Cranial Nerves
Origin
Inferior frontal lobe, primary olfactory cortex
I
Course
Cribiform plate of ethmoid bone
Olfactory
Symptoms
Anosmia
Aetiology
Meningioma, ethmoid tumour, basal skull fracture, pituitary surgery
Origin
Eye
Course
Optic foramen  optic chiasma in pituitary fossa  optic tract  lateral geniculate body  optic
radiation (connect with oculomotor nerve via superior colliculus)  internal capsule  temporal
lobe (lower quads), parietal lobe (upper quads)  occipital cortex
VA; visual fields; direct and consensual pupil reflex; pupil sizes; fundoscopy
Exam
Sudden bilateral blindness: bilateral occipital ischaemia (pupil
reflexes preserved), trauma, meths, functional
Gradual bilateral blindness: cataracts, glaucoma, diabetes,
chiasmal / optic nerve compression
II
Optic
Sudden unilateral blindness: anterior to optic chiasm; retinal
artery / vein thrombosis; temporal arteritis; glaucoma;
papilloedema; chorioretinitis; migraine
Bitemporal hemianopia: optic chiasm; may have RAPD
Homonymous hemianopia: on contralateral side to lesion; posterior to optic chiasm (may be macular sparing if in
radiation, in tract complete); light reflex gone, accommodation intact
Central scotoma: multiple sclerosis; meths; ETOH; optic glioma
Papilloedema: blurred pink disc; engored retinal veins; filled optic cup; haemorrhages; takes >6hrs
Caused by space occupying lesions, hydrocephalus, intracranial HTN, HTN, central retinal vein thrombosis
Origin
Anterior midbrain
Course
Between posterior cerebral artery and superior cerebellar artery  lateral
wall and roof of cavernous sinus  superior orbital fissure between 2 heads
of lateral rectus  superior division to SR and LPS, inferior division to MR, IR,
IO, parasympathetic ciliary ganglion (which runs on outside of nerve)
III
Oculomotor
Symptoms
Ptosis; down and out (can’t look up and in); mydriasis; no light / accommodation reflex
Aetiology
SR, MR, IR, IO
Parasympathetic
LPS
Diabetes + HTN most common cause – but spare pupil as ischaemic to central fibres first
Cancer (eg. Brain, nasopharyngeal), aneurysm, arteritis, multiple sclerosis, GBS (MFS), increased
intracranial pressure, diptheria, botulism
Origin
Midbrain
Course
Between posterior cerebral artery and superior cerebellar artery  in lateral
wall of cavernous sinus (lateral to III)  superior orbital fissure  SO 
makes you look down and in
IV
Trochlear
Symptoms
SO 4
Can’t look down and in; head tilted to opposite side
Mononeuritis multiplex; multiple sclerosis; GBS; increased intracranial pressure; diphtheria;
botulism; diabetes; HTN
Aetiology
VI
Origin
Pons
Course
Over petrous temporal bone  in cavernous sinus (anterior to ICA, inferior
and medial to III)  superior orbital fissure between 2 heads of LR  LR
Abducens
Can’t look out; convergent strabismus
Symptoms
LR 6
Wernicke’s encephalopathy; mononeuritis multiplex; multiple sclerosis; GBS; increased
intracranial pressure; diphtheria; botulism
Holmes Adie
Pupil
Lesion of parasympathetic nerve supply (ie. Opposite of Horner’s)
Aetiology: usually secondary to bacterial / viral infection
Symptoms: slow accommodate; won’t react to direct / consensual light
Marcus Gunn
Pupil
Lesion of afferent pathway
Aetiology: multiple sclerosis
Symptoms: RAPD; will react to consensual light, not to direct light (so dilates
when you shine your light on it with swinging light test)
Aetiology
Mydriasis
Also: III palsy; drugs (anticholinergics, TCA’s)
Argyl
Robertson
Pupil
Miosis
Pupil
Problems
Other
Origin
V
Course
Symptoms
Trigeminal
Horner’s
Syndrome
Lesion of iridodilator fibres in midbrain
