Cranial Nerve Flashcards
What equipment will you need?
Pen torch, snellen chart, ishihara plates, opthalmoscope and mydriatic eye drops, cotton wool, neuro-tip, tuning fork, glass of water
What are you looking for on general inspection?
Speech abnormalities : indicate glossopharyngeal or vagus nerve injury
Facial asymmetry: Facial nerve palsy
Eyelid abnormalities: oculomotor nerve pathology
Pupillary abnormalities: mydriasis in oculomotor nerve palsy
Strabismus: oculomotor, trochlear or abducens nerve palsy
Limbs: spasticity, weakness, wasting, tremor and fasciculation
What paraphernalia?
Walking aids e.g. Parkinsons, stroke cerebellar
Hearing Aids e.g. Menieres
Visual aids: strabismus
Prescriptions
Anosmia causes?
Mucous blockage, head trauma, genetics = congenital, Parkinsons and Covid 19
What to check for pupils?
Pupil size, shape and symmetry.
SHape may vary as congenital or pathology e.g. posterior synechiae with uveitis
Asymmetry in size (aniscoria) e.g. Large pupil in oculomotor nerve palsy and small and reactive in Horners syndrome
How do you assess visual acuity?
6 metres away from Snellen chart (with normal glasses if used). Record score e.g. 6/6-2 if two wrong on final line.
What to do if patient cannot read top line of Snellen chart?
Reduce distance to 3metres. Reduce distance to 1 metre. Counting fingers and gross hand movements. Detect light shone into each eye.
What are causes of decreased visual acuity>
Refractive errors, amblyopia, ocular media opacities e.g. cataract/corneal scarring, retinal disease e.g. Age related acular degeneration, Optic nerve pathologies like optic neuritis and lesions in higher visual pathways
What pupillary reflexes do you check?
Direct: pupillary restriction on same eye
Consensual: Pupillary restriction on contralateral eye
Swinging light test for relative afferent pupillary defect
Accommodation reflex = switch from far object to finger 30cm away for convergence and constriction
Describe afferent light reflex limb?
Sensory input to retina to optic nerve to ipsilateral pretectal nucleus in midbrain
Describe two efferent light reflex limbs?
Motor ouput from pretectal nucleus to Edinger-Westphal nuclei on both sides of brain. Then to efferent nerve fibres to oculomotor nerve to innervate ciliary sphincter and enable pupillary constriction
Which limb does each eye test affect?
Direct pupillary reflec = ipisilateral afferent and efferent limbs
Consensual pupillary reflex = contralateral efferent limb
Swinging light test = relative afferent limb defects
What is a relative afferent pupillary defect (RAPD)?
Marcus-Gunn pupil = dilation on swinging light test as damage to one of the afferent limbs
Example of unilateral efferent defect?
Compression of the oculomotor nerve cuasing loss of ipisilateral pupillary reflexes.
What are causes of colour vision deficiencies and how to test?
Ishihara plates.
Congenital and acquired. Acquired are optic neuritis, vitamin A deficiency and chronic solvent exposure.
Types of visual field defect?
Bitemporal hemianopia, homonymous field defect, scotoma and monocular vision loss.
Cause of bitemporal hemianopia?
Optic chiasm compression by tumour e.g. pituitary adenoma , prolactinoma or craniopharyngioma
Causes of homonymous field defects?
Stroke, tumour, abscess (pathology affecting the posterior visual pathways to optic chiasm)
Scotoma causes?
Demyelinating disease e.g. MS and diabetic maclopathy
Monocular vision loss causes?
Optic nerve pathology e.g. anterior ischaemic optic neuropathy or ocular diseases e.g. central retinal artery occlusion, total retinal detachment
What is ptosis associated with?
Oculomotor nerve pathology, Horners syndrome and neuromuscular pathology e.g. myasthenia gravis
Action of the sup and inf rectus muscles?
sup = primary is elevation, secondary is adduction and medial rotation. Inf is opposite
Action of sup and inf oblique?
Sup = depresses, abducts and medially rotates eyeball
What occurs in 3rd nerve palsy?
Eye is down and out with ptosis and mydriasis as oculomotor innervates all except sup oblique and lateral rectus. Also innervates levator palpebrae superioris and para fibres for sphincter pupillae muscles
What occurs on 4th nerve palsy?
