Download - Oculomotor nerve
Oculomotor nerve
Dr / Hytham Nafady
Introduction Oculomotor nerve consists of two components with distinct functions:
Somatic motor(general somatic efferent)
Supplies 4 of the 6 extraocular muscles of the eye and the levator palpebrae superioris muscle of the upper eyelid.
Visceral motor(general visceral efferent)
Parasympathetic innervation of the constrictor pupillae and ciliary muscles.
From To
Uncrossed fibers
ipsilateral oculomotor nucleus
Medial rectus.
Inferior rectus.
Inferior oblique.
Crossed fibers
Contralateral oculomotor nucleus
Superior rectus.
Crossed and uncrossed fibers
Both oculomotor nuclei
Levator palpebrae superioris muscle.
Uncrossed para-sympathetic fibers
Ipsilateral Edinger Westphal nucleus
Constrictor pupliae muscle.
Ciliary muscle.
•Medial rectus
•Inferior rectus
•Levator palpebrae superioris
•Superior rectus
•Inferior oblique
Oculomotor nerve anatomy
Origin
Oculomotor nucleus:
• Tegmentum of midbrain at the level of superior colliculus.
• Ventral to the peri-aqueductal grey matter.
• It is column shaped nucleus & consists of complex subnuclei.
Edinger Westphal nucleus:
• The Edinger Westphal nucleus form the parasympathetic general visceral efferent (GVE) component of the nuclear complex.
• It is located medial to the rostral end of the oculomotor nucleus.
Central segment
The central segment courses ventrally
• From the midbrain tegmentum,
• through the red nucleus,
• to emerge from the medial aspect of the cerebral peduncle.
Cisternal segment
• Course ventrolaterally through the interpeduncular cistern between the PCA & SCA.
Cisternal segment of oculomotor nerve
Cn 3
Interpeduncular cistern
Cisternal segment of oculomotor nerve
BA Cn 3SCA
PCA
Cisternal segment of oculomotor nerve
Cisternal segment of oculomotor nerve
Cisternal segment
ICA
Cavernous segment
• The oculomotor nerve enters the cavernous sinus superior to the petro-clinoid ligament and inferior to the inter-clinoid ligament.
• The cavernous segment of the oculomotor nerve course through the lateral wall of the cavernous sinus superiorly.
• It is surrounded by CSF dural cuff (oculomotor cistern).
4 5 O
6
3
5 mx
Oculomotor cistern
Orbital segment
• The oculomotor nerve enters the orbit through the superior orbital fissure within the annular ring or Zinn.
• It divides into superior and inferior divisions.• The superior division supplies the contralateral
superior rectus & levator palpebrae superioris muscles bilaterally.
• The inferior divison supply the ipsilateral inferior & medial recti & inferior oblique muscles.
Superior orbital fissure & annular ring of Zinn
Cn 3 i
Cn 3 s
Cn 6
Cn 4
Oculomotor palsy
Oculomotor nerve palsy with pupillary sparing(medical 3rd Cn palsy)
• DM.
• Hypertension.
Oculomotor nerve palsy without pupillary sparing
• Nucleus.
• Central segment.
• Cisternal segment.
• Cavernous segment.
• Orbital segment.
Oculomotor nucleus
Cisternal segment
Cisternal segment
PCoA aneurysm
Lymphoma
Lymphoma
Cavernous segment
Cavernous sinus lesion with 3rd cranial nerve palsy
Schwannoma
3
Right carotid cavernous fistula with 3rd & 4th Cn palsy
Orbital segment
• Lesions of the orbital apex cause 3rd , 4th and 6th cranial nerve palsies
Tolosa hunt syndrome
Tolosa Hunt syndromeophthalmoplegia
3
3
3
4
6
Testing accomdation reflex