A Synopsis of AFP's "Cutaneous Cryosurgery"

A Synopsis of; Cutaneous Cryosurgery
ETHAN E. ZIMMERMAN, MD, and PAUL CRAWFORD, MD 
Nellis Family Medicine Residency, Nellis Air Force Base, Nevada
http://www.aafp.org/afp/2012/1215/p1118.pdf
Am Fam Physician. 2012 Dec 15;86(12):1118-1124

     Cryotherapy is basically using liquid nitrogen to freeze part of your body to death. At low temperatures (-60'C) ice crystals form in the cells, break open, and the toxins and electrolyte come out.  It has excellent cosmetic results, low risk of infection, minimal aftercare, and can be used in pregnancy.  It can be very painful, so it should not be used on children younger than 7 years old. Topical lidocaine can be used to help relieve the pain. It is relatively contraindicated in patients with multiple myeloma, agammaglobulinemia, immunosuppression, raynaud disease and certain blood dyscrasias. 
     When using a spray gun, it should be held at a 90 degree angle about 1-2 cm away from the skin. There are different techniques, including tracing a spiral or going back and forth like using a paint brush. A cone shield can be used to avoid treating sensitive tissue that is in close proximity. 
     To treat a benign, superficial lesion, a Q-Tip dipped in liquid nitrogen is effective. When using the nitrogen spray, a continuous spray technique is used to minimize the depth of the tissue affected. When treating a malignant lesion,  it is important to freeze deep tissue. By using an intermittent spray technique,  an "ice ball" is created. An ice ball can penetrate down  up to 1 cm into the tissue.
     Cryotherapy has been very successful in treating genetal warts. Plantar warts and warts that are very large may need a longer treatment course. Cryotherapy may be combined with other therapy, such as salicylic acid, shaving down the lesion, intralesional steroids, or topical keratolytics.  Although cryotherapy has been used on molluscum contagiosum, patients should be aware that the lesions will resolve without treatment (in 6 months to two years).
     Actinic keratosis, bowen's disease, and keratoacanthoma (premalignant lesions) can be treated very effectively with cryotherapy. Biopsy should be performed beforehand. Lentigo maligna should be treated with excision if possible. Freezing pigmented nevi can cause atypical regrowth, which will need surgical excision anyway. It is difficult to differentiate melanoma form pigmented cells that were frozen. Referral to a dermatologist should be considered in difficult cases. 
     Treatment of a malignant lesion should be referred to a dermatologist.  Treatment of basal cell carcinoma and squamous cell carcinoma with low risk features may be undertaken.  A shave excision or curettage may need to be done beforehand. A 5 mm margin and depth is necessary for treatment to be considered successful. 
     After the therapy  the patient may experience bleeding, blisters, edema, pain, syncope or headaches. A dressing is not needed but if the area is large, then it may need daily cleansing with soap and water. The blister should turn into an echar in about 1-2 weeks. The area should be completely healed in about 4-6. The patient may end up with hypopigmentation, hair loss or permanent scarring in the area, but it is rare.