CRANIAL NERVES Flashcards by Maddie YEAR 3 & 4

Which cranial nerves are purely sensory?

Olfactory
Optic
Vestibular

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Which cranial nerves are purely motor?

Occulomotor
Trochlear
Abducens
Accessory
Hypoglossal

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Which cranial nerves have sensory + motor functions?

Trigeminal
Facial
Glossopharyngeal
Vagus

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Which occipital lobe does the right visual field come from?

The left occipital lobe

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Visual field defect when there is a lesion in the optic nerve e.g. demyelination or occlusion of retinal artery?

Total blindness of ipsilateral eye

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Visual field defect when there is a lesion in the optic chiasm e.g pituitary tumour?

Bitemporal hemianopia

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Visual field defect when there is a lesion in both optic radiations e.g. parietal and temporal lobe stroke?

Contralateral homonymous hemianopia

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Visual field defect when there is a lesion in the inferior radiation e.g. temporal lobe stroke?

Contralateral upper quadrantic anopsia

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Visual field defect when there is a lesion in the superior radiation e.g. parietal lobe stroke?

Contralateral lower quadrantic anopsia

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Visual field defect when there is a lesion in the occipital lobe e.g. occipital lobe stroke?

Contralateral homonymous hemianopia with macular sparing

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Abducens nerve supplies what and does what?

Lateral rectus muscle
Abducts the eye

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Trochlear nerve supplies what and does what?

Superior oblique muscle
(Hooks around the Trochlear which is a pulley on the medial aspect of the orbit)
Moves eye in down and out position

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Occulomotor nerve supplies what and does what?

Motor innervation to levator palpebrae superioris, superior rectus, inferior rectus, medial rectus and inferior oblique muscle = all movements other than “down and out”
Parasympathetic supply to sphincter pupillae and ciliary muscles of the eye = constriction of pupil

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Occulomotor nerve palsy signs…

Eye is down and out (loses superior, inferior and medial rectus muscles)
Pupil dilated (loss of parasympathetic tone of ciliary body)
Ptosis (loss of levator palpebrae muscle)

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Abducens nerve palsy signs…

Unable to abduct the affected eye = horizontal diplopia

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Trochlear nerve palsy signs…

Eye will be facing up and inwards
Defective downward gaze = vertical diplopia

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Function of trigeminal nerve?

Sensation to face and sensory part of corneal reflex
Motor supply to muscles of mastication and Jaw jerk reflex

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Function of the facial nerve?

Motor function to muscles of facial expression
Supplies anterior 2/3rds of the tongue for taste
Parasympathetic - glands of head and neck e.g. lacrimal, mucous glands and some salivary glands

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What is the facial motor nucleus?
Why is this clinically relevant?

A round aggregation of motor neuron cell bodies found in the pontomedullary junction which are paired on the left and right side of the brain stem and are neatly divided in half
The superior half of the nucleus represents superior half of face, and inferior half represents inferior half of face
Superior half of the face derives conscious control from left and right primary motor cortex
Inferior half derives conscious control from only the contralateral primary motor cortex

A supranuclear lesion to 1 side (UMN lesion) will cause paralysis of only the contralateral lower half of the face because the upper half of the face is supplied bilaterally - e.g. stroke
An infranuclear lesion (LMN lesion e.g. middle ear tumour, infection- Bell’s palsy if idiopathic) will cause paralysis/weakness in both the upper and lower halves of one side of the face

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What does Weber’s test tell you?

If pt hears louder in R ear then either conductive hearing loss in R ear OR conductive hearing loss in L ear

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What does Rinne’s test tell you?

Normal response - louder in front of ear than on mastoid as air conduction is greater than bone conduction

If louder on mastoid then bone conduction > air conduction = conductive hearing loss in that ear

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What type of hearing loss…
Webers test lateralises to the right
Rinnes test hear louder on mastoid on the right

Conductive hearing loss in the R ear e.g. ear wax

What type of hearing loss…
Webers test lateralises to the right
Rinnes test normal in both ears

Sensorineural loss in the left ear e.g. acoustic neuroma (note: anyone with unilateral sensorineural hearing loss should be investigated for an acoustic neuroma)

Function of the glossopharynegal nerve?

Taste to posterior 1/3rd of the tongue
Motor function for movement of the palate (along with vagus nerve)

Functions of vagus nerve?

