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B3 CAI > The Brainstem > Flashcards

The Brainstem Flashcards

1
Q

Describe the anatomical positioning of the brainstem

A

The brainstem is continuous with the thalamus and the cortex above, and the cerebellum posteriorly, with the spinal cord below

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2
Q

What is the reticular formation?

A

A network of neurons and poorly defined cell columns - responsible for core physiological processes and states of consciousness

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3
Q

How many cranial nerves are present on the brainstem?

A
  • 4x cranial nerves above the pons (though 1 and 2 are associated with the cortex)
  • 4x cranial nerves in/around pons
  • 4x cranial nerves in/around medulla
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4
Q

What are the significant anatomical features of the anterior midbrain?

A
  • The optic tract
  • Mamillary bodies (part of the limbic system)
  • Interpeduncular fossa (CN III emerging from within)
  • Cerebral peduncle (descending CST and CBT)
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5
Q

What are the signficant anatomical features of the anterior pons?

A
  • CN V
  • Cerebellar peduncle
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6
Q

Which cranial nerves peel off at the anterior pontomedullary junction?

A
  • CN VII
  • CN VIII
  • CN IX
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7
Q

What are the significant anatomical features of the anterior medulla?

A
  • The medullary pyramids
  • The pyramidal decussation point
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8
Q

Which cranial nerve arises from the posterior side of the brainstem?

A

CN IV (trochlear nerve)

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9
Q

What risks arise with the positioning of CN IV?

A

It makes the CN IV more vulnerable as it is long, thin and has an exposed trajectory

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10
Q

What are the main two blood supplies to the brain and the brainstem?

A
  • The internal carotid
  • The vertebral arteries
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11
Q

What is the contents of the brainstem?

A
  • 14 paired cranial nerve nuclei
  • Reticular system nuclei
  • Tracts to and from the spinal cord, cortex and cerebellum
  • Tracts connecting cranial nerve nuclei
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12
Q

More medial nuclei in the brain stem will primarily be…

A

Somatic motor

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13
Q

More lateral nuclei in the brainstem will primarily be…

A

Somatic sensory

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14
Q

What nuclei will you find in the central portion of the brain stem (central portion of each side, left and right)

A

Visceral motor and visceral sensory

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15
Q

What are the 5 functional fibre types cranial nerves can carry?

A
  • Somatic motor (+ branchial motor)
  • Visceral motor
  • Somatic sensory
  • Special sensory (taste, hearing, vision)
  • Visceral sensory
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16
Q

What 4 structures are at risk with a medial brainstem stroke?

A
  • Motor nuclei (CN III, IV, VI, XII)
  • Medial longitudinal fasciculus
  • Medial lemniscus
  • Motor corticospinal
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17
Q

What 4 structures are at risk with a lateral brainstem stroke?

A
  • Sensory nuclei (CNV)
  • Sympathetic nerves
  • Spinocerebellar tract
  • Spinothalamic tract (spinal lemniscus)
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18
Q

What would be the consequence of damage to the spinocerebellar tract?

A

Ipsilateral limb ataxia

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19
Q

What is the consequene of damage to the spinothalamic tract?

A

Contralateral loss of pain and temperature in the body

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20
Q

What is the consequence of damaging the sensory nucleus of CNV

A

Ipsilateral facial pain and temp sensation loss

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21
Q

What is the consequence of damaging sympathetic fibres in the brainstem?

A

Ipsilateral Horner’s syndrome

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22
Q

What is the consequence of damaging motor pathways in the brainstem (corticospinal)?

A

Contralateral weakness of Upper limb/Lower limb

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23
Q

What is the consequence of damaging the medial lemniscus in the brain stem (dorsal column)

A

Contralateral loss of vibration and proprioception in the body

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24
Q

What is the consequence of damage to the medial longitudinal fasciculus in the brainstem?

