Your insurance company is paying for your doctor to follow a protocol of 31 very specific injection sites approved by the FDA to treat your migraines. Unfortunately, this protocol is not perfect because everyone's anatomy is slightly different. I suspect that you have a low-lying frontalis muscle and when your injector is injecting your "procerus" and "corrugator" sites, he\she is actually injecting your frontalis muscle, resulting in your left medial eyebrow to droop. If you research FDA approved injection sites for Botox migraine you will see 3 sites straight across above the brow, but Botox cosmetic for frown lines will show 5 sites in a triangle shape with the procerus muscle injected much lower than when injected for migraines. A simple technique to help you: Draw a line from each medial (inside) eyebrow to the opposite medial canthus (inside corner of the eye). Where these 2 lines intersect is where to inject your procerus muscle. This is about a centimeter lower than the FDA approved procerus migraine site. The corrugators muscles are easy to visualize when you frown. If your injector goes straight in at a 90 degree angle and not up he/she should avoid injecting the frontalis muscle. Allergan does a great job at helping their physicians with any "adverse events". I am sure that if your injector presented your case to Allergan, they would provide assistance to help with your distorted eyebrows.