AN OPTHALMOLOGIST'S GUIDE TO DETAILED ANATOMY AND APPLIED ASPECTS OF THIRD NERVE.

1. THIRD CRANIAL NERVE – ANATOMY
AND ITS APPLIED ASPECTS
DR SHREYA TYAGI

2. OCULOMOTOR NERVE
! Motor In Function
! Supplies :All Extraocular Muscles Except Lateral Rectus
And Superior Oblique
! Also Supplies Intraocular Muscles- Sphincter Pupillae
And Ciliary Muscles.

3. FUNCTIONAL COMPONENTS
! SOMATIC EFFERENT COMPONENT :
Motor Supply To Muscles Derived From Head Myotomes - LPS, SR,MR,IR AND IO.
! GENERAL VISCERAL EFFERENT :
(Parasympathetic) For Accommodation And Contraction Of The Pupil – Motor Supply To Ciliaris
And Sphincter Pupillae.
! GENERAL SOMATIC AFFERENT :
Associated With Proprioceptive Impulses From The Extraocular Muscles.

5. OCULOMOTOR NUCLEAR COMPLEX
! Situated In Midbrain At Level Of Superior Colliculus In
The Ventromedial Part Of Central Grey Matter Surrounding
Cerebral Aqueduct
! 10mm Longitudnal Column
! Related Superiory With Floor Of Third Ventricle And
Inferiorly With Nucleus Of Trochlear Nerve.

6. COMPONENTS
1. MAIN MOTOR NUCLEUS:
BASED ON WARWICK’S CONCEPT:
❖ A. Dorsolateral Nucleus : I/L Inferior Rectus
❖ B. Intermediate Nucleus : I/L Inferior Oblique
❖ C. Ventromedian Ncleus : I/L Medial Rectus
❖ D. Paramedian Scattered Nucleus : C/L Superior Rectus
❖ E. Caudal Central Nucleus : B/L LPS
2.ACCESSORY MOTOR NUCLEUS (EDINGER WESTPHAL):

8. ACCESSORY MOTOR NCLEUS: EDINGER WESTPHAL
! Sends Preganglionic Parasympathetic Fibres Along With Other Oculomotor
Fibres
! Cranial Half: Light Reflex
! Caudal Half : Accomodation
! Median Part : Fork Shaped
! Previously Known As ‘ Nucleus Of Perlia’

9. CONNECTIONS OF THE NUCLEUS
1. Cerebral Cortex
• Motor Cortex (Precentral Gyrus) Of Both Sides Through Corticonuclear Tracts.
• Visual Cortex Through The Superior Colliculus And The Tactobulbar Tract.
• Frontal Eye Field.
2. Nuclei Of 4th, 6th And 8th Cranial Nerves Through The Medial Longitudinal Bundle.
3. Pretectal Nucleus Of Both Sides (For Light Reflex)
4. Vertical And Torsional Gaze Centers Through The Medial Longitudinal Bundle.
5. Cerebellum Through The Vestibular Nuclei.

11. COURSE AND DISTRIBUTION
❖ FASCICULAR
❖ BASILAR
❖ INTRACAVERNOUS
❖ INTRAORBITAL

12. 1. FASCICULAR PART
! Consists Of Efferent Fibres That Pass From Third Nerve Nucleus Through Red
Nucleus And The Medial Aspect Of Cerebral Peduncle .
! Emerge From Midbrain And Pass Into Interpeduncular Space

13. 2. BASILAR PART
! 15-20 Rootlets In The Interpeduncular Fossa.
! Coalase To Form A Large Medial And A Small Lateral Root,
Which Unite To Form A Flattened Nerve, Which Gets Twisted
Bringing The Inferior Fibres Superiorly And Superior Fibers
Inferiorly; And Thus The Nerve Becomes A Rounded Cord.
! The Nerve Then Passes B/W The Posterior Cerebral Artery And
The Superior Cerebellar Artery And Runs Forward In The
Interpeduncular Cistern ( Running Lateral To & Parallel With
The Posterior Communicating Artery) To Reach The
Cavernous Sinus.

