Treatment options are available to treat asymmetric eyebrows.
Botox Cosmetic is a great option to help adjust brow height a little bit, to produce a more symmetric eyebrow. It is better at lowering a brow, than elevating. Results with Botox may vary and last several months.
Endoscopic facial surgery is the next option. Brow asymmetry may be treated by endoscopic approach, or alternatively a traditional open approach. Most surgeons perform endoscopic brow lifts currently, but brow position is better controlled with an open or direct approach.
Lastly, everyone has some degree of asymmetry to the face, especially the eyes and eyebrows. Facial asymmetry is natural. Some degree of asymmetry may have been present before cosmetic surgery. A few patients have eyebrow asymmetry from tweezing or hair removal.
Speak with a plastic surgeon to be able to determine what treatment approach would be appropriate in your case.