This document summarizes the anatomy and function of the oculomotor nerve (CN III). It describes the afferent pathways and nuclei that control eye movements. The course of CN III is outlined, from its origin in the midbrain through the subarachnoid space and cavernous sinus. The nerve then divides into superior and inferior branches. Common lesions and their clinical presentations are listed, including microvascular causes, trauma, aneurysms, and compressive lesions. Various syndromes involving CN III palsies are also mentioned.

1. Oculomotor Nerve
Course and localisation of leision

2. Afferents
• PPARF (Horizondal eye movement)
• Rostral interstetial nucleus of MLF(Vertical movement)
• Vestibular nucleus
• Occipital cortex
• Cerebellum

3. The nuclear complex

4. • Several paired group of motor nerve cells adjacent to midline
and ventral to the aqueduct of sylvius at the level of superior
colliculus
• Centrally grouped nucleus innervate pupilary spinchter and
ciliary body
• Ventral to this group cells mediate the action of levator of
eyelid,superior and inferior recti ,inferior oblique and medial
rectus

5. • Medial rectus neurons occupy three separate location within
oculomotor nucleus.
• Superior rectus receives only crossed fibers
• LPS has bilateral innervation
• Arrangement of fibers is like that fibers for pupilary
constriction are less susceptible for microvascular changes
than deeper fibers.

7. Intramedullary Course

9. • In sub arachanoid space 3rd nerve passes in between superior
cerebellar and posterior cerebral arteries course forward near
the medial aspect of the temporal lobe pierces the dura matter
just lateral to the clinoid and enters into lateral wall of
cavernous sinus

11. • Then it divides into inferior and superior division
• Superior branch supplies-superior rectus and LPS
• Inferior branch supplies- Medial rectus
Inferior rectus
Inferior oblique
Parasympathetics to pupilary and
ciliary

12. • Extramedullary course

13. Lesions
• Pupilary sparing- Microvascular
Diabetes Mellitus
Hypertension
Vasculitis
Clotting disorders
Spirochateal disease
Pupilary involvement with acute onset , headache
Compressive aetiology like aneurysm

14. • Traumatic 3rd nerve palsy: Due to RTA high speed frontal
deceleration with skull fracture.
Cavernous sinus thrombosis: Multiple cranial nerve palsies .
Divisional palsies suggest orbital or anterior cavernous sinus
pathologies.
-Superior division: ipsilateral dysfunction of superior rectus and
LPS
-Inferior division: impaired down gaze,medial gaze, pupilary
constriction

16. • Isolated medial rectus palsy most often caused by INO or
myasthenia gravis or orbital disease involving horizontal rectus
palsy.
• Nuclear 3rd nerve palsy: ipsilateral medial rectus
inferior rectus
inferior oblique
contralateral superior rectus

17. • Cranial nerve 3 fasiculus leision:
BENEDICTS SYNDROME
WEBERS SYNDROME
Comatose patient: HUTCHINSON PUPIL (Uncal herniation)

18. Recovery
• Microvascular have complete recovery
• Traumatic palsy recovery may have synkinesis: pseudo von
grafe sign.
• Marcus gunn Jaw aberrant 5th nerve to 3rd nerve
• Differential diagnosis: Miller fischer variant of MG
Chronic progressive external opthalmoplegia

19. Mid brain fungal abscess

20. Tolosa–Hunt syndrome

21. left posterior communicating
artery aneurysm

22. Schwannoma