Photobiomodulation Activates Microglia/Astrocytes and Relieves Neuropathic Pain in Inferior Alveolar Nerve Injury

Objective: This study aimed to determine microglial/astrocyte changes and their associated analgesic effect in inferior alveolar nerve injury (IANI) model rats treated with photobiomodulation therapy (PBMT) using a 940-nm diode laser. Background: Very few basic studies have investigated microglial/astrocyte dynamics following PBMT aimed at relieving neuropathic pain caused by IANI. Methods: Rats were divided into an IANI-PBM group, IANI+PBM group, and sham+PBM group. Observations were made on the day before IANI or the sham operation and on postoperative days 3, 5, 7, 14, and 28. PBMT was delivered for 7 consecutive days, with an energy density of 8 J/cm2. Behavioral analysis was performed to determine pain thresholds, and immunohistological staining was performed for the microglia marker Iba1 and astrocyte marker glial fibrillary acidic protein, which are observed in the spinal trigeminal nucleus. Results: Behavioral analysis showed that the pain threshold returned to the preoperative level on postoperative day 14 in the IANI+PBM group, but decreased starting from postoperative day 1 and did not improve thereafter in the IANI-PBM group (p ≤ 0.001). Immunological analysis showed that microglial and astrocyte cell counts were similar in the IANI+PBM group and IANI-PBM group shortly after IANI (day 3), but the expression area was larger (p ≤ 0.001) and hypertrophy of microglia and astrocyte cell bodies and end-feet extension (i.e., indicators of activation) were more prominent in the IANI+PBM group. Conclusions: PBMT after IANI prevented hyperalgesia and allodynia by promoting glial cell activation shortly after injury.

Photobiomodulation reduces neuropathic pain after spinal cord injury by downregulating CXCL10 expression

BACKGROUND

Many studies have recently highlighted the role of photobiomodulation (PBM) in neuropathic pain (NP) relief after spinal cord injury (SCI), suggesting that it may be an effective way to relieve NP after SCI. However, the underlying mechanisms remain unclear. This study aimed to determine the potential mechanisms of PBM in NP relief after SCI.

METHODS

We performed systematic observations and investigated the mechanism of PBM intervention in NP in rats after SCI. Using transcriptome sequencing, we screened CXCL10 as a possible target molecule for PBM intervention and validated the results in rat tissues using reverse transcription-polymerase chain reaction and western blotting. Using immunofluorescence co-labeling, astrocytes and microglia were identified as the cells responsible for CXCL10 expression. The involvement of the NF-κB pathway in CXCL10 expression was verified using inhibitor pyrrolidine dithiocarbamate (PDTC) and agonist phorbol-12-myristate-13-acetate (PMA), which were further validated by an in vivo injection experiment.

RESULTS

Here, we demonstrated that PBM therapy led to an improvement in NP relative behaviors post-SCI, inhibited the activation of microglia and astrocytes, and decreased the expression level of CXCL10 in glial cells, which was accompanied by mediation of the NF-κB signaling pathway. Photobiomodulation inhibit the activation of the NF-κB pathway and reduce downstream CXCL10 expression. The NF-κB pathway inhibitor PDTC had the same effect as PBM on improving pain in animals with SCI, and the NF-κB pathway promoter PMA could reverse the beneficial effect of PBM.

CONCLUSIONS

Our results provide new insights into the mechanisms by which PBM alleviates NP after SCI. We demonstrated that PBM significantly inhibited the activation of microglia and astrocytes and decreased the expression level of CXCL10. These effects appear to be related to the NF-κB signaling pathway. Taken together, our study provides evidence that PBM could be a potentially effective therapy for NP after SCI, CXCL10 and NF-kB signaling pathways might be critical factors in pain relief mediated by PBM after SCI.

Effect of photobiomodulation on neuropathic pain of diabetic origin: a narrative review of the literature

To update the literature on the effectiveness of photobiomodulation (PBM) therapy in relieving pain in patients with diabetic peripheral neuropathy (DPN) compared to the effects of post-intervention, control/placebo groups, and other therapies. Search on the following databases: PORTAL PERIODICOS CAPES, PUBMED, GOOGLE ACADEMIC/SCHOLAR, SCOPUS, SCIELO, CENTRAL, and MEDLINE. Manual search: 1) manually capture the references of relevant articles originally selected to be included in the eligible studies. Two independent researchers performed the screening and selection of studies, methods assessment, and data extraction with unblinded authors and impressions. Subsequently, the full text of the originally selected studies was screened. The screening form registered the criteria for excluding literature from the full-text screening. The screening resulted in a total of 1692 citations. Out of these, 1402 citations were examined for titles and abstracts, followed by the removal of duplicated studies; therefore, 68 articles remained for full-text evaluation. 54 articles were excluded after full-text screening. Fourteen articles met the selection criteria, hence being selected and included in this narrative review. PBM showed to be a promising modality in relieving painful symptoms in DPN, especially when implemented in combination with other therapies, by improving the quality of life of diabetic patients.

