Radiofrequency Energy for Denervation of Selected Facial Muscles: Clinical Experiences at Six Months
glabellar frown reduction, radiofrequency rf, thermal denervation
J Newman. Radiofrequency Energy for Denervation of Selected Facial Muscles: Clinical Experiences at Six Months. The Internet Journal of Plastic Surgery. 2008 Volume 5 Number 2.
The goal of treatment with a unique, bipolar radiofrequency (RF) ablation device is to provide the surgeon with a minimally invasive and neurotoxin altrernative, percutaneous approach to glabellar frowning. Therapeutic RF energy delivered via the probe tip area produces thermal effects that inhibit the designated nerve and produce selective conduction block. In our prospective study, significant glabellar frown reduction was immediately achieved in 80% of patients (40). All 40 of these patients maintained significant results at the 3-month time period, and 78% at the 6-month time period. Bruising and swelling were seen in 6% and 92% of patients respectively, mostly during the first week and resolving within two weeks. The cohort continues to be followed for longer term follow up. Further studies will help determine mass market viability of thermal deneveration as an alternative to injectable nerve paralytic agents.
Radiofrequency (RF) energy has been used successfully in cardiac arrhythmias1 and facial pain conditions such as trigeminal neuralgia.2,3 Recently, a unique bipolar RF ablation device has been developed to produce selective thermal denervation of the eyebrow depressor muscles including the corrugator and procerus muscles. The goal of the procedure is to provide the surgeon with a minimally invasive, percutaneous approach to glabellar frowning without the use of temporary neurotoxins, such as botulinum toxin A (Botox®). The procedure uses an RF needle and generator specifically designed for peripheral motor nerves (RELAXED EXPRESSIONS System, BioForm Medical Inc., San Mateo, California; Figure 1). Thermal denervation can be performed in an office-based setting or in conjunction with aesthetic facial surgery.
Percutaneous facial branch denervation through thermal energy delivery was first reported by Hernandez-Zendejas and Guerrerosantos in 1994.4 Investigators found significant reductions in glabellar frowning with long term follow-up, up to 18 months. A similar study at Stanford University showed shorter term results.5 Current thermal energy application reflects improvements of this original concept by coupling sophisticated engineering with a thorough understanding of facial neuroanatomy.
Targeted Muscle Denervation
This technology can be used to weaken only the efferent pathway of the distal branches of the facial nerve as they enter the glabellar musculature. The result of the thermal energy delivery is selective relaxation of the forehead depressor function. Physicians use the RF probe to both locate and incapacitate the lateral nerve to the corrugators as well as the angular nerve to the procerus and medial corrugator complex, inclusive of the depressor supercilii, oblique head of the corrugator and medial head of the orbicularis in conjunction with the procerus muscle (Figure 2). Stimulation of this nerve results in visible superior-inferior movement of the brow complex.
Guidelines for Operation
After cleaning the facial skin, specific markings are made on the skin surface (Figure 3). Depths of the frown lines and the lateral extent of the corrugator muscle are marked. Another reference mark is made vertically on the forehead to identify the parasagittal plane of the midpupillary line.
To move freely within the soft tissues of the face, local anesthesia is used at the insertion sites in conjunction with nerve blocks of the main sensory nerves. The RF probe is placed through the dermis and orbicularis muscle in the approach from the lateral canthal skin, then advanced just under the temporoparietal fascia to localize the desired branch of the frontal nerve (Figure 4). Delivery of therapeutic RF energy to the probe tip area produces thermal effects that inhibit the nerve and produce a selective conduction block. At the conclusion of the thermal energy delivery a significantly diminished muscle activity is observed. Additional sites of RF energy delivery can then proceed in a distal direction.
After the delivery to the target nerves, there is a selective preservation of frontalis function that produces an aesthetically pleasing brow elevation. More natural appearances of the forehead complex are achieved without overarching of the brows or brow ptosis sometimes seen with neurotoxin administration.
Early Experiences with Selective Efferent Thermal Denervation in a Clinical Setting
In our clinical setting, we have experience with over 100 patients who have been treated for thermal denervation. A cohort of fifty patients treated for selected denervation has been systematically followed, with results reported here. In addition, another 50 patients have been treated; their results are included in the adverse events section. In the first group, a prospective study using the RELAXED EXPRESSIONS RF generator and probe was begun in February 2007 with IRB approval. Post informed consent, adult patients with moderate to severe glabellar frowning with an absence of botulinum toxin A were treated through July 2007. Patients returned at monthly intervals to assess degree of glabellar frown reduction and any evidence of return to baseline frowning. A quantitative wrinkle score and pre- and post-treatment photography were used as efficacy assessment tools. Potential adverse events were monitored and reported during the study period.
Significant glabellar frown reduction was immediately achieved in 80% of patients (40). All 40 of these patients maintained significant results at the 3-month time period, and 78% at 6-months. In addition, browlift improvement was also noted due to protection of the frontalis muscle and denervation of the depressors.
Figures 5 and 6 are representative of our results obtained through RF energy delivery. Figure 5 shows a female patient with treatment of the lateral nerve to the corrugators, 7 months post treatment. Figure 6 shows a male patient with moderate frowning who underwent lateral corrugator treatment. This patient continues to maintain results at 8 months post treatment.
Results from this procedure represent the possibility of a significant advance in the treatment of glabellar furrowing. In a single treatment session, the RELAXED EXPRESSIONS System offers physicians selective targeting of the depressor muscles. The benefits are reduction of frown lines and addition of aesthetic lift to the brows. We have shown that significant reduction in glabellar frowning and improved brow aesthetics can be achieved with a new RF device at 3 months, 6 months, and beyond. Longevity of clinical effects appear related to the degree of hindrance to the motor (efferent) nerves and the dual incapacitance of the lateral innervation of the corrugators (nerve to corrugator) and the medial innervation of the glabellar complex (angular nerve).
Other applications will likely arise as adoption of this device accelerates. For example, thermal denervation may also be useful in an open surgery setting in which the patient is undergoing other procedures. At present, an optimized algorithm for RF treatment is currently in development by principal investigator. Further studies are required to determine the mass market viability of the procedure as an alternative to injectable nerve paralytic agents.
The author expresses his appreciation to David J. Howell, PhD, RRT (San Francisco, CA) for his assistance in editorial development of this manuscript.
About the author
Dr. Newman is in private practice in San Mateo, California, where the study was conducted. In addition, he is an Assistant Clinical Professor, Department of Otolaryngology Head & Neck Surgery, Stanford University (Palo Alto).
Materials for the study described herein were supported by BioForm Medical, Inc. Portions of the study were shown in a poster format at the 2008 American Academy of Facial Plastic and Reconstructive Surgery (September, Chicago, IL). Dr. Newman has received compensation from BioForm Medical for presentations about RELAXED EXPRESSIONS to members of the medical community.