Risorius muscle and Botox?

Dear ashlibug,I would advise you against injecting your risorius muscle. As a plastic surgeon with facial expertise, I have a vast experience in facial surgery and you will be putting yourself at risk for an asymmetric smile. You should be able to smile as there are other muscles that control it but there are several muscles that control symmetric smiling and it is a delicate balance. If you are using Botox to correct an asymmetry then it may be indicated. It is extremely important that your injector is qualified, such as a board certified plastic surgeon, and that you see before and afters as injecting the wrong muscle will produce poor results.Nirmal R. Nathan, M.D.Certified, American Board of Plastic SurgeryMember, American Society of Plastic Surgeons

I don't think there are any positives with injecting this muscle. It can be weakened in error when the masseter is injected. I wouldn't get this muscle injected.

I would avoid injecting Botox or Dysport into the risorius muscle. Injection of the risorius can lead to an asymmetric smile. 

Anything that takes away the strength of risorius will influence the smile. Why would you want it in the first place?