Can Botox injected too deeply seep into the Zygomaticus muscle?

Hi Anna.  While it's certainly possible that Botox injected to the eye area could have migrated downward into the Zygomaticus, the duration of the Botox would not be causing the concerns you have currently.  Botox won't last more than about 6 months at most which means if you did have any droop in the area (which would more likely show up around the lip) it would be worn off by now.  It sounds like you may need some dermal fillers to give you back cheek volume that has been lost. 

Botox can be injected into any muscle, but there are certain muscles we stay away from because the results will actually be worse. We typically do not inject directly into the zygomaticus muscle, but it is possible that the muscle was inadvertently injected or the Botox migrated into the muscle. In any case, Botox effects only last 3-4 months and things should go back to normal once it wears off. If you are still having issues then you need to follow up with an experienced physician for an in-person examination. Best wishes. 

Botox results last up to 3-4 months and can be softened with venus legacy and thermage treatments. I recommend getting a formal evaluation with a cosmetic dermatologist. Best, Dr. Emer