Laser Photothermolysis Research Articles

Surgical Pearl: Intralesional electrodesiccation of sebaceous hyperplasia

From the Division of Dermatology, Department of Internal Medicine, Ohio State University Hospitals. Reprints are not available from the authors. J Am Acad Dermatol 2000;42:127-8. Copyright © 2000 by the American Academy of Dermatology, Inc. 0190-9622/2000/$12.00 + 0 16/74/101938 S ebaceous hyperplasia is a common, benign proliferation of sebaceous glands occurring predominantly on the face. Clinically, there is one or several, 2to 4-mm yellowish papules, often with a central umbilication representing the site of a ductal opening. Sebaceous hyperplasia has been found to occur with an increased frequency in patients receiving hemodialysis1 or immunosuppressive therapy,2,3 especially after kidney transplantation.2 Most often these lesions represent little more than a cosmetic concern, although they may be confused clinically with basal cell carcinoma. Many modalities exist for the treatment of sebaceous hyperplasia, including shave excision, electrodesiccation, curettage with electrodesiccation, bichloroacetic or trichloroacetic acid destruction,4 isotretinoin (Accutane) therapy,5,6 cryotherapy,7 carbon dioxide laser ablation, erbium:YAG laser ablation, and pulsed dye laser photothermolysis.8 Unfortunately, treatment of these lesions often result in a depressed scar or are followed by recurrence. Here we adapt a simple procedure, intralesional desiccation,9 for which we have had no clinical scar formation or recurrences in more than 30 treated lesions. Each lesion is anesthetized with approximately 0.3 mL of 1% lidocaine (Xylocaine) with 1:100,000 epinephrine. We use a 733 Birtcher hyfrecator at the 20 setting, which is an intermediate setting, with a fine, noninsulated epilating needle (Fig 1). The needle is inserted into each lobule (Fig 2), one by one, and desiccated for less than 1 second, resulting in a crackling or popping sound. When all visible lobules are treated, a plastic strip (Band-aid) is applied over triple antibiotic ointment (Polysporin). Patients are instructed to continue to apply ointment until completely healed. PEARLS

Comparison of different procedures for the treatment of benign and malignant skin tumours

SummaryBenign and malignant tumours of the skin comprise a large variety of nevi, malformations and tumour entities, among which non-melanoma skin cancer, as well as malignant melanoma and its respective precursor lesions, are the most important. Most of the more common superficial benign and smaller skin tumours can be treated using diverse techniques, such as curettage or cryotherapy. Many of the vascular or epithelial nevi and several other benign skin tumours can be selectively destroyed using laser photothermolysis, or removed by circumscribed laser ablation, with excellent results. The major objective in the management of malignant skin tumours is early recognition and elimination of potential precursors, or initial tumour lesions. The latest preventive strategies include laser resurfacing of large actinically-damaged skin areas. Some of the premalignant (e.g. actinic keratosis) or in-situ tumours (e.g. Bowen's disease), as well as certain superficial basal cell carcinomas, can be cured by diverse surface-destructive techniques, such as cryotherapy, laser ablation, or topical photodynamic therapy. However, surgical removal remains the treatment of choice in pigmented lesions prone to malignant transformation, in most types of invasive tumour growth and in all cases where a histological confirmation of diagnosis or control of complete eradication is necessary for effective cure.

Dynamic Epidermal Cooling During Pulsed Laser Treatment of Port-Wine Stain

The clinical objective in the treatment of a patient with port-wine stain (PWS) undergoing laser therapy is to maximize thermal damage to the PWS, while at the same time minimizing nonspecific injury to the normal overlying epidermis. With dynamic cooling, the epidermis can be cooled selectively. When a cryogen spurt is applied to the skin surface for an appropriately short period of time (on the order of tens of milliseconds), the cooling remains localized in the epidermis, while leaving the temperature of the deeper PWS vessels unchanged. Comparative measurements obtained by a fast infrared imaging detector demonstrated that the surface temperature prior to laser exposure could be reduced by as much as 40 degrees C using the dynamic cooling technique. No skin surface textural changes were noted on PWS test sites cooled with a 20- to 80-millisecond cryogen spurt after flashlamp-pumped pulsed dye laser (FLPPDL) exposure (lambda = 585 nm; tau p = 450 microseconds) at the maximum light dosage possible (10 J/cm2). In contrast, epidermal necrosis occurred on the uncooled sites after such exposure. Six months after laser exposure, clinically significant blanching on the cooled sites indicates laser photothermolysis of PWS blood vessels did occur. Our preliminary experiments demonstrate the feasibility of selectively cooling the normal overlying epidermis without affecting the temperature of the deeper PWS vessels. Furthermore, protection of the epidermis from thermal injury, produced by melanin light absorption at clinically relevant wavelengths, can be achieved effectively. An additional advantage of dynamic epidermal cooling is reduction of patient discomfort associated with FLPPDL therapy. Further studies are under way to determine an optimum strategy for applying this dynamic cooling technique during pulsed laser treatment of patients with PWS and others with selected dermatoses (dermal melanocytic lesions and tattoos).

