The oculomotor nucleus complex present in the midbrain, at the level of the superior colliculus Contains Main motor nucleus and Accessory parasympathetic nucleus (Edinger-Westphal nucleus) Fibers pass between the posterior cerebral artery and the superior cerebellar artery to reach the cavernous sinus. During this course, the oculomotor nerve lies lateral to the posterior communicating artery. The nerve then divides into a superior and inferior division and enters the orbit through the superior orbital fissure Third nerve palsy results from dysfunction of the nerve along its pathway from the midbrain to the extraocular muscles it innervates. Third nerve palsies can cause dysfunction of the somatic muscles (SR ,IR,MR,IO, levator palpebral superioris) and autonomic muscles (the pupillary sphincter and ciliary muscle.) classification 1. Complete or incomplete palsy Complete: Involves both superior and inferior divisions of the nerve. Incomplete: Involves superior division, inferior division (rarely), or an isolated muscle 2. Total palsy or partial paresis ● Total: Full restriction of extraocular muscles is present. ● Partial: Restriction of extraocular muscles is limited. 3. Pupil-involving or pupil-sparing palsy ● Pupil involving: Pupil is dilated, with an accommodative insufficiency. ● Pupil sparing: Pupil and accommodative function are normal.

1. UNIVERSITY OF GONDAR
College of Medicine & Health Science
Department of Optometry
Binocular vision and clinical neurology
Third nerve palsy
Getachew Kassahun ( B optom)
April, 2023
11/16/2023 1

2. Objecctives
At the end of this session you will be able to
 Discuss anatomy of oculo motor nerve
 Identify etiology of oculo motor nerve palsy
 Discuss classification of oculo motor nerve palsy
 Discuss evaluation of oculo motor nerve palsy
 Identify management options
11/16/2023 2

3. Outline
• Anatomy and physilogy of oculomotor nerve
• Third nerve palsy
• Etiology
• Classification of third nerve palsy
• Clinical features
• Evaluation
• Differential diagnosis
• Managment
11/16/2023 3

4. ANATOMY
• The oculomotor nucleus complex present in the midbrain, at the level of the superior
colliculus
• Contains Main motor nucleus and Accessory parasympathetic nucleus (Edinger-
Westphal nucleus)
• Fibers pass between the posterior cerebral artery and the superior cerebellar artery to
reach the cavernous sinus.
• During this course, the oculomotor nerve lies lateral to the posterior communicating
artery. The nerve then divides into a superior and inferior division and enters the orbit
through the superior orbital fissure
11/16/2023 4

5. Midbrain
3rd nucleus Posterior communicating
artery
Cavernous sinus
CN III
11/16/2023 5

6. Functions
• The third nerve innervates Four of six EOMs ( SR, MR, IR,IO) , levator palpebrae
superiers and fibers innervating the iris sphinictor and ciliary body.
• The parasympathetic fibers innervating the pupil and ciliary body are located on the
periphery of the nerve
• The superior divisions (superior rectus, levator palpebrae superioris) and inferior
divisions (medial rectus, inferior rectus, inferior oblique) as it enters the cavernous
sinus.
11/16/2023 6

7. 11/16/2023 7

8. Third nerve palsy
• Third nerve palsy results from dysfunction of the nerve along its pathway from
the midbrain to the extraocular muscles it innervates.
• Third nerve palsies can cause dysfunction of the somatic muscles (SR
,IR,MR,IO, levator palpebral superioris) and autonomic muscles (the pupillary
sphincter and ciliary muscle.)
11/16/2023 8

9. 11/16/2023 9
Right third nerve palsy. A, Right ptosis and eye in classic“down and out” position.
B, Inability of right eye to adduct in left gaze
C, Right exotropia in down gaze. D, Right hypoexotropia in primary gaze. E, Inability of right eye to
elevate.
E

10. Common in adults:
● Microvascular (diabetes, hypertension, atherosclerosis)
● Compression (tumor, aneurysms)
● Trauma
● Congenital
● Migrainous
● Infectious
common in children
11/16/2023 10
Etiology

11. Cont...
• Supranuclear lesions: Lesions at the level of the cerebral cortex or the supranuclear pathway cause
conjugate paresis of both the eyes.
• Nuclear lesions: Vascular diseases, demyelination, and tumors
• Fascicular lesions:Vascular diseases, demyelination, and tumors.
• Basilar portion: isolated and painful third-nerve palsy. causes include aneurysms, diabetes mellitus and
extradural hematoma. palsy results from either direct compression of the nerve by an aneurysm or due to
subarachnoid hemorrhage.
• Intracavernous portion: any lesion in the cavernous sinus will result in multiple nerve palsies. The
common etiology is diabetes, pituitary apoplexy, aneurysm, or carotid-cavernous fistula.
• Intraorbital portion: main causes are trauma, tumors, and Tolosa-Hunt syndrome
11/16/2023
11

