SAN DIEGO – In a 2006 report of complications from laser dermatologic surgery, one of the authors, Dieter Manstein, MD, PhD, who had subjected his forearm to treatment with a fractional laser skin resurfacing prototype device, was included as 1 of the 19 featured cases.
Dr. Manstein, of the Cutaneous Biology Research Center in the department of dermatology at Massachusetts General Hospital, Boston, was exposed to three test spots in the evaluation of the effects of different microscopic thermal zone densities for the prototype device, emitting at 1,450 nm and an energy per MTZ of 3 mJ.
Two years later, hypopigmentation persisted at the test site treated with the highest MTZ density, while two other sites treated with the lower MTZ densities did not show any dyspigmentation. But he noticed something else during the experiment: He felt minimal to no pain as each test site was being treated.
“It took 7 minutes without any cooling or anesthesia,” Dr. Manstein recalled at the annual meeting of the American Society for Laser Medicine and Surgery. “It was not completely painless, but each time the laser was applied, sometimes I felt a little prick, sometimes I felt nothing.” Essentially, he added, “we created cell injury with a focused laser beam without anesthesia,” but this could also indicate that if skin is treated with a fractional laser very slowly, anesthesia is not needed. “Current devices are meant to treat very quickly, but if we [treat] slowly, maybe you could remove lesions painlessly without anesthesia.”
The observation from that experiment also led Dr. Manstein and colleagues to wonder: Could a focused laser beam pattern be used to assess cutaneous innervation? If so, they postulated, perhaps it could be used to not only assess nerve sensitivity of candidates for dermatologic surgery, but as a tool to help diagnose small fiber neuropathies such as diabetic neuropathy, and neuropathies in patients with HIV and sarcoidosis.
The current gold standard for making these diagnoses involves a skin biopsy, immunohistochemical analysis, and nerve fiber quantification, which is not widely available. It also requires strict histologic processing and nerve counting rules. Confocal microscopy of nerve fibers in the cornea is another approach, but is very difficult to perform, “so it would be nice if there was a simple way” to determine nerve fiber density in the skin using a focused laser beam, Dr. Manstein said.
With help from Payal Patel, MD, a dermatology research fellow at MGH, records each subject’s perception of a stimulus, and maps the areas of stimulus response. Current diameters being studied range from 0.076-1.15 mm and depths less than 0.71 mm. “We can focus the laser beam, preset the beam diameter, and very slowly, in a controlled manner, make a rectangular pattern, and after each time, inquire if the subject felt the pulse or not,” Dr. Manstein explained.
“This laser could become a new method for diagnosing nerve fiber neuropathies. If this works well, I think we can miniaturize the device,” he added.
Dr. Manstein disclosed that he is a consultant for Blossom Innovations, R2 Dermatology, and AVAVA. He is also a member of the advisory board for Blossom Innovations.