Dr David Eccleston explores the treatment options for hyperhidrotic patients
Hyperhidrosis, or excessive sweating, is thought to affect almost 3% of the population.1 It can occur anywhere on the body or is localised to specific areas, most commonly the hands, feet, groin and armpits. To sufferers, the condition brings daily misery, restricting life style, affecting relationships and sometimes causing depression.2 This article reviews some of the treatments currently available for axillary hyperhidrosis, with a particular focus on the use of the novel modality, electromagnetic energy in the microwave spectrum.
A sweat gland is a tube with a coiled base that resides deep in the hypodermic and a duct that extends through the dermis, exiting at the surface of the skin. There are two main types of sweat gland:
For the majority of people, sweating takes place as a response to heat or stress. In hyperhidrotic patients, the amount of sweat produced is far greater than is required to cool the body. There are a number of ways to measure the severity of hyperhidrosis in an individual. The simplest is self-assessment by the patient using the hyperhidrosis disease severity scale (HDSS) developed by the International Hyperhidrosis Society.
HYPERHIDROSIS DISEASE SEVERITY SCALE
“How would you rate the severity of your hyperhidrosis?”
Fig. 2. The hyperhidrosis disease severity scale developed by the International Hyperhidrosis Society to help patients to self-assess the severity of their disease. The scale is completed before and after any treatment, in order to assess the efficacy of the treatment administered.
Microwave energy is described as an electromagnetic signal with a wavelength of between 1 mm and 1 m and a frequency of between 300 MHz and 300 GHz. Microwaves travel at the speed of light and are positioned in the electromagnetic spectrum between infrared (lasers) and radiowaves (RF). Microwaves are used in medical applications because of their ability to heat biological tissue, causing ablation (destruction).
As early as the 1930s, microwave-based therapy was conceptualised as a thermal therapy3, with the first practical experiments on living organisms taking place in 1946.4 Today, microwave thermal ablation is used in oncology, cardiology, gyneacology, opthalmology and a number of other areas of medicine. The process by which microwaves cause thermal ablation is called dielectric heating, which occurs when an alternating electromagnetic field (the microwave) is applied to an imperfect dielectric material. In the case of tissue, water molecules that are bound within the tissue act as the dielectric material. The water molecules rotate in an attempt to align with the rapidly alternating electromagnetic field. These very fast molecular movements result in frictional forces leading to heating.5
Tissues with a high water content (solid organs, for example) absorb electromagnetic energy better than low water content tissues, such as fat. For medical applications, microwaves are delivered to the treatment area using a microwave generator and an antenna, or group of antennae, to produce the desired absorption pattern in the tissue.
Microwave thermolysis of sweat glands as a treatment for axillary hyperhidrosis has been pioneered by Miramar Labs, Inc., a California based company. Miramar Labs launched the miraDry system in January 2012 and it remains the only microwave-based solution for the treatment of axillary hyperhidrosis.
miraDry consists of an applicator hand piece with four waveguide antennae, a cooling system and a vacuum acquisition system. The hand piece is attached to a console containing a microwave generator. Miramar Labs conducted extensive research6 in order to optimise the design of the hand piece so that the microwave energy is delivered precisely to the region of the axilla where it will have maximum thermolytic effect on the eccrine and apocrine glands. A propagating microwave signal travels down the antennae and out through an open face, through the cooling system and into the tissue below. It is known that there is a significant difference in the material properties of microwaves in the dermal/epidermal layer compared to adipose tissue; both velocity and absorption of microwaves are much higher in the dermal layer. When the energy meets the adipose layer, a large proportion of the microwave energy is reflected at the dermal/hyperdermal interface, which produces a region of constructive interference, maximising thermal damage in the region where the target glands reside. At the same time, the hand piece cooling system creates a protection region within the dermis and allows thermal conduction from the microwave region to spread within the target treatment zone. The cooling system consists of a circulating layer of water and a ceramic cooling plate and provides continuous cooling to the superficial layers of the skin, both during energy delivery and for 20 seconds afterwards, preventing surface damage. The hand piece also includes a vacuum acquisition system. As the energy is delivered, the vacuum lifts the skin and underlying fat layers. This helps to physiologically isolate the target region and optimise the heating effect.
A clinical study was carried out over a period of 12 months7 with a final assessment made at 24 months post treatment.8 Hyperhidrosis was assessed pre- and posttreatment using HDSS scores and gravimetric measurement of sweat.
