anatomy of cranial nerves: oculomotor nerve, trochlear nerve, abducent nerve;

1. rd,
3
th
4
and
th
6
CRANIAL NERVE
BY
DR. SUNITA KUMAWAT
Deptt. Of PHTHALMOLOGY
Sardar Patel Medical College, BIKANER

2. Oculomotor (Third cranial nerve)
• The oculomotor nerve is entirely motor nerve.
• Supplies Levator palpabrae superioris and all
extrinsic muscle of eye except lateral rectus and
superior oblique.
• Also innervates sphincter pupillae and cilliary muscle.

3. Functional components :1. Somatic efferent – concerned with
movements of eyeball.
2. General visceral efferent – accomodation and
contraction of the pupil.
3. General somatic afferent – proprioception.

4. Nucleus
• Is a nuclear complex
made up of cell
column and discrete
nuclei.
• Lies ventral to the
grey matter around
the cerebral
aqueduct, at the level
of superior collicuius.

5. • Superiorly it
approaches the floor
of 3rd
ventricle, inferiorly it
is continous with the
trochlear nerve
nucleus.

6. • Consists of :
• 1. Main oculomotor nucleus(large multipolar
cells)
2.Edinger – westphal or accessory oculomotor
nucleus(small multipolar cells)

7. Main motor nucleus:
1. One centrally placed caudal nucleus supplies
to both LPS.
2. Four lateral paired subnuclei that innervate
Superior rectus(paramedial),
Inferior rectus(dorsolateral),
Inferior oblique(intermedial).
Medial rectus(ventromedial)

8. – Axons from one superior rectus (SR) subnucleus
cross and pass through the opposite SR
subnucleus , to innervate cotralateral sup. rectus
thus, a lesion of one SR subnucleus results in
bilateral superior rectus palsy.
– LPS has bilateral supply while All other EOM get
ipsilateral supply

9. Course and relation
• Efferent fibres from 3rd
nerve nucleus.
• Pass through medial
longitudinal
fasciculus, red
nucleus, substantia
nigra and medial aspect
of cerebral peduncle.
• Emerges from ventral
aspect of mid brain and
pass into
interpeduncular space.

10. • Nerve descends anteriorly in interpeduncular
fossa between post. Cerebral and sup. Cerebellar
arteries.
• Unaccompanied by any other cr. nerve (isolated
3rd nerve palsies are frequently basilar).

11. • passing forward it
is superomedial to
trochlear nerve
and inferolateral
and parallel to
post.
Communicating
artery.
• It pierce the dura
b/w free and
attached margin
of tentorium, to
reach the
cavernous sinus.

12. • It traverse the post. Part
of roof of the sinus to
reach its lateral wall.
• In the wall trochlear
nerve and 1st & 2nd
divisions of trigeminal
nerve are inferolateral
to it.
• abducent nerve and
internal carotid artery
are Inferomedial.

14. • At the anterior part of sinus nerve divides into
a small superior and larger inferior branch.
• These two divisions of nerve enter the orbit
through middle part of sup. Orbital fissure(in
annulus of zinn).

15. • Nerve is crossed by trochlear nerve which
become superomedial to it. Abducent nerve lies
first inferior then lateral to the divisions of
nerve. Trochlear, frontal and lacrimal nerves
traverse the fissure above the anulus of zinn.

16. two divisions:
1. Superior division: diverges medially above
the optic nerve and behind the nasocilliary
nerve.Supplys to sup. rectus and levator
palpebrae superioris muscles.

17. 2. Inferior division:
• Divides immediately into branches to supplymedial rectus, inferior rectus and inferior
oblique muscle.
• Nerve to inf. Oblique enters the muscle as 2-3
branches, it also supplies a ramus to cilliary
ganglion.

18. Cilliary ganglion
Roots of cilliary ganglon:
1. Sensory root: comes from nasocilliary nerve
2. Parasypathetic root: arise from nerve to inf.
Oblique muscle.
3. Sympathetic root: is a branch from int. carotid
plexus.

19. • Branches :
• Gives 15-20 short cilliary nerve.
• Contains fibres of all three roots of cilliary
ganglion.

20. Edinger-Westphal:
• Parasympathetic nucleus.
• interposed between two main
nuclei.
• Composed of small multipolar
cells of preganglionic autonomic
type.
• Preganglionic neuronal axons
from this form the visceral
component of oculomotor
nerve.
• Earlier regarded as pupillomotor
centre.

21. Location of Pupillomotor fibres
In the part of
oculomotor nerve which
lies between brainstem
and cavernous sinus, the
pupillomotor
parasympathetic fibres
are located superficially
and superomedially

22. • Oculomotor nerve gets
blood supply from
various branches from
basilar artery(in brain
stem) and int.& ext
carotid artery.
• Pupillomotor fibres
derive their blood supply
from the pial blood
vessels, whereas the
main trunk is supplied by
vasa nervosum.

23. functions
• Elevation of lid (Levator palpabrae superioris)
• All movements of eye, except lateral, down
and out movements.
• Miosis,accomodation and light reflex
(Parasymp innervation)

24. Trochlear (4th cranial) nerve
1.
2.
3.
4.
It is purely motor nerve, Supplys to sup.
Oblique muscle.
The nerve is named for the trochlea, the
fibrous pulley through which the tendon of
the superior oblique muscle passes.
It is crossed, most slender, smallest nerve
and has longest intra cranial course(7.5cm)
of all cranial nerves.
It is Only cranial nerve to emerge from
dorsal aspect of brain.

