Cranial Nerves
I
Olfactory
II
Optic
Origin: inferior frontal lobe, 1Y olfactory cortex
Course: cribiform plate of ethmoid bone
Sx: anosmia
Causes: meningioma, ethmoid tumour, BSF, pituitary OT
Origin: eye
Course: optic foramen  optic chiasma in pituitary fossa  optic tract  lateral geniculate body  optic radiation (connect with OM nerve via sup
colliculus)  internal capsule  temporal lobe (lower quads), parietal lobe (upper quads)  occipital cortex
Sx: VA; visual fields; direct and consensual pupil reflex; pupil sizes; fundoscopy
Sudden bilateral blindness: bilat occipital ischaemia (pupil reflexes preserved),
trauma, meths, functional
Gradual bilateral blindness: cataracts, glaucoma, diabetes, chiasmal / ON
compression
Sudden unilateral blindness: ant to optic chiasm; retinal art / vein
thrombosis; temporal arteritis; glaucoma; papilloedema;
chorioretinitis; migraine
Bitemporal hemianopia: optic chiasm; may have RAPD
Homonymous hemianopia: on contralateral side to lesion; post to optic chiasm
(may be macular sparing if in radiation, in tract complete); light reflex gone,
accomodation intact
Central scotoma: MS; meths; ETOH; optic glioma
Papilloedema: blurred pink disc; engorged retinal veins; filled optic cup, haemorrhages; takes >6hrs; caused by SOL,
hydrocephalus,
intracranial HTN, HTN, central retinal vein thrombosis
III
Oculomotor
SR, MR, IR
IO
ParaS
LPS
Origin: ant midbrain
Course: between post cerebral art and sup cerebellar art  lat wall and roof of cavernous sinus  superior orbital
fissure between 2 heads of LR  sup division to SR and LPS, inf division to MR, IR, IO, parasympathetic ciliary
ganglion (which runs on outside of nerve)
Sx: ptosis, down and out (can’t look up and in), mydriasis; no light / accomodation reflex
Causes: DM + HTN most common cause – but spare pupil as ischaemic to central fibres first
Ca (eg. Brain, nasopharyngeal), aneurysm, arteritis
MS, GBS (MFS), incr ICP, diptheria, botulism
IV
Trochlear
SO 4
Origin: midbrain
Course: between post cerebral art and sup cerebellar art  in lat wall of cavernous sinus (lat to III)  superior
orbital fissure  SO  makes you look down and in
Sx: can’t look down and in; head tilted to opposite side
Causes: mononeuritis multiplex
MS, GBS, incr ICP, diptheria, botulism, DM, HTN
VI
Abducens
LR 6
Origin: pons
Course: over petrous temporal bone  in cavernous sinus (ant to ICA, inf and medial to III)  superior orbital fissure
between 2 heads of LR  LR
Sx: can’t look out, convergent strabismus
Causes: Wernicke’s encephalopathy, mono-neuritis multiplex
MS, GBS, incr ICP, diptheria, botulism,
Pupil
problems
Mydriasis: also III palsy (see above), drugs (anticholinergics, TCA)
Holmes Adie pupil: lesion of parasympathetic nerve supply (OPPOSITE OF HORNER’S)
Cause: usually 2Y to bacterial/viral infection
Slow accommodate, won’t react to direct / consensual light
Marcus Gunn pupil = RAPD: lesion of afferent pathway
Cause:
MS
Will react to consensual light, not to direct light – so dilates when you shine light in it
Miosis: also pontine lesions, drugs (morphine, phenothiazines, pilocarpine, olanzapine, clonidine)
Argyl Roberson pupil: lesion of iridodilator fibres in midbrain
Cause: DM, syphilis, alcoholic neuropathy, midbrain lesions
Will accommodate, won’t react to direct / consensual light
Horner’s syndrome: sympathetic nerve supply damaged (OPPOSITE OF HOLMES-ADIE)
miosis, ptosis, enophthalmus, anhydrosis (if present, central/preganglionic)
Cause: CVA, aneurysm, cavernous sinus thrombosis (if III, IV, VI involved),
