Brow droop is most commonly due to volume loss in bone and soft tissue supporting the brow. Strategic placement of a small amount of dermal filler on top of the bone above the  eyebrow  and /or underneath the eyebrow can replace lost infrastructure and lift the brow. Usually 1/2 to 1 syringe of product is required in this area. A 1-3 mm lift in this area can make quite a big difference.