Basically there is only one muscle that spans your total forehead -it is called the frontalis muscle and is innervated by the frontal branch of the facial nerve. This can get temporarily injured during fat transfer in the forehead and temples as well as after a brow lift. When this is injured, your ability to raise your eyebrows is diminished. Most of the time, fortunately, this fully recovers within 4 to 8 weeks. If it is completely cut, however, the situation is more serious. You should follow up with your surgeon to ascertain if this would be a possibility.