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Head, Neck & Neuro > Session 5 - Cranial Nerves I - VII > Flashcards

Session 5 - Cranial Nerves I - VII Flashcards

1
Q

How many pairs of cranial nerves are there?

A

12

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2
Q

Where do the cranial nerves come from? What do they supply?

A

Relate to brain stem, arising from CNS.

Innervate structures in the head + neck.

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3
Q

What types of axons are carried by cranial nerves?

A 
General sensory
Special sensory
Motor
Autonomic
(a mix of the above, or only one type)
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4
Q

What is the brainstem?

A

Brain structure connecting the brain to (continuous with) the spinal cord.

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5
Q

What are the brainstems main functions?

A

Regulation of cardio-repiratory functions, and maintaining consciousness.
Ascending sensory, and descending motor fibres run through it.

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6
Q

What are the cranial nerve nuclei, where are most found?

A

Nuclei = collections of cell bodies of nerve fibres.

In the brainstem.

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7
Q

How many Cranial nerves come from each part of the brainstem?

A 
Forebrain = 2 CNs
Midbrain  = 2 CNs
Pons         = 4 CNs
Medulla    = 4 CNs
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8
Q

Name the two CNs from the forebrain.

A

Olfactory CN I

Optic CN II

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9
Q

What is the route, function and type of axons in the olfactory system?

A

Special Sense.
Olfactory > Cirbriform foramina > Olfactory bulbs > Olfactory tracts > forebrain

Function: Olfaction (smell)

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10
Q

How is olfaction tested?

A

Not formally tested.
“have you noticed any change in sense of smell”
Testing one nostril at a time, with salts, or any alternative etc.

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11
Q

What is loss of sense of smell called? What can cause it?

A

Anosmia

  • A common cold is most common.
  • Head injury (basilar skull fracture, shearing forces)
  • Intracranial tumours, at base of frontal lobes, could interfere.
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12
Q

What is the route of the optic nerve, and its function?

A

Special Sense.
(complex pathway, goes through optic canal to eye)

Function: Vision

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13
Q

How is the optic nerve clinically tested for problems?

A

Test one eye at a time.
Visual test (snellen chart, visual fields)
Test pupil response/ reflexes using torch

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14
Q

What can cause issues with the optic nerve? How is it visualised?

A

Optic disc can be seen with ophthalmoscope.
- Raised intra-cranial pressure can cause nerve to swell (as they carry an extension of the meninges).
(can be seen on ophthalmoscope)

  • Lesions involving retina or nerve can cause visual disturbances (affecting one eye)
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15
Q

What is the optic disc?

A

The point where the optic nerve enters the retina.

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16
Q

Where is vision processed in the brain? Why is the brainstem involved?

A

Visual pathway extends from retina towards primary visual cortex in occipital lobe.
Communication with brainstem allows reflexes, e.g. puillary reflex to light.

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17
Q

What are the two cranial nerves from the midbrain?

A

Oculomotor CN III

Trochlear CN IV

18
Q

What is the route, and types of axons in the oculomotor nerve?

A

Motor (no sensory)
Autonomic (parasympathetic)

Route: From midbrain through cavernous sinus (sides of sella turcica) through superior orbital fissure in oribit.

19
Q

What is the sella turcica?

A

A depression in the sphenoid bone containing the pituitary gland.

20
Q

What is the function of the oculomotor nerve?

A

Motor

  • Most extra-ocular muscles
  • LPS (Levator palpebrae superioris)

Autonomic

  • Sphincter pupillae (pupil)
  • Ciliary muscle - lens
21
Q

Why is the oculomotor nerve often compress with raised intracranial pressure?

A

Uncus of temporal lobe can slip/ move over tentorium cerebelli, which is in close proximity to the entry of the nerve, compressing it.

22
Q

Under compression, why would autonomic function be affected first in the oculomotor? What is a sign?

A

Due to the autonomic (parasymp.) fibres being on the outer part of the nerve. (motor are inner).
Fixed dilated pupil (blown).
(continued compression, will compromise motor)

23
Q

How is the oculomotor nerve CN III tested? What may be seen?

A

Inspect eyelids and pupils.
Test eye movements.
Pupillary light reflex.

