This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and paranasal sinuses, Subject name: ENT
A patient with sinus infection develops chemosis,B/L proptosis and fever, the diagnosis goes in or of: 
Select and explain. 
A. lateral sinus thrombosis, B. Frontal lobe abscess, C. Cavernous sinus thrombosis, D. Meningitis
C: Cavernous sinus thrombosis
Answer: C: Cavernous sinus thrombosis 
Explanation: Angular vein which begins from medial angle of eye,continues as the facial vein.The facial vein communicates with the cavernous sinus through the deep facial vein and pterygoid plexus of veins. B/L proptosis,fever and chemosis point towards cavernous sinus thrombosis. Ref Dhingra 6/e,p 201.