12. Cont...
• Congenital causes: Development aplasia or hypoplasia of the oculomotor nucleus,
birth trauma due to molding forces acting on the skull during labor, intrauterine
trauma, and rarely infections such as meningitis.
11/16/2023 12

13. Epidemiology
• Third-nerve palsy is an important sign of life-threatening aneurysms. Keane et al. studied the
causes of TN and found the incidence of aneurysm to be 10%, and bilateral cases were seen
in 11% of patients.
• The incidence in females and males is not significantly different; whereas, it is less frequent
in children and young adults.
• The age group maximally affected by third-nerve palsy is more than 60 years
• Pupil involvement was seen in 43% of patients on presentation, 86% of patients presented
with ptosis on the first visit.
• The incidence of acquired third-nerve palsy in the US population-based survey by Chengbo
et al. was noted to be 4.0 per 100,000.
11/16/2023 13

14. Classification of oculomotor nerve palsy
1. Complete or incomplete palsy
 Complete: Involves both superior and inferior divisions of the nerve.
 Incomplete: Involves superior division, inferior division (rarely), or an isolated muscle
2. Total palsy or partial paresis
● Total: Full restriction of extraocular muscles is present.
● Partial: Restriction of extraocular muscles is limited.
3. Pupil-involving or pupil-sparing palsy
● Pupil involving: Pupil is dilated, with an accommodative insufficiency.
● Pupil sparing: Pupil and accommodative function are normal.
11/16/2023 14

15. Complete and partial palsy
 Complete third nerve palsy presents with
-Downward and outward deviation of the eye
-Complete ptosis
-The inability to adduct, infraduct, or supraduct the eye
 Partial third nerve palsies are more common and present with variable limitation of
upward, downward, adducting movements, ptosis and pupillary dysfunction.
11/16/2023 15

16. complete ptosis on the right; a nonreactive, dilated pupil; and severely limited extraocular movement except for abduction
11/16/2023 16

17. Pupil-involving third nerve palsy
• Results from loss of parasympathetic input and produces a mid- dilated pupil that
responds poorly to light.
• Patients may present with variable dysfunction of the levator palpebrae or extraocular
muscles.
• Aneurysms that arise at the junction of the posterior communicating artery and internal
carotid artery produce a CN III palsy as the initial manifestation of aneurysmal expansion
or rupture.
• Pupillary involvement occurs because the pupillomotor fibers reside superficially in the
medial aspect of the nerve.
11/16/2023 17

18. Pupil-sparing third nerve palsy
• Pupillary function is normal (ie, equal pupil size and reactivity), but there is
total loss of eyelid and ocular motor functions of CN III.
• These are the typical findings for ischemic cranial neuropathy, which
usually fully resolves within 6 months.
• Almost always benign and secondary to microvascular disease (diabetes
mellitus, hypertension, or hyperlipidemia).
11/16/2023 18

19. Clinical features
Symptoms
 Diplopia: Typically both horizontal and vertical, eliminated with monocular occlusion, and
may not be reported if ptosis is occluding the eye or if image separation is exceedingly
large
 Ptosis: Complete, incomplete, or absent due to aberrant regeneration
 Pain: May or may not be present
11/16/2023 19

20. Signs
 Ocular motility defect and ptosis
 Pupil: If involved, the pupil may be fixed and dilated, or partially dilated with a slow
response to light.
 Ocular deviation: In case of third-nerve palsy, the lateral rectus and superior oblique
are spared, and their unopposed action brings the eye in a “down and out” position.
 Head turn: A combination of head turns and/or tilts to alleviate diplopia may be
present.
 Aberrant regeneration: This is a misdirected regeneration of nerve fibers that more
commonly follows traumatic or compressive etiologies.
11/16/2023 20

21. Aberrant regeneration
 After nerve axons are damaged, the nerve fibers may regrow to innervate
muscles other than those they originally innervated.
 Classic findings include eyelid retraction with adduction or pupillary
miosis with elevation, adduction, or depression.
11/16/2023 21

22. Aberrant regeneration of the right CN III. A, In primary gaze, there is mild ptosis, pupillary mydriasis, and
exotropia, all on the right.
B, With attempted downward gaze, the right eyelid retracts as fibers of the right CN III supplying the inferior
rectus now also innervate the levator muscle.
A B
11/16/2023 22

