CRANIAL NERVES Flashcards
Which cranial nerves are purely sensory?
Olfactory
Optic
Vestibular
Which cranial nerves are purely motor?
Occulomotor
Trochlear
Abducens
Accessory
Hypoglossal
Which cranial nerves have sensory + motor functions?
Trigeminal
Facial
Glossopharyngeal
Vagus
Which occipital lobe does the right visual field come from?
The left occipital lobe
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
Visual field defect when there is a lesion in the optic chiasm e.g pituitary tumour?
Bitemporal hemianopia
Visual field defect when there is a lesion in both optic radiations e.g. parietal and temporal lobe stroke?
Contralateral homonymous hemianopia
Visual field defect when there is a lesion in the inferior radiation e.g. temporal lobe stroke?
Contralateral upper quadrantic anopsia
Visual field defect when there is a lesion in the superior radiation e.g. parietal lobe stroke?
Contralateral lower quadrantic anopsia
Visual field defect when there is a lesion in the occipital lobe e.g. occipital lobe stroke?
Contralateral homonymous hemianopia with macular sparing
Abducens nerve supplies what and does what?
Lateral rectus muscle
Abducts the eye
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
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
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)
Abducens nerve palsy signs…
Unable to abduct the affected eye = horizontal diplopia
Trochlear nerve palsy signs…
Eye will be facing up and inwards
Defective downward gaze = vertical diplopia
Function of trigeminal nerve?
Sensation to face and sensory part of corneal reflex
Motor supply to muscles of mastication and Jaw jerk reflex
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
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
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
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
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)
