Brainstem 1 Flashcards
(134 cards)
1
Q
Causes of Upper Motor Neuron Lesion (UMNL)
A
- Stroke
- Spinal Injury
- Brain Injury
2
Q
Signs of Upper Motor Neurone Lesions
A
- Spastic Paralysis
- Little Muscle Wasting
- Babinski Sign
- Spasticity –> Increases & Involuntary
- Velocity Dependent Muscle Tone (causing resistance to movement)
3
Q
Upper Midbrain Section
A
NB: Superior Colliculus (part of tectum) –> important in EYE MOVEMENTS
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
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)
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
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
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)
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
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
11
Q
What is the landmark for the open medulla (uppermost part)?
A
- Olives
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
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)
14
Q
Which structures are found at the open medulla (uppermost part)?
A
- Olives (inferior olivary nucleus)
- Inferior Cerebellar Peduncle
- Pyramids (corticospinal tract)
- No central canal
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
16
Q
What is found at the closed medulla?
A
- Central Canal
- Pyramids
- No Olives (that is in the open)
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
18
Q
What does the rubrospinal tract do?
A
- Controls voluntary movement
- Controlled from the cerebral cortex (therefore voluntary)
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
*
20
Q
Where is the Red Nucleus found in the brainstem?
A
- Midbrain
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
22
Q
What does the somatosensory system do?
A
- Allows you to feel precisely localised sensations?
- Cerebral Cortex –> is where you ‘perceive’ anything
23
Q
Describe the general route of a somatosensory pathway?
A
- Peripheral afferents from peripheral receptor
- Peripheral neurones synapses at the same level as ascending sensory neurone
- Neurone goes up sensory tract to the cerebral cortex (decussation varies)
- Cerebral cortex perceives somatosensation
24
Q
Are the motor & sensory control/sensations contralateral?
A
- Yes
- One cerebral cortex will control & sense the contralateral side
25
Where are the peripheral sensory neurones located?
- Cell Body
- Dendrites
- Axons
* **Cell Body** --\> in the DORSAL ROOT GANGLIA
* **Dendrites** --\> go out to the peripery (skin / bone etc.)
* **Axons** --\> goes into the CNS
26
What is the **_minimum_** **number** of **neurones** in the **pathway** between the **peripheral receptor** & **cerebral cortex**?
* 3
There is a minimum of 3 neurones between cerebral cortex & sensory receptor
27
Where are the **cell** **bodies** of **primary afferent nerve fibres** found?
* **Dorsal Root Ganglia**
* **Cranial nerve Sensory Ganglia**
28
What is the peripheral nerve classification for muscle physiologists?
Which side is smallest?
* **Peripheral** **Nerves** classified from **1-4**
* **4** is the **smallest**
29
What is the skin peripheral nerve classification for skin physiologists?
Which side is smallest?
* From A to C
* **C** --\> is **smallest**
30
Describe Class 4 & C-Fibres
* Unmyelinated
* Small Diameters
* Small Cell Bodies
31
Describe A-betas
* Large
* Myelinated Neurone
* Large Somas
32
Describe C-Fibres.
Which somatosensation do they usually convey?
Where do these fibres usually end in the spinal cord?
Where do they come from?
* **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)**
33
Pathology of neurone types
* Occasionally during **pathology** the **cerebral** **cortex** **interpretation** of **neurones** **_changes_**
* **_Chemoreceptors_** can be interpreted as **pain** or **touch** etc.
34
Where do **1alpha afferents** usually come from?
- What are they important for?
* Muscle Spindles (stretch reflex)
35
How is the intensity of stimuli coded?
* Frequency of action potentials
36
How are peripheral axons classified?
Is this linked to function?
* Peripheral axons are **classified** according to **_size_**
* **Size** is related to **function**
37
The functions of the following are ...
* C-Fibres ...
* 1a Afferents ...
* Abeta Afferents ...
* **C-Fibres** --\> PAIN
* **1a Afferents** --\> STRETCH RECEPTOR INFO (muscle spindles to spinal cord)
* **A-beta Afferents -**-\> mechanoreceptors from skin)
38
Describe 1a Afferents.
- Are they large or small?
- What do they innervate?
- Are they myelinated?
- Where do their axons end?
* **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**
39
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?
* 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)
40
What do primary sensory neurones do?