23. Classification Involved muscles Ocular alignment
Restricted
versions
Ptosis Comment
Complete
MR. SR, IR. IO
LPS
Exotropia;
hypotropia; intorted
Adduction;
elevation;
depression
Yes
Acquired type with pupil
involved is a medical emergency
Superior division
SR, levator Hypotropia Elevation
Yes More likely congenital
Inferior division
Medial rectus;
inferior rectus;
inferior oblique
Exotropia
hypertropia
intorted
Adduction
elevation
depression
No Rare
Isolated muscle
Medial rectus
Exotropia
Adduction
No
Very rare; suspect
myasthenia or mechanical
Isolated muscle Superior rectus Hypotropia
Elevation when
abducted
No
Rare; suspect superior oblique in
other eye
Isolated muscle
Inferior rectus Hypertropia Depression
when abduction
No Rare
Isolated muscle Inferior oblique Hypotropia
Elevation when
adducted
No
Very rare; suspect Brown’s
syndrome
11/16/2023 23

24. Evaluation
• Observe for
-ocular deviation
-ptosis
-palpebral fissure asymmetry
• History
• Vision assesment
• Pupillary assessment for relative size and reactivity.
11/16/2023 24

25. Evaluation cont...
History
• Onset and duration of symptoms? Diplopia (horizontal, vertical, or
oblique)? Orbital trauma? Headaches?
• Recent infections?
• Medical history (diabetes, hypertension,atherosclerosis, cancer)?
• Neurological symptoms (poor balance/coordination)?
11/16/2023 25

26. • Ocular motility monocularly and binocularly
 The extent of movement is assessed on the nine diagnostic positions of gaze
 Saccadic and pursuit movements.
• Lab workup :BP, CBC , blood sugar .
• Imaging ; MRI , CT in pupil involving case searching for aneurysm ,mass
11/16/2023 26
Evaluation cont...

27. Differential Diagnosis
 Thyroid ophthalmopathy
 Ophthalmoplegic migraine
 Myasthenia gravis
 Internuclear ophthalmoplegia
 Ptosis in adults or congenital ptosis
 Anisocoria
11/16/2023 27

28. Management
• Treatment initially involves medical management of systemic predisposing
factors and conservative measures
• Surgical intervention in non resolving oculomotor nerve palsy.
11/16/2023 28

29. Medical management
 Active systemic causes must be addressed
 Strict control of diabetes and hypertension
 Hyperlipidemia, anemia, and obesity should be adequately controlled
 Antivirals are used in herpetic oculomotor nerve palsy
 Pilocarpine can be used if there is Pupil involvement and there are no other
contraindications.
11/16/2023 29

30. Near add
• Diminished accommodation can also occur in pupil involving oculomotor palsy,
and near vision addition should be prescribed.
• This becomes also important when patching children for amblyopia treatment.
• Strabismus surgery is deferred until amblyopia management is complete
11/16/2023 30

31. Observation
• Strabismus surgery is usually deferred for a minimum of 6 months.
• If there is continuing improvement, surgery can be delayed further.
• Most oculomotor nerve palsy due to microangiopathy resolves completely in the first 2
to 3 months.
• Delays in surgery can result in irreversible amblyopia and increasing difficulties with
aberrant regeneration.
• Controlling diplopia by occluding one eye may be beneficial.
• Treatment of photophobia secondary to strabismus and pupil dilation by recommending
hat and sunglasses. Pilocarpine may be used in more extreme cases.
11/16/2023 31

32. Botulinum toxin
• Botulinum toxin acts by inducing temporary paralysis of the unopposed ipsilateral
antagonist muscle ,reducing the deviation
• Help to shorten the duration of symptoms in acute traumatic oculomotor nerve palsy .
• It might also be useful when the patient is not a candidate for neurosurgical
intervention or strabismus surgery, e.g due to unstable associated medical conditions.
11/16/2023 32

33. Surgical management
 Congenital palsy requires surgery
 In patients with partial oculomotor palsy and sufficient motility routine strabismus
surgery may be successful in restoring binocular single vision
 For complete third-nerve palsy; resection of the medial rectus and recession of the lateral
rectus muscle for correction of horizontal deviation.
 Superior oblique (SO) tendon transposition
 Surgical outcome is often better in partial oculomotor nerve palsy than complet
oculomotornerve palsy.
 Ptosis surgery is usually done 4–6 months following strabismus surgery
11/16/2023 33

34. References
• BCSC; section 5 neuro - ophthalmology.
• Erik_M._Weissberg,_OD_(Eds.)]_Essentials of Clinical binocular vision.
• Von Noorden GK, Campos EC. Binocular vision and ocular Motility: Theory and
management of strabismus. 6th ed.
11/16/2023 34

35. 11/16/2023 35