Effectiveness of Photobiomodulation Therapy on Neuropathic Pain, Nerve Conduction and Plantar Pressure Distribution in Diabetic Peripheral Neuropathy - A Systematic Review

BACKGROUND

Diabetic peripheral neuropathy is a severe complication of type 2 diabetes mellitus. The most common symptoms are neuropathic pain and altered sensorium due to damage to small nerve fibers. Altered plantar pressure distribution is also a major risk factor in diabetic peripheral neuropathy, leading to diabetic foot ulcers.

OBJECTIVE

The objective of this systematic review was to analyze the various studies involving photobiomodulation therapy on neuropathic pain and plantar pressure distribution in diabetic peripheral neuropathy.

METHODS

We conducted a systematic review (PubMed, Web of Science, CINAHL, and Cochrane) to summarise the evidence on photobiomodulation therapy for Diabetic Peripheral Neuropathy with type 2 diabetes mellitus. Randomized and non-randomized studies were included in the review.

RESULTS

This systematic review included eight studies in which photobiomodulation therapy showed improvement in neuropathic pain and nerve conduction velocity. It also reduces plantar pressure distribution, which is a high risk for developing foot ulcers.

CONCLUSION

We conclude that photobiomodulation therapy is an effective, non-invasive, and costefficient means to improve neuropathic pain and altered plantar pressure distribution in diabetic peripheral neuropathy.

Effects of photobiomodulation therapy on neuropathic pain in rats: evaluation of nociceptive mediators and infrared thermography

Nerve injury induces release of peptides and upregulation of receptors such as substance P and transient receptor potential receptor V1 (TRPV1), which contribute to the development and maintenance of chronic pain. Photobiomodulation therapy (PBMT) is a nonpharmacological strategy that promotes tissue repair and reduces pain and inflammation. However, the molecular basis for PBMT effects on neuropathic pain is still unclear. We investigated the effects of PBMT on substance P, TRPV1, and superficial temperature change in a rodent model of neuropathic pain. We evaluated substance P and TRPV1 in dorsal root ganglia (DRG L4 to L6) at baseline, 14 days after chronic constriction injury (CCI) and after PBMT. We also assessed the superficial temperature of tarsal, metatarsal, tibia, and fibula regions before and after PBMT using infrared thermography. Substance P and TRPV1 levels increased in DRG of CCI rats compared to naive and sham rats and decreased after PBMT. Infrared thermography showed increased temperature of tarsal, metatarsal, tibia, and fibula regions in CCI rats, which was decreased after PBMT. There were no statistical differences between CCI rats with PBMT, sham, and naive rats in any assay. PBMT reduces nociceptive mediators and hind paw and leg's temperature in a rodent model of neuropathic pain, suggesting that PBMT may play a modulatory role in thermoregulation, neurogenic inflammation, and thermal sensitivity in peripheral nerve injuries. Therefore, PBMT appears to be a valuable strategy for neuropathic pain treatment in clinical settings.

Practical considerations of linear accelerator-based frameless extracranial radiosurgery for treatment of occipital neuralgia for nonsurgical candidates

Occipital neuralgia generally responds to medical or invasive procedures. Repeated invasive procedures generate increasing complications and are often contraindicated. Stereotactic radiosurgery (SRS) has not been reported as a treatment option largely due to the extracranial nature of the target as opposed to the similar, more established trigeminal neuralgia. A dedicated phantom study was conducted to determine the optimum imaging studies, fusion matrices, and treatment planning parameters to target the C2 dorsal root ganglion which forms the occipital nerve. The conditions created from the phantom were applied to a patient with medically and surgically refractory occipital neuralgia. A dose of 80 Gy in one fraction was prescribed to the C2 occipital dorsal root ganglion. The phantom study resulted in a treatment achieved with an average translational magnitude of correction of 1.35 mm with an acceptable tolerance of 0.5 mm and an average rotational magnitude of correction of 0.4° with an acceptable tolerance of 1.0°. For the patient, the spinal cord was 12.0 mm at its closest distance to the isocenter and received a maximum dose of 3.36 Gy, a dose to 0.35 cc of 1.84 Gy, and a dose to 1.2 cc of 0.79 Gy. The brain maximum dose was 2.20 Gy. Treatment time was 59 min for 18, 323 MUs. Imaging was performed prior to each arc delivery resulting in 21 imaging sessions. The average deviation magnitude requiring a positional or rotational correction was 0.96 ± 0.25 mm, 0.8 ± 0.41°, whereas the average deviation magnitude deemed within tolerance was 0.41 ± 0.12 mm, 0.57 ± 0.28°. Dedicated quality assurance of the treatment planning and delivery is necessary for safe and accurate SRS to the cervical spine dorsal root ganglion. With additional prospective study, linear accelerator-based frameless radiosurgery can provide an accurate, noninvasive alternative for treating occipital neuralgia where an invasive procedure is contraindicated.

Pulsed radiofrequency for the treatment of chronic ilioinguinal neuropathy

BACKGROUND

Ilioinguinal neuropathy is a rare but disabling condition. The condition may arise spontaneously or in the setting of pelvic surgery. To date, most therapeutic options have been limited to neuropathic pain medications, anti-inflammatory medications, nerve blocks with local anesthetics, or neurectomy. Long-term results of non-surgical interventions are fair at best. We present a case of chronic ilioinguinal neuropathy treated with pulsed radiofrequency.

