Neuropathy is a widespread condition marked by damage to the peripheral nerves, often leading to weakness, numbness, and painful sensations, particularly in the hands and feet. This nerve damage can stem from various causes, including diabetes, chemotherapy treatments, or unknown origins (idiopathic neuropathy). Traditional treatments for this chronic pain and loss of function are often limited. Photobiomodulation (PBM) therapy, also known as low-level laser therapy (LLLT), is a non-invasive approach gaining attention. This article explores how this light-based treatment can offer relief for individuals suffering from neuropathy.
Defining Photobiomodulation for Nerve Treatment
Photobiomodulation is a therapeutic technique that utilizes light at specific wavelengths to stimulate biological processes within the body. The light source is typically a low-power laser or a light-emitting diode (LED), operating within the visible red (630–670 nm) and near-infrared (NIR) spectrum (700–1100 nm). PBM is distinct from high-power surgical lasers because it is a non-thermal process that does not generate heat or cause tissue ablation. The equipment often falls into Class IIIB or Class IV medical device categories. NIR wavelengths are preferred for nerve treatment because they penetrate deeper into the body’s tissues than visible red light. The goal is to reduce pain and inflammation while promoting improved nerve and cellular function.
Biological Mechanism of Nerve Repair
The therapeutic effect of PBM begins at the cellular level when photons of light are absorbed by specific molecules. The primary target is cytochrome c oxidase, a chromophore found in the mitochondria, the cell’s powerhouses. This interaction accelerates the mitochondrial respiratory chain, increasing metabolic activity and leading to greater production of Adenosine Triphosphate (ATP), the main energy currency of the cell.
This surge of cellular energy supports the repair mechanisms of damaged nerve cells and can potentially enhance nerve cell regeneration, known as neurogenesis or axonal sprouting. Light stimulation also prompts the release of nitric oxide, a molecule that causes local blood vessels to widen, thereby improving blood flow to the affected nerves.
Improved local circulation delivers more oxygen and nutrients while helping to remove waste products. This cascade of events reduces oxidative stress and inflammation, factors that perpetuate nerve damage and pain in neuropathy. PBM can also modulate pain signals by influencing the function of nociceptive nerves.
Clinical Efficacy and Treatment Protocols
Current evidence suggests that Photobiomodulation can be an effective adjunctive treatment for various forms of peripheral neuropathy. Studies on diabetic peripheral neuropathy (DPN) and chemotherapy-induced peripheral neuropathy (CIPN) have shown encouraging outcomes, including symptom relief and nerve function improvement. Success varies based on the patient’s underlying condition and severity of nerve damage.
Treatment protocols typically involve multiple sessions to achieve a sustained therapeutic effect, often scheduled two to three times per week for six to twelve sessions or more. Dosage is defined by energy density, measured in Joules per square centimeter (J/cm²). This fluence is often targeted between 3 and 48 J/cm², depending on the depth and area of treatment.
Near-infrared wavelengths (780–850 nm) with a fluence of 3 to 48 J/cm² have been shown in trials to alleviate sensory symptoms and improve function. The treatment is non-invasive and painless, usually resulting in only a mild warmth or no sensation. Consistency in adhering to the treatment frequency and energy parameters is important for maximizing clinical benefit.
Safety Considerations and Contraindications
Photobiomodulation therapy maintains a high safety profile when administered correctly by a trained healthcare professional. The primary safety concern involves eye protection, as the intense light from Class IIIB and Class IV lasers can be harmful to the retina. Both the patient and the practitioner must wear appropriate protective eyewear throughout the procedure.
Certain patient conditions or areas of the body are considered contraindications for PBM. Application directly over a known cancerous lesion must be avoided, as the light’s ability to stimulate cellular activity could accelerate tumor growth. Caution is also advised against treating directly over the thyroid gland, as stimulation could potentially alter its function.
PBM is generally avoided over the abdomen or lower back during pregnancy due to a lack of safety testing on the developing fetus. Treatment directly over implanted electronic devices, such as pacemakers, is also avoided to prevent potential interference with the device’s function. A full medical history must be reviewed to ensure the safe application of the therapy.