This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Orbit and Adnexa, Subject name: Ophthalmology
Cause of pulsating proptosis 
Select and explain. 
A. Lymphoma, B. Caroticocavernous fistula, C. Orbital cellulitis, D. Mucocele of paranasal sinuses
B: Caroticocavernous fistula
Answer: B: Caroticocavernous fistula 
Explanation: Causes of Pulsatile Proptosis Caroticocavernous fistula Aneurysms of Ophthalmic aery Transmitted cerebral pulsation from deficient orbital roof like congenital meningocele / meningo-encephalocele