carotid dissection
Ca (brain, lung, Pancoast, thyroid, cervical, jugular foramen ), glioma
encephalitis, infection, sinusitis
MS, syringomyelia
trauma (thyroid, laryngeal OT, stab), BSF
Lesion in medulla if IX, X, XI involved; lesion in middle cranial fossa if V involved
V
Trigeminal
Diencephalic: mid position pupils, reactive; forebrain
Midbrain: mid position pupils, non-reactive
Pontine: pinpoint, reactive, look away from side of lesion
Medulla: large, non-reactive
Metabolic: small, reactive
Uncal herniation: unilateral dilated non-reactive (medial temporal lobe herniates  III compression)
Origin: pons
Course: post cranial fossa  over petrous temporal bone  middle cranial fossa (trigeminal ganglion besude greater wing of sphenoid)  lateral
wall of cavernous sinus
Sensory: lower face and ant head, MM of nose/sinuses/mouth/ant 2/3 of tongue, orbit, dura, cornea; test corneal reflex, facial sensation
Motor: muscles of mastication, mylohyoid, ant belly digastric, tensor palati / tympani, buccinator; test MOM, jaw jerk
V1 = opthalmic = sensory  Nasociliary  orbit through head of LR  infratrochlear, ant ethmoid
Lacrimal  orbit above LR
Frontal  orbit above LR  supraorbital, supratrochlear
If opthalmic only lost = cavernous sinus; if all lost = central
V2 = maxillary = sensory  through foramen rotundum  pterygomaxillary fissure  infraorbital
groove  meningeal, infraorbital, post sup /ant sup alveolar nerve, zygomaticofacial/temporal
V3 = mandibular = sensory + motor  through foramen ovale  meningeal, med / lat pterygoid,
buccal, deep temporal, masseter, auriculotemporal, inf alveolar, lingual
VII
Facial
Origin: pons
Course: int auditory meatus  stylomastoid foramen  postmedial parotid gland
Chorda tympani: sensory, paraS; submandibular and sublingual glands, taste ant 2/3 tongue
Muscular: temporal, zygomatic, buccal, mandibular, cervical, post belly digastric, stylohyoid; facial expression (LMN involves occipitofrontalis)
Post auricular, meningeal; hyperacusis
Causes: UMN – Ca, vascular
LMN – Ca, vascular
acoustic neuroma, Bell’s palsy (HSV 1), MS, Ramsay Hunt syndrome, parotid, BSF
meningitis, OM, diptheria
Sarcoidosis tends to be bilateral not unilateral
VIII
Vestibulocochlear
IX
Origin: pons
Course: int auditory meatus  cochlear and vestibular branches
Whispering test, Rinnes (behind ear, air should be > bone, if not = conductive deafness), Webers (forehead; conductive localises to affected side,
sensory to opposite), Hallpike
Causes: acoustic neuroma, TORCH, # petrous temporal bone, aspirin, gent, brainstem disease, vascular, conductive
Origin: medulla
Course: jugular foramen  between IJV and ICA  between ICA and ECA  into pharyx and tongue
Glossopharyngeal
Tympanic (MM of middle ear and auditory tube, parotid), stylopharyngeus, pharyngeal sesnation, carotid sinus; taste
X
Origin: medulla
Course: jugular foramen  in carotid sheath  ant to subclavian artery, post to brachiocephalic artery
Mengingeal, auricular (TM), pharyngeal, sup laryngeal (MM above cords), recurrent laryngeal (MM below cords), cardiac, visceral
Vagus
Uvula deviation away, absent gag, hoarseness, bovine cough
XI
Accessory
XII
Hypoglossal
and sensation to
post 1/3 of tongue, tonsils, post 1/3 palate, ant epiglottis
Origin: pons
Course: foramen magnum  spinal root and cranial root
Drooping of shoulder, downward rotation and protraction of scapula, wasting of traps
Origin: medulla
Course: hypoglossal canal
To all except palatoglossus; tongue deviates to side of lesion
Notes from: Dunn