- Where is the cell body found?
- Where does the axon terminate?
- What types of neurones could these be?
* 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**
41
What do second order neurones do?
- Where is the cell body found?
- Where does the axon terminate?
* 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
42
What do thalamic neurones (third afferent) neurones do?
* Where is the cell body found?
* These send information from **thalamus** to **somatosensory cortex**
* Thalamus --\> essentially a somatosensory cortex relay
* **Cell body** is found in the **thalamus**
43
Which **sensory modalities** are carried by the **spinothalamic tract**?
* **Pain** (nociception)
* **Temperature**
* **Touch (non-discriminative touch)**
44
What are the 2 somatosensory pathways in the spinal cord?
* Spinothalamic Tract
* Dorsal Column/Medial Lemniscus System
45
Where are (pain) collaterals given off to the reticular formation during ascent to the thalamus?
- Why is it important?
* Many CNS neurones have **axons** with **terminals** in **more than 1 nucleus**
* Nociception --\> response to b**urns / 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**
46
What does the reticular formation do?
* Keeps you **awake/alert**
* Other **things**
**NB**: Pain fibres send collaterals to the reticular formation
47
What are the 2 types of pain fibres?
* C-fibres (slow)
* A-delta (fast)
48
Why is the thalamus important in the context of communication with the cortices?
* 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**
49
Describe the general pathway of the spinothalamic tract
* **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_**
50
What are the sensory modalities of the **dorsal column / medial lemniscus system**.
* 2-Point Discrimination
* Conscious Propioception
* Vibration Sense
51
What is the main difference between the **dorsal column / medial lemniscus pathway** and the **spinothalamic tract**?
* 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
52
What is discriminative touch?
- How can we test it?
- What is the sensitivity of the palm compared to the back of your hand?
* **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
53
What is conscious propioception?
* 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
54
What is unconscious propioception?
* This is **propioception** that goes to the **_cerebellum_** which has **nothing** to do with **conscious**
55
Give 2 reasons why propioception is helpful?
1. Helpful in reflexes
2. Letting you know about your surroundings (conscious propioception)
56
What is the difference between conscious and unconscious propioception?
* **Conscious** --\> you know about it --\> goes to the **cerebral cortex**
* **Unconscious** --\> you do not know about it --\> goes to **cerebellum**
57
How do you test for vibration sense?
* There is **_no_** **distinct** **vibration** **sense**
* Place **vibrating** **object** onto a **bony prominence** & **play vibrating tune**
* See if they can detect it
58
Describe the **general pathway** of the **dorsal column / medial lemniscus pathway**.
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
What are the main similarities & differences between the **spinothalamic pathway** & **dorsal column / medial lemniscus pathway**?
60
Where do C-fibres terminate in the dorsal horn?
* Lamina 1 or 2 (usually 2)
61
Where is the spinothalamic tract located in the spinal cord?
* Ventro-Lateral White Matter
62
What does the secondary neurones of the spinothalamic tract do?
* 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
Where does the second order neurone of the spinothalamic pathway pass the midline relative to the central canal?
* It passes **anterior** to the **central** **canal**
64
Where are the locations of the following in the spinal cord:
* Spinothalamic Tract ....
* Dorsal Columns .....
* Corticospinal Tract ....
* **Spinothalamic Tract -**-\> Ventro-Lateral
* **Dorsal Columns** --\> Dorsal
* **Corticospinal Tract** --\> Dorso-Lateral
65
What are the 2 parts of the dorsal column called?
* 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
Where does the fasciculus gracilis get its neurones from?
- Where is it found
* Lower Limb
* Found on the medial side
*
67
Where does the fasciculus cuneatus get its neurones from?
* **Upper Limb**
* Found on the **lateral** side
68
At what level is the **fasiculus** **cuneatus** seen in the dorsal column?
* 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
Which one is medial the cuneatus or gracilis?
* **_Gracilis_** --\> from **Lower** **Limb** --\> is **Medial**
* **Cuneatus** --\> is **added** **onto** the **outside** at **T6**
70
How does the dorsal column travel
* Neurones stay on the same side
* Travels up to dorsal nuclei
* This is in the medulla
71
Where in the brainstem is the dorsal column & spinothalamic tract in a similar position?
