Tackling submental fat – A review of management strategies

Injectable deoxycholic acid (DCA)

DCA is a by-product of intestinal bacteria acting on the primary bile acids discharged by the liver.^[5] However, DCA is also a surfactant which can alter the integrity of the cell membrane and ultimately break it down.^[5,6] When it is injected in optimal dosage, DCA can be cytotoxic and dissolve the cell completely. Subcutaneous injection causes localized adipolysis and tissue necrosis. After cell disintegration, there is macrophage recruitment which clear any cellular fragments and fibroblasts following which neocollagenesis is stimulated.^[7]

DCA is available as sodium deoxycholate and is currently the only United States Food and Drug Administration (USFDA) approved treatment for moderate submental adipose tissue.^[8]

Several studies have been conducted to measure the efficacy of DCA. Refine 1 ATX-101 trial was a randomized, double blind, and placebo controlled study done on 500 patients who were either injected with DCA or Saline. The study found that over 70% of the DCA subjects and 18.6% of placebo subjects found a ≥1-grade composite response, whereas 13.4% of the DCA subjects and 0% of placebo subjects found a ≥2-grade composite response (P < 0.001 for both). A smaller cohort also underwent magnetic resonance imaging for evaluation. About 46.3% of DCA subjects of the cohort showed a response versus only 5.3% of the placebo – making the proportion more than 8 times.^[9]

Side effects of DCA include injection site swelling, pain, bruising, and anesthesia lasting up to 4 days. About 4.3% of patients suffered temporary mandibular paresis lasting for a mean of 31 days which settled without complications.^[9] There may be other associated complications of skin necrosis if the injections are given too superficially.

Cryolipolysis

Cryolipolysis acts by causing apoptosis of fat cells by cooling. Cryolipolysis – caused panniculitis used for fat reduction was first described by Manstein et al. in 2008.^[10,11] No immediate changes are seen on contact with the cool temperature. However, within 3 days, the inflammatory process begins due to apoptosis of fat cells. Within the next 2–4 weeks, phagocytosis of the lipids takes place by macrophages and other phagocytes.^[10,12] No changes have been observed in lipid profile.

In a study conducted by Suh et al., cryolipolysis showed a reduction in SMF in nine out of ten subjects with a mean reduction of 4 mm (range 0–13 mm) as measured by caliper. High-resolution ultrasound also showed a reduction in the subcutaneous fatty layer.^[13]

Another study by Kilmer et al.^[14] used a prototype small volume applicator on 60 patients. Results were measured by blinded reviewers as well as by ultrasound. After one or two treatments, 6 weeks apart, 83% of the subjects reported satisfaction with this treatment. A study involving 464 subjects who had undergone cryolipolysis also experienced an improvement in skin texture and laxity post-procedure.^[15]

Side effects typically seen are swelling, anesthesia, bruising, and erythema. Paradoxical adipose hyperplasia has been reported as a rare event.^[16]

Radiofrequency (RF)

RF makes use of alternating electrical current to increase intermolecular motion and thereby collisions.

The resistance of the tissues is used to create thermal energy which is not transferred. Both monopolar and bipolar devices can be used. Bipolar RF devices can cause controlled localized heating of dermal tissue, sparing the epidermis.^[17,18] On exposure to heat, the structure of collagen unravels and shortens resulting in tighter, compacter collagen. There is also stimulation of neocollagenesis.^[19,20] Chawvavanich et al. treated 22 patients with submental laxity with RF every 2 weeks. Progress was recorded with three-dimensional photographs. All patients showed a statistically significant decrease in fat volume by 6^th month of treatment.^[21]

Inappropriate power and depth or inadequate number of sessions used may lead to unsatisfactory results.

Ultrasound

High-intensity-focused ultrasound is commonly used as a non-invasive method to treat SMF. Laubach et al. first demonstrated the effects of a prototype intense focused ultrasound device on post-mortem skin. The skin showed highly confined thermal damage in the dermis seen as thermal cell necrosis and collagen denaturation.^[22] Oni et al. investigated the effects of a micro focused ultrasound device on the lower face of 103 adults. Ninety-three patients completed the study – out of which 65.6% of patients were satisfied with the results. Blinded reviewers assessed that 58.1% of patients showed improvement.^[23] The use of ultrasound devices spares the epidermis and provides heat in the dermis. Sparing of the epidermis minimizes adverse outcomes such as bruising, pain, and blisters. Thermal damage to the dermis leads to new collagen formation and thereby, tightening of the skin.^[24] Suh et al. obtained biopsy specimens from patients who had undergone ultrasound tightening. The specimens showed an increase in dermal thickness and collagen fibers.^[25]

Ultrasound also is advantageous as it is independent of skin color and chromophores.

Inappropriate depth may lead to suboptimal results. The marginal mandibular nerve should be avoided to prevent paralysis of the lower lip muscles.

Threads

Threads help to stimulate collagen synthesis by means of a tissue-suture interaction. The thread-induced fibrosis also helps to provide a lift.^[26,27] Barbed and monofilament threads are available. The “barbs” help to lift and anchor the sagging tissue. A study conducted by Wanitphakdeedecha et al. on 27 Thai patients using absorbable barbed threads showed that lifting effect provided by the threads was seen up to 6 months, while some patients showed the lifting effect even at the 12-month mark. Neocollagenesis was most likely initiated around the 1^st month post-implantation.^[26] Lifting helps in obliterating the look of the fatty neck by stretching it. Polydioxanone (PDO) threads also help with lipolysis. Monofilament PDO threads may also be used to tackle SMF by causing stretching and lipolysis.^[27] Threads can be combined with other modalities to achieve optimum clinical results.

Adequate number of threads and insertion in the right plane is important to deliver the desired results.

Liposuction and laser lipolysis

The results of liposuction are usually enhanced using laser lipolysis. Laser-assisted lipolysis was approved by USFDA in 2006. Laser lipolysis helps to reduce adipose tissue and stimulate neocollagenesis leading to improvements in neck contour and rhytids. It also has a reduced recovery period. Usually, tumescent liposuction is done of SMF as it will help to eliminate large amounts of fat.^[29] Badin et al. demonstrated that laser-induced thermal damage caused coagulation of vasculature, damage to membrane of adipocytes, and reorganization of collagen. Badin et al. also found laser lipolysis to be less traumatic and improved the post-procedure recovery time.^[30] Both 1064 nm and 1320 nm wavelengths have been used. McBean and Katz also used 1064 and 1320 sequentially.^[31]

DCA and cryolipolysis

Jalian et al. conducted a study with sequential treatment of cryolipolysis and DCA. Subjects underwent two sessions of cryolipolysis and one session of Kybella. About 100% of subjects showed a ≥1 grade improvement, and 71.4% showed a ≥2 grade (Clinician Rated SMF Rating Scale improvement).^[32]