14. 3. INTRACAVERNOUS PART
! The Nerve Enters The Cavernous Sinus By Piercing The Posterior Part Of Its Roof On The Lateral
Side Of The Posterior Clinoid Process.
! It Then Descends To The Lateral Wall Of The Sinus, Where It Lies Above The Trochlear Nerve.
! In The Anterior Part Of The Cavernous Sinus, The Nerve Divides Into Superior And Inferior
Divisions Which Enter The Orbit Through The Middle Part Of The Superior Orbital Fissure
Within The Annulus Of Zinn.
! In The Fissure, The Nasociliary Nerve Lies In B/W The Two Divisions, While The Abducent
Nerve Lies Inferolateral To Them.

15. 4. INTRAORBITAL PART
! In The Orbit, The Smaller Superior Division Ascends On The
Lateral Side Of Optic Nerve & Supplies The Superior Rectus And The LPS .
! The Larger, Inferior Division Divides Into Three Branches :
1. Nerve To The Medial Rectus Passes Inferior To The Optic Nerve.
2. Nerve To Inferior Rectus Passes Downward And Enters The Muscle On
Its Upper Aspect, And
3. Nerve To Inferior Oblique (Longest Of The Three Branches) Passes In B/
W The IR & LR And Supplies The Io From Its Posterior Border. It Gives
Off The Motor Root To The Ciliary Ganglion.

17. CILIARY GANGLION
❖ Peripheral Parasympathetic Ganglion .
❖ Lies Near The Apex Of Orbit
❖ Between Optic Nerve And Tendon Of LR Muscle
❖ Approx. 1 Cm In Front Of Annulus Of Zinn.
❖ Lies Lateral To Ophthalmic Artery.

19. ROOTS
SENSORY ROOT:
! Comes From Nasociliary Nerve
! Do Not Relay In The Ganglion
! Supplies Ciliary Body,iris And Cornea Through Short Ciliary Nerve
SYMPATHETIC ROOT:
! Branch From Internal Carotid Plexus
! Contains Postganglionic Fibres Which Come From Superior Cervical Ganglion
! Do Not Relay In Ciliary Ganglion
! Supply Blood Vessels Of Eye Ball Through Short Ciliary Nerve.
* Also Supplies Dilator Pupillae If Not Supplied By Nasociliary Nerve.
PARASYMPATHETIC:
! Arise From Nerve To Inferior Oblique
! Contains Preganglionic Fibres That Begin In Edinger Westphal Nucleus.
! Relay In Ganglion
! Post Ganglionic Fibres Supply Sphincter Pupillae And Ciliary Muscle Through Short Ciliary Nerves.

20. BRANCHES OF CILIARY GANGLION
! Ganglion Gives 8 – 10 Branches That Divide Into 15-20 Short Ciliary Nerves.
! Short Ciliry Nerve Pierces Sclera At Around Entrance Of Optic Nerve .
! Runs Forward In Between Sclera And Choroid , Reaches Ciliary Muscle

21. CLINICALLY APPLIED ASPECTS

22. CLINICAL FEATURES OF COMPLETE THIRD NERVE PALSY
1 PTOSIS - Paralysis Of LPS Muscle.
2 DEVIATION – Out, Down And Intorted – Unopposed Action Of LR And SO.
3 OCULAR MOVEMENTS :
! Adduction – MR
! Elevation – SR And IO
! Depression – IR
! Extorsion – IR And IO
4 PUPIL IS FIXED AND DILATED – Paralysis Of Sphincter Pupillae Muscle.
5 ACCOMMODATION Is Completely Lost – Paralysis Of Ciliary Muscle.
6 CROSSED DIPLOPIA: Seen On Raising The Eyelid. Occurs Due To Paralytic Divergent Squint.
7 HEAD POSTURE : Head Turned On Opposite Side,tilted Towards Same Side,chin Slightly Raised.

