This document discusses cranial nerves III, IV, and VI which control the extraocular muscles and eye movements. It covers the anatomy and pathways of these nerves, common causes of palsies including diabetes, aneurysms and tumors. Specific palsy syndromes are described like internuclear ophthalmoplegia and one involving both CN III and IV. Signs on examination for each nerve palsy are provided along with diagrams to aid localization. Causes of binocular and conjugate gaze palsies are also summarized.

1. Oculomotor, Trochlear and Abducent Nerves
Dr M D Mohire MD, DM.
Neurology Centre & Research, Kolhapur

2. Subjective complaint of Double Vision
Misalignment of Visual Axis results in diplopia.
Monocular diplopia is often due to Optical Causes
Monocular Diplopia – 25 %
Binocular Diplopia – 75 %
Diplopia

3. Diplopia-Cranial N Palsies
Infranuclear
1) Cranial Nerve III
Diabetes/Vascular
Pituitary Tumor
2) Cranial Nerve IV
Congenital
Diabetes/Vascular
Trauma
3) Cranial Nerve VI
Dibetes/Vascular
MS
CNS Tumor
IIH

4. Diplopia
Supranuclear Lesions
1) Internuclear Ophthalmoplegia
2) Brainstem Ischemia
3) Migraine
4) Wernicke’s Encephalopathy

5. Diplopia - History
 Is Diplopia Monocular or Binocular
 Is there Exophthalmos or Proptosis
 Is there any Associated Ptosis
 Is the Onset Acute or Gradual
 Is there any Variability or Remission
 Is there any Pain, H/O Trauma

6. Diplopia – Signs and Symptoms
 Severe Headache ?
 Weakness ?
 Fatigue ?
 Clumsiness / Unsteadiness
 Multiple Cranial Nerve Palsies
If so there are Life Threatening Problems

7. Diplopia – Acute or Gradual
 Acute
Stroke
Ocular Muscles
 Gradual
Infiltrative Lesions
Myopathy
Tumors
CNS Infections

8. Diplopia - Pain
 SAH – Aneurysm
CNS Infections
 Myopathy (Ocular Myositis )

9. Diplopia – Examination
 Physical – BP, Pulse, Obesity, Thyroid Disease
 CNS examination – Detailed Cranial Nerves III, IV, VI
 ENT Examination
 CNS Examination
 Cardiac Examination

10. Supranuclear Control of Eye Movements
N Engl J Med 1956; 254:461-464
Nuclear Complex-3rd, 4th,6th

11. 3rd, 4th and 6th Nerves From Brainstem
Oculomotor Nerve
Trochlear Nerve
Abducent Nerve

12. Somatic motor
(general somatic efferent)
Supplies four muscles of the eye
and levator palpebrae superioris
Visceral motor
(general visceral efferent)
Parasympathetic innervation of
the constrictor pupillae and
ciliary muscles.
Controls muscles of Eye for precise movements in visual tracking.
Visceral motor component is involved in the pupillary light and
accomodation reflexes.
CN III

13. CN III originates at the
level of the superior
colliculus.
Nucleus is located near
the midline just ventral to
the cerebral aqueduct.
Nucleus is "V-shaped“ is
bordered medially by the
Edinger-Westphal nucleus
and laterally by the MLF
MLF controls
communication between
various brainstem nuclei.
CN III, Origin
Superior Colliculus Cerebral Aqueduct Periaquiductal Grey

14. 3rd nerve passes between the posterior cerebral and superior
cerebellar arteries and to enter the cavernous sinus.
CN - 3rd , 4th, 6th Nerves from Brainstem

15. Oculomotor Nerve - Nucleus
Medial Subnucleus
Central Nucleus Edinger Westpal Nucleus
Lateral Subnucleus
Parasympathetic

16. Cavernous Sinus and Sup Orbital Fissure
CN III then runs along the lateral wall of the cavernous sinus just
superior to the trochlear nerve and enters the orbit via the superior
orbital fissure

17. .
.
Actions of External Ocular Muscles
Adductors
Elevators
Depressors
All muscles work Synchronously
by Contraction of some & Relaxation
of others
Sup Rectus
Inf Rectus
Inf Oblique
Sup Rectus
Sup Oblique
Inf Rectus

