OCULAR MOTOR NERVE PALSIES

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OCULAR MOTOR NERVE PALSIES
1. Third nerve
2. Fourth nerve
3. Sixth nerve
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Anatomy of third nerve
Oculomotor nucleus
Pituitary gland
Red nucleus
Carotid artery
Cavernous sinus
Pons
III nerve
Post cerebral artery
Clivus
Basilar artery
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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
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Signs of right third nerve palsy

• Ptosis, mydriasis and cycloplegia
• Abduction in primary position

• Normal abduction

• Intorsion on attempted
• downgaze

• Limited depression

• Limited adduction

• Limited elevation

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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

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Important causes of isolated third nerve palsy
Idiopathic - about 25 Vascular disease -
hypertension, diabetes
Posterior communicating aneurysm
Trauma
Extradural haematoma
Aneurysm
Chiasm
Midbrain pushed across
Edge of tentorium
Prolapsing temporal lobe
Posterior cerebral artery
Third nerve
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Anatomy of fourth nerve
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Signs of right fourth nerve palsy

• Right underaction on depression
• in adduction
• Vertical diplopia

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

• Right overaction on left gaze

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Positive Bielschowsky test in right fourth nerve
palsy
Absence of right hyperdeviation on
contralateral head tilt
Increase in right hyperdeviation on ipsilateral
head tilt
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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

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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
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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
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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

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Old right sixth nerve palsy
Straight in primary position due to partial
recovery
Limitation of right abduction and horizontal
diplopia
Normal right adduction
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Important causes of isolated sixth nerve palsy
Vascular - hypertension, diabetes
Acoustic neuroma
Raised intracranial pressure
Dilated ventricles
Petrous tip
Brainstem pushed downwards