This document discusses the anatomy and function of the oculomotor nerve (cranial nerve 3). It describes the nucleus and course of the nerve, causes of lesions, clinical features of total oculomotor nerve palsy, treatment options which may include surgery or monitoring, and differential diagnoses. History, examination, and investigations are outlined to evaluate patients presenting with oculomotor nerve palsies.
2. 3rd
cranial nerve
Oculomotor nerve
Entirely motor in function
Supplies –
• All the Extraocular muscles except superior
oblique and lateral rectus
• Levator palpebrae superioris
• Intra ocular muscles- Sphincter pupillae and cilliary
muscle
3. Nucleus
Located in midbrain at the level of superior colliculus,
ventral to the Sylvian aquiduct.
Composed of
• Unpaired levator subnucleus
• Paired superior rectus sub nuclei
• Paired medial rectus, inferior rectus and inferior
oblique subnuclei
• Unpaired Edinger-Westphal nucleus
4. Course
Can be divided into –
Fascicular
Basilar
Intracavernous
Intraorbital part
9. Major causes of nuclear complex
lesion of 3rd
nerve palsy
Vascular occlusion – Diabetes & Hypertension
Neoplastic lesions – primary tumour or metastasis
Haemorrhage
10. Major causes of fascicular lesion of
3rd
nerve palsy
Vascular occlusion – Diabetes & Hypertension
Neoplastic lesions – primary tumour or metastasis
Haemorrhage
Demyelination
11. Syndromes of Fascicular lesion
Benedikt syndrome- Ipsilateral 3rd
nerve palsy and
contralateral extrapyramidal signs
Weber syndrome- Ipsilateral 3rd
nerve palsy and
contralateral hemiparesis
Nothnagel syndrome- Ipsilateral 3rd
nerve palsy and
cerebellar ataxia
Claude syndrome-
12. Major causes of lesion in Basilar
region
The 3rd
nerve traverses the basilar part unaccompanied
by any other cranial nerves.
Isolated 3rd
nerve palsies are commonly basilar.
The important causes are
Aneurysm
Head trauma-Extradural or subdural haematoma
17. Pupillomotor fibers
Parasympathetic fibers
Located superficially between the brainstem and the
cavernous sinus
Blood supply derived from the pial blood vessels
Main trunk of 3rd
nerve supplied by the vasa nervorum
19. Causes of isolated 3rd
nerve palsy
Idiopathic – about 25%
Vascular – Hypertension & Diabetes (commonly pupil
sparing)
Aneurysm – posterior communicating artery at its
junction with internal carotid artery
Trauma – subdural haematoma with uncal herniation
Miscellaneous
20. Clinical features of total 3rd
nerve
palsy
SYMPTOMS
Drooping of eyelid
Binocular double vision
Pain (may be present)
21. SIGNS
Ptosis
Abduction of globe
Intortion of the globe which increases on attempted
down gaze
Limitation of adduction
Limitation of elevation
Limitation of depression
Dilated pupil with defective accommodation
25. Investigations
Age < 50 years CT or MRI, Cerebral angiography
Age > 50 years
Pupil sparing FBS and 2HABF, HbA1c, Lipid profile,
Check BP, CBC with ESR, CRP
Pupil involving FBS and 2HABF, HbA1c, Lipid profile,
Check BP, CBC with ESR, CRP, CT or
MRI, Cerebral angiography
29. Follow-up
Pupil sparing – Observe daily for 5 days for pupil
involvement
Recheck every 4 to 6 weeks
If secondary to ischemia function usually returns
within 3 months