This document discusses the anatomy and functions of the 12 pairs of cranial nerves. It provides details on each nerve including their origin, course, functions for sensory, motor and autonomic fibers. It discusses various cranial nerve palsies and related clinical signs that help localize lesions in the brainstem or surrounding structures. Specific syndromes and diseases that can cause cranial nerve involvement are also outlined. Visual field defects, nystagmus, Horner's syndrome and bulbar signs are explained in relation to underlying anatomical locations.

1. Anatomy of Cranial Nerves & its
usage
Dr Yogiraj Ray , MD
Assistant Professor
Tropical Medicine
Calcutta School of Tropical Medicine

2. Cranial nerves
• bundles of sensory or motor fibers that
innervate muscles or glands; carry impulses
from sensory receptors, or show a combination
of these fiber types
• emerge through foramina or fissures in the
cranium and are covered by tubular sheaths
derived from the cranial meninges
• 12 pairs
• named as per functions

5. Cranial nerves

6. Olfactory

7. Optic

8. Occulomotor, Trochlear, Abducent

9. Trigeminal

10. Facial

11. Vestibulo-cochlear

12. Glossopharyngeal

13. Vegus

14. Branches of X

15. Spinal accessory

16. Hypoglossal

17. Autonomic nerve supply of glands

18. Nerve Foramen General
destination
Sensory function Somatic
motor
function
Autonomic
motor
function
I (s) Olfactory
foramina
Olfactory bulb Olfaction
II (s) Optic canal Optic chiasma,
midbrain
vision
III (m) Superior
orbital fissure
(middle part)
muscles of eye Extra occular
ms (except
LR, SO) & LPS
Miosis &
accommod
ation
IV (m) Superior
orbital fissure
muscles of eye Superior
Oblique
V
(m+s)
Ophthalmic
(V1): superior
orbital fissure
Maxillary (V2) :
F. rotundum
Mandibular (V3)
: F. ovale
Sensory
neurons : Pons
Motor neurons
: muscles of
mastication
V1 : forehead, upper
eyelid, nose, nasal
cavity
V2 : nose, lower
eyelid, upper lip,
cheek, gum, palate,
pharynx
V3 : lower lip, palate,
gum,tongue
Muscles of
mastication

19. Nerve Foramen General
destination
Sensory
function
Somatic
motor
function
Autonomic
motor
function
VI (m) Superior orbital
fissure
muscles of eye Lateral
Rectus
VII
(m+s)
Internal acoustic
meatus &
stylomastoid
fotamen
Sensory: Pons
Motor: muscles
of facial
expression ,
lacrimal, sub
mandibular,
sublingula gland,
mucosa
Taste from
anterior 2/3rd of
tongue
Facial, scalp,
neck muscles
lacrimal,
sub
mandibular,
sublingula
gland,
mucosa of
nose &
palate
VIII
(s)
Internal Acoustic
Meatus
Sensory :
Medulla, Pons,
Cerebellum,
Thalamus
Vestibular :
equilibrium
Cochlear:
hearing
IX
(m+s)
Jugular foramina Sensory: medulla
Motor: Speech,
swallowing,
parotid gland
Taste from
posterior 1/3rd
of tongue
Pharynx, Post
tongue, baro &
Chemoreceptors
Ms of
Pharynx &
tongue
Saliva
production
& secretion
: parotid

20. Nerve Foramen General
destination
Sensory function Somatic
motor
function
Autonomic
motor
function
X
(m+s)
Jugular
foramina
Sensory:
Mesulla
Motor: throat,
heart, lung,
abdominal
viscera
Skin at back of ear,
external auditory
meatus, tympanic
membrane,larynx,
trachea, oesophagus,
thoracic and
abdominal viscera,
chemo &
baroreceptors
Taste from epiglottis,
pharynx.
Swallowing,
coughing,
voice
production
Smooth
muscle
contraction
of viscera,
secretion of
visceral
glands
Relaxation
of airways
& ↓ heart
rate
XI (m) Jugular
foramina
Motor: soft
palate, throat,
sternocleidoma
stoid, trapezius
Swallowing &
head
movement
XI (m) Hypoglossal
canal (occipital
bone)
Tongue muscles
except
paltoglossus
Speech &
swallowing
via muscles
of tongue

21. Visual field defects
• Central, cecocentral, arcuate scotoma
(maccula & peri maccular lesions) – glaucoma,
optic drusen, AION, optic neuropathy
(demyelination, toxic/nutritional, syphilis)
• Enlarged blind spot - ↑ ICT (papilloedema)
• Ring scotoma – Retinitis pigmentosa,
glaucoma (ring with horizontal nasal step),
Bull’s eye retinopathy, severe myopia

22. Visual field defect: hemianopia
• Vertical (nasal/temporal) or Altitudinal (sup./inf.)
• Quadrantopia: 1/4th
• As per correspondence to visual field:
homonymous/bipolar(similarity of field) or
congruous/incongruous (point to point
correspondence)
• Monoocular defect → lesion of eye, retina/optic nv
• Binocular defect → lesion localised to or beyond optic
chiasm
• Optic tract upto LGB →incongruous
• Beyond LGB →congruous

