*4.8.2 Liquid nitrogen therapy*

Having a temperature of −196°C, the coldest freeze, is the most commonly used method in medical practice. It is very effective in elimination of a large

variety of very common benign and premalignant skin lesions (verrucas, *Molluscum contagiosum*, seborrheic and actinic keratoses) [25]. Wart clearance may be through necrotic destruction of HPV-infected keratinocytes or by inducing local inflammation that triggers an effective cell-mediated response [25]. Liquid nitrogen can easily be stored and used by simple equipment in clinic-based practice. Available techniques are dipstick, roller, spray gun and Probe. Dipstick is the simplest technique where a cotton swab is dipped in liquid nitrogen and applied on a lesion. It is suitable only for superficial, benign lesions. Cryoroller, whose tip is cylindrical, is dipped in liquid nitrogen and then rolled over the lesional area. It acts better in severe acne and hypertrophic scar. The most popular method is spray technique using cryoprobes [10]. There are variations in freeze times, mode of application and intervals between treatments. Freeze time is the time elapsed from start to end of freeze cycle, i.e., from formation of uniform ice field until lesion is thawed, varying from 5 to 20 s. In short freeze for warts, cryotherapy continued till a 2-mm white halo develops around the lesion; this is enough for plane wart or filiform warts. But long freeze time (maintaining white halo for 5–20 s) is required for plantar warts. The cycle is repeated every 3 weeks on 8–10 occasions. It is better to pare hyperkeratotic lesions before cryosurgery as it acts as insulator. A cure rate of 60–80% can be anticipated [28]. Longer freeze is more effective than traditional (shorter) freeze, and blistering is significantly greater [29]. Plantar warts need comparatively more aggressive therapy. There is no difference between single freeze-thaw cycle and double freeze-thaw cycle in palmer warts but in plantar warts, and double freeze-thaw is more effective [30]. The number of session is important, not the interval between sessions for percentage cure [31]. Two-week intervals between sessions may be an optimal treatment [31].

### **4.9 Ablation radiofrequency**

Localised heating with radiofrequency heat generators and surgical excision with radiofrequency electrosurgical knives have been used with moderate success [32, 33].

Radiofrequency ablation is a common mode of treatment, and it involves the principle of tissue destruction with various waveforms of alternating electric current whose frequencies fall within the range of radiofrequency (500–4000 khz) [34]. The overall cure rate for warts with radiosurgery ranges between 33 and 80% depending on the number of sittings and the type of warts [35, 36].

Electrocautery is a form of electrosurgery that utilises galvanic or direct current for generating heat. Although rarely used nowadays in the developed nations, it is still widely used in the developing countries and is considered more effective for treating thicker lesions with an overall success rate of 56–80% [7].

### **4.10 Infrared coagulation**

It is an instrument that produces noncoherent infrared light with a spectrum of 400–2700 nm. It has been reported as a cheaper, safer and more easily handled alternative to CO2 laser treatment. Direct application of infrared contact coagulators causes thermal injury to a depth dependent on the duration of exposure [37]. A bulla arises after IRC that may protect the lesion against infection. Cure rate was 66.7% for warts treated with IRC. The instrument allows adjustable tissue necrosis without tissue adhesion and has yielded remissions with a 10.8% recurrence rate [38]. In comparison to electrocoagulation, infrared coagulation produces similar outcomes [37], but it is safer than EC in side effect profile.

**37**

*Human Papillomavirus Infection: Management and Treatment*

The CO2 laser was the initial laser modality used to treat warts and has been used since 1980s [39–41]. The CO2 laser emits infrared light of wavelength 10,600 nm. It is absorbed by tissue water and results nonselective thermal tissue destruction. The CO2 laser treats warts via two mechanisms. A focused CO2 laser beam used as a scalpel to excise the wart down to the subcutaneous tissue, followed by the base of the wart, which is vaporised by a defocused beam until a clean surgical field is obtained [42–45]. Cohort studies report that simple and recalcitrant common, palmar, plantar, periungual and subungual warts have been successfully treated with CO2 laser, with response rates ranging from 50 to 100% [40, 43, 46–53]. Usually, excision by focused mode followed by vaporisation and haemostasis with defocused mode is the common practice. Deeper warts need more passes. Using two to four passes per wart is adequate [46–49]. CO2 laser treatment may be used for recalcitrant warts but also as a first-line of therapy for warts—mainly in the sole, hands and other parts also [46]. Single verruca lesions usually result better (66.7%) than multiple verruca (62.5%) [46]. It can be used for first-line therapy for periungual and subungual warts. It has been seen that patients with subungual and periungual warts, who have failed previous conventional therapy, respond less than in patients when CO2 laser therapy was given as first line (47.9% compared to 80.0%) [47]. Subungual warts respond better than periungual warts [47]. Usually one or two sessions are adequate [48]. Patients with one session heal earlier than patients with more than one session [48]. Adverse effects include permanent nail matrix damage and scarring, and nail changes such as distal onycholysis and thickening may occur [47, 48, 51]. CO2 laser may also be used as excision tool, with a remission rate of 95.5%, but requires specialised unit [49]. Scarring is a possibility [49]. 'En bloc' excision of wart is very much effective [100%] in paediatric age group also with no recurrence, and usually single session is adequate [50]. Many treatment modalities are not feasible in immunosuppressive patients. CO2 laser can be a safe and comparably effective modality of treatment, even in one intervention [51]. Complete excision of the lesional skin with a portion of deeper tissue and 1-mm non-lesional margin leads to the complete clearance of HPV DNA, which leads to very lower recurrence, though chance of scar formation is there. Dressing with artificial dermis leads to less scar formation [52]. Application of Imiquad after CO2 laser in recalcitrant wart reduces or stops recurrences [53]. Vapour produced by CO2 laser with any power density and fluence contains intact papillomavirus DNA. This infected vapour may cause pulmonary infection [54]. Plume produced from laser procedure collected and used as inoculum may produce identical lesions [55]. So, safety precautions during laser surgery may be strictly maintained [55]. It is important to wear surgical masks as it is capable of removing all laser- or electrocoagulation-derived viruses [56], even gas scavenging system to be in use [57]. But a study among CO2 laser surgeons in all the members of American Society of Laser Medicine shows that the plume does not possess enough infectious material to produce significantly more amount of warts in laser surgeons in comparison to population-based common subjects [58]. But, sitewise, CO2 laser surgeons have a greater risk of acquiring nasopharyngeal lesions, especially when they treat genital warts with HPV types 6 and 11 [58]. Scar formation is a known side effect of CO2 lasers, and there are more chances of hypertrophic scar formation if the patient is on cyclosporine for other reasons [59]. In superpulsed CO2 LASERs, the high irradiances and brief duration make possible very precise removal of target lesion volumes and controlled excision. Here, thermal damage is very less leading to less inflammation and less scarring [60].

*DOI: http://dx.doi.org/10.5772/intechopen.92397*

*4.11.1 Carbon dioxide (CO2) laser*

**4.11 Laser therapy**