At baseline, all subjects had an HDSS core of 3 or 4 (indicating severe hyperhidrosis) and a gravimetric measurement of at least 50 mg in 5 minutes in each axilla7. At 12 months, the average percentage reduction of sweat by gravimetric measurement was 82% and 90% of subjects had an HDSS score of 1 or 2 (a 2 point improvement is associated with an 80% sweat reduction).7 At 24 months, the reduction in HDSS score remained >90% and was stable.8
Biopsy samples were taken from one patient before and at intervals after a miraDry procedure and assessed by histology.9 This revealed thermal necrosis and a clear reduction of viable sweat gland structures post treatment, with no significant evidence of adverse effects on other structures. Sweat glands cannot regenerate10, so it is unlikely that thermally destroyed glands will regrow or recover viability. It is therefore predicted that microwave ablation will provide treated patients with a permanent solution for axillary hyperhidrosis.
Miramar Labs has been granted FDA clearance for the use of miraDry to treat axillary hyperhidrosis and it remains the only device currently on the market to receive this certification. In the two years since its introduction to the USA, miraDry has been installed in around 250 clinics and 20,000 patients have so far been treated. The technology is now installed at three clinics in the UK. In May 2014, the International Hyperhidrosis Society updated its Treatment Algorithm for primary axillary hyperhidrosis11 to place microwave thermolysis as a second line treatment option, when topical antiperspirants are found to be ineffective. This is a clear indication of support that this technology has received amongst dermatologists in the USA and elsewhere.
Practical considerations for microwave ablation
The majority of excessive underarm sweat patients can be successfully treated using microwave ablation. Exceptions include those who are fitted with a pacemaker or other electronic device implant, use supplemental oxygen or have had a previous reaction to local anaesthetic. Skin tags or raised moles must be removed and the patient must shave the armpits prior to treatment. Following treatment, the armpits must be kept clean and an antibiotic cream may be prescribed. Most importantly, the area must be iced immediately after the procedure and regularly in the days following treatment. Two treatments are recommended, at least three months apart.
Some patients may find, however, that one procedure is sufficient to produce the desired result.
Additional effects of the procedure include a reduction in bromhidrosis due to the elimination of apocrine glands along with the eccrine glands. In most cases there is also a permanent reduction in underarm hair, which is normally perceived to be an additional benefit for female patients.
Treatment side effects are swelling, soreness and bruising, which generally lasts for no longer than eight weeks, and altered sensation in or around the treatment area, which usually disappears in about three months.
Botulinum Toxin: Botulinum toxin type A provides temporary relief from the symptoms of axillary hyperhidrosis and was licensed to treat axillary hyperhidrosis in 2001. The toxin is injected at multiple sites in the armpit, rendering the sweat glands inactive. The treatment usually takes effect within a week but is only effective for about three – 12 months, with an average duration of seven months12, after which the procedure must be repeated.
Iontophoresis: Another temporary treatment for hyperhidrosis is Iontophoresis, where the hands or feet are placed in water and a small electrical current is passed through the skin. The underarm areas can also be treated by placing water soaked pads and electrodes under the arms. The exact mechanism of action is unknown. Iontophoresis must be used every other day to start with, then reduced to once a week or so, but if stopped altogether, the symptoms will return.
Laser Sweat Ablation: Laser Sweat Ablation (LSA) uses a laser to destroy the sweat glands and was developed in the UK by Dr Mark Whiteley. Performed under local anaesthetic, the laser fibre is inserted between the dermis and the sub-cutaneous fat via two small incisions; the laser is fired, destroying the sweat glands, which are then removed by curettage. LSA does provide a permanent solution, but is to some degree an experimental procedure and at present not widely used in the UK.
Surgery: Patients who have exhausted temporary treatments may be considered for surgical intervention, a radical step that should not be undertaken lightly, as complications and side effects may outweigh the benefits gained. Almost every patient who has an Endoscopic (or Video-assisted) Thoracic Sympathectomy (ETS) will experience compensatory sweating on other areas of the body and, in 5% of cases this is severe.
During the procedure, the surgeon enters the chest and using video guidance, destroys small areas of the sympathetic chain to interrupt the nerves that stimulate the sweat glands.
Until the development of microwave ablation of the sweat glands, there was no safe, effective, non-invasive and lasting treatment for axillary hyperhidrosis. Aesthetic clinics can now offer patients an effective alternative to temporary treatments such as toxin injections, without recourse to surgical methods. Microwave ablation is quick and easy to perform and can be carried out in a clinic by a trained aesthetician.