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What is False regarding fourth cranial nerve and explain in detail?
Answer: (a) Innervate external rectusTROCHLEAR NERVE* 4th cranial nerve, supplies only the superior oblique muscle.* Most slender cranial nerve.* Longest intracranial course.* Undergo complete internal decussation within the superior medullary velum before emerging.* Nucleus is situated in Ventro medial part of grey matter (mid brain) at the level of inferior colliculus.* The only nerve to arise from the dorsal aspect of the brain stem.* It enters the cavernous sinus by piercing the posterior corner of its roof.* Enters the orbit through superior orbital fissure thro' lateral compartment.* Lesion at superior medullary velumr> B/L 4th nerve palsy.* Palsy leads to diplopia on looking downwards.CAVERNOUS SINUS* Also called Lateral Sellar Compartment* Situated bilaterally on each side of the Sella turcica on body of Sphenoid bone* Occupies the middle cranial fossa.* Tributaries of Cavernous SinusFrom Orbitfrom Brainfrom MeningesSuperior Opthalmic.VInferior Opthalmic.VCentral.V of RetinaMiddle Superficial Cerebral VeinInferior Cerebral.VSpheno - Parietal Sinus Middle Meningeal.V * Cavernous sinuses of both sides communicate with each other through basilar plexus connecting inferior petrosal sinus on each side.Draining channelsStructures passing throughStructures in the lateral wall* Transverse Sinus - Via Superior Petrosal Sinus* Internal Jugular Vein - Via emissary Vein* Facial Vein - Via Superior Ophthalmic Vein* Abducent Nerve (6th Nerve)* Internal Carotid Artery* Carotid Plexus of Sympathetic nervesFrom above downwards* Oculomotor Nerve* Trochlear Nerve* Ophthalmic Nerve* Maxillary nerve