This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Anatomy
The only cranial nerve to emerge from dorsal aspect of brainstem is 
Select and explain. 
A. 3rd nerve, B. 4th nerve, C. 5th nerve, D. 6th nerve
B: 4th nerve
Answer: B: 4th nerve 
Explanation: .Surface attachment. Trochlear nerve is attached to the superior medullary velum one on each side of the frenulum veil just below the inferior colliculus. It is the only cranial nerve which emerges on the dorsal aspect of the brainstem. Ref : B D Chaurasia's Human Anatomy, sixth edition, volume 3 , pg. no. 364 Ref : B D Chaurasia's Human Anatomy, sixth edition, volume 3 , pg. no. 364 ( fig . 24. 1 )