25. FUNCTIONAL COMPONENETS :-
1. Somatic efferent – concerned with the
movement of eyeball.
2. General somatic afferent – carries
proprioceptive impulses from S.O. muscle to
the mesencephalic nucleus of trigeminal
nerve.

26. Nucleus
• Trochlear nucleus
situated At the level of
sup. border of inferior
colliculus.
• It is In the dorsum of
tegmentum of mid
brain, ventrolateral to
the cerebral aqueduct.
• Dorsal to the medial
longitudinal fasciculus.

27. • continous with 3rd nerve
nucleus superiorly.

28. Course and relation
• From each nucleus nerve fibres first run laterally
to mesencephalic nucleus of 5th nerve, then
somewhat downwards and parallel to aqueduct

29. • At lower border of
inf. Colliculus they
turn medially to
decussate in
superior medullary
velum.
• Hence each sup.
Oblique is supplied
from contralateral
trochlear nucleus.

30. • After crossing in sup. Medullary velum the Nerve
emerge on dorsal aspect of sup. Cerebellar
peduncle, then curves around the peduncle at
upper border of pons.
•
•

31. • Passes b/w post. Cerebral & sup. Cerebellar
arteries. While this course nerve is inferomedial
to free margins of tentorium.

32. • Nerve enters in
cavernous sinus on
post. Part of its roof
and goes to its
lateral wall.
• where it is supero
medial to1st & 2nd
division of trigeminal
nerve, abducent
nerve& int. carotid
artery.

33. • While passing through the sinus Oculomotor
nerve first superomedial to trochlear nerve
• then trochlear nerve cross over and become
itself medial to it at the entry in superior orbital
fissure.

34. • Trochlear nerve run in upper region of
fissure above the annular tendon where
Frontal & lacrimal nerves are superolateral
to it.

35. • The nerve enter in orbit and fans out into 3-4
branches to supply sup. Oblique muscle on its
sup. Surface.

36. • Number of fibres in intraorbital part of
trochlear nerve are greater than its
intracranial part.
• These extra fibres carrying the proprioceptive
impulses from sup. Oblique muscle, leave the
trochlear nerve to join ophthalmic division of
the 5th nerve, in the cavernous sinus.
• Ultimately these fibres relay in mesencephalic
nucleus of 5th nerve.

37. Function
• Sup. Oblique muscle Primarily rotates the tip
of the eye towards the nose (Intorsion)
• Secondarily moves the eye downwards
(depression)
• Tertiary function is to moves the eye outwards
( abduction)
• Trochlear nerve typically allows a person to
view the tip of his or her nose.

38. Abducent (sixth cranial) nerve
• Entirely motor nerve, supplys to lateral rectus
muscle.
• Most vulnerable cranial nerve, to damage in
traumas involving cranium.

40. FUNCTIONAL COMPONENT :
1.Somatic efferent – for lateral movement of
eye.
2.General somatic afferent : for proprioceptive
impulses which are carried to mesencephalic
nucleus of 5th nerve.

41. Nucleus
• Abducent nucleus is Small mass of large
multipolar cells, in floor of fourth
ventricle, ventral to colliculus fascialis. where
it is closely related to the horizontal gaze
centre(PPRF).
• fasciculus of the 7th nerve curves around the
abducent nucleus.

42. • Numerous small multipolar cells intermingled
with these large cells which form so called
nucleus para-abducens.
• Fibres from these cells relay in the oculomotor
nucleus via medial longitudinal fasciculus.

43. Course and relation
• Efferent fibre starts from nucleus, traverse
through tegmentum, Parapontine raticular
formation(pprf) and pyramidal tract .
• Then leave the brainstem at pontomedullary
junction, just lateral to pyramidal prominance.
• Lateral to each abducent there is the emergence
of facial nerve.

44. • B/w two Abducent nerves there is basilar
artery at its formation.
• just after emergence, nerve enters in
prepontine basilar cistern. Then it passes
upwards close to the base of skull and is
crossed by ant. Inf. Cerebellar artery.

45. • It pierces the dura below the post. Clinoid and
angles forwards over the tip of petrous
temporal bone.
• Nerve passes around inf.Petrosal sinus in
anterolateral direction,under the petroclinoid
ligament(dorello canal), to enter in cavernous
sinus.

46. • In sinus Nerve runs forwards almost
horizontally, being inferolateral to int. carotid
artery and its symp. Plexus.
• Abducent nerve is usually in the sinus.
• Nerve runs out, at ant. end of sinus and enter in
sup. Orbital fissure.

47. • It traverse the fissure
through its middle
part within annulus
of zinn.
• At first it is below the
divisions of 3rd nerve
then in b/w the two
divisions.
• It is lateral to
nasocilliary nerve.

48. In the orbit:
• Nerve divides into 34 filaments which
enter the ocular
surface of lateral
rectus muscle behind
its mid point.
• Function:
• Lateral movement of
eye.

49. variations in 6th nerve:
• nerve may arise by 2 roots, which pass
separately to the sup. Orbital fissure.
• It may give rise to a branch to cilliary ganglion.
• The nasocilliary nerve may be a branch of it.
• Abducent nerve may be absent, being
replaced by oculomotor nerve.

50. References
• Wolfs anatomy of eye and orbit; 8th edition.
• Kanski bowlings clinical ophthalmology; 7th
edition.
• Adler’s physiology of eye, 6th edition.
• Gray’s gross anatomy, 27th edition.
• Anatomy and physiology of eye, ak khurana;
2nd edition.

51. THANK YOU