24. Compressive chiasmal syndromes
• Pituitary tumor, Chiasmal glioma, Meningioma,
Craniophayngioma
• Empty sella, pituitary apoplexy
• Hydrocephalus
• Chronic fungal infection/sinusitis
• Crypto meningitis
• Encephalitis, TB, EBV,
• SLE, Neuro-sarcoid
• Shunt infection

25. Homonymous hemianopia
• More posterior to LGB more congruous
• Optic tract lesion – contralateral eye RAPD/
Marcus Gunn pupil with normal visual acuity
bilaterally with complete HH
• SQ(pie in sky)–temporal OR /Meyer’s loop
• IQ (pie on floor)- Parietal OR/ Occipital OR
• HH with maccular sparing
• Key hole vision (b/l HH)

26. RAPD
https://www.youtube.com/watch?v=DqTj5BUrKgk
• Bilaterally normal constriction when normal eye is
illuminated but Pupillary dilatation when flashlight is
switched to diseased eye
• Contralateral optic tract disease (as more crossed fibre run
in optic tract; 53:47) → dilated pupil directs the side of
lesion
• Contralateral Pretectal lesion (RAPD without visual loss)
Unilateral RAPD →
• Optic neuritis : MS (usually with Uhthoff symptom-
worsening of vision with exercise/bright light), NMO (Optic
neuritis preceded/followed by transverse or ascending
myelopathy)
• Large retinal disease

27. Raised ICT
• Causes???????

28. Syndromes causing ↑ICT
• Hydrocephalus
• Mass lesion: tumor, haemorrhage, abscess, large
infraction
• Meningo-encephalitis
• SAH
• Trauma
• Primary pseudotumor ceribri
• Secondary pseudotumor ceribri : pregnancy,
diseases, drugs

29. Localization with 3rd nerve: GUESS?
• 3rd nv nucleus
• 3rd nv nucleus + MLF
• 3rd nv fascicle + Red nucleus/substantia nigra
• 3rd nv fascicle + Sup cerebeller peduncle
• 3rd nv fascicle + cerebral peduncle
• Cavernous sinus
• Superior orbital fissure
• Inside orbit

30. Localization with 3rd nerve
• 3rd nv nucleus → ipsilateral 3rd palsy
• 3rd nv nucleus + MLF → ipsilateral 3rd palsy + INO
• 3rd nv fascicle + Red nucleus/S.nigra → 3 + contra.
choreiform movement (Benedict)
• 3rd nv fascicle + Sup cerebeller peduncle → 3 + contra.
ataxia (Claude)
• 3rd nv fascicle + cerebral peduncle → 3 + contra.
Hemiparesis (Weber)
• Cavernous sinus → painful or painless 3 ± 4,6, ophthalmic;
Horner’s Syndrome
• SOF → 3 ± 4,6, ophthalmic with proptosis
• Inside orbit → 3 + visual loss, chemosis, lid swelling

31. Diplopia
Monocular
• Cover test
• Disease of eye
Binocular
• Supranulear
• Ocular motor nerve
• N M junction
• Diseases of eye
muscle
• Sinusitis

33. Horner syndrome : sympathetic
dysfunction
• Central (hypothalamus, brain stem, spinal chord)–
meningitis, brain abscess, tumor, haemorrhage, GC
arteritis, midbrain infract, Wallenberg syndrome,
Syringomyelia
• Preganglionic intermediate (neck, head, lung, brachial
plexus) – lung ca, thyroid malignancy, metastasis, Glomus,
Syringomyelia, TOO, mediastinal widening, Herpes Zoster
(T3-T4), Klumpke paralysis
• Postganglionic – Cavernous sinus lesion, headache
syndromes, inflammation of adjuscent structures, CSOM,
Herpetic geniculate neuralgia, systemic
peripheral/autonomic ds (DM, MM due to CMV, Shy-Drager
syndrome), vascular ds of ICA (GCA, TA, Fibromuscular
dysplasia)

35. Cavernous sinus / SOF disorders
• Aneurism
• Thrombosis
• Tuberculoma
• Tumours – pituitary adenoma, meningioma,
lymphoma, arachnoids' cyst, myeloma,
nasopharyngeal ca, metastasis
• Sphenoidal sinusitis & mucocele
• Tolosa Hunt Syndrome & other granulomatous
disease
• CC fistula

36. Nystagmus
• involuntary, jerky, oscillations
• Rapid movement indicates the direction
• Lasting ≤2 beats is normal (at the extremes of
gaze)
• UP-AND-DOWN—
• upbeat nystagmus classically occurs with lesions
in the midbrain or at the base of the 4th ventricle
• downbeat nystagmus in foramen magnum
lesions.

