Oculomotor NerveCourse and localisation of leision

Afferents

• PPARF (Horizondal eye movement)

• Rostral interstetial nucleus of MLF(Vertical movement)

• Vestibular nucleus

• Occipital cortex

• Cerebellum

The nuclear complex

• 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

• 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.

Intramedullary Course

• 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

• 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

• Extramedullary course

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

• 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

• 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

• Cranial nerve 3 fasiculus leision: BENEDICTS SYNDROME WEBERS SYNDROME

Comatose patient: HUTCHINSON PUPIL (Uncal herniation)

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

Mid brain fungal abscess

Tolosa–Hunt syndrome

left posterior communicating artery aneurysm

Schwannoma