A

No ipsilateral eye adduction on lateral gaze

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25
Q

What is the consequence of damage to motor nuclei in the brain stem (CN III, IV, VI, XII)

A

Ocular or lingual palsy (depends on the level of lesion)

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26
Q

Describe the pattern of innervation for motor nuclei in the brainstem

A

Nearly all cranial nerve motor nuclei receive ipsilateral and contralateral upper motor neuron innervation from the motor cortexes, though the majority of innervation to a nuclei ccomes from the contralateral side

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27
Q

How does CN VII differ in innervation pattern to other motor nuclei in the brainstem?

A

The top part of the nucleus is associated with the top of the face and receives bilateral innervation

The bottom part of the nucleus is associated with the bottom of the face and receives unilateral innervation (only innervated by the contralateral cortex)

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28
Q

How would an upper motor neuron lesion of CN VII present?

A

A forehead sparing presentation as the upper face is innervated bilaterally, only the contralateral lower face would be without innervation

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29
Q

What is Bell’s palsy?

A

Complete paralysis of one side of the face, caused by a lower motor lesion of CN VII (when the ipsilateral and bilateral LMNs travel together as a single LMN in the periphery)

30
Q

What is Bulbar palsy?

A

Lower motor neuron lesion affecting CN VII - XII, before they have a chance to exit the brainstem

31
Q

What are the symptoms of Bulbar palsy?

A

Paralysis of pharynx, soft palate, larynx, tongue

Dysarthria, dysphonia, drooling, poor swallowing, prone to aspiration

Lower motor neuron signs

32
Q

What are some causes of Bulbar palsay?

A
  • Polio
  • Radiotherapy
  • Stroke
33
Q

What is Pseudobulbar palsy?

A

Bilateral corticobulbar tract disorder, upper motor neurone lesion

34
Q

What are the symptoms of Pseudobulbar palsy?

A

Similar symtoms to bulbar palsy but can develop spastic paralysis (UMN signs) of the pharynx and larynx, airway occlusion emergency

35
Q

What are potential causes of pseudobulbar palsy?

A
  • Head injury
  • Stroke
  • High brainstem tumour
36
Q

Which cranial nerve would be affected in an upper midbrain lesion?

A

CN III as it emerges from the upper midbrain

CN III motor nucleus damage = eye positioned down and out and ptosis

CN III EWN = loss of pupillary light reflex and accommodation

37
Q

What would be the presentation in a Left cranial nerve IV motor nucleus lesion?

A

Damage would lead to contralateral loss of superior oblique function as the CN decussates before leaving the posterior brainstem

Diplopia when reading and descending stairs, head tilted towards the side of damaged nucleus to compensate

38
Q

The spinal part of the CN V nuclei is utilised by which cranial nerves?

A
  • CN VII
  • CN IX
  • CN X
39
Q

Outline the path that all sensations from the face take to get to the cortex

A

Sensory information from the face will synapse on the CN V nuclei in the brainstem

2nd order trigeminal neurons will decussate at different levels and collectively become the Trigeminothalamic Tract (trigeminal lemniscus) that travels to the VPM nucleus of the thalamus

3rd order neurons continue towards the face region of the sensory cortex

40
Q

What is the Nucleus Solitarius?

A

A sensory that serves multiple cranial nerves (CN VII, IX, X)

It receives special sensory information from visceral afferent fibres

Taste: CN VII and IX

Visceral sensation (resp and GI system): CN IX and X

Baroreceptors and chemoreceptors (carotid body and sinus): CN IX and X

41
Q

What is the Dorsal Vagus Nucleus responsible for?

A

Parasympathetic vagus nerve outflow to the body (innervation to smooth muscle of trachea, bronchi, GI tract, cardiac muscle)

42
Q

What is the Nucleus Ambiguus responsible for?

A

The motor nucleus for CN IX, X and XI

Providing motor supply to branchial motor (skeletal) muscles of the Pharynx, Larynx and Palate

43
Q

What are the 3 main nuclei present in the medulla

A

Nucleus Solitarius

Dorsal Vagal Nucleus

Nucleus Ambiguus

Super Dense Area

44
Q

What are the four somatic motor nuclei and where in the brainstem are they?

A

III - Oculomotor - midbrain
IV - Trochlear - midbrain
VI - Abducens - pons
XII - Hypoglossal - medulla

45
Q

What are the 3 regions of the brainstem?