18. Actions of External Ocular Muscles
Abductors
Medial Rotators
Lat Rotators
Sup & Inf Obliques are Abductors
Sup & Inf Recti are Adductors
Inf Oblique
Sup Oblique
Sup Oblique
Sup Rectus
Inf Oblique
Inf Rectus

19. Superior division ascends
lateral to the optic nerve
to innervate the superior
rectus and and levator
palpebrae superioris
muscles
Inferior division splits into
three branches to innervate
the medial rectus and
inferior rectus muscles and
the inferior oblique muscle.
Intraorbital Course of CN III
Superior Division
Inferior Division

20. Muscle Innervation Primary action Secondary action Tertiary action
Medial rectus CN III Adduction -- --
Superior rectus CN III Elevation Intortion Adduction
Inferior rectus CN III Depression Extortion Adduction
Inferior oblique CN III Extorsion Elevation Abduction
Superior oblique CN IV Intorsion Depression Abduction
Lateral rectus CN VI Abduction --
Movements of External Ocular Muscles

21. Examination
Cranial nerves III, IV, and VI are usually tested together.
Observing the Eye Movements and Eyelids
Observe Lid-lag, Ptosis, Pupils, nystagmus, Fatiquability
Paralysis results in Ophthalmoparesis

22. Causes of Paralysis of the CN - III
Trauma
Multiple Sclerosis
Aneurysm
Raised ICT leading to Uncal Heniation
Space-occupying lesion , Carotico-cavernous fistula
Spontaneous Subarachnoid Hemorrhage (SAH)
Microvascular disease, e.g., diabetes.
Diabetes Mellitus
Can impair eye movements, Dilated Pupil, or both.
Diplopia in all Directions except looking laterally.

23. Nuclear Midbrain
Dorsal midbrain infarction. Small lesions with few associated
neurologic symptoms or signs.
Fascicular midbrain
Benedikt syndrome
third cranial nerve palsy on the side of the lesion, ipsilateral flapping
hand tremor (rubral tremor from red nucleus involvement), and
ataxia.
Nerve Lesions
Diabetes, Aneurysm, Giant Cell Arteritis, Infection
Brainstem Lesions causing CN III Palsy

24. Diabetic 3rd N Palsy – Pupillary Sparing
Paralysed Eye is Outward & Downward
Caused by microvascular infarction, Down and Out,
Horizontal and vertical diplopia
Pupil-sparing , Parasympathetic nerve fibers ( Superficial ) unaffected.

25. Orbital Myositis( Levator Palpebral Superioris )
Complete right ptosis and very poor levator function

26. CT Scan of Orbits in Thyrotoxicosis
Bahn R. N Engl J Med 2010;362:726-738
Thyrotoxicosis Normal

27. CN 3rd Palsy - Pcom Aneurysm
Dilated Pupil

29. Trochlear nerve (CN IV)
Innervates Superior Oblique Muscle operates thr the Pulley
Smallest nerve in number of axons.
Greatest intracranial length.
Exits from the dorsal aspect of the Brainstem
Supplies the opposite side Superior Oblique
It causes rotation in a vertical plane (intorsion), Elevation, Abduction

30. Oblique Section Through Cavernous Sinus
Medial
Lateral

31. CN IV Nerve Palsy
Diplopia is subtle
Difficulty in reading or going down the stairs is main complaint.
Tilting the head to side opposite the affected eye eliminates Diplopia
Affected eye cannot turn inward and down.
Images above and slightly to the side of the other.

