Successful Management of Diabetic Peripheral Neuropathic Pain Using MiS MLS Laser Therapy: A Case Report

Introduction

Neuropathic pain (NP) is a particularly severe form of chronic pain, arising as a direct consequence of a lesion or disease affecting the somatosensory nervous system¹. This condition is the result of a series of different pathological mechanisms, and it is usually described based on the anatomic localization or etiology. The conditions and the pathophysiological states that determine the onset of neuropathic pain mostly involved are metabolic disorders (e.g. peripheral diabetic neuropathy), neuropathies associated with viral infections (e.g. post-herpetic neuralgia, HIV, leprosy), autoimmune disorders affecting the central nervous system (e.g. multiple sclerosis and Guillain–Barre syndrome), chemotherapy-induced peripheral neuropathies, damage to the nervous system of traumatic origin (e.g. spinal cord injury and amputation), inflammatory disorders, hereditary neuropathies, and channelopathies².

Estimates of NP in the general population suggest the prevalence is 7% to 10%³, increasing to around 20% to 30% in people with diabetes⁴. Studies have also reported greater prevalence of neuropathic pain, as with chronic pain overall, in older people, women, and people from areas of high social deprivation⁵.

The principal clinical signs associated to NP are allodynia (pain due to a stimulus that does not normally provoke pain), hyperalgesia (an increase in the perception of pain generated by a stimulus that causes pain) and paresthesia (a condition that determines the perception of anomalous sensations comparable to needle bites, tingling, itching, reduced, or even loss of sensitivity). In patients suffering from NP, the perceived pain is usually spontaneous, manifesting itself without needing a stimulus. This pathological condition substantially affects the quality of life of patients, compromising their psychological state⁶.

It is important to distinguish NP from other forms of pain which arises from actual or threatened damage to non-neural peripheral tissue. NP is generally unresponsive to analgesics such as nonsteroidal anti-inflammatory drugs (NSAID) or opioids. Rather, gabapentinoids, tricyclic antidepressants, and serotonin–norepinephrine reuptake inhibitors are recommended as first- and second-line treatments⁷.

Nonetheless, these medications for NP provide greater than 50% pain relief in less than half of people treated. Furthermore, analgesics in general, particularly opioids and gabapentinoids, can potentially cause harm, providing an even greater emphasis on appropriate use⁸.

Peripheral neuropathic pain (PNP) is a direct consequence of a lesion or disease affecting the peripheral nerves. There are two main types of PNP. The pain experienced in the nerve trunk is a result of chemical or mechanical insults to sensitized nociceptors in the nervi nervorum. This pain can have a deep aching quality and often approximates the course of the involved nerve. Dysesthetic pain, on the other hand, is a consequence of damaged or regenerating neuronal fibers. It can have an electrical, burning, or launching quality. Finally, a combination of both types could occur.

PNP is typically worsened by activities that compress or stretch the involved nerves. The signs of PNP include pain with active and passive range of motion of the involved limb; tenderness to palpation of the involved nerve; tenderness or inflammation of the tissue innervated by the involved nerve⁹.

The management of PNP mostly require a multidisciplinary approach based on medication¹⁰; cognitive-behavioral therapy¹¹ to reduce distress and worrying thoughts; education regarding peripheral nerve physiology; gentle movement without undue tension on the nerve bed to help restore the endoneurial circulation; treatment of the local dysfunction affecting the nerve / manual therapy; physical agents that gate the sensation of pain such as electric stimulation, cold or heat¹².

Among physical therapies, laser therapy has emerged as a promising approach for the management of peripheral neuropathies. However, the efficacy of laser therapy in treating peripheral neuropathies remains a subject of ongoing study and debate. Some studies have suggested that laser therapy may be beneficial in improving the symptoms of peripheral neuropathies, primarily through its anti-inflammatory, analgesic, and tissue healing-promoting effects. The theory proposes that laser light may stimulate cellular metabolism, increase local blood flow, and reduce inflammation, thereby contributing to the alleviation of neuropathic symptoms. Nevertheless, the results of studies on laser therapy for peripheral neuropathies are inconclusive, with some studies demonstrating significant benefits while others have not. Factors influencing the efficacy of laser therapy include the duration of treatment, the power of the laser used, the type of neuropathy, and the severity of symptoms.

The following clinical case presents the use of a particular type of therapeutic laser, the multiwave-locked system (MLS^®) laser, at high power (Paverage>500mW). This system spatially and temporally combines two wavelengths, 808nm and 905nm, with programmable emission in continuous/frequency-modulated mode for 808nm and pulsed mode for 905nm.

Previous clinical evidence indicates that lasers belonging to the MLS^® family have been effective in the treatment of diabetic polyneuropathies^(14-17).

In this case report, the MiS laser device was utilized. This laser belongs to the MLS^® family of devices, and it is distinguished by a maximum peak power of 1 kW and maximum average power of 6W± 20%, which enables the safe targeting of deeper tissue layers, a common site of neuropathic pain onset.

In a pre-clinical study, Micheli et al.¹⁸, through a model of sciatic nerve chronic constriction in the rat, that mimics the neuropathic pain, demonstrated that the treatment with MLS^® MiS laser therapy reduced pain significantly and protected nerve structure through different mechanisms. This included inhibition of the enzymes involved in the inflammation process, myelin sheath restoration, and modulation of pain-stimulating signaling at the central nervous system level.

In a preliminary clinical experience, Mezzalira et al.¹⁹ tested the safety and efficacy of MiS laser in a group of patients suffering of peripheral neuropathy of different origins, obtaining an average pain reduction of 79.5%.

Based on its characteristics and the previous evidence on mechanism of action and clinical effects, the MiS laser was considered a valid device to treat neuropathic pain in diabetic polyneuropathies.