Laser Treatment for Pigmentation

Picosecond and nanosecond lasers are far more effective for treating individual lentigines, compared with other types of devices, but ultrashort pulses carry a higher risk for postinflammatory hyperpigmentation than intense pulsed light or the long-pulsed laser, according to Mathew M. Avram, MD, JD.

For treating melanosomes with selective photothermolysis, some of the peak wavelengths include 532 nm, 694 nm, 755 nm, and 1064 nm, Avram, director of laser, cosmetics, and dermatologic surgery at Massachusetts General Hospital, Boston, said during the virtual annual Masters of Aesthetics Symposium. “The ideal target is fair skin with a dark, pigmented lesion,” he said. “That way you’re going to get energy focused to the melanin that’s in the lesion itself.”

Q-switched and picosecond lasers are effective for pigmented lesions. These employ as much energy as the city of Boston for 20-30 billionths of a second, or 750 picoseconds. “This raises the temperature to 1,000° C in that time, which produces the characteristic epidermal whitening,” he said. “This targets pigment cells only, whether it’s exogenous or endogenous pigment.”

Benign pigmented lesions amenable to the Q-switched nanosecond and picosecond laser include lentigines and nevus of Ota/Ito. The mechanism of action for clinical lightening is fragmentation and release of melanin-laden cells and the gradual uptake and removal of fragments by activated macrophages into lymphatic vessels. “For effective results, do not blindly memorize settings or replicate recommended settings from a colleague or a device manufacturer,” advised Avram, who practiced law prior to becoming a physician. “Some lasers are not externally calibrated, so what you have to do is pay attention to the laser endpoint, which in this case is epidermal whitening. Tissue ‘splatter’ is an unsafe endpoint and may lead to scarring. Safe and unsafe laser endpoints and close clinical observation are the best means to avoid complications and get the best results for your patients. The key finding is the endpoint, not the energy settings.”

Pigmented lesions that should not be treated with a laser include atypical nevi, lentigo maligna, and other forms of melanoma. “When in doubt, perform a biopsy,” he said. “Regardless of who referred the case, you are liable if you treat a melanoma with a laser. This is not only misdiagnosis but it probably delays diagnosis as well. If you cannot recognize basis pigmented lesion morphology, do not treat pigmented lesions. At some point, it’s going to catch up with you.”

Patients with more pigment to their skin face a higher risk for postinflammatory hyperpigmentation, Avram continued. While longer pulsed lasers produce less hyperpigmentation, they’re also less effective at getting rid of lesions. “You can combine a long-pulsed laser with fractional resurfacing or IPL [intense pulsed light] to optimize improvement,” he said. “If you don’t have two lasers to use, you can just use a longer-pulsed laser. The desired treatment endpoint for this approach is an ashen gray appearance.” Options include a 532-nm Nd:YAG laser with or without cooling, a 595-nm pulsed dye laser without cooling, and a 755-nm alexandrite laser without cooling.

One advance in the treatment of seborrheic keratoses is Nano-Pulse Stimulation (NPS), a novel technology being developed by Pulse Biosciences. With this approach, nanosecond electrical energy pulses cause internal organelle disruption, which leads to regulated cell death. “The cell-specific effect is nonthermal, as a typical nano-pulse delivers 0.1 joules of energy distributed in a volume of tissue,” Avram said. Early human studies established safe doses and validation of mechanism hypothesis for benign-lesion efficacy. “What you have are tiny nanopores that allow calcium ions to flow into the cell,” he explained. “The nanopores in the endoplasmic reticulum allow calcium ions to flow out of the endoplasmic reticulum, stressing it. These nanopores in the mitochondria disrupt the ability to generate energy, and the cell dies.”

Histology has revealed that within days the procedure causes regulated cell death with no thermal effects. The ability of NPS energy to clear seborrheic keratoses (SK) was confirmed in a study of 58 subjects who had 174 SK lesions treated. The majority of SKs (82%) were rated as clear or mostly clear 106 days post treatment. All results reflected a single treatment session.

Another novel treatment, “cryomodulation,” a technology being developed by R. Rox Anderson, MD, Dieter Manstein, MD, PhD, and Henry Chan, MD, PhD, expresses cold-induced change to the skin as a way to pause melanin production. “You get melanin production paused but melanocyte function is preserved,” Avram explained. “There is a normal epidermal barrier and no persistent inflammatory response, so there’s no hyperpigmentation.” He characterized it as an ease-of-use clinical procedure for treating benign lesions in all skin types. A mask is applied to confine freezing to the desired treatment area, and hydrated gauze is used to help facilitate ice crystal propagation. A prototype of the device features a parameter selection based on lesion type, anatomical location, and skin type. “It uses between 107 and 166 kJ/m2 of extracted energy, and you take photos at baseline and follow-up,” he said. “You get 2-3 days of redness, darkening, and swelling. It’s well tolerated, with minimal discomfort. There’s no long-term dyschromia. This is nice, because patients have little, if any, downtime.”

Avram disclosed that he has received consulting fees from Allergan, Merz, Sciton, and Soliton. He also reported having ownership and/or shareholder interest in Cytrellis.