24. FEATURES OF THIRD NERVE LESIONS AT DIFFERENT LEVELS :
1. SUPRANUCLEAR LESION
! Lesions Of The Cerebral Cortex And Supranuclear Pathway
Conjugate Paresis
Affect Both Eyes Equally.
! In Supranuclear Lesions Position And Movements Of The Eyes Are Abnormal,
! Relative Co-ordination MAINTAINED
! NO DIPLOLPIA

25. 2. NUCLEAR LESIONS
! Lesions Involving Purely Third Nerve Nucleus - Relatively Uncommon.
! Common Causes : Vascular Diseases, Demyelination, Primary Tumors And Metastasis
! Lesions Involving Entire Nucleus Causes Ipsilateral Third Nerve Palsy With Ipsilateral Sparing And Contralateral Weakness Of
Elevation.
! Lesions Involving Paired Medial Rectus Subnuclei (Ventromedial Nucleus) Cause A Wall-eyed Bilateral Internuclear
Ophthalmoplegia ( WEBINO ) Characterised By Defective Convergence And Adduction.

26. 3. FASCICULAR LESION
! Causes Are Similar To Nuclear Lesions.
❑ Benedikt Syndrome : Involves The Fasciculus As It Passes Through Red Nucleus.
Characterised By Ipsilateral 3rd Nerve Palsy And Contralateral
Extrapyramidal Signs Such As Tremor And Jerky Movements.
❑ Weber Syndrome : Involves The Fasciculus As It Passes
Through The Cerebral Peduncle
Characterised By Ipsilateral 3rd Nerve Palsy And Contralateral Hemiplegia And
and Facial Palsy Of Upper Motor Neuron Type.

27. ❑ Nothnagel Syndrome : Lesion Within Midbrain Tectum
Involving Quadrigrminal Plate And Is Characterised
By U/L Or B/L 3rd Nv Paralysis And Ipsilateral Cerebellar Ataxia.
❑ Claude Syndrome : ( Brainstem Stroke Syndrome) , A Combination Of
Benedikt And Nothnagel Syndromes.

28. 4. LESIONS INVOLVING BASILAR PART OF THE NERVE
The Nerve Runs In The Subarachnoid Space At The Base Of Skull Unaccompanied By Any Other Cranial Nerve
, Isolated Third Nerve Palsies Are Frequently Basilar.
! Causes :
Aneurysms At The Posterior Communicating Artery Cause Isolated
Third Nerve Palsy With Involvement Of Pupil.
Extradural Hematomas Which May Cause Tentorial Pressure Cone
With Downward Herniation Of The Temporal Lobe. This Compresses The Third Nerve.
Initially There Occurs Fixed, Dilated Pupil,
Which Is Followed By A Total Third Nerve Palsy.
Diabetes Causes Isolated 3rd Nerve Palsy With Sparing Of The Pupillary Reflexes.

30. 5. LESIONS INVOLVING INTRACAVERNOUS PART OF THE NERVE
! Because Of Its Close Proximity To Other Cranial Nerves, Intracavernous 3rd Nerve Palsies Are
Usually Assoc. With Inv. Of The 4th And 6th Nerves, And The 1st Division Of Trigeminal Nerve.
! In Intracavernous 3rd Nerve Palsy, Pupil Is
Spared. Sometimes, Pupil May Be Constricted
Owing To Inv Of Sympathetics.

31. ! CAUSES :
1. Diabetes May Cause Vascular Palsy.
2. Pituitary Apoplexy – May Cause A Third Nerve Palsy As A Result Of Hemorrhagic Infarction Of A Pituitary Adenoma (After Child
Birth), With Lateral Extension Into Cavernous Sinus.
3. Intracavernous Lesions – Aneurysms, Meningiomas, Carotid-cavernous Fistulae And Tolosa-hunt Syndrome (Granulomatous
Inflammation

32. 6.LESIONS INVOLVING INTRAORBITAL PART OF THE NERVE
! May Cause Isolated Extraocular Muscle Palsies
Or May Involve Either Superior Division Or
Inferior Division Or Both.
! Causes : Orbital Tumors, Pseudotumors, Trauma
And Vascular Diseases.

