Brainstem and cranial nerves

Question 1

Brainstem

Answer 1

That part of the CNS, exclusive of the cerebellum, that lies between the cerebrum and the spinal cord

Question 2

Major divisions of the brainstem

Answer 2

• medulla oblongata
• pons
• midbrain

SITS IN POSTERIOR CRANIAL FOSAA

Question 3

Lateral medullary syndrome presentation

Answer 3

Thrombosis of vertebral artery or of PICA (posterior inferior cerebellar artery)

Symptoms:

• vertigo
• ipsilateral cerebellar ataxia
• ipsilateral loss of pain/thermal sense in face
• Horner’s syndrome=loss of sympathetic control resulting in droopy upper eyelid (ptosis), pinpoint pupils (miosis), lack of sweating of face (anhidrosis) and eyeballs sinking into bony cavity (enophthalmos)
• Hoarseness, difficulty in swallowing
• Contralateral loss of pain/thermal sense in trunk and limbs

Question 4

Lateral medullary syndrome symptom and structure links

Answer 4

BLOOD CLOT STOPS BLOOD SUPPLY TO LATERAL AREA OF THE MEDULLA OBLONGATA

In this area of the medulla oblongata there is:

• vestibular nuclei= results in vertigo (loss of balance perception)
• inferior cerebellar peduncle= loss of normal gait resulting in ataxia
• spinal nucleus of the trigeminal nerve= results in loss of pain/temp sensation
• nucleus ambiguus= results in hoarseness, swallowing difficulties and problems with normal speaking
• spinothalamic tract= results in contralateral loss of pain/thermal sense in the body
• sympathetic tract= loss of sympathetic innervation to eye area results in Horner’s syndrome

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Question 5

Midbrain structure

Answer 5

• MRI shows ‘mickey mouse’
• cerebral aqueduct only present in midbrain
• cerebral peduncles represent mickey mouse ears
• roof of midbrain at level of inferior colliculus
• black area represents substantia nigra (neuromelanin in dopaminergic cells projecting up to basal ganglia=pale substantia nigra is a key pathological find for Parkinson’s motor symptoms)

Question 6

Pons structure

Answer 6

• tranverse fibres are unique to the pons

- fourth ventricle observed once cerebellum is removed

Question 7

Upper medulla oblongata structure

Answer 7

• inferior olivary nucleus=distinctive wavy shape indicates upper medulla
• pyramids are obvious in medulla

Question 8

Lower medulla oblongata structure

Answer 8

• dorsal columns analogous to spinal cord

- identified by pyramidal decussation (fibres crossing over)

Question 9

General functional classification of cranial nerves

Answer 9

General Somatic Afferent (GSA)
-sensation from skin and mucous membranes 
General Visceral Afferent (GVA)
-sensation from GI tract, heart, vessels and lungs
General Somatic Efferent (GSE)
-muscles for eye and tongue movements
General Visceral Efferent (GVE)
-preganglionic parasympathetic

Question 10

Special functional classification of cranial nerves

Answer 10

Special Somatic Afferent (SSA)
-vision, hearing and equilibrium 
Special Visceral Afferent (SVA)
-smell and taste 
Special Visceral Efferent (SVE)
-muscles involved in chewing (mastication muscles), facial expression (facial muscles), swallowing,  vocal sounds and turning head (CN XI)

Question 11

Features of the posterior view of the brainstem

Answer 11

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Question 12

Features of the anterior view of the brainstem

Answer 12

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Question 13

Brainstem development

Answer 13

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Question 14

Order of the cranial nerves

Answer 14

I:Ooh->Olfactory
II:Ooh->Optic
III:Ooh->Oculomotor
IV:To->Trochlear
V:Touch->Trigeminal
VI:And->Abducens
VII:Feel->Facial
VIII:Very->Vestibulocochlear
IX:Good->Glossopharyngeal
X:Velvet->Vagus
XI:Ah->Accessory
XII:Heaven->Hypoglossal

Question 15

Olfactory nerve

Answer 15

• CN I
• Component fibres: sensory
• Structures innervated: olfactory epithelium via olfactory bulb
• Function: olfaction

Question 16

Optic nerve

Answer 16

• CN II
• Component fibres: sensory
• Structures innervated: retina
• Function: vision

Question 17

Oculomotor nerve

Answer 17

• CN III
• Component fibres: motor, parasympathetic
• Structures innervated: levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, inferior oblique, sphincter pupillae and ciliary muscles of the eyeball via the ciliary ganglion
• Function: movement of the eyeball, pupillary constriction and accommodation of the lens for near vision

Question 18

Trochlear nerve

Answer 18

• CN IV
• Component fibres: motor
• Structures innervated: superior oblique muscle
• Function: movement of the eyeball

Question 19

Trigeminal nerve

Answer 19

• CN V
• Component fibres: sensory, motor
• Structures innervated:
• Function:

Question 20

Abducens nerve

Answer 20

• CN VI
• Component fibres: motor
• Structures innervated: lateral rectus muscle
• Function:

Question 21

Facial nerve

Answer 21

• CN VII
• Component fibres: sensory, motor, parasympathetic
• Structures innervated:
• Function:

Question 22

Vestibulocochlear nerve

Answer 22

• CN VIII
• Component fibres: sensory, motor, parasympathetic
• Structures innervated:
• Function:

Question 23

Glossopharyngeal nerve

Answer 23

• CN IX
• Component fibres: sensory, motor, parasympathetic
• Structures innervated:
• Function:

Question 24

Vagus nerve

Answer 24

• CN X
• Component fibres: sensory, motor, parasympathetic
• Structures innervated:
• Function:

Question 25

Accessory nerve

Answer 25

• CN XI
• Component fibres: motor
• Structures innervated:
• Function:

Question 26

Hypoglossal nerve

Answer 26

• CN XII
• Component fibres: motor
• Structures innervated:
• Function: