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Block 3 > Cranial Nerves > Flashcards

Cranial Nerves Flashcards

1
Q

How can you tell roughly where along a Cranial Nerve (CN) pathway damaged has occurred based on symptoms?

A

CNs often have more than one function e.g. CN V sensory nucleus has 3 regions that perceive different sensations (proprioception, light touch + pain/temp)

Loss of all these functions indicate damage to the actual CN, whereas loss of a single function (e.g. light touch) indicates damage to nuclei or supranuclear damage e.g. cortex

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2
Q

How do neurovascular structures enter and leave the skull?

A

Via cranial fossa foramen’s in the skull base anteriorly, medially and posteriorly (areas of potential CN compression)

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3
Q

What foramen do the meningeal arteries pass through?

A

Foramen ovale: accessory meningeal artery

Foramen spinosum: middle meningeal artery

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4
Q

What foramen does the internal carotid artery pass over?

A

Foramen lacerum

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5
Q

What foramen does the internal jugular vein pass through?

A

Jugular foramen

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6
Q

What pathology can foramens of the skull be involved in?

A

Skull fracture e.g. cribriform plate fracture

Meningeal tumours

Skull-base tumours

Pituitary adenoma which can compress CNII

Acoustic neuroma: tumour that develops on CNVIII + close to CNVII

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7
Q

When can Cranial Nerve (CN) IV become compressed?

A

If there is raised ICP because it is very delicate

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8
Q

What is Cranial Nerve (CN) I (olfactory nerve)?

A

What: sensory

Where: olfactory mucosa of superior nasal cavity through the cribriform plate to the olfactory bulb, tract and then cortex

Why: Sense of smell

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9
Q

What is special about Cranial Nerve (CN) I (olfactory nerve)?

A

Olfactory neurons can regenerate so unilateral anosmia may be due to a meningioma or anterior cranial fossa trauma

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10
Q

How would you clinically test Cranial Nerve (CN) I (olfactory nerve)?

A

Test each nostril individually with familiar scents e.g. orange, coffee - ask can you smell it? what is it? (not routinely tested in absence of other signs/issues)

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11
Q

What symptoms may patients experience if Cranial Nerve (CN) I (olfactory nerve) is affected?

A

Anosmia (lack of smell)

Phantosmia + Cacosmia (smelling things that aren’t there)

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12
Q

Why might patients experience symptoms affecting Cranial Nerve (CN) I (olfactory nerve)?

A 
Viral infection
Parkinsons/Alzheimer's (early sign)
Meningioma of olfactory groove
Anterior cranial fossa fracture (CSF rhinorrhoea may present)
Warning of seizure (may smell burning)
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13
Q

What is Cranial Nerve (CN) II (optic nerve)?

A

What: sensory

Where: from retina to optic tract, optic canal (sphenoid bone), lateral geniculate nucleus of thalamus + primary visual cortex of occipital lobe

Why: sight

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14
Q

How can you clinically test Cranial Nerve (CN) II (optic nerve)?

A 
Visual acuity (Snellen chart)
Visual fields
Pupil light reflex
Accomodation
Fundoscopy
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15
Q

What does the pupillary light reflex test?

A

Functioning of retina, midbrain, CNII + CNIII

Shining light in 1 eye should make both pupils constrict/contract (consensual light reflex) due to bilateral distributions of brainstem fibres

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16
Q

What is the Cranial Nerve (CN) III (oculomotor nerve)?

A

What: motor + parasympathetic

Where: oculomotor nucleus (midbrain) to cavernous sinus, superior orbital fissure, 4/6 extraocular eyeball muscles

Why: move eyeball + eyelid and constrict pupils

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17
Q

What are venous cavernous sinuses?

A

Pockets of venous blood on either side of sella turcia (containing pituitary) that have the internal carotid artery and 5 CNs passing through (CN III, IV, VI, Va + Vb)

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18
Q

What can happen as structures pass through the venous sinuses?

A

CNs and internal carotid artery can be compressed or affected by a bacterial infection tracking into sinus - infection can cause cavernous sinus thrombosis in attempt to stop infection spread

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19
Q

Where does Cranial Nerve (CN) III (oculomotor nerve) originate?

A

In midbrain near to its parasympathetic Edinger-Westphal nuclei and motor/parasympathetic fibres exist the brainstem via interpeduncular fossa

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20
Q

What does Cranial Nerve (CN) III (oculomotor nerve) supply?

A

Motor supply to 4 muscles that move eye: superior, inferior + medical recti and inferior oblique

Muscle that opens eyelid: levator palpebrae superioris

Sphincter pupillae (lens accommodation) + ciliary body (constricts pupils)
)
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21
Q

Where can Cranial Nerve (CN) III (oculomotor nerve) lesions occur?

A 
Midbrain (near parasympathetic nuclei)
Interpeduncular fossa
Posterior cerebral artery
Cavernous sinus
Superior orbital fissure
Ischaemia
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22
Q

What symptoms might Cranial Nerve (CN) III (oculomotor nerve) lesions cause?

A

Complete ptosis on affected side
Exotropia
Dilated non-reactive pupil
Diplopia (vertical/horizontal)

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23
Q

What is the Cranial Nerve (CN) IV (trochlear nerve)?

A

What: motor

Where: trochlear nucleus (lower midbrain) to cavernous sinus, superior orbital fissure + 1 extraocular eyeball muscle (superior oblique - looped through pully/trochlea hence nerve name)

Why: move eyeball (depression)

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24
Q

What is special about Cranial Nerve (CN) IV (trochlear nerve)?

A

Only CN to emerge from dorsal side of brainstem and to decussate before it emerges from the brainstem

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25
Q

What symptoms can a Cranial Nerve (CN) IV (trochlear nerve) lesion cause?

A

Upward deviation + extorsion (outward rotation of eye)

Vertical diplopia (worst when looking down)

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26
Q

What is Cranial Nerve (CN) VI (abducens nerve)?

A

What: motor

Where: abducens nucleus (lower pons) to cavernous sinus, superior orbital fissure (middle cranial fossa) to 1 extraocular eyeball muscle (lateral rectus)

Why: move eyeball laterally

27
Q

What Cranial Nerves (CNs) exit the brainstem via the pontomedullary junction?

A

VI (abducens)
VII (facial)
VIII (vestibulocochlear)

28
Q

When is Cranial Nerve (CN) VI (abducens nerve) at risk of compression?

A

Raised ICP (quite exposed as it turns upwards)

Internal carotid artery aneurysm in cavernous sinus

29
Q

What symptoms will present if a patient has a Cranial Nerve (CN) VI (abducens nerve) lesion?

A

No lateral eye movement - eyes rested in adducted position (convergent squint)

Horizontal diplopia (worst when looking toward affected side)

30
Q

What is Cranial Nerve (CN) V (trigeminal nerve)?

A

What: sensory + motor

Where: trigeminal sensory nucleus (spans entire brainstem) + motor nucleus (pons) to lateral pons, trigeminal nucleus, through cavernous sinus (CN Va + Vb), to facial sensation (cornea, anterior 2/3rds tongue + teeth) + muscles of mastication

Why: sensory to face + chewing

31
Q

What are the divisions of Cranial Nerve (CN) V (trigeminal nerve) and what foramen do they use to leave the cranium?

A

Va (ophthalmic): superior orbital fissure

Vb (maxillary): foramen rotundum

Vc (mandibular): foramen ovale

32
Q

Where should you not test Cranial Nerve (CN) V (trigeminal nerve) function? Why?

A

Angle of the mandible as this is innervated by cervical nerves instead

33
Q

What are the 3 large sensory territories of Cranial Nerve (CN) V (trigeminal nerve)?

A

All supply anterior half of head

Va: from vertex of head to angle of eye/side of nose

Vb: from angle of eye/side of nose to angle of mouth

Vc: from angle of mouth to tragus + point of chin

34
Q

Where does the motor nerve component of Cranial Nerve (CN) V (trigeminal nerve) come from?

A

A small motor only nucleus of the pons and the fibres exist next to sensory CNV fibres from lateral pons accompanying the mandibular division to muscles of mastication

35
Q

What do you clinically test the motor part of Cranial Nerve (CN) V (trigeminal nerve)?

A

Bite down on tongue depressors and look at tooth mark impression (is it even?)

Clench teeth + feel is masseter/temporalis contract

Open mandible

36
Q

What symptoms will be shown if there is a Cranial Nerve (CN) V (trigeminal nerve) motor lesion?

A

Exaggerated jaw jerk in UMN lesions (hyper-reflexia)

Mandible will deviate toward weak side due to opening action of medial pterygoid muscle

37
Q

Why do Upper Motor Neuron (UMN) lesions how hyper-reflexia?

A

In normal working reflexes, the reflex occurs within a LMN spinal cord loop and if UMNs are not working to moderate these loops via Renshaw cells then the reflex loops are in overdrive due to LMNs working too well + UMN not being able to moderate it

38
Q

What are the different sensory divisions of the Cranial Nerve (CN) V (trigeminal nerve)?

A

Proprioception

Touch

Pain/temp

39
Q

What is Cranial Nerve (CN) VII (facial nerve)?

A

What: motor, special sense + parasympathetic

Where: facial nucleus + superior salivatory nucleus (pons) to internal acoustic meatus, facial canal, stylomastoid foramen, muscles of facial expression (5 branches), salivary/lacrimal glands + taste to anterior 2/3rds of tongue

Why: facial expression, taste + secretomotor

40
Q

Where does the lessor petrosal nerve exist the cranium?

A

Foramen ovale

41
Q

Where does the meningeal nerve exit the cranium?

A

Foramen spinosum

42
Q

Once in the parotid gland, what 5 main branches does the Cranial Nerve (CN) VII (facial nerve) give off?

A
  1. Temporal
  2. Zygomatic
  3. Buccal
  4. Marginal mandibular
  5. Cervical
43
Q

How does the Cranial Nerve (CN) VII (facial nerve) motor fibres innervate the face?

A

UNEQUALLY travelling in corticobulbar tract: upper face (L + R) receives bilateral innervation whereas lower face just receives contralateral innervation

44
Q

How might a patient present if there is a Cranial Nerve (CN) VII (facial nerve) motor lesion?

A

UMN lesion e.g. Stroke: spare forehead - lower facial palsy on contralateral side

LMN lesion e.g. Bells Palsy: full ipsilateral facial palsy

45
Q

What is Cranial Nerve (CN) VIII (vestibulocochlear nerve)?

A

What: special sense

Where: cochlear + vestibular nucleus (pons) to internal acoustic meatus into petrous portion of temporal bone + cochlea and vestibular apparatus

Why: hearing + balance

46
Q

How do you test Cranial Nerve (CN) VIII (vestibulocochlear nerve) function?

A

Balance: test if patient complains of vertigo episodes using Hallpike Manoeuvre - +ve test produces vertigo rotatory nystagmus toward affected side

Hearing: Rinne + Weber test

47
Q

What is the Cranial Nerve (CN) IX (glossopharyngeal nerve)?

A

What: motor, sensory, parasympathetic, special sense + visceral afferent

Where: inferior salivatory, nucleus ambiguous, nucleus solitarius (lateral medulla) through jugular foramen to pharynx, parotid gland, tongue + chemo/baroreceptors

48
Q

What is the Cranial Nerve (CN) X (vagus nerve)?

A

What: motor, sensory, parasympathetic, special sense + visceral afferent

Where: dorsal motor (nucleus ambiguous + nucleus solitaries) of lateral medulla through jugular foramen to muscles of palate, pharynx, larynx, parotid gland + tongue

49
Q

What muscles of the pharynx does Cranial Nerve (CN) X (vagus nerve) supply?

A

Pharyngeal constrictors: palatopharyngeus, salpingopharyngeus, palatoglossus + levator veli palatine

50
Q

What muscles of the larynx does Cranial Nerve (CN) X (vagus nerve) supply?

A

All intrinsic muscles of larynx, cricothyroid + upper oesophagus

51
Q

Where does the right recurrent laryngeal nerve recur under?

A

R subclavian artery before it comes up to larynx to innervate all muscles except cricothyroid + sensory innervation below vocal folds

52
Q

How does the Cranial Nerve (CN) X (vagus nerve) supply the larynx?

A

Forms a superior laryngeal nerve which splits into internal (sensory above vocal folds) + external (motor to cricothyroid)

53
Q

How do you test Cranial Nerve (CN) X (vagus nerve) function?

A

Test motor and sensory together via the gag reflex

54
Q

What is the Cranial Nerve (CN) XI (accessory nerve)?

A

What: motor

Where: nucleus in C1-5 spinal cord entering cranium via foramen magnum then exits cranium via jugular foramen to sternocleidomastoid (SCM) + trapezius

Why: move head + shoulders

55
Q

How do you test Cranial Nerve (CN) XI (accessory nerve)?

A

Shrug shoulders + axial rotation of neck to feel SCM (can do against Drs hand to test weakness too) - SCM weakness can sometimes lead to head turning to weak side at rest

56
Q

What might cause a Cranial Nerve (CN) XI (accessory nerve) lesion?

A

Neck surgery
Trauma
Traction injury

57
Q

What is the Cranial Nerve (CN) XII (hypoglossal nerve)?

A

What: motor

Where: hypoglossal nucleus (ventral medulla) through hypoglossal canal to tongue muscles (EXCEPT palatoglossus)

Why: tongue movement

58
Q

How do you test Cranial Nerve (CN) XII (hypoglossal nerve)?

A

Protrude tongue - if lesioned it will deviate TOWARDS the weak side (LMN lesions lead to unilateral weakness)

Look for tongue muscle wasting/fasciculation

59
Q

What does Cranial Nerve (CN) X (vagus nerve) do?

A

Motor: muscles of palate, pharynx, larynx
Sensation: laryngopharynx, ear
Parasympathetic: heart, lungs, GI tract
Special senses: swallowing, vocalisation, taste
Visceral afferents: autonomics

60
Q

What does Cranial Nerve (CN) IX (glossopharyngeal nerve) do?

A

Motor: stylopharyngeus muscle
Sensation: pharynx, auditory tube, middle ear + chemo/baroreceptor from carotid body + sinus
Special senses: taste to posterior 2/3rd of tongue
Parasympathetic/autonomic: parotid gland
Visceral afferents

61
Q

How does the pupillary light reflex work?

A
  1. CN II: some retinal cells + afferent info to PTN
  2. PTN linked to eachother by PC + to both EWN by interneurons
  3. Pre-ganglionic PS fibres enter CN III + synapse in ciliary ganglion
  4. Post-ganglionic PS fibres of CN III in short ciliary nerves enter iris + control sphincter pupillae
62
Q

What might have occurred if just one function of a Cranial Nerve (CN) II (optic nerve) is not working, what should you do?

A

Think about where the functions are separate e.g. nuclei, lens of eye etc.

63
Q

What is the difference between the direct and consensual light reflex?

A

Direct: some CNs go directly back to nuclei without decussating (reflex occurs in 1 ipsilateral eye)

Consensual: bilateral distribution of brainstem fibres that decussate (reflex occurs in both eyes even if only 1 is stimulated by light)

Block 3 (40 decks)

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