37. Nystagmus contd.
• HORIZONTAL NYSTAGMUS –
• vestibular lesion (acute: nystagmus away from
lesion; chronic: towards lesion), or cerebellar
lesion (unilateral lesions cause nystagmus
towards the affected side)
• more in whichever eye is abducting (INO)
• deafness/tinnitus, suspect a peripheral cause (eg
8th nerve lesion, barotrauma, Meniere’s)
• varies with head position (BPV)

38. INO
https://www.youtube.com/watch?v=_rXQmDZva8Y
• Adduction weakness on the side of MLF lesion
and contralateral monocular nystagmus of
abducting eye
• MS, stroke, trauma, SOL
• One-and-a-half Syndrome
(contralateral eye
no movement → lost
Horizontal gaze centre)

39. Localization with 4th nv
• In isolation very rare
• Nuclear/fascicle: RAPD without visual loss/INO
• Sub arachnoid space : raised ICD false
localisation

40. Localization with 6th nv
• Nuleus → Gaze palsy
• Fascicle (paramedian pons) → Ipsilateral 6th palsy +
Ipsilateral 7thpalsy + contralateral hemiparesis (Millard-
Gubler)
• 6th nv (petrous apex) → 6 + deafness + facial (retro-orbital)
pain (Gradenigo)
• Sub arachnoid space → longest EC course through cisterna
pontis and sharp bend over petrous apex (commonest false
localizing sign)
• Cavernous sinus
• SOF
• Orbit

41. Multiple ocular motor palsy (b/l)
• Myasthenia gravis
• Demyelineting ds
• Botulism
• Diphtheria
• Wernicke encephalopathy
• Miller Fischer syndrome
• Whipple’s ds
• Brainstem ischemia/haemorrhage

43. Localization with 7th nv
• Supranuclear (central)→ contralateral paresis of
lower face with relative sparing of upper face
(supranuclear control of upper face has both
ipsilateral & contralateral components but lower
face only has contralateral supranuclear
connection)
• Peripheral type facial palsy → ipsilateral both
upper & lower face
• Brain stem: associated INO/6th nv palsy or CP
angle lesion

44. 7th nv : CP angle lesion
• Classic feature→ ipsilateral peripheral type 7th
nv palsy (with loss of taste anterior 2/3rd of
tongue) without hyperacusis + ipsilateral
tinnitus, deafness, vertigo
• Other extentions : Pons (nystagmus/ipsilateral
gaze palsy), 5th nv (facial pain, sensory
changes), 6th (gaze palsy), rarely bulbar palsy
• Cause : acoustic neuroma, meningioma, HIV
neurology

45. Localization with peripheral 7th palsy
• Facial canal: loss of taste + hyperacusis +
neuralgia (Ramsay Hunt → blisters)
• After stylomastoid foramen : isolated motor
paralysis
Causes: Idiopathic (Bell’s palsy), DM, Uremia,
Infections (HSV,EBV, VZV, Mumps, Leprosy, HIV
seroconversion), CTD (PAN, GCA, WG, Sarcoid,
Bechet, RA), Neoplasms, Drugs (Ribavirin,
Cyclosporin), Vaccines, Barotrauma, Altitude
sickness, Melkersson Rosenthal syndrome

46. B/L facial nerve palsy
• Granulomatous & CTD
• Infections
• Neoplasm
• Trauma
• GBSyndrome
• Fisher type GB (ophthalmoplegia, ataxia,
arreflexia)
• MS
• DM
• B/L Bell’s palsy

47. 9,10,11th palsy
Bulbar (LMN)
• Gag reflex – absent
• Tongue – wasted, fasciculations
“wasted, wrinkled, thrown into
folds and increasingly
motionless”.
• Palatal palsy
• Jaw jerk – absent or normal
• Speech – nasal
“indistinct (flaccid dysarthria),
lacks modulation and has a nasal
twang”
• Emotions – normal
• signs of the underlying cause, e.g.
limb fasciculations.
Pseudobulbar (UMN)
• Gag reflex – increased or normal
• Tongue – spastic
“it cannot be protruded, lies on the
floor of the mouth and is small and
tight”.
• Palatal movement – absent.
• Jaw jerk – increased
• Speech – spastic: “a monotonous,
slurred, high-pitched, ‘Donald
Duck’ dysarthria” that “sounds as if
the patient is trying to squeeze out
words from tight lips”.
• Emotions – labile
• bilateral upper motor neuron (long
tract) limb signs

48. 9,10,11th palsy
Bulbar (LMN)
• Motor neuron disease
• Syringobulbia
• Guillain-Barre syndrome
• Poliomyelitis
• Subacute menignitis
(carcinoma, lymphoma)
• Neurosyphilis
• Brainstem CVA
• HIV neurology
Pseudobulbar (UMN)
• Bilateral CVAs affecting the
internal capsule
(commonest)
• Multiple sclerosis
• Motor neuron disease
• High brainstem tumors
• Head injury
• HIV neurology

49. THANK YOU
Further reading
1. Localization in clinical neurology : Paul Brazis
2. Neurological Differential Diagnosis : John Patten