OCULAR MOTOR NERVE PALSIES 1. Third nerve 2. Fourth nerve 3. Sixth nerve

Anatomy of third nerve Oculomotor nucleus Pituitary gland Red nucleus Carotid artery Cavernous sinus Pons III nerve Post cerebral artery Clivus Basilar artery

Applied anatomy of pupillomotor nerve fibres Blood vessels on pia mater supply surface of the nerve including pupillary fibres ( damaged by compressive lesions ) Vasa nervorum supply part of nerve but not pupillary fibres ( damaged by medical lesions ) Pupillary fibres lie dorsal and peripheral

Signs of right third nerve palsy Ptosis, mydriasis and cycloplegia Abduction in primary position Normal abduction Intorsion on attempted downgaze Limited adduction Limited elevation Limited depression

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 palsy Idiopathic - about 25% Vascular disease - hypertension, diabetes Trauma Posterior communicating aneurysm Extradural haematoma Aneurysm Chiasm Midbrain pushed across Edge of tentorium Prolapsing temporal lobe Posterior cerebral artery Third nerve

Anatomy of fourth nerve Only cranial nerve to emerge dorsally Crossed cranial nerve Very long and slender Internal carotid artery Postr. communicating artery III VI Postr.cerebral artery Supr.cerebellar artery Basilar artery IV

Signs of right fourth nerve palsy Right hyperdeviation in primary position when left eye fixating Excyclotorsion Right underaction on depression in adduction Vertical diplopia Right overaction on left gaze

Positive Bielschowsky test in right fourth nerve palsy Increase in right hyperdeviation on ipsilateral head tilt Absence of right hyperdeviation on contralateral 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 nerve Basilar artery Pituitary gland Medial lemniscus Carotid artery 4th ventricle Cavernous sinus Petroclinoid ligament Clivus Vestibular nucleus VI nerve Pyramidal tract

Recent right sixth nerve palsy Right esotropia in primary position due to unopposed action of right medial rectus Marked limitation of right abduction due to right 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 palsy Vascular - hypertension, diabetes Raised intracranial pressure Acoustic neuroma Dilated ventricles Petrous tip Brainstem pushed downwards