What are the risks of a stroke or necrosis after fat grafts to the cheeks? Is the risk only immediate or there even years after?

These side effects are extremely rare. Keep in mind, fat transfer technique is important for successful fat transfer. I recommend water-assisted fat harvesting which gives pure fat to transfer and combine with platelet rich plasma (PRP) to get the most viable and sustainable fat cells. I combine with Sculptra (depending on area) to improve results. I recommend getting a formal evaluation with an expert. Best, Dr. Emer

The risks of fat transfer to the face are not prevalent and typically the procedure goes along without a hitch - I love using this technique to soften and rejuvenate the face. Volume is conservative to avoid fattening the face. There may be some bruising, and absorption of the fat happens. The surgeon needs to know what he/she is doing to avoid complications. Problems like arterial injection can cause skin necrosis, but that is rare in well trained hands - you need a board certified plastic surgeon. Stroke would be a risk if you have medical issues that set you up for that risk - stroke risk is extremely low in healthy patients. This is a very short procedure with minimal anesthesia requirement.
Best of luck!

Fat grafts to the cheeks are pretty low risk when done correctly.  For one this means using a blunt cannula for injection, and not a sharp needle.  There are higher risk areas on the face such as:  glabella, and base of nose where most instances of necrosis and vessel compromise occur with fillers due to the vasculature in these areas.  This is usually seen immediately as it occurs.  There would not be any risk after it is done.  
It is possible to have some irregularities with fat or any filler as some of the fat will reabsorb.  These may not be seen for several weeks. 
 

Fat grafts to the facial cheeks, done properly, offer little risk of stroke, blindness, skin necrosis (death) or significant fat necrosis, but those are all possible risks.  Except for fat necrosis (and contour irregularities), most of these risks would be in the immediate time frame (at or within hours/days of the surgery).  Fat necrosis and contour irregularities (lumpy/bumpy areas) would generally not be expected to be seen/felt for weeks to months after surgery.  It would be best to consult with an ABMS Board Certified plastic surgeon to discuss the surgery and risks.  

A board certified plastic surgeon who does a ton of facial fat transfer and operates at a certified facility, is qualified and experienced enough to prevent both. I’ve never seen, or even heard, of a stroke caused by a cheeck fat tranfer done with the right canula, and my take rate is close to 95%. That rate didn’t come overnight, it took years of trial and error to reduce necrosis (at first it was 50/50).See a surgeon who fits the criteria above and ask her, or him; “how many fat grafts to the checks did you perform on patients like me, last year?” Do not settle for vague answers and you’ll be in good hands. All surgeries carry risks so choose your surgeon carefully and good luck.