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: ENT
Not included in Gredenigo syndrome 
Select and explain. 
A. Retro-orbital pain, B. Ear discharge, C. Nystagmus, D. Diplopia
C: Nystagmus
Answer: C: Nystagmus 
Explanation: None