Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

2 - HNA > The Cranial Nerves > Flashcards

The Cranial Nerves Flashcards

1
Q

Importance of testing cranial nerve function

A
  • Localise site of lesions
  • Gauge function in unconscious patients
  • Can test bilaterally, sensory and motor function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Test: CN I

A

Damage: fracture of anterior cranial fossa causes anosmia can substantially affect ‘taste’. CSF rhinorrhoea major problem - infection.

  • Rarely tested
    • Nerves continually replaced
  • Close one nostril, ensure airway is clear
  • Test detection of smell with non-irritant substance (peppermint/perfume)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Test: CN II

A

Visual Fields:

  • Binocular: cover one eye to test other
  • Test: detect moving object (e.g. finger)
  1. Optic nerve: monocular anopia
  2. Optic chiasm: bitemporal hemianopia
    • E.g. pituitary tumour
  3. Optic tract: homonymous hemianopia

Simple function: pupillary light reflex

NB: more complex problems can be revealed: e.g. neglect of half the visual field results from contralateral parietal lobe lesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Test: foveal vision

A
  • Can be affected in macular degeneration & diabetic retinopathy
  • Peripheral vision remains, lose fine detail
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Test: visual acuity

A

Snellen chart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Discuss examination of the optic fundi

A
  • Using ophthalmoscope - see optic nerve head & retinal blood vessels
  • Papilloedema: enlarged & ‘wooly’ optic disk
    • Raised intracranial pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Test: CN III

A

Pupillary light reflex: tests CN II (afferent) & CN III (efferent - parasympathetic):

  • Can be tested in unconscious patients
  • Shine light in one eye - both pupils should constrict (consensual response)
  • Brainstem reflex
  • Can be abolished by damage due to raised intracranial pressure or physical stretch
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Eyelid innervation

A
  • CN III innervates LPS, sympathetic hitchhiking innervate superior tarsal muscle (raise eyelid)
  • Damage to III gives complete ptosis
  • Sympathetic loss (e.g. Horner’s) - partial ptosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Testing CNs III, IV, VI (general)

A

Extraocular muscles work synergistically

  • Inspect eye position at rest
  • Look for non-consensual movement/nystagmus

Accommodation/convergence reflex:

  • Look in distance then focus on near object
  • Eyes converge (medial recti) & pupils constrict

Damage due to brainstem artery aneurysm, cavernous sinus disease, tumours, strokes, raised intracranial pressure

NB: get diplopia & tilting head to compensate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

CN III lesion

A
  • Complete ptosis
  • Fixed dilate pupil with lack of accommodation
  • Inability to look up/medially (down & out)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

CN IV lesion & test

A
  • Eye turned medially (adducted)
  • Diplopia when looking down
  • Test by looking down and in to exclude inferior and lateral rectus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

CN VI lesion

A
  • Most commonly damaged
    • 1st damaged in raised intracranial pressure
  • Squint & diplopia with inability to abduct eye
    • Adducted at rest
  • Test: ask patient to follow finger moving side to side in horizontal plane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Test: CN V (general)

A
  • Facial sensation, light touch with cotton wool:
    • Forehead: Va
    • Medial cheek: Vb
    • Chin: Vc
  • Corneal reflex: aversive, rapid, involuntary response blink to touching cornea
    • Brainstem reflex (Va - nasociliary afferent, VII efferent)
  • Herpes zoster can map out divisions
  • Damage to roots = anaesthesia over respective areas: anterior scalp, skin, cornea, conjunctiva, mucosa of nose & mouth, general sensation to anterior two-thirds of tongue
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Test: CN Vc

A
  • Motor branches to muscles of mastication
    • Feel bulk of temporalis/masseter on firm closing
    • Open against resistant (lateral pterygoid)
  • Damage: tumours (middle CF), stroke
    • Deviation to weak side (CL to lesion)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Complications of testing CN V with example

A
  • Many autonomic fibres hitchhike
    • S which reach head via blood vessels
    • PS emerging with CNs III, VII, IX, X
  • E.g. lingual branch (Vc) lesions peripherally can cause loss of taste to anterior 2/3 of tongue & salivation depending on site of lesion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Test: CN VII

A

Test motor fibres

  • Raise eyebrows
  • Screw up eyes
  • Smile
  • Squeeze lips together & blow out cheeks
  • Bare teeth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

CN VII lesions

A

Symptoms depend on location:

Stroke (‘upper motorneuron lesion):

  • Loss of muscles of facial expression BUT forehead sparing
    • Bilateral innervation of frontalis by brain

Bell’s Palsy - inflammation at stylomastoid foramen

  • Paralysis of facial muscles, no forehead wrinkles, excessive tear production, dribbling

Lesions in middle ear:

  • Affects chorda tympani - loss of taste (ant 2/3) & secretion by sub-lingual/mandibular glands
  • Hyperacusis (loss of stapedius)

More proximal in temporal bone: acoustic neuroma

  • Dry eyes + the above
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Test: CN VIII

A

Hearing:

  • Conductive vs sensorineural deafness
    • Rinne’s & Weber test

Balance:

  • Postural stability with eyes closed
  • Irrigation of ear canal with warm/ice-cold water causes nystagmus

NB: VIII afferents to oculomotor efferents allows both to be tested, in unconscious patients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

CN VIII lesion

A
  • Dizziness & nausea
  • Vestibulo-ocular reflexes keep eyes pointing in fixed direction when head moves
    • Gives Dolls-eye reflex
    • Gaze shouldn’t move if head tilted
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Test: CNs IX, X, XI

A

Best considered as a group, damage rarely individual

IX, X:

  • Gag reflex: brisk stimulation of posterior tongue/oropharynx - IX afferent, X efferent
    • Can be tested in unconscious patients

X:

  • Patient says ‘aah’ uvula should move up/down but not deviate from midline
  • Coughing tests closing of vocal cords (recurrent laryngeal)

XI:

  • Turning head against resistance or shrugging
    • Test sternocleidomastoid & trapezius
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

CNs IX, X, XI lesions

A
  • Inflammation oropharynx/tonsillitis: referred pain to middle ear (CN IX)
  • X - affect speech. Cord adducted in partial lesions, in mid-position in complete lesions
  • Dysfunction of sensory/motor innervation of larynx/pharynx = major issues for swallowing
    • E.g. bulbar palsy
  • XI - rarely peripheral, can be neurological

NB: parasymp of X only important if lesion bilateral

22
Q

Test: CN XII

A
  • Look for wasting/fasciculation of tongue
  • Stick out tongue: deviation to side of lesion due to unopposed genioglossus on unaffected side
  • Damage most common following stroke
    • Central connections bilateral, many cases function recovers after time
  • Also vulnerable to tumours & penetrating trauma
23
Q

Path of CN VII

A
  1. Arises as two roots
    • Large motor root
    • Smaller nervus intermedius (parasympathetic & sensory)
  2. Enter IAM & join in the facial canal (PTB)
  3. Turn posteriorly on medial wall of middle ear
    • Forms geniculate ganglion
  4. Runs inferiorly on posterior wall of middle ear
  5. Exits skull via stylomastoid foramen
  6. Enters parotid giving its terminal branches
24
Q

Branches of VII in middle ear

A
  1. Greater petrosal nerve (geniculate ganglion)
    • Parasympathetic to lacrimal gland (via PPG)
  2. Nerve to stapedius
    • Dampens vibrations
  3. Chorda tympani (to tongue via lingual n.)
    • Taste & parasympathetic to submandibular & sublingual glands
25
Q

Branches of VII before parotid gland

A
  1. Nerve to occipitalis
  2. Nerve to stylohyoid
  3. Nerve to posterior belly of digastric
26
Q

Branches of VII in parotid gland

A
  1. Temporal
    • Frontalis, orbicularis oculi
  2. Zygomatic
    • Muscles of eyelid
  3. Buccal
    • Buccinator, orbicularis oris, muscles of external nose
  4. Mandibular
    • Muscles of lower lip & chin
  5. Cervical
    • Platysma
27
Q

Describe CN II

A

Optic nerve - purely sensory, path:

  • Axons originate from the retinal cells
  • Partial decussation at optic chiasma
  • Optic tracts continue to LGN

NB: CN II is an outgrowth of the brain ⇒ covered in meningeal layers which pierce sclera.

A small subarachnoid space means increased intracranial pressure is visualised by papilloedema

28
Q

Path of CN III

A
  1. Exits midbrain, pierces roof of cavernous sinus
  2. Runs in lateral wall of sinus
  3. Splits into two divisions when leaving sinus
    1. Superior division (SOF): LPS, superior rectus
    2. Inferior division (tendinous ring): rest
29
Q

Discuss the parasympathetic fibres of CN III

A
  • For ciliary muscles and sphincter pupillae
  • Carried in inferior division
  • Fibres leave to reach ciliary ganglion
    • Post-ganglionic leave as short ciliary nerves
30
Q

Nerves running in the cavernous sinus

A

Lateral wall:

  • III, IV, Va

NB: VI runs in sinus, lateral to ICA

31
Q

Path of CN V

A
  • Leaves brainstem as two roots (sensory & motor)
    • Sensory is larger, cell bodies form trigeminal ganglion (branches come from ant edge)
    • Motor root is smaller, joins Vc
  • Pass forwards under tentorium cerebelli through oval opening in dura mater at trigeminal impression (apex of PTB)
32
Q

