Cranial nerves Flashcards
Name the cranial nerves
1 - olfactory 2 - optic 3 - oculomotor 4 - trochlear 5 - trigeminal 6 - abducens 7 - facial 8 - acoustic/vestibularcochlear 9 - glossopharyngeal 10 - vagus 11 - accessory 12 - hypoglossal
Which originate from the forebrain?
1 and II
Which originate from the medulla?
IX and XII
Which goes outside the head and neck?
Vagus
Opfactory nerve functions?
Smell
Damaged = impaired smell
Olfactory nerve origin? Where does it travel to?
Receptor cells in nasal epi
Travels to olfactory cerebral cortex
How to examine the olfactory nerve?
Change in smell or taste? Get pt to clear nose Hold one nostril closed and eyes closed Place recognisable scent under the nostril (e.g. coffee) Repeat with other nostril
What is anosmia? What does this indicate?
Loss of sense of smell (flu, nasal polyps)
Causes of anosmia?
Nasal congestion
Lesions - nose, cribriform plate of the ethmoid bone
Base of skull or frontal skull fracture
Nasal or frontal lobe tumour
Function of the optic nerve?
Vision
Damage = blindness in visual field
Where does the optic nerve travel?
From the retinal neuro-epithelium
Rods and cones activate the bipolar cells, synapsing on the ganglion cells in the retina
To: 2nd order neurones converge on the optic disc
Where does interpretation of vision occur?
Occipital cortex
How to test visual fields?
Tests for which part of vision works
Sit arms length and at eye level
Aim is to compare vision with the pts
Check left eye = pt covers right eye and you cover left eye and ask pt to look into your eye
Test for the blind spot with a red pin
Move wagging finger from periphery to the centre and get pt to tell them when they see your finger move
How to exam the optic nerve? (visual acuity)
Visual acuity - snellen chart
Pt 6 metres from chart
Pt covers one eye at a time
Record the lowest line the pt can read
Colour vision - ishihrara test
If not see snellen chart - see if they can see hand/finger moving and if not then test perception of light - if not = blind
How to record a fundoscopy? (do not worry about)
Pt gazes into distance, look at cornea (for ulcers), the iris and then the lens for a red reflex
If red reflex absent = cataracts
Optic disc - examine colour and edge
Causes of papilloedema?
Optic nerve conditions
- Inflam (optic neuritis) - MS, neuromyelitis optica
- Vascular - central retinal vein occlusion, ischaemic optic neuropathy
Intracranial conditions - raised intracranial pressure:
- Space occupying lesions
- CSF obstruction
- Venous obstruction: cerebral venous thrombosis
- Idiopathic intracranial hypertension
- Malignant hypertension
Causes of optic atrophy?
Primary:
- Leber’s OA
- Compressive lesions/tumours
- Toxic/nutritional - alcohol, tobacco, B12 def
2ndy:
- Following papilloedema
- Following optic neuritis/neuropathy
- Glaucoma
- Consecutive OA: 2ndry to disease of the retina or its blood supply
How to measure the light reflex?
What is dilation and constriction of the pupil? (pupillary reflexes)
Shine light in one eye and both pupils constrict
Pupil dilation: Symp control of radial muscles of iris
Pupil constriction: parasymp control of constrictor muscles
What is horners syndrome?
…..
Clinical syndrome Unilateral Associated with anhydrosis - reduced sweating on one side - a constricted pupil - drooping of the upper eyelid (ptosis)
3rd nerve palsy….
Pupil involving or sparing
Symp chain wraps around 3rd nerve
Not getting enough blood = damage inside = pupil sparing
Relative afferent pupillary defect
Swing light back and forth to each pupil:
- Normal eye = both will constrict
- Bad eye = it will dilate
Which nerves are responsible for eye movements and which muscles
Oculomotor nerve:
- Superior rectus - up
- Medial rectus
- Inferior rectus
- inferior oblique (inwards and upwards)
Trochlear (superior oblique muscle - down and inward)
abducens (lateral rectus muscle = away from nose)
Oculomotor’s function?
Moving the eye
Opening of eyelid
Focusing
What occurs in 3rd nerve palsy?
Left eye will be pointing down and outwards
Ptosis
Failure of adduction
Symp chain wraps around 3rd nerve = poor blood supply
6 nerve palsy?
Draw a H with finger - double vision?
Oculomotor nerve palsy: if the pupils are involved or pupil sparing?
- Pupils involved:
Compressive lesion (painful): tumour, posterior communicating artery aneurysm
Uncal herniation
Trauma
Basal meningitis: infection (TB)/malignant
Migraine
Idiopathic- 25% - Pupil sparing:
Microvascular: DM, HT, vasculitis
Could be diabetes, hypertension, vasculitis
What does the trochlear nerve do?
Eye to go down and invert (superior oblique muscle)
Damage - (vertical diplopia) double vision and inability to rotate eye laterally
Sign of a IVth nerve palsy?
Vertical diplopia on looking straight down
Usually pt lift their heads sideways to make the diplopia less severe
Causes of a IVth nerve palsy?
Congenital Idiopathic-20% Microvascular: DM, HT Cavernous sinus lesions Head injuries Aneurysms + tumours
Abducens nerve function?
Lateral rectus muscle - moves eye away from body (laterally)
Damage: inability to rotate eye laterally and at rest eye rotates medially
VI nerve palsy sign?
Pt cannot move eye laterally so eye turns medially at rest
Diplopia
Causes of VI nerve palsy?
Pontine lesions: vascular, sol, demyelination Cerebello-pontine angle sol Cavernous sinus lesions Trauma Microvascular
How to test for VI nerve palsy?