33. 7. LESIONS OF PUPILLOMOTOR FIBRE
! B/W The Brainstem And The Cavernous Sinus, Pupillomotor
Fibres Are Located Superficially In The Superior Median
Quadrant Of The Nerve.
! They Derive The Blood Supply From The Pial Blood Vessels
Whereas The Main Trunk Of The 3rd Nerve Is Supplied
By Vasa Nervorum.

34. ! Surgical Lesions - Aneurysms, Trauma And Uncal Herniation Characteristically Involve The Pupil By Compressing The Pial
Blood Vessels And The Superficially Located Pupillary Fibres.
! Medical Lesions - Diabetes And Hypertension Usually Spare The Pupil. This Is Because The Microangiopathy Assoc. With These
Diseases Involves The Vasa Nervorum, Causing Infarction Of The Main Trunk, But Sparing The Superficial Pupillary Fibres

35. CAUSES OF ISOLATED THIRD NERVE PALSY
1. IDIOPATHIC - In About 25% Cases
2. VASCULAR DISEASES – Diabetes And HYPERTENSION, Is The Most Common Cause Of Pupil-sparing 3rd Nerve Palsy. In
Most Cases Spontaneous Recovery Occurs Within 3 Months. Diabetic 3rd Nerve Palsy Is Often Assoc. With Periorbital Pain And
May Occasionally Be The Presenting Feature Of Diabetes. The Presence Of Pain Is Therefore Not Helpful In Differentiating B/W
Aneurysmal And Diabetic 3rd Nerve Palsy.

36. 3. ANEURYSM Of The PCA At Its Junction With The ICA Is Very Imp Cause Of Isolated Painful 3rd
Nerve Palsy With Involvement Of Pupil.
4. TRAUMA, Both Direct And Secondary To Subdural Hematoma With Uncal Herniation, Is Also A
Common Cause.
5. MISCELLANEOUS. Other Rare Causes Include Tumors, Vasculitis Assoc. With Collagen Vascular
Disorders, Syphilis And TB.

39. INVESTIGATIONS OF THIRD NERVE PALSY
! BASIC INVESTIONS: BLOOD SUGAR/ BLOOD PRESSURE/ LIPID PROFILE/ESR- TO RULE OUT
GIANT CELL ARTERITIS.
! 1. X-RAY SKULL LATERAL VIEW : To rule out sellar lesions involving the cavernous sinus.
! 2. MRI /MRA : In complicated third nerve palsies where other neural structures are
involved.
! 3.CEREBRAL ANGIOGRAPHY: Based on age and pupil involvement.
! 4. LUMBAR PUNCTURE : A. To demonstrate the presence of blood in csf, an
inflammatory reaction,neoplastic infiltrate, or infection.
B. Cytological examination of csf to diagnose meningeal
carcinomatosis and lymphomatous or leukaemic infiltration.

41. ABERRANT REGENERATION
TRAUMA/COMPRESSION
DAMAGE OF ENDONEURAL NERVE SHEATH
ABERRANT REGENERATION
* NO ABERRANT REGENERATION IN VASCULAR LESIONS SINCE ENDONEURAL
NERVE SHEATH IS SPARED.

42. ABERRANT REGENERATION – CLINICAL FEATURES
! LID GAZE DYSKINESIS PUPIL GAZE DYSKINESIS
PSEUDO VON GRAEFE SIGN PSEUDO ARGYLL ROBERTSON PUPIL
FIBRES TO INNERVATE IR FIBRES TO INNERVATE IR
ALSO SUPPLY LPS ALSO SUPPLY SPHINCTER PUPILLAE
INVERSE DUANEIS SYNDROME
FIBRES TO SUPPLY MR
ALSO SUPPLY LPS