Vertical diplopia due to loss of sup oblique. Also torsional diplopia
What occurs in 6th nerve palsy?
Unopposed adduction of the eye by medial rectus as lateral rectus by abducens. Therefore convergent squint. Present with horizontal diplopia
How do you assess strabismus?
Light reflex test (corneal or Hirschberg test) = Focus on object and use corneal light reflex test to see misalignement
Or Cover test
Types of strabismus?
Temporally = exotropia
Nasally - esotropia
Superiorly = hypertropia
and inferiorly = hypotropia
How to test sensory of trigeminal nerve/
Light touch or pinprick of forehead for ophthalmic, cheek for maxillary and lower jaw for mandibular
How to test for Motor of trigeminal nerve?
Muscles of mastication are in mandibular so inspect temporalis and masseter for wasting and palpate while clenching jaw. Then patient opens mouth against resistance to feel for lateral pterygoids
Trigeminal reflecs?
Jaw jerk and Corneal
Sensory assessment of facial nerve?
Ask patient if any recent changes to sense of taste
Motor assessment of facial nerve?
Raised eyebrows (frontalis), closed eyes (obicular oculi), blow out cheeks (orbicularis oris), smiling (levator anguli oris and zygomaticus major) and pursed lips (orbicularis oris and buccinator)
Facial nerve palsy types?
Lower motor neuron lesion = all ipsilateral weakess of facial muscles e.g. Bells Palsy
Upper motor neuron lesion = unilateral facial muscle weakness sparing forehead as bilateral cortical representation of frontalis) e.g. stroke
How to test vestibulocochlear nerve?
Gross hearing assessment and Rinnes test.
Rinnes: 512Hz tuning fork on mastoid and confirm they can hear until they cant, then move to air to test air conduction at external auditory meatus. If air conduction>bone then Rinnes positive (good)
Describe the Rinne’s results?
Normal = air>bone conduction
Sensorineural = Aid conduction > bone conduction as both equally
Conductive deafness: Bone > air
What is Webers test?
512Hz tuning fork on midline of forehead. Ask patient where they hear the sound.
Normal = heard in both ears
Sensorineural= heard louder in intact ear
Conductive = sound heard louder in affected ear
Conductive hearing loss examples?
Excessive ear wax, otitis externa, otitis media, perforated tympanic membrane and otosclerosis
Sensorineural hear loss causes?
Dysfunction of the cochlea and or CNVIII. e.g. Prebycusis, excessive noise exposure, genetic mutations, viral e.g. CMV and ototoxic agents e.g. gentamicin
What are the other vestibular tests?
Turning/Untberger test = Patient marches on spot with eyes closer and arms out. If vestibular lesion -> patient turns towards side of lesion
Vestibulo-ocular reflex = Explain to patient whats happening. Normal response is ocular fixation is maintained while you move their head. Abnormal = eyes move in direction first before corrective refixation saccade
Function of CN 9 and 10?
9 is motor for stylopharyngeus muscle to elevate pharynx for swallowing and speech. Also sensory information from posterior third of the tongue. Finally afferent limb of gag reflex
10: mototr for speech muscles of mouth and efferent limb of gag reflex
Test for CN9 and 10?
Ask patient for any changes to swallowing voice and cough. Inspect soft palate and uvula and say ahh. Vagus nerve lesions have uvula deviation to unaffected side unsymmetrical palate elevation. Vagus nerve lesion for cough shows weak non-explosive bovine cough by inability to close glottis
Swallow Test and gag reflex
Innervation and assessment of CN 11?
Motor for SCM and trapezius.
Lift shoulders and turn head both ways against resistance
CN12 innervation and test?
Motor for extrinsic muscles of the tongue except palatoglossus which is vagus.
Inspect tongue for wasting or fascicultations. Protrude and look for deviation which would be towards side of the lesion.
Place finger on cheek and get tongue to push against to assess power
What further assessments and investigations?
Full neurological exam of upper and lower limbs.
Neuroimaging e.g. MRI if concerns of SOL or demyelination
Formal hearing assessment (including pure tone audiometry) if concerned about Vestibulocochlear function