Flashlamp-excited dye laser therapy of idiopathic vulvodynia is safe and efficacious

Objective: The management of chronic vulvovaginal pain, not explicable on specific histologic grounds, presents a major problem in referral centers for lower genital tract diseases. Study design: This article reports on a two-step protocol in a sample of 175 medical nonresponders, drawn from a 2-year cohort of 725 women with vulvovaginal pain. The first maneuver was the use of a flashlamp-excited dye laser to selectively photocoagulate symptomatic subepithelial blood vessels in 168 women; the second was the microsurgical removal of chronically painful Bartholin's glands in 52 women not responsive or not suited to flashlamp-excited dye laser photothermolysis. Results: Dye laser response rates werer independent of whether patients manifested macroscopic focl of painful erythema (“vestibular adenitis”) or just colposcopically apparent hyperemia-ectasia of the individual blood vessels (“pruritic papillomatosis”) (55% vs 45% after a single surgical procedure; 76% vs 65% after serial retreatment; p not significant). Conversely, response rates were much lower among women in whom pressure on the Bartholin's glands produced sharp, lancinating pain (15% vs 66% after a single surgical procedure; 22% vs 93% after serial retreatment; p < 0.001). Forty-two (85%) of 50 patients with flashlamp-excited dye laser failure had deep pain; however, the impasse to progress was broken by gland removal. Final response rates were 92.5% (complete response 62%; partial response 30%) in the “surface-only” group and 80.3% in the “surface-plus-deep” group (χ 2 = 14.9; p < 0.001). The major complication was acute bacterial cellulitis, occurring in the first postoperative week. Modification of the treatment protocol to include topical antibiotics with an occlusive dressing reduced the cellulitis rate from 17.2% to 2.5%. In four women (1.8%) Koebner-like exophytic condylomas also developed within 1 month of flashlamp-excited dye laser surgery. Conclusion: The availability of a safe, efficacious, and relatively noninvasive treatment should reduce the need for resective surgery in most patients with idiopathic vulvodynia. 1995; 172; 1684–1701.)

Differential Vascular Response to Laser Photothermolysis

Individual blood vessels in the chick choriallantoic membrane were selectively coagulated through photothermolysis, using pulsed laser irradiation at 585 nm. Pulse durations were chosen to be 0.45 ms and 10 ms, which correspond to the thermal relaxation times in blood vessels of 30 microns and 150 microns diameter, respectively. The short pulses, at a light fluence F = 3 Jcm-2, caused permanent occlusion of vessels of 40 microns diameter or less, whereas larger caliber vessels (60-120 microns) required F = 4-5 Jcm-2. The long-duration pulses, at F = 7 Jcm-2, caused coagulation of the larger diameter vessels; the small-caliber vessels and capillaries showed resistance to photothermolysis and required multiple exposures to achieve coagulation. The fluence versus diameter (F versus d) relationship for coagulation was calculated for the two pulse durations. The energy deposited in a cylindrical absorber of diameter d by an optical field, incident perpendicular to the vessel, was expressed analytically and compared with the energy required to coagulate a blood vessel of the same lumen dimeter. When thermal diffusion is incorporated into the model, our findings can be accounted for quantitatively. This information will be of use for improving the laser treatment of port wine stains and other vasculopathies. A surprising observation was that arterioles were damaged at lower incident energy densities than venules having the same lumen diameter, despite the fact that absorbance in oxygen-rich and oxygen-poor blood is the same at 585 nm.