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Neuro > Cranial Nerves > Flashcards

Cranial Nerves Flashcards

1
Q

Central Nervous System

A

Brain and spinal cord
Carry sensory/ motor/ autonomic info between the brain and the head and neck
Collections of cell bodies = nuclei

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2
Q

What are collections of cell bodies in the PNS called?

A

Ganglia

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3
Q

Mnemonic to remember whether the cranial nerves are sensory, motor or both

A

Some Say Marry Money But My Brother Says Big Brains Matter Most

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4
Q

Which cranial nerves also carry parasympathetic signals?

A

III (oculomotor)
VII (facial)
IX (glossopharyngeal)
X (vagus)

3,7,9 and 10

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5
Q

Where are the cranial nerve nuclei for nerves III-XII?

A

In the brainstem (midbrain, pons and medulla oblongata)
Cells whose axons convey motor / efferent signals to periphery.

Some nerves share nuclei.

Some nerves with both motor and sensory components have a motor nucleus and a sensory nucleus

Parasympathetic fibres arise from specific nuclei in the brainstem

(beware this is v complicated!)

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6
Q

CN I

A

Olfactory nerve

Axons travel through cribriform plate
(olfactory bulb, tracts, temporal lobe)

Connection with limbic system

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7
Q

CN II

A

Optic nerve

Attached to brain not brainstem

(retina, primary visual cortex, calcarine sulcus, medial aspect of occipital lobe)

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8
Q

Optic chiasm

A

Nasal retinae decussates but info from temporal retinae remains ipsilateral.

Each optic tract contains fibres carrying info about the contralateral visual field

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9
Q

Testing CN II

A

Visual acuity (Swellen chart)
Visual fields
Pupillary light reflex
Fundoscopy (to see image at back of your retina)

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10
Q

Pupillary light reflex

A

Normally: both pupils constrict when light shone into either eye (direct and consensual)

Involves CN II (optic) and parasympathetic fibres in CN III (oculomotor)

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11
Q

CN III

A

Oculomotor nerve

Innervates MR, SR, IR, IO and LPS (extraocular muscles)

Parasympathetic nerves constrict pupil

Nuclei = midbrain
Nerves exit at junction between midbrain and pons
Close to PCA

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12
Q

Testing CN III

A

Test eye movements
Test pupillary light reflex
Test LPS

Bell’s Palsy
Lesion symptoms:
Ptosis
Lateral deviation of eye
Dilated pupil that doesn’t constrict

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13
Q

CN IV

A

Trochlear nerve
Innervates superior oblique
Lesions causes diplopia (double vision) on looking down

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14
Q

How to test CN IV

A

Ask to move eye medially and down

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15
Q

CN VI

A

Abducens nerve

Innervates lateral rectus

Nuclei in pons

Paralysis means not able to abduct eye on examination.

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16
Q

CN V

A

Trigeminal

Attached to pons
3 branches
ophthalmic, maxillary and mandibular

Mandibular is only one to carry motor fibres for mastication

17
Q

CN V sensory functions

A

Dra, face and scalp, cornea, nose and mouth.
Anterior 2/3 of tongue general sensation.

Carries proprioception from TMJ and mastication muscles

18
Q

Testing CN V

A

General sensation of face

Corneal reflex (both sensation of CN V and muscles of facial expression CN VII)
Gently touching cornea should result in blinking

19
Q

CN VII

A

Facial nerve

Sensory, motor and parasympathetic fibres

Attached to brainstem at pontomedullary junction

2 roots - medial (motor fibres) and lateral (sensory and parasympathetic fibres, the nervus intermedius)

20
Q

Facial nerve fibre types

A

Special sensory - anterior 2/3 of tongue

Motor - muscles of facial expression

Parasympathetic - lacrimal gland, submandibular and sublingual salivary glands

In parotid, facial nerve divides into 5 branches to innervate muscles in face

21
Q

Testing CN VII

A

Special sensory:
Ask about taste
Is the eye dry?

Motor:
Any sagging or asymmetry in face
Frown and raise eyebrows
Screw up eyes
Puff out cheeks
Smile

22
Q

CN VII Pathology

A

Bell’s Palsy - inflammation or nerve, related to viral infection

Tumours, inflammation of parotid gland, middle ear infection, fractures of temporal bone

23
Q

Damage to facial nerve

A

Stroke = affects primary cortex can cause facial weakness

Cell bodies of UMNs in motor cortex.

Axons travel to facial motor nuclei in pons. Cross midline and travel to contralateral facial motor nucleus in pons to synapse to LMN.

Lower part of face is only innervated by contralateral nucleus whereas upper part of face goes to both sides, both facial motor nuclei.

This means if UMNs injured on one side the the lower contralateral face is weak but the upper contralateral face is not weak as muscles are also innervated by unaffected side as both sides of motor cortex innervate one side of upper face.

Therefore, the forehead muscles are preserved.

However, if the facial nerve (LMN) is injured on one side, all the ipsilateral facial muscles are weak.

24
Q

CN VIII

A

Vestibulocochlear

Sensory nerve

Vestibular afferents:
Connections to spinal cord, cerebellum, nuclei of CN III, IV and VI, cerebral cortex.

Posture, balance, eye movements, conscious perception of position of head.

Cochlear afferents:

Primary auditory cortex (superior temporal gyrus)
Auditory association cortex (Wernicke’s area)

25
Q

Testing CN VIII

A

Testing cochlear component:
Covering each ear and whispering into opposite one
Rinne and Weber’s tests
Audiometry

Testing vestibular component:
Observing balance and gait
Caloric testing (uses temperature)

26
Q

Pathology of CN VIII

A

Acoustic neuroma (vestibular schwannoma)
Tumour, benign, compresses nerve, progresses to compress facial nerve

Hearing loss, dizziness, facial paralysis, facial pain.

27
Q

CN IX

A

Glossopharyngeal

Sensory, motor, parasympathetic

Attached to medulla via small rootlets

Taste - posterior 1/3 of tongue, general sensation of this area + pharynx, Eustachian tube

Afferents from carotid sinus (baroreceptors) and carotid body (chemoreceptors)

Parasympathetic –> parotid gland

28
Q

CN X

A

Vagus

Sensory, motor, parasympathetic

Attached to medulla via small rootlets

General sensation (pharynx, larynx, oesophagus, EAM, tympanic membrane)

Visceral afferents - thoracic and abdominal, parasympathetic

Afferents from aortic bodies and arch

Motor fibres = soft palate, pharynx, larynx

29
Q

Testing CN X

A

Hoarseness - sign of vocal cord paralysis
Nasal sound - sign of soft palate paralysis

Elicit gag reflex (afferent fibres are CN IX and efferent fibres are CN X)
Look for reflex contraction of the palate

Ask patient to say “ahhh” and look for elevation of palate
Unilateral lesion of CN X causes palate and uvula to deviate away from side of lesion .

30
Q

CN XI

A

Accessory nerve

Innervates sternocleidomastoid and trapezius

Cranial part: Rootlets from medulla, leaves via jugular foramen by joining vagus

Spinal part: from ventral horn, C1-C5.

Patient turns head against resistance
Look for symmetry, ask patients to shrug shoulders.

31
Q

Cn XII

A

Hypoglossal

Motor nerve for muscles of tongue

Arises from medulla, through hypoglossal canal

32
Q

Testing and Pathology of CN XII

A

Look for atrophy on tongue

Is there deviation of tongue to one side?

Nerve lesion means ipsilateral tongue muscles are paralysed.
Tongue deviates towards affected side.

Neuro (27 decks)

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