Brow and Eyelid drop after dermal fillers.

I recently had dermal fillers injected in my forehead - above my eyebrows to combat some minor volume loss to help lift the brow. However, my eyebrow ended up dropping, and so did my upper eyelids. No Botox was performed. My surgeon agreed, but told me to reassess in a week to let any swelling subside first. Why would this happen as I would have expected this with Botox and not fillers. It's been 5 days now and no improvement.