs here too
  1. Cross over occurs at a different level
  2. 1st synapse occurs at a different level
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52
Q

What is discriminative touch?

  • How can we test it?
  • What is the sensitivity of the palm compared to the back of your hand?
A
  • How close can you detect how close 2 points are
  • Ask patients if they are being touched by 1 or 2 points (e.g. on skin of palm)
  • You should be able to differentiate between the 2 points touching you (even if they are close - depending on how close you get)

Palm of Hands sensitivity –> High Discriminative Touch

Back of Hand sensitivity –> Low Discriminative Touch

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53
Q

What is conscious propioception?

A
  • Body Sense
  • Example - telling you if your hand is behind your back without looking at it
  • It is the ‘conscious knowledge of spatial placement’ without seeing it
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54
Q

What is unconscious propioception?

A
  • This is propioception that goes to the cerebellum which has nothing to do with conscious
55
Q

Give 2 reasons why propioception is helpful?

A
  1. Helpful in reflexes
  2. Letting you know about your surroundings (conscious propioception)
56
Q

What is the difference between conscious and unconscious propioception?

A
  • Conscious –> you know about it –> goes to the cerebral cortex
  • Unconscious –> you do not know about it –> goes to cerebellum
57
Q

How do you test for vibration sense?

A
  • There is no distinct vibration sense
  • Place vibrating object onto a bony prominence & play vibrating tune
  • See if they can detect it
58
Q

Describe the general pathway of the dorsal column / medial lemniscus pathway.

A

Still has a minimum of 3 neurones in its pathway

  1. Afferent receptors go into spinal cord
  2. They go straight up the dorsal column (on the surface - you can touch it)
  3. Synapses in the dorsal column nucleus in the medulla (bottom of brainstem)
  4. Second order neurone leaves dorsal column nucleus –> crosses midline –> then ascends the medial lemniscus pathway
  5. Synapses at the thalamus –> which relays to S1
59
Q

What are the main similarities & differences between the spinothalamic pathway & dorsal column / medial lemniscus pathway?

60
Q

Where do C-fibres terminate in the dorsal horn?

A
  • Lamina 1 or 2 (usually 2)
61
Q

Where is the spinothalamic tract located in the spinal cord?

A
  • Ventro-Lateral White Matter
62
Q

What does the secondary neurones of the spinothalamic tract do?

A
  • Crosses the midline (anterior to central canal)
  • Enters spinothalamic tract (ventral surface)
  • Ascends to thalamus

NB: Second order neurones are not the c-fibres

63
Q

Where does the second order neurone of the spinothalamic pathway pass the midline relative to the central canal?

A
  • It passes anterior to the central canal
64
Q

Where are the locations of the following in the spinal cord:

  • Spinothalamic Tract ….
  • Dorsal Columns …..
  • Corticospinal Tract ….
A
  • Spinothalamic Tract --> Ventro-Lateral
  • Dorsal Columns –> Dorsal
  • Corticospinal Tract –> Dorso-Lateral
65
Q

What are the 2 parts of the dorsal column called?

A
  • Fasiciculus Gracilis
  • Fasiciculus Cuneatus

Central Branch of the axon goes into the spinal cord and up the dorsal column. It travels in the white matter of the spinal cord to the medulla (dorsal nuclei)

66
Q

Where does the fasciculus gracilis get its neurones from?

  • Where is it found
A
  • Lower Limb
  • Found on the medial side
    *
67
Q

Where does the fasciculus cuneatus get its neurones from?

A
  • Upper Limb
  • Found on the lateral side
68
Q

At what level is the fasiculus cuneatus seen in the dorsal column?

A
  • T6
  • Below T6 --> there is just (1) Dorsal Column on each side –> the fasiculus gracilis (lower limb)
  • Above T6 –> there is an extra Dorsal Column –> added to the Lateral Side –> called the Fasiculus Cuneatus (upper limb)
69
Q

Which one is medial the cuneatus or gracilis?

A
  • Gracilis –> from Lower Limb –> is Medial
  • Cuneatus –> is added onto the outside at T6
70
Q

How does the dorsal column travel

A
  • Neurones stay on the same side
  • Travels up to dorsal nuclei
  • This is in the medulla
71
Q

Where in the brainstem is the dorsal column & spinothalamic tract in a similar position?

A
  • Lower Medulla (where decussation takes place)
72
Q

Summary view of the 2 somatosensory pathways.

73
Q

At what level of the brainstem does the dorsal column / medial lemniscus pathway have its cross over?

