INTRODUCTION
Injectable botulinum toxins for medical and aesthetic indications
are among the most popular therapies worldwide, their general purpose being to inhibit neural impulses and achieve a desired effect, usually the therapeutic mitigation of a condition via relaxation of involved musculature. In the case of aesthetic medicine, injection of toxin into specific areas of the face inhibits facial muscles to reduce the appearance of wrinkles and slow their onset. While effects are temporary, treatment is proven safe and effective, and the variety of indications for injectable neurotoxin continues to proliferate.
An alternative modality has similar possibilities, especially in situations where persistence of outcomes is desirable. Using radiofrequency (RF) energy emitted by a thin cannula, specific nerves can be damaged, causing an effect comparable to that seen with injectable neurotoxin. The duration is much greater; while injected neurotoxin wears off after a few months, a neural pathway inhibited by ablative lesion will take much longer to re-establish itself, if at all, depending on the extent of trauma. Keys to successful therapy in a clinical setting include effective low level stimulation of nerves to precisely locate and identify targets, anesthesia to enhance tolerability of treatment, and a cannula capable to delivering RF energy at that specific location for a therapeutically relevant length of time.
An investigation by Kim and colleagues1 of 27 patients (22 women, mean age 54.5 years) documented the basic protocol, using a cannula containing a direct current nerve stimulator to test neural connections and a 22-gauge monopolar RF probe to create lesions. Monopolar RF was chosen for its spherical
radius of effect focused at tissue in proximity to the tip,2 making correct identification of targets crucial to success. This radius of effect is demonstrated in Figure 1. A peripheral nerve stimulator was used to non-invasively target nerves from the surface, in this case the frontal branch of the facial nerve to the corrugator supercilli and angular nerve. Local anesthetic of 1% lidocaine with 1:100,000 epinephrine was applied to skin at insertion points and for supraorbital and infraorbital nerve blocks. Supplemental anesthesia was allowed on a case-by-case basis; 93% of patients elected to receive intravenous sedation, requiring an anesthesiologist. After bilateral treatment
additional assessment of neural ablation determined the need for further lesioning. Post-operative protocol consisted of site bandage with topical antibiotic. Suturing was unnecessary. Statistically significant improvement was noted at follow-up, averaging approximately 1.9 points on the Lemperle Wrinkle Assessment Scale3 (from a mean value of 3.7 to a mean of 1.8), which persisted for more than 12 months in 78% of patients. Subjects returned to normal activities within 24 hours of treatment.
Minor adverse events included two incidences of severe swelling and bruising, two incidences of temporary paresthesia, and one superficial second- degree burn.
A version of this novel RF therapy, ThermiRase, employs monopolar
RF to elevate the temperature of the target nerve to 85°C for 70 seconds causing consistent, predictable, and therapeutically effective nerve ablation. The goal is to achieve a level 5 nerve ablation on the Sunderland scale of nerve injury,4 classified as complete transection of the nerve whereby recovery
is impossible without surgical intervention. Coupled with low-level stimulation capability and a delivery port for anesthetic, the treatment is safe, effective, and tolerable as well as
