Cranial Nerve Exam Flashcards
What are you looking for in general inspection?
- Speech abnormalities
- Facial Asymmetry
- Eyelid abnormalities
- Pupillary abnormalities
- Strabismus
- Limbs
What could speech abnormalities indicate?
glossopharyngeal or vagus nerve pathology
What would facial asymmetry indicate?
facial nerve palsy
What would eyelid abnormalities indicate?
ptosis may indicate oculomotor nerve pathology
What would pupillary abnormalities indicate?
mydriasis occurs in oculomotor nerve palsy
What would strabismus indicate?
oculomotor, trochlear or abducens nerve palsy
Why do you look at limbs?
any abnormalities (e.g. spasticity, weakness, wasting, tremor, fasciculation) which may suggest the presence of a neurological syndrome
What objects or equipment are you looking for around the bed?
- Walking aids
- Hearing aids
- Visual aids
- Prescriptions
What could walking aids indicate?
gait issues are associated with a wide range of neurological pathology including Parkinson’s disease, stroke, cerebellar disease and myasthenia gravis
What would hearing aids indicate?
patients with vestibulocochlear nerve issues (e.g. Ménière’s disease).
What would visual aids indicate?
use of visual prisms or occluders may indicate underlying strabismus
What are causes on anosmia (CN1)?
- Mucous blockage of the nose: preventing odours from reaching the olfactory nerve receptors.
- Head trauma: can result in shearing of the olfactory nerve fibres leading to anosmia.
3 Genetics: some individuals have congenital anosmia. - Parkinson’s disease: anosmia is an early feature of Parkinson’s disease
- COVID-19
What is asymmetry in pupil size between pupils called?
aniscocoria
What are examples of asymmetry of pupil size?
- large pupil in oculomotor nerve palsy and
2. small and reactive pupil in Horner’s syndrome
What could peaked pupils suggested?
in the context of trauma are suggestive of globe injury
What are possible causes of decreased visual acuity?
- Refractive errors
- Amblyopia
- Ocular media opacities such as cataract or corneal scarring
- Retinal diseases such as age-related macular degeneration
- Optic nerve (CN II) pathology such as optic neuritis
- Lesions higher in the visual pathways
How does papilloedema and optic nerve pathology different for visual acuity?
- Optic nerve (CN II) pathology usually causes a decrease in acuity in the affected eye
- Papilloedema (optic disc swelling from raised intracranial pressure), does not usually affect visual acuity until it is at a late stage
What does afferent limb of pupillary reflex?
each afferent limb has two efferent limbs, one ipsilateral and one contralateral
What is the function of the afferent limb?
sensory input (e.g. light being shone into the eye) transmitted from retina, along the optic nerve to the ipsilateral pretectal nucleus in the midbrain
How do the two efferent limbs function?
motor output is transmitted from the pretectal nucleus to the Edinger-Westphal nuclei on both sides of the brain (ipsilateral and contralateral)
What does each Edinger-Westphal nucelus give rise to?
efferent nerve fibres which travel in the oculomotor nerve to innervate the ciliary sphincter and enable pupillary constriction
What does the direct pupillary reflex test?
ipsilateral afferent limb and ipsilateral efferent limb
What does consensual pupillary reflex test?
contralateral efferent limb
What does the swinging light test detect?
relative afferent limb defects
What is ptosis associated with?
- occulomotor nerve path
- horner;s
- neuromusc patho (e.g myasthenia gravis)
What is function of superior rectus muscle?
- elevation
- adduction
- medial rotation
What is function of inferior rectus?
- depression
- adduction
- lateral rotation
What is function of medial rectus?
adduction of eyeball
What is function of lateral rectus?
abduction of the eyeball
What is function of suprior oblique?
- depresses
- abducts
- medially rotates
What does inferior oblique test?
- elevates
- abducts
- laterally rotates
What is occulomotor palsy known as?
3rd nerve palsy
What does 3rd nerve palsy look like?
down and out appearance of affected eye
What muscles are still going in 3rd nerve palsy?
superior oblique and lateral rectus is unopposed
What else can occulomtor nerve palsy cause and why?
- ptosis as loss of innervation of levator palpebrae
2. mydriasis as loss of parasympathetic fibres that innervate sphincter pupillae muscle
Which muscle does the trochlear nerve innervate?
superior oblique
What does 4th nerve palsy result in?
vertical diplopia
What can 4th nerve palsy also result in?
torsional diplopia (as the superior oblique muscle assists with intorsion of the eye as the head tilts)
How do people with 4th nerve palsy compensate?
tilt their head to the opposite side, in order to fuse the two images together
What does the abducens nerve innervate?
lateral rectus muscle
What does abducens nerve palsy result in?
convergent squint
Why does abducens nerve palsy result in this?
unopposed adduction of the eye (by the medial rectus muscle)
How do patients with abducens nerve palsy usually present?
horizontal diplopia worsened when attempt to look towards affected side
What is strabismus?
eyes do not properly align with each other when looking at an object
What can cause strabismus?
pathology affecting oculomotor, abducens or trochlear nerve
What is exotropia?
- Direction of eye at rest: temporally (laterally or outwards)
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