* **Lower Medulla** (where decussation takes place)
72
Summary view of the 2 somatosensory pathways.
73
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?
* 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
What does the spinothalamic tract do at the upper closed medulla level?
* Simply **runs** **through** the **closed medulla** going on to the **thalamus**
75
What does the cerebral cortex do with the somatosensory inputs?
* **Modulates** Inputs --\> then decides what you **perceive** (feel) and **not feel**
76
Can you see the fasiculus gracilis & cuneatus on the brainstem surface?
* 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
At what level does the 4th ventricle begin?
* **Dorsal** to the **_OPEN_** **MEDULLA**
* This is where the **central** **canal** has **_opened_** into the **4th ventricle**
78
What is found at the level of the open medulla?
* Inferior Olivary Nucleus
* Corticospinal Tract (Pyramids)
* Medial Lemniscus
* 4th Ventricle (back)
* Inferior Cerebellar Peduncle
* Spinothalamic Tract (similar posiiton as spinal cord)
79
Briefly describe the first synapse for the dorsal column & spinothalamic tract
* **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
What are the changes in location for the spinothalamic tract & medial lemniscus tract going from the medulla to the pons?
* They become closer together in the pons
* **Medial Lemniscus** --\> MEDIAL (flattened out)
* **Spinothalamic Tract** --\> LATERAL (but moved in)
81
At what levels is the 4th ventricle found?
**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
Where is the location of the **corticospinal** **tract** in the **lower** **pons**?
* Broken up into bundles
* Ventral Part (basilar part)
83
Label the following
84
What does the red nucleus give rise to?
* **Rubrospinal Tract**
* It is a **motor** **nucleus**
85
What is the superior colliculus important for?
Eye movements & (some) visual reflexes
86
What is the **periaqueductal grey** important for?
- Where is it found?
* 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
What is the affect of adrenaline on pain?
* Brain controls pain percept
* High adrenaline situations such as rugby match or war
* Adrenaline stimulates the periaqueductal grey --\> which causes profound analgesia
88
How does adrenaline affect pain sensation?
* 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
What is syringomyelia?
At what level is it usually found?
What can be the danger
* Fluid-filled cavity (syrinx) in the spinal cord
* Cervical Level
* Lower Cervical Levels innervatate Upper Limb
90
Which pathway is affected by syringomyelia?
Which sensory modalities does this carry?
* Spinothalamic Tract
* Nociception & Temperature & Non-Discriminative Touch (light)
91
What can cause **syringes** in the **spinal cord**?
1. Trauma
2. Unknown reasons
92
What can a syringomyelia damage and what does this lead to?
* **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
Which levels does a syringomyelia affect?
* Bilateral Effect
* Only the levels the syrinx is found
* It does not affect the ascending tract --\> just the crossing fibres
94
What can be done for someone who has a tumour in the pelvis causing a lot of pain? (pain cannot be controlled)
* **Ventrolateral Cordotomy**
These people are usually in a lot of pain and find it difficult to treat
95
What does ventrolateral cordotomy involve?
* **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
How is ablation carried out?
* 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
Why does pain sensation come back after ventro-lateral cordotomy?
* Not due to **nerve fibre regeneration (CNS)**
* There are **other pathways** which can **carry pain sensation too**
* These do **_not_** **usual**ly **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
Where is the parabrachial nucleus found?
* Rostral (upper) Pons
* Next to cerebellar peduncle
99
Where is the amygdala found and what is it important for?
* Found in the temporal lobe
* Important in terms of emotion
100
What is the spino-parabrachial pathway?
* 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
What does the basilar artery (ventral surface) supply?
* Bundles of Corticospinal Axons (get a branch)
* Medial Lemniscus
* Spinothalamic Tract
102
What transmitter is found in the raphe nuclei?
* Neurones using **monoamines** such as **5HT** found in **raphe** **nuclei**
103
Where is the raphe nuclei found?
* Midline of the Brainstem
Lowest Raphe Nucleu --\> found in the **Medulla**
104
What is another name for 5HT?
Seratonin
105
How does the raphe nuclei affect pain?
* **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
How does the periaqueductal grey & raphe nuclei work together?
* 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
Why can seratonin uptake inhibitor drugs be helpful in chronic pain?
