Cranial Nerves Flashcards
What are the cranial nerves?
I - Olfactory
II - Optic
III - Oculomotor
IV - Trochlear
V -Trigeminal
VI - Abducens
VII - Facial
VIII - Vestibulocochlear
IX - Glossopharyngeal
X - Vagus
XI - Accessory
XII - Hypoglossal
Olfactory nerve (I)
Smell
- Ask about any changes in smell - if present, is it unilateral or bilateral?
- Can test each nostril separately using a strong smelling substance like soap or coffee
What are the steps for assessing the Optic nerve (II)?
- Visual acuity
- Pupillary responses ( Afferent = CN II, Efferent = CN III)
- Visual fields
- Visual inattention
- Accommodation
- Fundoscopy
Optic nerve (II)
Visual Acuity
- Ask if the patient can see equally well with each eye
- A Snellen chart can be used
Optic nerve (II)
Pupillary responses
- Inspect size and shape of pupil, checking for symmetry
- Assess for pupillary reflex with the patient fixated on one point - look for constriction of the pupil both ipsilateral and contralateral
- Ideally a dark room for pupillary reflex
Optic nerve (II)
Visual Fields
- Sit at same level as patient, about 1m apart. Ask patient to cover one eye and to look at your nose. You cover your opposite eye (i.e. your left and patient’s right). Bring your finger from the
furthest periphery towards the central vision and ask the patient to say ‘yes’ when they can see your finger moving.
Test each quadrant in turn. Positioning your hand equi-distant between you and the patient will allow you to compare your visual field with that of the patient. Repeat for the other eye.
*A visual field defect may be a cranial nerve problem
(e.g. bitemporal hemianopia) or a hemisphere problem
(e.g. homonymous hemianopia).
Optic Nerve (II)
Visual Inattention
- Sit facing the patient an ask them to look at your face and point to the hand that has a finger moving
- Test in the upper and again in the lower visual fields
- Move the fingers on both sides together - the intact patient sees both while someone with right- sided inattention would only notice the finger on their left side moving
Optic Nerve (II)
Accommodation
- Ask the patient to focus on your finger or a pen held at a distance and to keep focusing on it as you move closer to them
- The pupils should constrict as the eyes converge
Remember to say you would also complete fundoscopy
What is the function of the Oculomotor Nerve (III)?
- Innervates superior, medial and inferior rectus muscles, inferior oblique and levator palpebrae superioris muscles
- Also parasympathetic innervation of constrictor pupillae (pupil size) and ciliary muscle (accommodation)
Test cranial nerves III, IV & VI together
Eye movements
- Inspect eyes, looking for pupil abnormality, presence of ptosis or any abnormality of gaze
- Ask the patient to keep their head still and ask them to follow your finger as you move it in a ‘H’ pattern
What are you looking for when completing the ‘H’ movement for CN III, IV and VI?
- Ask the patient to tell you if they get double vision
- Note if their eyes always move in parallel
- Look for nystagmus, particularly at the extremes of eye movement
What is the function of the trochlear nerve (IV)?
Innervates the superior oblique muscle of the eye
What is the function of the abducens nerve (VI)?
Innervates lateral rectus muscle
What is the function of the Facial nerve (VII)?
- Supplies muscles of facial expression
- Also taste to anterior 2/3rd of tongue and secretomotor to submandibular and sublingual glands
Facial Nerve (VII)
- Inspect the face for any asymmetry
- Look at facial movement, asking the patient to wrinkle their forehead, then screw up their eyes, and then smile/ show their teeth
- Ask the patient to puff out their cheeks, then gently press on their cheeks to try expel air
- Taste sensation is rarely tested
