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