* These **increase the levels of 5HT (seratonin) floating around** --\> therefore **_decreasing_** **pain** **input**
108
What is the effect of 5HT (seratonin) on pain?
* Decrease in pain input
109
What does the locus ceruleus do?
- What types of neurotransmitter does it send out?
Where does it send its axons to?
* Sends Noradrenaline (NA) axons all over the CNS
* It is one of many NA nuclei but it is the most prominent
110
Where is the locus cereleus found?
* Floor of the 4th Ventricle
* Pons
* Close to the Parabrachial Nuclei (a pain nuclei)
111
What is the effect of NA on pain?
What modulates its release?
* Powerful analgesic effect
* Modulated by the cerebral cortex
* NA has a bigger effect on pain than 5HT
112
Where do the locus ceruleus send its fibres?
Which part of the spinal cord does it affect?
* Down the spinal cord & all over the CNS
* **Controls** **pain** **transmission** in the **dorsal** **horn**
* It sends **non-discriminative informatio**n --\> thus it **modulates** **signals** **_all_** over the **CNS** & **Spinal cord** (not sending specific info)
113
Compare the effect of 5HT & NA
Where do they come from?
Summary of the system
* 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
What is leprosy and what can its effect be on pain?
* **Bacterial** **Infection**
* Affects neural response
* Neural response to it causes **analgesia**
* It causes the **loss** of **_peripheral_ sensory axons**
115
Which **cranial** **nuclei** receives all the **somatosensory information** in the cranial nerves?
* Trigeminal Sensory Nuclei (cranial nerve 5)
116
What are the 3 parts of the trigeminal sensory nuclei?
* **Midbrain (mesencephalic) nucleus**
* **Chief Nucleus**
* **Spinal nucleus** (continuous dorsally with superficial dorsal horn of spinal cord)
117
What are cranial nerves?
* Nerves which arise directly from the brain
118
Where are the cell bodies of the sensory fibres in cranial nerves found?
* Ganglia on the Cranial Nerves
119
Where is the trigeminal nuclei located?
* Deep cranial fossa
120
Why is the trigeminal nuclei important?
* Any cranial nerve which has somatosensory fibres in them will always end up in the trigeminal sensory nuclei
121
Where are the 3 parts of the trigeminal sensory nuclei found?
* **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
Describe the chief (sensory) prinicpal nucleus.
* 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
Describe the spinal nucleus of the trigeminal nerve
* 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
Describe the mesencephalic (midbrain) nucleus.
* 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
If you has a pain condition to do with the trigeminal nerve. Which part would the neurosurgeon ablate?
* Spinal Nucleus of the trigeminal nerve
* This contains lots of C-fibres
* Leads to trigeminal nerve analgesia
126
Summarise what each part is most important for:
## Footnote
**Midbrain Nucleus (mesencephalic)**
**Chief Nucleus**
**Spinal Nucleus**
* **Midbrain (mesencephalic) Nucleus** --\> JAW PROPIOCEPTION
* **Chief Nucleus** --\> DISCRIMINATIVE TOUCH (A-betas)
* **Spinal Nucleus** --\> C-FIBRES (nociception)
127
Other than ablation, what can cause trigeminal neuralgia?
* Can occur due to **blood vessels squashing** the **trigeminal nerve root**
* It can affect **1** or 2 **divisions** (unilaterally or bilaterally)
128
Which cerebellar artery can cause trigeminal neuralgia?
* **_Superior_ Cere**_bellar_** Artery**
It is found near the trigeminal roots and thus can give rise to trigeminal neuralgia
129
What pathogenic condition can affect the trigeminal nerve?
* Post herpetic neuralgia (more common than blood vessels)
130
Which virus can cause post herpetic neuralgia?
* Shingles Virus (Varicella Herpes Zoster)
131
Where does the shingles virus stay latent?
* Stays latent in **primary sensory neurones** for many years
132
What can trigger shingles?
What happens when virus is activated?
* 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
What are the 2 possible places where shingles can occur?
* Dorsal Root Ganglia
* Trigeminal Nuclei (aka ganglia)
If patient is **unfortunate** to have it in **trigeminal nuclei** --\> can lead to **trigeminal neuralgia** --\> meaning they wil**l 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
What are the effects of shingles?
* Damage along the dermatome
* Post-traumatic neuropathy
The changes caused by the virus means pain can be perceived all the time