34. Examination in case of vertical diplopia
• Patient should be asked to look on a
horizontal straight line on a paper placed
below and to the right and left
• If diplopia is present, he should be asked to
draw the false image
• The false image of the line falls below the
true image and is tilted one side, forming
an arrow

35. If the arrow points to right, it is right superior oblique palsy
If the arrow points to left, it is left superior oblique palsy

36. IV nerve palsy versus skew deviation
• In skew deviation
– The range of eye movements is normal
• the misalignment is same in all directions of gaze
• Whereas it is asymmetrical in IV nerve palsy
– The higher eye is intorted and the lower eye is
extorted
• whereas the higher eye is extorted in a fourth nerve
palsy
– because of weakened intortion

37. How to detect rotation of eye?
• Compare the relationship between the optic
disc and macula

38. How to detect rotation of eye?
• Compare the relationship between the optic
disc and macula

39. Skew deviation
Right higher eye is intorted (left photo) & left lower eye extorted (right photo)
Right eye Left eye

40. Right IV nerve palsy
Showing extorsion of right eye

41. IV nerve palsy versus skew deviation
• Compare the vertical deviation in upright vs.
supine positioning
– Skew disappears on lying down
• Skew deviation is secondary to dysfunction of the
graviceptive pathway from the urticle
– Lying reduces gravitational effects on the utricles

43. Worse on downgaze and gaze away from side of affected muscle
Diplopia in Trochlear N Palsy
Vertical Diplopia Torsional Diplopia Or Both

44. Ask patient to look 'down and in' as the action of the superior
oblique is greatest in this motion.
Alfred Bielschowsky ‘s test for palsy of the superior oblique
muscle.
Trochlear Nerve - Examination

45. Alfred Bielschowsky (1871 –1940)
Vertical diplopia and introduced head-tilt test.

46. Bielschowsky's head tilt test
Step 1: Determine which eye is hypertropic in primary position. If
there is right hypertropia in primary position, it is right 4th N Palsy
Step 2: Determine whether the hypertropia increases on right or left
gaze. If increase on Left gaze, it is Right 4th N Palsy
Step 3: Determine whether the Diplopia decrease on right or left
head tilt. Better on Left head tilt indicates Right 4th N Palsy
Diplopia, is abolished by tilting the head towards the shoulder on the
unaffected side.

47. Left - Superior Oblique Paralysis
Primary Position
Right and Down
Failure to Depress Left Eye
Right Gaze – Left Eye Elevates Left Gaze - Normal
Left and Down, restricted

48. Causes of CN IV Nerve Palsy

49. In primary position there is right head tilt. In gaze right and down
failure to depress the left eye fully (middle). In right gaze the left eye
also elevates,
Microvascular left IV nerve palsy
Primary Position Gaze Right & Down Gaze to the Right
Right Head Tilt Failure to Depress Left Eye Left Eye Elevates

50. After the Head Injury After Recovery
No Vertical Deviation
Torsional diplopia and on downgaze horizontal diplopia are chief
problems
Bilateral Traumatic 4th N Palsy after Head Injury,

52. 2yr, Right - 4th N palsy After Surgery
Congenital 4th Nerve Palsy

53. Diagnosis of Congenital Trochlear Nerve Palsy
Ophthalmoscopy
Excyclotorsion - Line drawn horizontally from the inferior 1/3 of the disc in the left
(normal) eye intersects the fovea. Line drawn in the same manner in the right eye crosses
superior to the fovea.
Sign of fundus excyclotorsion.
Trochlear Nerve Palsy Normal

54. Fourth cranial nerve palsy and 3rd CN Palsy together
Difficult to diagnose in the presence of third cranial nerve palsy
In 3RD N Palsy alone, Intorsion of the globe on attempted down gaze.
If no intorsion is present, one should suspect concomitant fourth
cranial nerve palsy as part of a cavernous sinus syndrome.

55. Abducent nerve (CN - VI) is a Somatic efferent Nerve for Lateral Rectus
The abducens nerve leaves the brainstem at the junction of the Pons and Medulla

56. Abducent nerve (CN - VI)
Abducent Nerve

57. The long course of the vulnerable to injury at many levels.
Abducent nerve (CN - VI)
Abducent Nerve

58. Abducent Nerve

59. Cavernous Sinus

60. Abducent Nucleus
Abducent Nucleus
Turn the eye outward.

61. Causes of CN VI (Abducent Nerve Palsy)
Head injuries,Tumors, Multiple sclerosis, Aneurysm, Meningitis, a brain
abscess, or a parasitic infection
SAH, Diabetes, Stroke,
Wernicke encephalopathy
IIH, Tolosa Hunt Syn, Cavernous Sinus Thrombosis
Idiopathic
Unknown