  • i.e. where is the dorsal column nuclei found?
A
  • Upper Closed Medulla
  • First order neurones synapse at dorsal nuclei
  • Second order neurones cross over to the medial lemniscus pathway on contralateral side

NB: Closed Medulla means the central canal is still present (have not reached the 4th ventricle)

74
Q

What does the spinothalamic tract do at the upper closed medulla level?

A
  • Simply runs through the closed medulla going on to the thalamus
75
Q

What does the cerebral cortex do with the somatosensory inputs?

A
  • Modulates Inputs –> then decides what you perceive (feel) and not feel
76
Q

Can you see the fasiculus gracilis & cuneatus on the brainstem surface?

A
  • Yes
  • You can follow it up and feel it as a bump at the back of the brainstem
  • You can also feel the bump at the top where the nuclei are
77
Q

At what level does the 4th ventricle begin?

A
  • Dorsal to the OPEN MEDULLA
  • This is where the central canal has opened into the 4th ventricle
78
Q

What is found at the level of the open medulla?

A
  • Inferior Olivary Nucleus
  • Corticospinal Tract (Pyramids)
  • Medial Lemniscus
  • 4th Ventricle (back)
  • Inferior Cerebellar Peduncle
  • Spinothalamic Tract (similar posiiton as spinal cord)
79
Q

Briefly describe the first synapse for the dorsal column & spinothalamic tract

A
  • Dorsal Column: 1st order neurones –> synapse in dorsal nuclei (lower medulla) on the same side and then converge onto medial lemniscal tract as second order neurone
  • Spinothalamic Tract: 1st order neurones –> synapse on the same side with second order neurones –> which then cross over and go up the spinothalamic tracts to the thalamus
80
Q

What are the changes in location for the spinothalamic tract & medial lemniscus tract going from the medulla to the pons?

A
  • They become closer together in the pons
  • Medial Lemniscus –> MEDIAL (flattened out)
  • Spinothalamic Tract –> LATERAL (but moved in)
81
Q

At what levels is the 4th ventricle found?

A

Dorsal Surface of Open Medulla (upper part) & Pons –> is 4th Ventricle

Spinothalamic tract comes alongside the lateral side of the medial lemniscus (leaving original ventro-lateral position)

They run along together to the thalamus on the contralateral side to stimulus

82
Q

Where is the location of the corticospinal tract in the lower pons?

A
  • Broken up into bundles
  • Ventral Part (basilar part)
83
Q

Label the following

84
Q

What does the red nucleus give rise to?

A
  • Rubrospinal Tract
  • It is a motor nucleus
85
Q

What is the superior colliculus important for?

A

Eye movements & (some) visual reflexes

86
Q

What is the periaqueductal grey important for?

  • Where is it found?
A
  • Descending control over pain
  • It can turn off nociceptive transmission over most of the body
  • Not under conscious control (cannot just choose to switch off pain)
  • Found around the aqueduct
  • It has many other functions
  • One Function –> Descending Analgesic System for Turning off pain
87
Q

What is the affect of adrenaline on pain?

A
  • Brain controls pain percept
  • High adrenaline situations such as rugby match or war
  • Adrenaline stimulates the periaqueductal grey –> which causes profound analgesia
88
Q

How does adrenaline affect pain sensation?

A
  • Forebrain/Cerebral Cortex –> can ‘turn off’ nociception –> by sending axons to the periaqueductal grey
  • When this is activated it sends axons down to medulla
  • Medulla has neurones which send axons to spinal cord to turn off nociceptive transmission coming into dorsal horn

NB: Body system can turn pain percept up or down via descending fibres (controlled by cerebral cortex)

89
Q

What is syringomyelia?

At what level is it usually found?

What can be the danger

A
  • Fluid-filled cavity (syrinx) in the spinal cord
  • Cervical Level
  • Lower Cervical Levels innervatate Upper Limb
90
Q

Which pathway is affected by syringomyelia?

Which sensory modalities does this carry?

A
  • Spinothalamic Tract
  • Nociception & Temperature & Non-Discriminative Touch (light)
91
Q

What can cause syringes in the spinal cord?

A
  1. Trauma
  2. Unknown reasons
92
Q

What can a syringomyelia damage and what does this lead to?

A
  • Destruction of spinothalamic crossing fibres
  • Leads to loss of pain & temperature over the affected segments (usually cervical)
  • Sensation from BELOW the lesion is usually UNAFFECTED (tracts themselves are not damaged)
  • Therefore affects on pain & light touch & temperature sensation of the levels of the syrinx
  • Analgesia is bilateral usually
93
Q

Which levels does a syringomyelia affect?

A
  • Bilateral Effect
  • Only the levels the syrinx is found
  • It does not affect the ascending tract –> just the crossing fibres
94
Q

What can be done for someone who has a tumour in the pelvis causing a lot of pain? (pain cannot be controlled)

A
  • Ventrolateral Cordotomy

These people are usually in a lot of pain and find it difficult to treat

95
Q

What does ventrolateral cordotomy involve?

A
  • Lesioning/ablating the spinothalamic tract for pain relief
  • This will stop pain & temperature & light touch
  • It will not affect motor fibres

NB: But pain comes back after a few weeks/months. Why?

96
Q

How is ablation carried out?

A
  • Electrode used to stimulate the tract until anaesthesia is produced
  • This means spinothalamic tract is identified
  • It can now be burned out
  • Produces good analgesia for all the segments below ablasion

However, pain returns after a few weeks

97
Q

Why does pain sensation come back after ventro-lateral cordotomy?

A
  • Not due to nerve fibre regeneration (CNS)
  • There are other pathways which can carry pain sensation too
  • These do not usually carry pain (shown by temporary analgesia)
  • The brain rewires these other pathways and can start to relay pain information after a few weeks/months
98
Q

Where is the parabrachial nucleus found?

A
  • Rostral (upper) Pons
  • Next to cerebellar peduncle
99
Q

Where is the amygdala found and what is it important for?

A
  • Found in the temporal lobe
  • Important in terms of emotion
100
Q

What is the spino-parabrachial pathway?

A
  • Another pain pathway
  • Pain Fibres –> go to the parabrachial nucleus via the spino-parabrachial pathway

Therefore pain can go up the this pathway to the parabrachial nucleus and is then relayed to the forebrain

NB: It is the major nociceptive pathway in experimental animals

101
Q

What does the basilar artery (ventral surface) supply?

A
  • Bundles of Corticospinal Axons (get a branch)
  • Medial Lemniscus
  • Spinothalamic Tract
102
Q

What transmitter is found in the raphe nuclei?

A
  • Neurones using monoamines such as 5HT found in raphe nuclei
103
Q

Where is the raphe nuclei found?

A
  • Midline of the Brainstem

Lowest Raphe Nucleu –> found in the Medulla

104
Q

What is another name for 5HT?

105
Q

How does the raphe nuclei affect pain?

A
  • Sends axons down the spinal cord –> to control pain transmission in dorsal horns (among other functions)
  • They help to modulate –> pain transmission & motor functions in spinal cord
106
Q

How does the periaqueductal grey & raphe nuclei work together?

A
  • Periaqueductal Grey can turn off pain transmission in superficial dorsal horn
  • It sends axons through nucleus raphe magnus
  • These send axons down to spinal cord to superficial dorsal horn
  • Fibres in dorsal horn can turn up or down pain (depending on forebrain descending pathway)
107
Q

Why can seratonin uptake inhibitor drugs be helpful in chronic pain?

A
  • These increase the levels of 5HT (seratonin) floating around –> therefore decreasing pain input
108
Q

What is the effect of 5HT (seratonin) on pain?

A
  • Decrease in pain input
109
Q

What does the locus ceruleus do?

  • What types of neurotransmitter does it send out?

Where does it send its axons to?

A
  • Sends Noradrenaline (NA) axons all over the CNS
  • It is one of many NA nuclei but it is the most prominent
110
Q

Where is the locus cereleus found?

A
  • Floor of the 4th Ventricle
  • Pons
  • Close to the Parabrachial Nuclei (a pain nuclei)
111
Q

What is the effect of NA on pain?

What modulates its release?

A
  • Powerful analgesic effect
  • Modulated by the cerebral cortex
  • NA has a bigger effect on pain than 5HT
112
Q

Where do the locus ceruleus send its fibres?

Which part of the spinal cord does it affect?

A
  • Down the spinal cord & all over the CNS
  • Controls pain transmission in the dorsal horn
  • It sends non-discriminative information –> thus it modulates signals all over the CNS & Spinal cord (not sending specific info)
113
Q

Compare the effect of 5HT & NA

Where do they come from?

Summary of the system

A
  • 5HT & NA is released by fibres which have descending control over pain transmission in dorsal horns
  • 5HT –> comes from RAPHE NUCLEI (lowermost one is in medulla)
  • NA –> comes from LOCUS CERULEUS (main one in the pons but there are others)

They are BOTH controlled by PERIAQUEDUCTAL GREY –> which is controlled by complex functions of the cerebral cortex

114
Q

What is leprosy and what can its effect be on pain?

