What causes nose necrosis? What is the chance of getting necrosis in a revision rhinoplasty?

Tip necrosis, which is what I presume you mean, is very rare (fortunately!) With each subsequent rhinoplasty there's more disruption to the blood supply of the nose and if too little blood is able to reach the tip skin, the tip skin will die (necrosis). This is something that can be noticed almost immediately and is generally obvious within a day or two. It doesn't occur months or years later unless there was some other problem that arose such as an infected or rejected implant. Rough handling of the skin and soft tissues, post-op taping that's too tight increase the risk of tip necrosis. Patient's who smoke are at MUCH greater risk of tip necrosis and I recommend they quit smoking a month prior to surgery and a month post-op (and ideally forever!). Patients with vascular disease such as coronary artery disease or poorly controlled diabetes are probably at higher risk as are patients with advanced COPD.All the best,--DCPPearson Facial Plastic Surgery®

I believe you are referring to necrosis of the overlying skin. In short, a good blood supply to the soft tissue envelope/skin of the nose is what allows it to remain healthy. Poor blood supply to this same area can lead to necrosis. Poor blood supply to this area can be due to patient factors (smokers, coagulopaths, etc.), surgical errors (aggressive thinning of the skin, for example), or post op complications (hematoma or seroma that compress venous outflow which in turn limits arterial inflow). Signs of poor blood flow can sometimes be detected while in surgery, which should prompt your surgeon to manage this immediately. 

Thank you for your question. I suggest that you move forward and consult with a board certified facial plastic surgeon to determine your candidacy for neck lift.
Best wishes,