Aetiology: diabetes, syphilis, alcoholic neuropathy, midbrain lesions
Symptoms: will accommodate; won’t react to direct / consensual light
Sympathetic nerve supply damage (ie. Opposite of Holmes Adie Pupil)
Lesion in medulla if IX, X, XI involved; lesion middle cranial fossa if V involved
Aetiology: CVA, aneurysm, cavernous sinus thrombosis (if III, IV, VI
involved), carotid dissection, cancer (brain, lung, pancoast, thyroid,
cervical, jugular foramen), glioma, encephalitis, infection, sinusitis,
multiple sclerosis, syringomyelia, trauma (thyroid, laryngeal surgery, stab
wound), basal skull fracture)
Symptoms: miosis; ptosis; enopthalmus; anhydrosis (if present = central /
preganglionic)
Diencephalic:
Mid position pupils
Reactive
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)
Pons
Posterior cranial fossa  over petrous temporal bone  middle cranial fossa (trigeminal ganglion
beside greater wing of sphenoid)  lateral wall of cavernous sinus
V1 = ophthalmic = sensory  Nasociliary  orbit through head of LR  infratrochlear, anterior
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, medial / lateral
pterygoid, buccal, deep temporal, masseter, auriculotemporal, inferior alveolar, lingual
Sensory: lower face and anterior head; mucous membranes of nose / sinuses / mouth / anterior
2/3 of tongue / orbit / dura / cornea; test corneal reflex; facial sensation
Motor: muscles of mastication; mylohyoid; anterior belly digastric; tensor palate / tympani;
buccinators; test muscles of mastication and jaw jerk
Pons
Course
Int auditory meatus  stylomastoid foramen  postmedial parotid gland
Symptoms
Chorda tympani: sensory, parasympathetic; submandibular and sublingual glands, taste anterior
2/3 tongue
Muscular: temporal, zygomatic, buccal, mandibular, cervical, posterior belly digastric, stylohyoid;
facial expression (LMN involves occipitofrontalis)
Post auricular, meningeal; hyperacusis
Aetiology
VII
Origin
UMN: cancer, vascular
LMN: cancer, vascular; acoustic neuroma, Bell’s palsy (HSV 1), multiple sclerosis, Ramsay Hunt
syndrome, parotid, basal skull fracture, meningitis, otitis media, diphtheria, sarcoidosis (tends to
be bilateral not unilateral)
Facial
X
Whispering test, Rinne’s (behind ear, air should be > bone, if not = conductive deafness), Webers
(forehead; conductive localises to affected side, sensory to opposite), Hallpike
Acoustic neuroma, TORCH, # petrous temporal bone, aspirin, gentamicin, brainstem disease,
vascular, conductive
Origin
Medulla
Course
Jugular foramen  between IJV and ICA  between ICA and ECA  into pharynx and tongue
Tympanic (mucous membrane of middle ear and auditory tube, parotid), stylopharyngeus,
pharyngeal sensation, carotid sinus; taste and sensation to posterior 1/3 of tongue, tonsils,
posterior 1/3 palate, anterior epiglottis
Origin
Medulla
Course
Jugular foramen  in carotid sheath  anterior to subclavian artery, posterior to brachiocephalic
artery
Symptoms
Glossopharyngeal
Int auditory meatus  cochlear and vestibular branches
Symptoms
IX
Course
Aetiology
Vestibulocochlear
Pons
Symptoms
VIII
Origin
Mengingeal, auricular (tympanic membrane), pharyngeal, superior laryngeal (mucous membranes
above cords), recurrent laryngeal (mucous membranes below cords), cardiac, visceral
Uvula deviation away, absent gag, hoarseness, bovine cough
Vagus
Origin
Pons
Course
Foramen magnum  spinal root and cranial root
XI
Accessory
Symptoms
Hypoglossal
Origin
Medulla
Course
Hypoglossal canal
Symptoms
XII
Drooping of shoulder; downward rotation and protraction of scapula; wasting of trapezius
To all except palatoglossus; tongue deviates to side of lesion