Cranial nerve ONE
- name?
- function? 1
- effect of palsy / lesion? 1
1 = OLFACTORY
function = SMELL
lesion = Loss of smell
Cranial nerve TWO
- name?
- function? 1
- effect of palsy / lesion? 1
2 = OPTIC
function = ACUITY / SIGHT
lesion = ↓Acuity and Sight
nb commonest causes of monocular or binocular blindness is not a cranial nerve lesion but a problem with the eye itself (cataracts, retinal problems)
- neurological disorders more commonly cuase loss of part of the visual field
Cranial nerve THREE
- name?
- functions? 4
- effect of palsy / lesion? 3
3 = OCCULOMOTOR
functions = Eye movements (MR, IO, SR, IR) = Pupillary constriction = Accommodation = Eye lid opening
lesion
= eye is DOWN and OUT
= Ptosis (droopy eye lid)
= dilated fixed pupil
nb pupil isn’t always dilated - can have causes that ‘spare’ the pupil!
Cranial nerve FOUR
- name?
- function? 1 (name of muscle moved!)
- effect of palsy / lesion? 2
4 = trochlea
functions
= supplies SUPERIOR OBLIQU (SO) muscle
= down and inward movement of eye
“SO4 = sulphate”
lesion
= Defective downward gaze → vertical diplopia
= Head tilt
Cranial nerve FIVE
- name?
- functions? 4 (1 sensory, 1 motor, 2 reflex)
- effect of palsy / lesion? 5
TRIGEMINAL
functions = facial sensation (3 zones) = muscles of mastication = corneal reflex (efferent) = jaw jerk reflex
lesion = Trigeminal neuralgia (shock paroxysms of U/L V1-V3) = Loss of corneal reflex (afferent) = Loss of facial sensation = Paralysis of muscles of mastication = Deviation of jaw jerk to weak side
nb Sensory branches
V1 = Opthalmic
V2 = Maxillary
V3 = Mandibulary
Cranial nerve SIX
- name?
- function? 1 (name of muscle moved!)
- effect of palsy / lesion? 1
ABDUCENS
function
= ABDUCTS the eye
= controls LATERAL RECTUS (LR) nuscle
“LR6 - ie not sulphate…”
lesion
= Defective abduction (left eye abn) → horizontal diplopia
Cranial nerve SEVEN
- name?
- function? 5 (2 sensory, 2 motor, 1 reflex)
- effect of palsy / lesion? 4
FACIAL nerve
functions = facial muscles = lacrimation + salivation = taste (anterior 2/3rds) = some hearing thing... = corneal reflex (afferent)
lesions
= flaccid paralysis of upper AND lower face (bell’s palsy)
= Loss of corneal reflex (efferent)
= loss/change of taste
= Hyperacusis - ↑sensitivity to certain frequencies
BELL’S PALSY:
- upper or lower motor neurone lesion?
- which cranial nerve affected?
- main symptoms? 3
- management? 1
- main way to differentiate from stroke? 1
LMN
cranial nerve 7 = facial!
- ipsilateral facial nerve paralysis (WITH inability to raise eyebrow)
- ipsilateral ear numbness and pain (hyperacusis)
- decreased taste
high dose prednisalone
get forehead sparing if UMN lesion (eg stroke) - so would still be able to raise eye brows if stroke!
nb bell’s palsy is norm idiopathic (70%) but can be secondary to weird things like sarcoidosis, ramsay hunt, MS etc
Cranial nerve EIGHT
- name?
- function? 2 (2 sensory)
- effect of palsy / lesion? 3
8 = VESTIBULOCOCHLEAR nerve
“the number 8 is curly like a cochlear?”
functions
= hearing
= balance
lesion
= SEONSORI-NEURAL hearing loss
= Vertigo
= Nystagmus
nb things like pagets, excess noise and acoustic neuroma and can damage
Cranial nerve NINE
- name?
- function? 3 (1 sensory, 1 motor, 1 reflex)
- effect of palsy / lesion? 4
GLOSSOPHARYNGEAL = 9
functions
= taste (posterior 1/3rd)
= swallowing
= gag reflex (afferent)
(sensation from posterior tongue and and pharynx)
lesion = loss of gag reflex (afferent) = difficulty swallowing? = change in taste? = Hyper-sensitive carotid sinus reflex
Cranial nerve TEN
- name?
- broad functions? 5 (4 mixed, 1 reflex)
- effect of palsy / lesion? 2 (just in head + neck)
VAGUS = 10
functions = phonation (muscles of vocal cords) = swallowing = gag reflex (efferent) = cardiac inhibition = autonomic functions of gut
(sensation from larynx and pharynx)
lesion
= Uvula deviates to CONTRALATERAL side of lesion (e.g. left deviating uvula = R vagus lesion)
= Loss of gag reflex (efferent)
also other effects with heart and gut etc but don’t need to know in detail!
Cranial nerve ELEVEN
- name?
- function? 1
- effect of palsy / lesion? 1
ACCESSORY NERVE = 11
functions
= trapezius + deltoid muscles (shrug shoulders, turn herad to left and right)
lesion
= Weakness turning head to contralateral side of lesion e.g. cannot turn head left = R accessory nerve lesion
Cranial nerve TWELVE
- name?