A
  • Bacterial Infection
  • Affects neural response
  • Neural response to it causes analgesia
  • It causes the loss of peripheral sensory axons
115
Q

Which cranial nuclei receives all the somatosensory information in the cranial nerves?

A
  • Trigeminal Sensory Nuclei (cranial nerve 5)
116
Q

What are the 3 parts of the trigeminal sensory nuclei?

A
  • Midbrain (mesencephalic) nucleus
  • Chief Nucleus
  • Spinal nucleus (continuous dorsally with superficial dorsal horn of spinal cord)
117
Q

What are cranial nerves?

A
  • Nerves which arise directly from the brain
118
Q

Where are the cell bodies of the sensory fibres in cranial nerves found?

A
  • Ganglia on the Cranial Nerves
119
Q

Where is the trigeminal nuclei located?

A
  • Deep cranial fossa
120
Q

Why is the trigeminal nuclei important?

A
  • Any cranial nerve which has somatosensory fibres in them will always end up in the trigeminal sensory nuclei
121
Q

Where are the 3 parts of the trigeminal sensory nuclei found?

A
  • Mesencephalic Nucleus –> extends into the MIDBRAIN
  • Chief Principal Nucleus –> lives in the PONS
  • Long Spinal Nucleus –> continuous with SUPERFICIAL DORSAL HORN of the SPINAL CORD
122
Q

Describe the chief (sensory) prinicpal nucleus.

A
  • particularly important
  • Has a large diameter due to A-beta myelinated fibres of the trigeminal sensory nerves
  • Relays discriminative touch
  • Relays information up to the thalamus –> then to S1
123
Q

Describe the spinal nucleus of the trigeminal nerve

A
  • Lots of C-fibres are found here (nociceptors)

This includes pain from:

  1. Upper Teeth
  2. Lower Teeth
  3. Face Skin
  4. Nasal Cavity
  5. Larynx
124
Q

Describe the mesencephalic (midbrain) nucleus.

A
  • This contains cell bodies of primary sensory neurones
  • They innervate the propioceptors for the jaw (only primary sensory neurones found in CNS)

NB: Important evoluntarily as if you did not have teeth you would die –> you cannot bite down too hard otherwise break teeth

125
Q

If you has a pain condition to do with the trigeminal nerve. Which part would the neurosurgeon ablate?

A
  • Spinal Nucleus of the trigeminal nerve
  • This contains lots of C-fibres
  • Leads to trigeminal nerve analgesia
126
Q

Summarise what each part is most important for:

Midbrain Nucleus (mesencephalic)

Chief Nucleus

Spinal Nucleus

A
  • Midbrain (mesencephalic) Nucleus –> JAW PROPIOCEPTION
  • Chief Nucleus –> DISCRIMINATIVE TOUCH (A-betas)
  • Spinal Nucleus –> C-FIBRES (nociception)
127
Q

Other than ablation, what can cause trigeminal neuralgia?

A
  • Can occur due to blood vessels squashing the trigeminal nerve root
  • It can affect 1 or 2 divisions (unilaterally or bilaterally)
128
Q

Which cerebellar artery can cause trigeminal neuralgia?

A
  • Superior Cerebellar** Artery**

It is found near the trigeminal roots and thus can give rise to trigeminal neuralgia

129
Q

What pathogenic condition can affect the trigeminal nerve?

A
  • Post herpetic neuralgia (more common than blood vessels)
130
Q

Which virus can cause post herpetic neuralgia?

A
  • Shingles Virus (Varicella Herpes Zoster)
131
Q

Where does the shingles virus stay latent?

A
  • Stays latent in primary sensory neurones for many years
132
Q

What can trigger shingles?

What happens when virus is activated?

A
  • Stress
  • Immunosupression

It goes down the axon –> to the skin –> replicates in skin cells –> causing blisters –> leaving scars on the skin

It is very nasty & painful

133
Q

What are the 2 possible places where shingles can occur?

A
  • Dorsal Root Ganglia
  • Trigeminal Nuclei (aka ganglia)

If patient is unfortunate to have it in trigeminal nuclei –> can lead to trigeminal neuralgia –> meaning they will feel pain from its distribution down the trigeminal nerve –> this can cause pain for the rest of the patient’s life

NB: Multiplies in skin cells (only can in non-neuronal cells)

134
Q

What are the effects of shingles?

A
  • Damage along the dermatome
  • Post-traumatic neuropathy

The changes caused by the virus means pain can be perceived all the time

Neuroanatomy (7 decks)

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