A

Midbrain

Pons

Medulla

46
Q

What connects the cerebellum to the:

midbrain

pons

medulla

A

midbrain - Superior cerebellar peduncle

pons - Middle cerebellar peduncle

medulla - Inferior cerebellar peduncle

47
Q

Why is the pons round in shape?

A

Due to the masses of fibres crossing it to enter the cerebellum.

48
Q

How do cranial nerves enter/leave the cranium?

A

Via foramen in the skull floor

49
Q

Label this diagram of the anterior brainstem

A
50
Q

Label this diagram of the posterior brainstem

A
51
Q

Which cranial nerves are close to the superior cerebellar and posterior cerebral arteries and are therefore at risk of compression if there is an aneurysm?

A

CN III and CN IV

52
Q

What is the blood supply to the brainstem?

A

The blood supply of the brainstem is derived entirely from branches of the vertebrobasilar circulation.

Midbrain

Basilar artery

Branches of basilar artery:

Posterior cerebral artery and its peduncular branch

Superior cerebellar artery

Posterior choroidal artery

Interpeduncular branches of the basilar artery

Pons

Branches of basilar artery:

Pontine arteries

Anterior inferior cerebellar artery

Superior cerebellar artery

Medulla

Posterior spinal artery

Anterior inferior cerebellar artery

Vertebral arteries

Branches of vertebral artery:

Posterior inferior cerebellar artery

Anterior spinal artery

53
Q
A
54
Q

How are the somatic sensory, visceral motor and visceral sensory, and somatic motor nuclei arranged in the brainstem?

A
55
Q

What are the 5 different fibre types that can be found in a cranial nerve?

A
56
Q

State which cranial nerve nuclei are somatic sensory, which are somatic motor and which are visceral motor and visceral sensory

A

S - (somatic) sensory, M - (somatic) motor, B - both visceral motor and visceral sensory

CN I: S ome

CN II: S ay

CN III: M oney

CN IV: M atters

CN V: B ut

CN VI: M y

CN VII: B rother

CN VIII: S ays

CN IX: B ig

CN X: B rains

CN XI: M atter

CN XII: M ore

57
Q

What are branchial motor fibres?

A

Somatic motor fibres that innervate skeletal muscles that developed from the pharyngeal arches.

58
Q

What structures are located in the lateral and medial medulla and pons? (HINT: rule of 4)

If blocked, what artery could knock out all the structures in the lateral part?

A
59
Q

Where does the corticobulbar tract descend from?

A

genu

60
Q

Describe innervation to CN VII motor nuclei?

A

The top part of the nucleus associated with the top of the face receives bilateral innervation (innervation from both sides of cortex)

The bottom part of the nucleus associated with the bottom of the face receives unilateral innervation (innervation by contralateral cortex)

61
Q

Consider a lesion at the lightning bolt. How would the patient present?

A

Stroke on motor cortex - left side will be weaker but still have some function

62
Q

An UMN lesion can be forehead sparing. What does this mean and why does it happen

A
63
Q

A LMN can cause Bell’s Palsy - paralysis on one side of your face. How can this happen?

A
64
Q

Where are UMNs and LMNs found?

A

The UMN is a motor neuron, the cell body of which lies within the motor cortex of the cerebrum, and the axon of which forms the corticobulbar and corticospinal tracts.

The LMNs, lying in the brainstem motor nuclei and the anterior horns of the spinal cord, directly innervate skeletal muscles.

65
Q

What can damage to CN III cause?

A

Eye positioned down and out at rest, and a full ptosis

66
Q
A
67
Q

What can damage to CN IV cause?

A

Contralateral loss of superior oblique function

Diplopia when reading and descending stairs; head tilted toward side of damaged nucleus to compensate

68
Q

Which nerves hitchhike on CN V sensory/spinal nucleus?

A

CN VII, IX and X

69
Q

Read this overview of brainstem nuclei

A
70
Q

What does the dorsal vagal nucleus supply parasympathetic innervation to?

A

Smooth muscle of trachea, bronchi, GI tract, cardiac muscle

B3 CAI (13 decks)

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