This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diseases of orbit, Lids and lacrimal apparatus, Subject name: Ophthalmology
Pulsatile proptosis is a feature of- 
Select and explain. 
A. orbital varix, B. Retinoblastoma, C. Coico - cavernous fistula, D. Covernous sinus thrombosis
C: Coico - cavernous fistula
Answer: C: Coico - cavernous fistula 
Explanation: *Coicocavernous fistula causes pulsatile proptosis. Ref: Clinical ophthalmology 2nd/e p.786