OCULAR MOTOR NERVE PALSIES

1. Third nerve

2. Fourth nerve

3. Sixth nerve

Anatomy of third nerveOculomotor nucleus

Pituitary gland

Carotid artery

Cavernous sinus

III nerveClivus

Basilar artery

Post cerebral artery

Red nucleus

Pons

Applied anatomy of pupillomotor nerve fibresBlood vessels on pia mater supply surface of the nerve including pupillary

fibres ( damaged by compressive lesions )

Vasa nervorum supply partof nerve but not pupillaryfibres ( damaged by medicallesions )

Pupillary fibres lie dorsal and peripheral

Signs of right third nerve palsy

• Ptosis, mydriasis and cycloplegia

• Abduction in primary position

• Limited depression • Limited adduction

• Normal abduction

• Limited elevation

• Intorsion on attempted downgaze

Hess chart of right third nerve palsy

• Contraction of right chart and expansion of left• Right chart - underactions of all muscles except lateral rectus and superior oblique• Left chart - overactions of all muscles except medial rectus and inferior oblique

Important causes of isolated third nerve palsyIdiopathic - about 25%Vascular disease - hypertension, diabetes

Posterior communicating aneurysmTrauma

Extraduralhaematoma

Prolapsingtemporallobe

Edge oftentorium

Aneurysm

Chiasm

Third nerve

Posterior cerebralartery

Midbrainpushedacross

Anatomy of fourth nerve

• Only cranial nerve to emerge dorsally• Crossed cranial nerve• Very long and slender

Internal carotid artery

Postr. communicating artery

IIIVI

Postr.cerebral arterySupr.cerebellar artery

Basilar arteryIV

Signs of right fourth nerve palsy

• Right overaction on left gaze

• Right underaction on depression in adduction • Vertical diplopia

• Right hyperdeviation in primary position when left eye fixating• Excyclotorsion

Positive Bielschowsky test in right fourth nerve palsy

Absence of right hyperdeviation on contralateral head tilt

Increase in right hyperdeviation on ipsilateral head tilt

Hess chart of right fourth nerve palsy

• No significant difference in chart size• Upward deviation of right fixation spot on inner chart (hypertropia)• Downward deviation of left fixation spot on inner chart• Right chart - underaction of superior oblique and overaction of inferior oblique• Left chart - overaction of inferior rectus and underaction of superior rectus

Anatomy of sixth nerveBasilar artery

Pituitary gland

Carotid artery

Cavernous sinus

VI nerve

Petroclinoidligament

Clivus

Pyramidal tract

Vestibularnucleus

Mediallemniscus

4th ventricle

Recent right sixth nerve palsy

Right esotropia in primary position due to unopposed action of right medial rectus

Marked limitation of right abduction due toright lateral rectus weakness

Hess chart of recent right sixth nerve palsy

• Contraction of right chart and expansion of left• Right chart - marked underaction of lateral rectus and mild overaction of medial rectus• Left chart - marked overaction of medial rectus

Old right sixth nerve palsy

Straight in primary position due to partial recovery

Limitation of right abduction and horizontal diplopia

Normal right adduction

Important causes of isolated sixth nerve palsyVascular - hypertension, diabetes

Acoustic neuromaRaised intracranial pressure

Dilated ventricles

Petroustip

Brainstem pushed downwards