What can be done for persistent nasal bunny lines that are refractory to botulinum toxin (Botox) injections?

Management of Bunny Lines Resistant to Botulinum Toxin Injections

When bunny lines persist after standard botulinum toxin injections, redirect your injection strategy to target the surrounding muscle borders rather than the wrinkle itself, as recent anatomical evidence demonstrates that bunny lines overlie a non-muscular triangular zone where toxin cannot act. 1

Understanding Why Standard Injections Fail

The anatomical basis for treatment resistance has been clarified through cadaveric and ultrasonographic studies:

• Bunny lines appear over a "bunny triangle"—a non-muscular connective tissue area bounded by the procerus, nasalis, orbicularis oculi, and levator labii superioris alaeque nasi (LLSAN) muscles. 1
• Conventional injection directly into the wrinkle targets connective tissue rather than muscle, explaining suboptimal results. 1
• The thin skin between the medial canthus and nasal dorsum is pulled by the borders of these four surrounding muscles, not by underlying muscle directly beneath the wrinkle. 1

Revised Injection Strategy for Resistant Cases

Target the muscle borders surrounding the bunny triangle rather than the wrinkle itself:

• Inject along the borders of the procerus muscle (superiorly), nasalis muscle (medially and inferiorly), orbicularis oculi (laterally), and LLSAN (inferolaterally). 1
• Use 2-5 units per injection site, with total doses of 2.5-5 units for the nasolabial/bunny line region. 2
• Divide the total dose into 1.25-unit aliquots (0.1-0.2 mL per site) to minimize diffusion to adjacent structures. 2

Expanded Treatment Approach for Persistent Wrinkles

When initial nasalis injections fail, anatomical wrinkle patterns guide additional injection sites:

• Approximately 60% of patients have remaining nasal rhytids after bilateral nasalis injections (3 units each side). 3
• 30% demonstrate persistent nasal orbicular wrinkles at the root of the nose, requiring additional injections at the nasal root. 3
• 30% show nasociliary wrinkles extending between the eyes, necessitating treatment at both the nasal root and glabellar region. 3
• Anatomically-guided injection into these additional locations achieves excellent resolution without complications. 3

Technical Considerations

• Use electromyographic guidance with a monopolar hollow bore, Teflon-coated needle to ensure precise muscle targeting. 2
• Effects typically appear within 24-72 hours and last 3-6 months. 2
• The American Academy of Otolaryngology-Head and Neck Surgery emphasizes that precise dosing and anatomically accurate injection placement minimize adverse events. 4

Common Pitfalls to Avoid

• Do not repeatedly inject the same location directly into the wrinkle itself—this targets non-contractile tissue and wastes toxin. 1
• Avoid excessive doses in the perioral region, as this can cause mouth incompetence. 5
• The primary risk involves toxin diffusion to adjacent structures; adjust dose, distribution, and timing to minimize this. 6
• Watch for temporary mild weakness of adjacent facial muscles, the most common adverse effect in this region. 2

Integration with Full-Face Treatment

• Bunny lines are commonly treated as part of comprehensive facial rejuvenation, with 71.8% of patients receiving bunny line injections during full-face treatment protocols. 7
• Mean total dose for full-face treatment is 113.8 units, with bunny lines representing a small fraction of this total. 7
• Complications occur in only 3.2% of full-face treatments and are typically minor and self-limited. 7