OBJECTIVE

To examine the efficacy of pulsed radiofrequency (PRF) lesioning on pain in ilioinguinal neuropathy.

METHOD

A 58-year old man with chronic ilioinguinal neuropathy was treated with PRF and was followed for 3 months.

RESULTS

The patient had significant pain relief at 3 months follow up.

CONCLUSION

Pulsed radiofrequency lesioning may be a good treatment for chronic ilioinguinal neuropathy in cases refractory to conservative management.

Pulsed radiofrequency for the treatment of ilioinguinal neuralgia after inguinal herniorrhaphy

BACKGROUND AND PURPOSE

Ilioinguinal neuralgia secondary to inguinal hernia repair is frequently a chronic, debilitating pain. It is most often due to destruction or entrapment of nerve tissue from staples, sutures, or direct surgical trauma. Treatment modalities, including oral analgesics, nerve blocks, mesh excision, and surgical neurectomy, have varied success rates. Pulsed radiofrequency (PRF) has recently been described as a successful method of treating chronic groin pain. Unlike conventional radiofrequency, PRF is non-neurodestructive and therefore less painful and without the potential complications of neuritis-like reactions and neuroma formation. Although the mechanism is unknown, it appears that the interaction of an electromagnetic field and c-fos proteins may alter normal transmission of painful impulses. Our study examines five patients treated with PRF for ilioinguinal neuralgia secondary to inguinal herniorrhaphy.

METHOD

Five patients were diagnosed with chronic ilioinguinal neuralgia secondary to inguinal hernia repair at our institution. Each patient was treated at vertebral T12, L1, and L2 with root PRF at 42 degrees C for 120 seconds per level.

RESULTS

Four out of five patients reported pain relief lasting from four to nine months on follow-up visits. Only one patient reported no pain relief whatsoever.

CONCLUSION

Ilioinguinal neuralgia is challenging to treat. We have demonstrated the successful use of PRF for four out of five patients seen in our office.

Palliative-radiotherapy in lumbosacral carcinomatous neuropathy

The authors report their own experience in obtaining pain relief in 13 recurrent or disseminated cancer patients affected by lumbosacral carcinomatous neuropathy (LCN). The site, where the disease involved the lumbosacral plexus or its branches, was palliatively irradiated with a few large fractions. The average duration of response was 196 days. Median survival (uncensored) was 185 days (range 47-636 days).

Evaluation of analgesic effect of low-power He:Ne laser on postherpetic neuralgia using VAS and modified McGill pain questionnaire

In order to investigate the efficacy of low-power He:Ne laser in treatment of pain, we irradiated 18 outpatients with severe postherpetic neuralgia. The efficacy of the low-power laser treatment was evaluated using a four-grade estimation, visual analog scale (VAS), and modified McGill pain questionnaire (m-MPQ) after every 10 of as many as 50 irradiations. The efficacy rate using a four-grade estimation at the end of 50 treatments was 94.4%. VAS decreased from 6.2 before irradiation therapy to 3.6 after 50 treatments, and the degree of pain relief was reduced to 44.6% and correlated with the number of treatments. The total numbers of words and the total scores of the m-MPQ decreased as the number of treatments increased. No complications attributable to the laser therapy were observed. These results suggest that repeated irradiation with low-power He:Ne laser is an effective and safe therapy for postherpetic neuralgia.

Prevention of post-herpetic neuralgia. Evaluation of treatment with oral prednisone, oral acyclovir, and radiotherapy

The effects of prednisone, oral acyclovir, and radiotherapy were compared with placebo in the prevention of post-herpetic neuralgia. No treatment used was able to prevent, with statistical significance, post-herpetic neuralgia, although prednisone and acyclovir showed some pain reduction in the acute phase. Radiotherapy was of no value in either the acute or post-herpetic phase.

Effect of repeated irradiation of low-power He-Ne laser in pain relief from postherpetic neuralgia

In order to investigate the efficacy of repeated irradiation of low-power helium-neon laser in pain relief, we irradiated 36 outpatients suffering from postherpetic neuralgia. Each patient underwent 20 trials of irradiation on several points around the painful area at a frequency of 2 or 3 times a week. The efficacy of the laser at the end of 20 trials was noticed on 88.9%, and the degree of pain relief was 55.3%, which correlated with the number of trials. These results suggest that the irradiation of He-Ne laser is an effective and safe treatment for postherpetic neuralgia.

The value of roentgen irradiation in the treatment of painful degenerative and inflammatory musculoskeletal conditions. A double-blind study

A double-blind trial was carried out to study the effect of roentgen radiation treatment in 104 patients presenting 127 painful disorders of the joints and muscles. 64 disorders received genuine treatment and 63 had sham treatment. Improvement occurred in 59% of the genuinely treated group and in 65% of the placebo group. The results were about the same 2 weeks and 6 weeks after termination of treatment. Thus there was no significant difference between the groups.