Pupillary dilation and/or double vision
‘Down and out’ position of eyes, severe ptosis (eyelid droop)

24
Q

Which things can cause oculomotor nerve damage?

A
  • Raised IC pressure
  • Aneurysms
  • Vascular (2ndry to diabetes, hypertension/ often pupil sparing)
  • Cavernous sinus thrombosis
25
Q

What does ‘pupil sparing’ mean?

A

That the nerve damage/ compression is not affecting the pupillary response, but the eyelids, or other parts.

26
Q

What is the route, and functions of the Trochlear nerve CN IV?

A
  • Motor fibres.
    Route: Midbrain > Cavernous sinus > Superior orbital fissure.

Function: one extra-orbital muscle (superior oblique)

27
Q

Where does the trochlear nerve originate on the brainstem?

A

Emerges from the dorsal brainstem, has longest intracranial course.
(only CN to do so)

28
Q

How is the trochlear nerve CN IV tested? Whar causes and signs are there of damage?

A
  • Eye movements (more in session 6)

Signs: Diplopia (worse on downward gaze, when reading, or walking downstairs)

Causes: Head injury (most common), congenital palsies.

29
Q

What are the names of the four cranial nerves from the pons?

A

Trigeminal (V)
Abducens (VI)
Facial (VII)
Vestibulocochlear (VIII)

30
Q

What is the function of the trigeminal nerve?

What are its branches?

A

Main sensory nerve of the face.
Supplies muscles of mastication.

Split into three branches:
CN V 1 - Ophthalmic
CN V 2 - Maxillary
CN V 3 - Mandibular

31
Q

How is the trigeminal nerve tested?

A
  • Sensation to face (dermatomal areas)
  • Muscles of mastication
  • Corneal reflex (blink reflex when cornea stimulated, e.g. touch)
32
Q

Which clinical conditions can affect the trigeminal nerve?

A
  • Vulnerable to facial trauma
  • Trigeminal neuralgia: severe facial pain, unknown causes. (over 50s, fairly rare)
  • Shingles can affect the dermatomes.
33
Q

What effects can shingles have on the face/ eyes?

A

Will cover one dermatome.

Can cause corneal ulcers, if dermatome affected includes nerves to part of eye.

34
Q

How can a blow to the eye socket cause damage? How is it tested?

A

Blow causes increased intraorbital pressure.
This can damage the the infraorbital nerve.
Sensation would be reduced in the skin under the eyelid.

35
Q

What is the route and function of the Abducens nerve CN VI?

A
  • Motor Nerve only
    Route: through cavernous sinus > Superior orbital fissure.

Function: 1 eye muscle! > Lateral rectus

36
Q

How is the abducens nerve CN VI tested? What are some clinical signs/ causes?

A

Test eye movements. (more session 6)

  • Diplopia
  • Can be injured in > IC pressure.
37
Q

What is the route, type, and function of the facial nerve CN VII?

A

Motor fibres + Autonomic
Route: Through petrous part of temporal bone

Function:

  • Muscles of facial expression (5 branches)
  • Taste - anterior 2/3 tongue
  • Parasympathetic fibres to lacrimal + salivary glands.
38
Q

How is the Facial nerve CN VII tested?

A

Test the muscles of facial expression.
Test corneal reflex (efferent limb)
Taste (not usually tested)

39
Q

What is Bell’s palsy?

A

Idiopathic facial nerve palsy

40
Q

Which nerve do dentists inject anaesthetic into in order to perform tooth extractions? How does it work?

A

The area which relates to the mandibular foramen.

Numbs the lower gums, jaw, teeth.

41
Q

How would you check if someone had had a mandibular fracture?

A

Patient would present with numbness over the lip and the chin (teeth, lower gums).
Due to damage to the inferior alveolar branch of the mandibular nerver (itself a branch of the trigeminal), which also branches to the mental nerve (teeth/ lower gum).

42
Q

Why would a local anaesthetic cause numbness of the tongue?

A

Anaesthetic may travel to the lingual nerve via trigeminal.
Can cause numbness of tongue.
(does not affect taste)

Head, Neck & Neuro (7 decks)

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