Can Low-Level Laser Therapy Have An Impact For Small Fiber Neuropathy?

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Kerry Zang, DPM, Janna Kroleski, DPM, Shahram Askari, DPM, and Sanford Kaner, DPM

   In addition, we utilized the Total Neuropathy Score-reduced (TNSr) to objectively evaluate each patient’s response to laser therapy. The Total Neuropathy Score-reduced is a combination of subjective questions and physical examination results, and gives a score ranging from 0 to 44 with a higher score representing worse neuropathic pain (see "Measuring Patient Response To Laser Therapy With The Total Neuropathy Score-Reduced"). We quantified both the percent increase in epidermal nerve fiber density in the foot and the leg, and the change in the TNSr. In addition, we asked patients to quantify their overall improvement in neuropathic pain as a percent improvement. (See the table “How Patients Were Asked To Quantify Their Improvement In Neuropathic Pain.”)

   The average Total Neuropathy Score (TNS) for patients at baseline was 22.83 with a range between 17 to 26. In comparison to baseline, the average post-treatment TNS exhibited a significant decrease of 8.91 points or 40.05 percent with a range between 24.00 and 70.59 percent. (See the table “Comparison of Total Neuropathy Scores Between Baseline And Post-Treatment Assessment.”)

   Assessment of epidermal nerve fiber density of the legs showed a change in the average epidermal nerve fiber density of 0.595 points or 33.15 percent between baseline and post-treatment evaluation points (see the table “Comparison Of Baseline And Post-Treatment Epidermal Nerve Fiber Density Of The Legs”). The average change observed between baseline and post-treatment epidermal nerve fiber density testing was not statistically significant. However, seven of the 11 patients demonstrated an increase in epidermal nerve fiber density of the legs from baseline with a range in percent improvement between 2.15 percent and 1578 percent.

   Assessment of epidermal nerve fiber density of the feet showed an average change between baseline and post-treatment evaluation periods of 0.648 points or 56.54 percent. This change was not statistically significant. However, a majority of participants (6 of 11) revealed an improvement in epidermal nerve fiber density of the feet with a range between 32.44 percent and 220 percent. (See the table “Comparison of Baseline And Post-Treatment Epidermal Nerve Fiber Density Scores Of The Feet.”)

   We have included figures showing actual histological specimens of a 65-year-old study patient before and after laser therapy. As one can see in figures a and c, at the start of the study, the patient has very few small fiber nerves that cross the basement membrane into the epidermis. The epidermal nerve fiber density before laser therapy for this patient was significantly less than the normal range, resulting in a diagnosis of small fiber neuropathy. In figures b and d, after laser therapy, there has been a significant increase in the number of small fibers penetrating into the epidermis and the calculated epidermal nerve fiber density increased to the normal range.

   For each participant in the study, we reported an improvement in the overall perceived pain rating. Study participants exhibited an average improvement in neuropathic pain of 75 percent.

In Conclusion

The data acquired from this prospective, non-randomized, non-controlled study demonstrates the potential utility of low-level laser therapy. These data show a clinically meaningful outcome for the treatment of neuropathic pain without an adverse event. However, a placebo-controlled, randomized, double-blind, multi-centered clinical investigation is warranted in order to elucidate the complete efficacy of this therapeutic approach. Furthermore, it would be important to enroll study participants who demonstrate similar baseline epidermal nerve fiber density of the legs and feet in order to appropriately quantify any improvement produced by low-level laser therapy.

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