- function? 1
- effect of palsy / lesion? 1
HYPOGLOSSAL = 12
function = muscles of tongue
lesion
= tongue deviates to IPSILATERAL side (eg Left deviating tongue = Left hypoglossal lesion)
Possible causes of ALL / ANY cranial nerve lesions? (4 common, 3 rarer)
nb exclude causes that tend to only affecdt one or two specific nerves (this is on a seperate flashcard)
= tumour (secondary or primary)
= stroke
= MS
= diabetes mellitus
- sarcoidosis
- vasculitis (eg PAN or SLE)
- syphillis
What are the causes of a unilateral ptosis? 4
what other features would each cause have?
3rd NERVE PALSY
- Down and out eye + fixed dilated pupil
HORNER’S SYNDROME
- Ptosis + anhidrosis + miosis
MYASTHENIA GRAVIS
- Bilateral facial weakness + proximal weakness with fatiguability + weak voice
CONGENITAL
Specific cause to rule out of a 3rd nerve palsy? 1
what is the difference between a ‘medical’ and ‘surgical’ third nerve palsy in presentation? 1
remember this is OCULOMOTOR nerve
cause to rule OUT
= Compression from a posterior communicating artery aneurysm (ie berry aneurysm)
“Medical”: pupil sparing (and painless)
“Surgical”: pupil fixed and dilated
nb Pathology
Parasympathetic fibres are situated on the periphery of the 3rd nerve trunk and so are the first to be affected by compression resulting in a fixed and dilated pupil.
The classic cause of a “surgical” 3rd nerve palsy is a posterior communicating artery aneurysm. The vaso vasorum which supplies the 3rd nerve starts from the centre and supplies out radially.
In “medical” 3rd nerve palsies the centre of the 3rd nerve is affected first leaving the parasympathetic fibres and therefore pupillary constriction intact until the end.
Horner’s syndrome:
- describe features? 3
Disruption of the sympathetic nervous supply to the face resulting in:
= PTOSIS: unilateral partial drooping of eyelid
= MIOSIS: unilaterally constricted pupil
= ANHIDROSIS: unilateral loss of sweating
nb have Normal light and accommodation reflexes/eye movements
Common causes of damage to cranial nerve ONE? 5
- BLOCKED nasal passages e.g. common cold/flu
- Head TRAUMA
(Shearing of the olfactory bulbs as they pass through the holes of the cribriform plate) - ALZHEIMER’S and PARKINSON’S disease
(One of the earliest signs of cognitive decline and Alzheimer’s can be a loss of smell. This is the reason why patients with dementia often prefer stronger/more pungent foods) - MALIGNANCY: especially if unilateral (Meningioma / glioma / basal skull / frontal tumour)
- MENINGITIS
What visual field defect does a pituatory tumour classically cause?
fancy name and actually describe it
BITEMPORAL HEMIANOPIA
- loose OUTSIDE bit of vision on both sides (ie loose peripheral vision)
PITUATORY ADENOMA is the classic cause for a lesion at the OPTIC CHIASM
ALSO look for any other signs of pituatory disease (eg cushings, acromegaly, hypopituatirism, gynaecomastia)
Nb other causes of lesions at the optic chiasm include:
- Sarcoidosis/Tuberculosis
- Metastatic disease
- Internal carotid artery aneurysm
Causes of bell’s palsy? 5
which cranial nerve affected? 1
- VIRAL infection (likely Herpes Simplex Virus)
NB Treat with high dose steroids (60-80mg OD for 5 days) if diagnosed promptly
- BRAINSTEM LESION: demyelination / stroke / tumour
- CERELLOPONTINE ANGLE LESION: acoustic neuroma (vestibular schwannoma)
- MIDDLE EAR INFECTION
- PAROTID GLAND: tumour / post-surgical resection of tumour
affects cranial nerve 7 (facial)
UNILATERAL CEREBELLOPONTINE ANGLE (CPA) lesion:
- most common causes? 2
- three main cranial nerves affected? 3
- other neurological signs that may be present?
most common = acoustic neuromas (vestibular schwannomas)
2nd most common = meningiomas
nb need MRI imaging to image the lesion
CRANIAL NERVES AFFECTED
- TRIGEMINAL (5) (reduced facial sensation on affected side + loss of corneal reflex + impaired muscles of mastication)
- Lower FACIAL (7) (Weakness in upper and lower aspects of the face + loss of taste in anterior 2/3rds of the tongue)
- VESTIBULOCOCHLEAR (8) (Sensorineural hearing loss on affected side)
also get CEREBELLAR signs
nb If the Cerebellopontine angle lesion is very large it can extend and affect IX → XII nerves in order
Which way does the tongue deviate in a CN12 lesion?
which way does the uvula deviate in a CN10 lesion?
The tongue deviates TIOAWRDS the side of the CN12 lesion
Uvula is deviated AWAY from the side of the CN10 lesion
What are the final peripheral nerves that supply the arms? 5
1) musculocutaneous
2) axillary
3) radial
4) median
5) ulnar
MUSCULOCUTANEOUS nerve
- which nerve routes originate from? 3
- how normally injured? 1
- affect of injury? 2
MUSCULOCUTANEOUS
- C5-7
brachial plexus injury
effect of lesion
= inability to flex and supinate arm at elbow