Branches of Va

A
  • Frontal: skin on forehead & ant. 1/2 of scalp
    • 2 branches: supratrochlear & supraorbital
  • Lacrimal: skin of upper eyelid
    • Carry PS fibres: PPG → lacrimal ganglion
  • Nasociliary: ethmoidal & sphenoidal sinuses, root of the nose
    • Gives long ciliary nerves:
      • Sensation to cornea
      • Sympathetics to dilator pupillae

NB: Va distributes sympathetic fibres from internal carotid plexus to vessel, orbit, sweat glands of forehead & dilator pupillae

33
Q

Branches of Vb

A
  • Zygomatic: skin of lateral forehead & cheek
    • 2 branches: zygomaticotemporal & zygomaticotemporal
  • Ganglionic: branches to PPG
  • Infraorbital: maxillary teeth
34
Q

Sensory branches of Vc

A
  • Buccal: mucous membrane/skin of cheek
  • Auriculotemporal: TMJ, skin of upper 1/2 ear, EAM, scalp above EAM
  • Inferior alveolar: mandibular teeth
    • Mental nerve: skin of lower lip
    • *motor fibres: nerve to mylohyoid
      • Mylohyoid & anterior belly of digastric
  • Lingual: ant. 2/3 of tongue, floor of mouth
    • Sensory fibres → submandibular ganglion
    • Joined by chorda tympani
35
Q

Motor branches of Vc

A
  • N. to medial pterygoid
    • + tensor tympani & tensor palati
  • Deep temporal n.
  • N. to lateral pterygoid
  • N. to masseter
36
Q

Sensory distribution of V on the face

A
37
Q

CN I summary

A
  • Olfactory nerve
  • Cribriform plate
  • Special sensory - smell
38
Q

CN II summary

A
  • Optic nerve
  • Optic canal
  • Special sensory - vision
39
Q

CN III summary

A
  • Oculomotor nerve
  • Superior orbital fissure

Somatomotor:

  • LPS, S/M/I recti, inferior oblique

Visceromotor:

  • PS to ciliary muscle & sphinctoer pupillae
40
Q

CN IV summary

A
  • Trochlear nerve
  • Superior orbital fissure
  • Somatomotor: superior oblique
41
Q

Va summary

A
  • Ophthalmic branch of the trigeminal nerve
  • Superior orbital fissure

Somatosensory:

  • Skin of forehead, ant. 1/2 scalp & upper eyelid
  • Cornea
  • Ethmoidal & sphenoidal sinuses, & root of nose
42
Q

Vb summary

A
  • Maxillary branch of the trigeminal nerve
  • Foramen rotundum

Somatosensory:

  • Skin of lateral forehead & cheek
  • Maxillary teeth
43
Q

Vc summary

A
  • Mandibular branch of the trigeminal nerve
  • Foramen ovale

Somatosensory:

  • Mucous membrane/skin of cheek & lower lip
  • TMJ, upper 1/2 ear, EAM, scalp above EAM
  • Mandibular teeth

Branchiomotor:

  • Muscles of mastication
44
Q

CN VI summary

A
  • Abducent nerve
  • Superior orbital fissure
  • Somatomotor: lateral rectus
45
Q

CN VII summary

A
  • Facial nerve
  • Internal auditory meatus/stylomastoid foramen

Somatosensory:

  • Ear & tympanic membrane

Special sensory:

  • Taste to the anterior 2/3 of the tongue

Branchiomotor:

  • Muscles of facial expression

Visceromotor:

  • PS to all glands of H/N except parotid
46
Q

CN VIII summary

A
  • Vestibulocochlear nerve
  • Internal auditory meatus
  • Special sensory: hearing and balance
47
Q

CN IX summary

A
  • Glossopharyngeal nerve
  • Jugular foramen

Somatosensory:

  • Posterior 1/3 of tongue, internal surface of tympanic membrane

Viscerosensory:

  • Pharynx, carotid body

Special sensory:

  • Taste to posterior 1/3 of tongue

Visceromotor:

  • Parasympathetics to parotid gland
48
Q

CN X summary

A
  • Vagus nerve
  • Jugular foramen

Somatosensory:

  • External ear

Viscerosensory:

  • Larynx & viscera

Special sensory:

  • Taste to epiglottis and valleculae

Branchiomotor:

  • Muscles of pharynx & larynx

Visceromotor:

  • PS to neck, thorax and abdomen
49
Q

CN XI summary

A
  • Spinal accessory nerve
  • Jugular foramen
  • Somatomotor: trapezius & sternocleidomastoid
50
Q

CN XII summary

A
  • Hypoglossal nerve
  • Hypoglossal canal
  • Somatomotor: muscles of tongue except palatoglossus

2 - HNA (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions