Treatment of nevus of OTA by Q-switched, frequency doubled, ND: Yag laser

Post 3 laser sessions response.

Post 3 laser sessions response.

Skin hyperpigmentation - Post laser therapy - Day 20-30.

Skin hyperpigmentation - Post laser therapy - Day 20-30.

Skin hypopigmentation - Post laser therapy - Day 7.

Skin hypopigmentation - Post laser therapy - Day 7.

Skin whitening following laser therapy.

Skin whitening following laser therapy.

Pre laser therapy.

Pre laser therapy.

Q-Switched, frequency doubled, Nd-YAG laser.

Q-Switched, frequency doubled, Nd-YAG laser.

Introduction

Nevus of Ota is a dermal melanocytic nevus usually manifesting in the early childhood and progressively increasing in size and color till puberty. The nevus rarely regresses and disfigures the face and psyche of the patient. Occasionally malignant melanoma has been reported in the nevus. The present case report discusses the usefulness of Q-Switched, Frequency doubled Nd: YAG Laser therapy in treating this condition.

Case Report

A 40-year school teacher with history of brownish pigmentation over the left cheek, present since birth was the first case treated with Q-Switched, Frequency doubled Nd- YAG Laser. The patient′s skin type was Fitzpatrick V. The brownish pigmentation was confined to the left maxillary area. No ocular involvement was present.

The Q-Switched, Frequency Doubled Neodymium: Yttrium Garnet (QSFD Nd-YAG) Laser [MEDLITE-IV, manufactured by Continuum Biomedical, Bublin, California] has treatment repetition rates: 1, 2, 5 and 10 Hertz and spot size: 3, 4, 6 and 8 mmk at 1064nm. At spot size 3mm the maximum fluence is around 14J/cm2- The pulse duration of the laser is in the range of 1040.

The laser ablation was done in three sessions′ using Q-Switched, Frequency doubled, Nd-YAG laser with the following treatment parameters [Table - 1].

Topical EMLA cream was applied under occlusion for 1 hour prior to laser therapy. The patient during the procedure experienced slight stinging sensation. In the post procedure period there was mild purpura and edema. This usually settled by about 2 to 3 days.

The lasered area developed hypopigmentation, after about a week. This was followed by post inflammatory hyperpigmentation, which started after 2 to 3 weeks and persisted on an average for 2 to 3 months. The pigmentary change was effectively tackled by sunscreens, hydroquinone in conjuction with topical corticosteroids.

Nevus resolved in three sessions of Qswitched, Frequency doubled, Nd-YAG laser ablation without any complications. [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5] & [Figure - 6]

Laser Basics

Lasers are monochromatic electromagnetic radiation source used to treat various skin disorders.[2] Of the various lasers used to treat the dermal pigmentary dosorders the Q-switched Nd-YAG (1064nm), Ruby (694nm) and Alexandrite (755nm) lasers are best suited because they selectively target the melanosomes in the melanocytes and that too in the dermis. This is because of their longer wavelength, which facilitates dermal penetration. Melanin′s broad absorption spectrum (from 250-1200nm) makes it a good target for laser light.[3]

The fundamental principle behind laser removal of cutaneous pigment is the GrothusDraper Law which states that absorption of the laser light is necessary for any ensuing mechanical or chemical alteration to occur. Secondly the laser source should have a suitable wavelength so as to reach the target at a specified length in the skin. Third the laser should confine the thermal damage within the melanosomes without heat diffusion to the adjacent structures after absorption by the chromophore i.e, melanosome. This is the thermal relaxation time. Thermal relaxation time is defined as the time it takes for half of the heat absorbed by the targeted chromophore to dissipate to the surrounding tissue. Melanosomes have short thermal relaxation time in the range of 50-100ns.

A given laser system will deliver its energy, which is of a specific wavelength. This laser output can be continuos or pulsed. This means that the energy can be delivered continuously or only for a few fractions of seconds in a repetitive manner. This is known as pulsed laser. If the pulse duration is less than the Thermal relaxation time of a given target then the specificity of the laser increases. This pulsing can be done by Q-Switching. Qstands for quality. Q switching is a means of shuttering the laser output so that it is delivered in extremely short of high-intensity radiation. The duration is in the nanosecond range about 10 nanoseconds for the Q-switched Nd-YAG laser.[4]

Discussion

Literature is replete with therapies for Nevus of Ota like cryosurgery, dermabrasion to name a few. These therapies are associated with long standing complications like scars.[5] With the advent of lasers this had changed for good. Q-switched Lasers like Nd-YAG, Ruby and Alexandrite Lasers have proven effective in treating dermal melanocytic nevus of Ota.

The purpose of publishing this case is to report the efficacy of Q-switched Nd-YAG laser in successfully treating Nevus of Ota in an Indian patient. There are many doubts raised about its efficacy in skin types of IV-VI. But this case report lightens these apprehensions.

Even though this is a single case report since the starting of the centre in December 1999 till date nearly 14 cases are under therapy. All cases are in various stages of resolution of pigmentation. All cases had postoperative mild purpura, post therapy hypopigmentation and post inflammatory hyperpigmentation, which were transient. None of the cases treated have shown any skin textural changes.