Following a Botox or Dysport treatment, bunny lines can exist for one of two reasons – either they were not treated, or they have resulted from compensated/recruited muscle activity.
Bunny lines result from contraction of the nasalis muscle. Frown lines occur from contraction of the corrugator and procerus muscles, and this produces the vertical lines (the “11s”) between the eyebrows and the horizontal crease across the upper nose. When many people frown they also contract the nasalis muscle. Since the focus is usually on the “11s”, patients may not notice their bunny lines.
If the corrugator and procerus muscles are treated, but the nasalis muscle is left untreated, the bunny lines will persist (will be unmasked, in some sense) and these are then noticed by the patient. So if the bunny lines are significant then it is best to include these with the initial treatment.
If you ask some patients who have had just their frown lines treated, to “frown” …the lack of feedback as a result of this muscle paralysis often causes them to contort their faces and recruit surrounding muscle groups (usually the nasalis and orbicularis oculi muscles) in an attempt to move those muscles which are paralyzed. This attempt to compensate results in the appearance of bunny lines and crow’s feet. I do not mean to suggest that this is a common problem, but it is possible that some patients are subconsciously moving these muscles more because they no longer sense the movement of the frown. If this problem does arise, it is easy to treat the offending muscles.
A skilled injector should evaluate each patient individually, at rest and during animation, and then make treatment recommendations based upon the patient’s goals.
Best wishes, Ken Dembny