Ask pt to look left and right
H pattern
Diplopia?
Common causes of abnormal eye movements?
Microvascular - diabetes, high BP, aneurism Central lesions Tumour Vascular - basilar thrombosis Vasculitis Basal cell fracture
Trigeminal function?
Largest CN
Supplies sensation to face, mucous membranes and other structures
Sensory to opthalmic, maxillary and mandibular branches
Motor nerve supply to MoM (temporalis, massester, medial and lateral pterygoid)
Motor to tensor veli palatini, mylohyoid, anterior belly of digastric, tensor tympani
= Chewing, biting, swallowing
How to test the sensory function of the trigeminal?
Soft touch using cotton wool
V1 - opthalmic - forehead up to top of head
V2 - maxillary
V3 - mandibular (up to angle of mandible)
Say yes when it’s felt
Test for pain using sharp object - feel sharp or dull?
Causes of trigeminal sensory problems?
MS
trigeminal neuralgia
How to test for the motor function of the trigeminal?
Inspect for wasting of temporal and masseter muscles
Clench teeth and palpate - feel for wasting
Open mouth and hold it open while examiner shuts it (pterygoid muscles)
Jaw jerk
- Pt open mouth fully and close halfway
- Place index finger on chin and tap with hammer
How to test the corneal reflex?
Look up and away
Touch corneal
Reflex blinking of both eyes is normal
Pathology of the corneal reflex?
Bells palsy - unable to blink due to the efferent limb CNVII
CNV forms the afferent limb
What does a unilateral weakness of motor function of the trigeminal nerve cause?
Jaw deviates towards weak side
Get pt to move jaw laterally against resistance - Jaw can move towards the affected muscle but not the normal side
Upper motor neurone
In cns
Lower motor neurone
Distal to cns (brain and spine)
Upper motor neurone lesion?
LEARN
Spasticity
Weakness
Brisk reflexes
Forehead is spared, weakness everywhere else, can raise eyebrows
= Stroke
Lower motor neurone lesion?
LEARN
Weakness
Flaccid arm
Wasting
Perciculations
Complete paralysis of face
= Bells palsy
Functions of the facial nerve?
Somatic motor - facial expressions
Autonomic motor - salivary and lacrimal glands, nasal and palatine mucosa
Sensory - taste to anterior 2/3 of tongue via chorda tympani
What does damage to the facial nerve cause?
Sagging of facial muscles and disturbed sense of smell
How to test the motor function of the facial nerve?
Motor:
- Pt shut eyes tightly
- Try to force open eyes
- If lower motor lesion detected (weakness on 1 side of face) = check ear and palatal for herpes zoster vesicles (ramsay hunt syndrome)
Look up and wrinkle forehead
Feel muscle strength - push down on forehead
- If UMN lesion the movement is preserved
- LMN (bells palsy/ramsay hunt)
Pt show teeth
Compare nasolabial grooves - smooth on weak side
Left UMN lesion = drooping of corner of mouth, flattened nasolabial fold and sparing of forehead on left
Block out cheeks and push against
Facial nerve palsy?
LMN Lesions
- Bells palsy
- Ramsey hunt syndrome
- Acoustic neuroma
- Sarcoidosis
UMN Lesions
- CVA
- SOL
Vestibularcochlear nerve function?
Provides hearing (cochlear branch) and sense of balance (vestibular)
Damage - deafness, dizziness, nausea, loss of balance and nystagmus
How to test the vestibularcochlear nerve for hearing?
Any problem with hearing? Hearing aids?
Cover ear and whisper number, get pt to repeat it
Deafness indicated = Rinne or webers test
What is rinne’s test?
Base of tuning fork on mastoid process
- Can you hear it, tell me when it stops
- Points on tuning fork to ear = can you hear it? Stopped?
Not hear = rinne negative
What is Weber’s test?
Vibrating tuning fork placed on centre of forehead
Hear more in centre or left or right ear?
Conduction deafness = sound is louder in abnormal ear
Glossopharyngeal nerve function?
Somatic motor - swallowing, voice production using pharyngeal muscles
Autonomic motor - salivation, gagging
Sensations from posterior 1/3 of tongue
Sensations from baroreceptors and chemoreceptors
How to test glossopharyngeal and vagus nerve?
Uvula:
- Open mouth
- Symmetry and “ahh” = uvula drown to one side = unilateral nerve palsy, moves towards normal side
Gag reflex
- Touch back of pharynx on each side with spatula
- Feel it?
- Contraction of soft palate
What can damage of the vagus nerve result in?
Increases risk of aspiration Hoarseness or lost voice, impaired swallowing, GI dysfunction
Causes of vagus nerve damage?
Lateral medullary syndrome - sensory loss in face (same side) and body (opposite)
Same side = cerebellar and horners sign
Progressive bulbar palsy
Jugular foramen syndrome
Accessory nerve function?
Swallowing, head, neck and shoulder movement via trapezius, sternocleidomastoid and pharyngeal muscles
How to test the accessory nerve?
Trapezius
- Shrug shoulders and dont let me push them down
Sternocleidomastoid
- Pt turn head against resistance and feel SCM
- Repeat with other side
- Muscle weakness?
Hypoglossal nerve functions?
Tongue movements for speech, food manipulation and swallowing
What occurs if the hypoglossal nerve is damaged?
Both sides - can’t protrude tongue
One side - tongue deviates towards injured side
How to test for hypoglossal function?
Tongue at rest
- Wasting
- Deviation
Stick tongue out straight - deviation?
Deviates towards injured side
Wiggle tongue side to side
