Patient selection in the treatment of glabellar wrinkles with botulinum toxin type A injection

Objectives: To determine the dose-response characteristics and side-effects profile of Clostridium botulinum type A exotoxin (Botox) used to treat glabellar wrinkles and develop guidelines for patient selection based on the nature and severity of the treated wrinkles. Design: Prospective, nonrandomized pilot and electromyogram (EMG)-guided studies. Setting: Two ambulatory care clinics at university hospitals. Participants: For the pilot study, volunteer samples of 23 patients with glabellar wrinkles; for the EMG-guided study, volunteer samples of 57 patients with glabellar wrinkles. Interventions: For the pilot study, 23 patients were serially injected with up to 10.0 mouse units (MU) of Botox into each corrugator muscle; for the EMG-guided study, 57 patients were injected under EMG guidance with an initial dose of 10.0 MU of Botox into each corrugator muscle. Eleven patients with persistent corrugator activity were reinjected with 10.0 MU of Botox. Main Outcome Measures: For the pilot study, slide photographs were obtained before and 2 weeks after injection; for the EMG-guided study, slide photographs were obtained before and at 2 weeks and at 2 months after injection. Patients were asked to evaluate results numerically. Results: For the pilot study, injection of up to 10.0 MU of Botox into each corrugator muscle produced a satisfactory improvement in 12 patients; for the EMG-guided study, 43 patients were satisfied with improvement after full abolition of corrugator or accessory lateral brow muscle activity. Women were more likely to achieve satisfactory results than were men (80% [40/50] vs 43% [3/7]; P less than or equal to.03). Improvement was not age related. No significant side effects or complications were observed. Conclusions: Glabellar wrinkles may be satisfactorily treated with Botox injection into the corrugator supercilii muscles. Improvement is temporary, dose dependent, and may not be seen in some patients even with successful denervation of the treated muscles. Clinicians may begin treatment with a dose of 10.0 MU of Botox into each corrugator muscle, and may select candidates for injection by determining the type of wrinkle to be treated and its spreadability (glabellar spread test).