Without a doubt, the most useful treatment modality I’ve acquired in my career is the proper use of liquid nitrogen. Cryotherapy is the standard treatment for small epidermal lesions, because it allows for removal without the need for anesthesia, with no broken skin or bleeding, and with a tolerable amount of pain.
Over the years, I’ve learned—often the hard way!—how to work with liquid nitrogen. For example, for the past 25 years, I’ve used a cryogun (or “unit,” as it’s sometimes called), having discovered that applying LN2 with anything else (eg, a cotton-tipped applicator) is a huge exercise in futility.
As with any tool in medicine, there are uses and misuses of cryotherapy. It is not intuitive—but it does yield to common sense. So allow me to give you the benefit of my experience.
APPROPRIATE AND INAPPROPRIATE TARGETS
In general, only epidermal lesions of obvious origin are treated with liquid nitrogen. This includes ordinary skin tags, small warts, and seborrheic and actinic keratosis. Utterly common and easy to treat, these lesions have no potential for malignant transformation and have relatively poor vasculature, which makes them ideal candidates for controlled, localized frostbite. This process (which can take as long as two weeks) kills the cells, disrupts the blood supply, and causes the lesions to die and fall away.
Other uses for cryotherapy include softening keloids or hypertrophic scars sufficiently to facilitate intralesional injection; treating condyloma, molluscum contagiosum, and small chondromdermatitis nodules; and even to destroy skin cancers (basal cell and squamous cell carcinomas)—the latter, however, only by clinicians with specialized training.
Inappropriate targets for cryotherapy include “moles” (nevi), vascular lesions such as hemangiomas, “birthmarks,” or any lesion of unknown nature. There are two reasons not to use liquid nitrogen in these cases: First, relatively well–vascularized lesions will be superficially blistered but will survive the treatment. Second, these lesions have at least a theoretical chance of having undergone malignant transformation. (As such, these lesions may need to be sampled to determine whether they are malignant; but that is a discussion for another column.)
THE NEED FOR CAUTION
For all its positive features, there are drawbacks to using cryotherapy. Here are six to consider:
• Blistering, which can be severe in sensitive patients
• Dyschromia (color changes in treated skin), especially in darker-skinned patients
• Pain, particularly in children
• Loss of function (eg, nerve or cartilage damage)
• Scarring, usually from overtreatment
• Disability—walking (let alone running or working) may be painful for a day or two after treatment, especially following brisk cryotherapy of a larger plantar wart
TREATING WARTS WITH CRYOTHERAPY
First, you must confirm the diagnosis: “Seeds” (black dots on the surface, which really represent vertically aligned thrombosed capillaries) are pathognomic. Warts lack surface skin lines (dermatoglyphics) and do not umbilicate on paring (unlike clavi or corns).
Always discuss indications, procedure, alternatives, and risks prior to performing cryotherapy. Patients (and parents) need to understand that the “perfect” treatment for warts has yet to be devised. All currently available methods have shortcomings.
Consider using an ear speculum (3 to 5 mm) to concentrate the spray of liquid nitrogen, reducing pain and shortening the length of treatment. Particularly with thicker plantar warts, you might want to pare away surface keratotic material first, then use the “freeze-thaw-freeze” technique. The average length of a single treatment seldom exceeds five seconds, particularly if a speculum or other dam is used.
Arrange for follow-up, typically one month later, since it’s a rare wart that clears with a single treatment.