This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuroanatomy, Subject name: Anatomy
False regarding fourth cranial nerve 
Select and explain. 
A. Innervate external rectus, B. Innervate superior oblique, C. Runs along the lateral wall of cavernous sinus, D. Enters into the orbit through the superior fissure
A: Innervate external rectus
Answer: A: Innervate external rectus 
Explanation: 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