This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
Paralysis of 3rd, 4th, 6th nerves with involvement of ophthalmic division of 5th nerve, localizes the lesion to - 
Select and explain. 
A. Cavernous sinus, B. Apex of orbit, C. Brainstem, D. Base of skull
A: Cavernous sinus
Answer: A: Cavernous sinus 
Explanation: Paralysis of 3rd, 4th, 6th nerve and involvement of ophthalmic division of 5th nerve → cavernous sinus thrombosis.
Paralysis of 3rd, 4'h, 6th nerve, ophthalmic division of 5th nerve plus optic nerve signs→ orbital apex syndrome.