Botox injected into the forehead is not a good treatment for a heavy brow. The muscle that lifts the brows is the frontalis muscle. The activity of this muscle causes horizontal wrinkles in the forehead; these can be improved by weakening the muscle activity but if the frontalis is weakened too much or totally paralyzed, the brows will sink even lower.
The ideal treatment for sagging eyebrows is a brow lift (also called forehead lift). With the minimal incision endoscopic approach, there is little scarring and a relatively short recovery. Because the brows are lifted, patients use their frontalis muscles less and will see significant improvement in the forehead wrinkles.