Sensation to larynx, heart and stomach Parasympathetic activity - fatal tone, regulates heart rate Motor function to movement of the palate (along with glossopharynegal nerve) Gag reflex

Function of accessory nerve?

Motor supply to trapezius and sternocleidomastoid muscle (Remember left sternocleidomastoid muscle turns head to the right!!)

Function of hypoglossal nerve?

Motor supply to your tongue Tongue muscles push i..e left side moves tongue to the right

Signs of hypoglossal nerve injury?

Ipsilateral wasting and fasciculations Tongue will deviate towards the side of the lesion

Which cranial nerves emerge from the midbrain?

Occulomotor nerve Trochlear nerve

Which cranial nerves e,merge from the pons?

Trigeminal Adbucens Facial Vestibular

Which cranial nerves emerge from the medulla?

Glossopharyngeal Vagus Accessory Hypoglossal

Causes of a myotonic pupil?

Holmes-Adie pupil Occulomotor nerve palsy Traumatic iridoplegia Phaeochromocytoma Congenital Drugs - topical mydriatics, sympathomimetic drugs and Anticholinergics

Causes of meiosis (pupil constriction)

Argyll Robertson pupil Horners syndrome Drugs - opiates, parasympathomimetics

What causes Argyll Robertson pupil?

Neurosyphilis Can also be caused by diabetes “Prostitutes pupil” - it accommodates but doesnt react. Or remember by ARP but PRA

Horner syndrome symptoms?

Ptosis Meiosis Apparent endophthalmosis Anhydrosis ipsilateral

Causes of abducens nerve palsy?

Tumours MS Infarction Trauma

Most common palsy: Occulomotor? Trochlear nerve? Absuecens nerve?

Occulomotor

What is Ramsay-Hunt syndrome?

Herpes zoster oticus Caused by the reactivation of the varicella zoster virus in the geniculate ganglion of CN7 Causes auricular pain, facial nerve palsy and a vesicular rash around the ear other features include vertigo and tinnitus

Causes of conductive hearing loss?

Wax Perforation Chronic otitis media Otosclerosis

Causes of sensorineural hearing loss?

Age Acoustic neuroma Infections e.g. meningitis or mumps Ménière’s disease Drugs e.g. gentamicin

How does Ménière’s disease present?

Sudden attacks of vomiting, vertigo, tinnitus, balance loss, feeling of pressure in the ear and sensorineural hearing loss Over time hearing may get worse and pt may get constant tinnitus

What is and what is the presentation of Pseudobulbar palsy?

I.e. UMN lesion of the bulbar cranial nerves (9, 10, 11, 12) - UMN are the corticobulbar tract nerves Small spastic tongue No fasciculations Emotional lability Exaggerated jaw jerk

What is and what is the presentation of bulbar palsy?

I.e. LMN of the bulbar cranial nerves (9, 10, 11, 12) - LMN is anything distal to the nucleus of CN Wasting of the tongue Fasciculations Normal jaw jerk

2 causes of permenant anosmia or hyposmia?

Frontal meningioma - tumour affecting olfactory bulb Trauma i..e fracture of ethmoid bone - as nerve fibres from the olfactory bulb pass through the ethmoid bone

How does temporal arthritis cause monocular vision loss?

Vasculitis occlusion of posterior ciliary artery (a branch of the ophthalmic artery) → ischaemia of the optic nerve head

How can MS cause monocular vision loss?

By causing demyelination of the optic nerve

Common cause of contralateral homonymous hemianopia with macular sparing? Why?

Posterior stroke This is because the macula has collateral flow from the middle cerebral artery

What nearly always causes UMN facial nerve palsy i..e frontalis and orbicularis muscles spared?

Stroke

What nearly always causes LMN facial nerve palsy i..e frontalis and orbicularis muscles not spared so whole face affected?

Bell’s palsy Or sometimes parotid tumours

Symptoms of bulbar nerve lesions (CN9-12)?

Dysarthria Dysphagia

What are the features of internuclear ophthalmoplegia?

Impaired adduction of the eye on the same side as the lesion Horizontal nystagmus of the abducting eye on the contralateral side

Causes of internuclear ophthalmoplegia?

MS Vascular disease

What is internucelar ophthalmoplegia?

A cause of horizontal disconjugate eye movement due to a lesion in the medial longitudinal fasciculus (this controls horizontal eye movements by interconnecting the 3rd,4th and 6th cranial nuclei)