Sensory phisiology (Strabismus, Ophthalmology)

1. Innervation of the
Extraocular Muscles
Tukezban Huseynova, MD
Specialist in Strabismus and Refractive Cornea,
Briz-L Eye Clinic, Baku, Azerbaijan
Tukezban@gmail.com

2. • The third, fourth, and sixth cranial
nerves innervate six extraocular muscles
in each orbit.

3. a
Oculomotor Nerve

4. Anatomy

5. Anatomy
Origin: From 2 nuclei in the rostral midbrain:
1. Oculomotor nucleus: General Somatic Efferrent
fibers to superior, medial, and inferior recti muscles, to
the inferior oblique muscle, and to the levator
palpebrae superioris muscle.
2. Edinger- Westphal nucleus: General Visceral Efferent
preganglionic fibers to the ciliary ganglion.

6. Anatomy

7. • The Oculomotor Nerve supplies all the extra
ocular muscles except Lateral Rectus and
Superior Oblique.
• Has 2 components:
Somatomotr: Extraocular Muscles
Visceromotor: Ciliary Gamglion
Anatomy

8. Pathway

9. Pathway

10. Pathway
• Scheme showing
central connections
of the optic nerves
and optic tracts.

11. Pathway
Within the orbit:
- Superior ramus (to the superior rectus and levator
muscles)
- Inferior ramus (to the medial and inferior rectus
muscles, and the ciliary ganglion).
- Postganglionic fibers from the ciliary ganglion
innervate the sphincter pupillae muscle of the iris as
well as the ciliary muscle.

12. Pathway

13. Lesion results in:
• Paralysis of the 3 rectus muscles and the inferior
oblique muscle(causing the eye to rotate
downward and slightly outward)
Lesions

14. Lesions
• Paralysis of elevator palpebrae superious
muscle (drooping of the eyelids).

15. Lesions
• Paralysis of Sphinkter pupillae and ciliary
muscles (so that the pupil will remain dilated
and the lens will not accommodate).

16. Lesions
Lesion due to:
• Transtentorial uncal herniation(tumor/hematoma)
• Aneurysms: Carotid and Posterior communicating
arteries.
• Cavernous sinus Thrombosis
• Diabetis Mellitus.

17. -
Abducens Nerve

18. Nucleus
• There are two cell populations within the sixth nerve
nucleus.
- One group of cell bodies contains motor neurons
that innervate the ipsilateral lateral rectus.
- The other group of cell bodies produces axons, which
decussate and enter the contralateral medial
longitudinal fasciculus.
- There they ascend via the medial longitudinal
fasciculus to the oculomotor nerve complex, forming
synapses in the region of the medial rectus subnucleus.

19. Nucleus

20. Fascicle
• The abducens fascicle courses ventrally, laterally,
and caudally to emerge at the junction of the pons and
medulla.
• During its course, the fascicle is in close proximity to
the facial nerve nucleus, the facial nerve fascicle,
motor and sensory nuclei of the trigeminal nerve, and
the pyramidal tract.

21. Nerve
• The nerve exits the brainstem just lateral to
the pyramid. It ascends in the subarachnoid
space along the clivus, passing near the
inferior petrosal venous sinus and then
beneath the petrosphenoid ligament . This
space is called Dorello's canal.

23. • The abducens nerve, or abducent nerve, is a
motor nerve. It innervates the lateral rectus
muscle (responsible for lateral gaze, i.e., moving
the eyeball outwards) of the ipsilateral orbit.

24. Lesion
• Due to its long path inside the skull, the
abducens nerve is often damaged in fractures
of the base of the skull, or by a disorder, such
as a tumor, that distorts the brain. Such
damage may give rise to double vision or a
squint.

25. Lesion
Abducens nerve palsy

26. Trochlear Nerve

27. Nucleus
• The nuclei of the trochlear nerve are a paired
group of motor cells located in the floor of the
cerebral aqueduct. They are positioned just
caudal to the oculomotor nerve complex in
the midbrain.

28. Nucleus

29. Fascicle
• About 2,100 axons emerge from each nucleus,
passing first laterally and then dorsally to converge
and decussate over the roof of the cerebral aqueduct
just caudal to the inferior colliculi, where they exit the
brainstem . The short fascicular course makes it
clinically difficult to separate nuclear from fascicular
involvement.

30. Nerve
• The trochlear nerve has the longest subarachnoid
course of the ocular motor nerves.
• Within the cavernous sinus, the nerve is positioned
in the lateral wall just below the third cranial nerve
and above the ophthalmic division of the trigeminal
nerve.
• The nerve continues forward, passing through the
superior orbital fissure above and medial to the
annulus of Zinn to reach the superior oblique muscle.
It is the only ocular motor nerve that does not pass
through the annulus of Zinn

31. Nerve

32. Lesion
• Fourth (trochlear)
nerve palsy

33. Development.
• The oculomotor, trochlear, and abducens nerve
nuclei develop from specific neuronal populations in
the hindbrain (rhombencephalon). Abnormal
development of extraocular muscle innervation
produces a number of complex strabismus syndromes,
known collectively as the “congenital cranial
dysinnervation disorders. These disorders have been
considered myopathic in origin, but recent work
suggests that many may be of neuropathic origin.

34. Thank You