62. Left 6th Nerve Palsy
On Recovery
Left Eye Turn
Medially

63. Multiple Sclerosis – 6th N Palsy

64. Site Common causes Nerves involved
Brainstem  Stroke  IIIrd – midbrain
 Demyelination  Vith – pontomedullary junction
 Intraxial neoplasm
Meningeal  Meningitis  IIIrd, IVth and Vith
 Raised intracranial pressure  Vith; IIIrd(uncal herniation)
 Aneurysms  IIIrd (posterior communicating
 Cerebellopontine angle tumour artery aneurysm)
 Trauma  VIth
 IIIrd, IVth and VIth
Cavernous sinus  Infection/ Thrombosis  IIIrd, IVth and VIth
 Aneurysm
 Caroticocavernous fistula
Superior orbital  Granuloma, tumour  IIIrd, IVth and Vith
fissure
Orbit  Ischaemic (diabetes, vasculitis)  IIIrd, IVth and Vith
 Infection
 Tumour  Trauma
Common causes of IIIrd, IVth and VIth nerve paralysis

65. Copyright restrictions may apply.
Keane, J. R. Arch Neurol 2005;62:1714-1717.
Tuberculous meningitis with bilateral 3rd, 4th, 6th Cranial nerve palsies

66. Rapid diagnosis of rhinocerebral mucormycosis in a diabetic by videoendoscopy
Bilateral 3rd, 4th & 6th Cranial Nerve Palsies

67. Cavernous sinus thrombosis

68. Myasthenia Gravis - Tensilon Test

69. Internuclear ophthalmoplegia
Impairment of horizontal eye movements caused by damage to MLF . These fibers
connect 3rd cranial nerve and 4th cranial nerve and the 6th Nerves.
Stroke (Unilateral)
Multiple Sclerosis, (sometimes bilateral)
Head injuries.
People with internuclear ophthalmoplegia may have double vision.

70. Vertical Gaze : Eye
movements in the
vertical plane,
superior rectus,
inferior rectus, inferior
oblique, and superior
oblique muscles must
work precisely
together.
These muscles are
coordinated by
vertical gaze center
Thr MLF

71. In conjugate gaze palsies, the two eyes cannot move in one direction (side to side, up, or down)
at the same time.
Conjugate gaze palsies affect horizontal gaze +most often. Upward gaze is affected less
often, and downward gaze is affected even less often. People may notice that they cannot look
in certain directions.
There are no specific treatments.
Horizontal gaze palsy
The most common cause is damage to the brain stem, often by a stroke. Often, the palsy is
severe. That is, moving the eyes past the midline to the opposite side is very difficult.
Palsies can also be caused by damage to the front part of the cerebrum, usually by a stroke. The
resulting palsy may not be as severe as that caused by damage to the brain stem, and symptoms
often lessen with time.

72. Vertical gaze palsy
Vertical gaze decreases gradually with age,
Usually, upward gaze is affected. The most common cause is damage to
the top part of the midbrain, usually by a stroke or tumor.
Parinaud syndrome is an upward vertical gaze palsy. It usually results
from a tumor or stroke. People with this syndrome tend to look down.
Their eyelids are pulled back, and the pupils are dilated.
Downward gaze palsy
If downward gaze but not upward gaze is impaired, the cause is usually
progressive supranuclear palsy Progressive Supranuclear Palsy (PSP)

73. Nuclear lesions
Horizontal gaze palsy that affects both eyes simultaneously.
Medial longitudinal fasciculus (MLF), a nerve tract that connects the three extraocular motor
nuclei (abducens, trochlear and oculomotor) into a single functional unit. Lesions of the
abducens nucleus and the MLF produce observable sixth nerve problems, most notably
internuclear ophthalmoplegia (INO).

74. Supranuclear lesions
The sixth nerve is one of the final common pathways for numerous cortical systems that control
eye movement in general. Cortical control of eye movement (saccades, smooth pursuit,
accommodation) involves conjugate gaze, not unilateral eye movement.