Occulomotor Nerve

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Oculomotor (III) Nerve Palsy (Applied Anatomy): 

Oculomotor (III) Nerve Palsy (Applied Anatomy) Nucleus Located in midbrain at the level of superior colliculus inferior to Sylvian aqueduct Composed of paired and unpaired sub-nuclei

PowerPoint Presentation: 

Causes of 3 rd nerve palsy involving nucleus and fasiculus are : Demyelinating diseases like multiple sclerosis (MS). Vascular lesions like diabetes (DM) and hypertension Neoplastic lesions

PowerPoint Presentation: 

Because the 3 rd nerve traverses the basilar part of its course unaccompanied by any other cranial nerves, isolated 3 rd nerve palsies are frequently basilar in origin. The important causes are Aneurysm at the junction of posterior communictaing artery (PCA)and internal carotid artery (ICA). Extradural hematoma

Posterior Communicating Artery aneurysm & 3rd Nerve (Basilar Part): 

Posterior Communicating Artery aneurysm & 3 rd Nerve (Basilar Part)

Raised Intracranial Pressure due to intracranial haematoma: 

Raised Intracranial Pressure due to intracranial haematoma

Oculomotor nerve: 

Oculomotor nerve

Orbital part: 

Orbital part Superior division innervates levator and superior rectus muscles Inferior division supplies the medial rectus, the inferior rectus and the inferior oblique muscles The inferior branch of 3 rd nerve also contain parasympathetic fibers of Edinger-Westphal subnucleus, which innervate the sphincter pupillae and the ciliary muscle. These fibers travel along nerve to inferior oblique

3rd nerve at orbital apex: 

3 rd nerve at orbital apex

Pupillomotor fibers: 

Pupillomotor fibers The location of parasympathetic pupillomotor fibers in the trunk of the 3 rd nerve is clinically important Between the brainstem and the cavernous sinus, the pupillary fibers are located superficially in the supero-median part of the nerve. They derive their blood supply from the pial blood vessels

Pupillomotor fibers: 

Pupillomotor fibers

Clinical features of total 3rd nerve palsy: 

Clinical features of total 3 rd nerve palsy A total 3 rd nerve palsy is characterized by Ptosis due to levator weakness Abduction of globe (unopposed action of lateral rectus ) Intorsion of the globe on attempted down-gaze ( SO ) Limitation of adduction ( MR weakness )

Clinical features of total 3rd nerve palsy: 

Clinical features of total 3 rd nerve palsy Limitation of elevation ( weak SR ) Depression ( weak IR ) A fixed and dilated pupil, non reactive both for near and light direct and consensual. Accommodation weakness ( ciliary muscle denervation )


APPLIED ANATOMY NUCLEUS The 4 th nerve nucleus is situated at the level of the inferior colliculus in the aqueductal grey matter, beneath the aqueduct. It is caudal and continuous with the 3 rd nerve complex It innervates the contralateral superior oblique muscle.

Anatomy of the 4th nerve: 

Anatomy of the 4 th nerve

Trochlear Nerve: 

Trochlear Nerve




CLINICAL FEATURES A unilateral superior oblique palsy is characterized by -ipsilateral hyper deviation -excyclotorsion -limited depression in adduction -AHP to avoid diplopia by depressing the chin and tilting the head and occasionally turning face to the opposite side

PowerPoint Presentation: 

Loss of function of superior oblique results in overaction of inferior oblique resulting in hypertropia and extorsion (compensated by tilting of head towards opposite shoulder)


CLINICAL FEATURES A bilateral superior oblique palsy is characterized by -bilateral hyper deviation -excyclotorsion -limited depression in adduction -AHP to avoid diplopia by depressing the chin

Right Superior Oblique Palsy: 

Right Superior Oblique Palsy

Treatment : 

Treatment For 6 months, patients are kept under observation and spontaneous resolution occurs in many cases. If after 6 months, no significant improvement is seen, then surgical intervention is done.




APPLIED ANATOMY NUCLEUS The sixth nerve nucleus innervates the ipsilateral lateral rectus muscle. It lies in mid portion of Pons, inferior to the floor of the fourth ventricle, where it is closely related to the fasciculus of 7 th cranial nerve which causes a small elevation in the floor of the fourth ventricle called facial colliculus.



6th Nerve pathway: 

6 th Nerve pathway

Peripheral part: 

Peripheral part Basilar The sixth nerve leaves the midbrain at the pontomedullary junction and enters the prepontine basilar cistern. It may be involved here with cerebellopontine angle tumors such as acoustic neuroma . First sign of acoustic neuroma is hearing loss and loss of sensation in cornea . It is important to test both hearing and corneal sensation in patients of sixth nerve palsy

Raised intracranial pressure and sixth nerve: 

Raised intracranial pressure and sixth nerve The sixth nerve may be stretched over the petrous tip between its point of emergence from the brainstem and its dural attachments on the clivus as a result of raised intracranial pressure . This is due to the downward descent of the brainstem and may occur with posterior fossa tumors as well as in patients with benign intracranial hypertension (pseudotumor cerebri ). Sixth nerve palsy which may be bilateral is a false localizing sign.

Cavernous : 

Cavernous Occasionally an intra-cavernous 6 th never palsy is associated with Horner’s syndrome as in its intra-cavernous course, the sixth nerve branches are joined sympathetic branches from the para-carotid plexus which innervated the dilator pupillae.

6TH Nerve in Cavernous Sinus: 

6 TH Nerve in Cavernous Sinus

PowerPoint Presentation: