A systematic review found that there is very low certainty of evidence to support the use of injectable biologic treatments for neuropathic pain. These findings were published in Pain Medicine.
Investigators at the Mayo Clinic searched publication databases through November 2020 for studies evaluating biologic therapy for the treatment of neuropathic pain. The primary outcome was pain reduction and secondary outcomes were functional improvement and safety.
A total of 14 studies investigated platelet-rich plasma (PRP) and 10 studies mesenchymal stem cell (MSC) therapies for the treatment of chronic neuropathic pain, spinal cord injury, diabetic peripheral neuropathy, painful scars, pudendal neuralgia, trigeminal neuralgia, and carpal tunnel syndrome.
PRP treatment for carpel tunnel syndrome was evaluated by 10 studies. One study found no improvement in Boston Carpal Tunnel Syndrome Questionnaire (BCTSQ) scores at 10 weeks compared with controls.
Another study found more modest improvement in VAS scores (P =.018) and BCTSQ severity scores (P =.045) at 6 months. There was more evidence to support PRP for improving BCTSQ function scores (P =.001) or Quick-Disabilities of the Arm, Shoulder, and Hand (Q-DASH) scores (P =.011) in 2 studies, but a third found less evidence for BCTQ function score improvement (P =.044).
In peripheral neuropathic pain, perineural PRP at multiple nerve locations improved visual analog scores (VAS) scores at 6 months (P <.001) and another study identified improved pain symptoms in 39 of 45 patients.
For spinal cord injury, 1 study reported significant reduction in VAS 10 months after administration of MSC derived from autologous bone marrow (P =.003). Another study reported improved pain rating index at 1 year after administration of MSC derived from allogenic umbilical cord tissues.
In diabetic retinopathy, autologous bone marrow-derived stem cell therapy halved Toronto Clinical Scoring System (TCSS) scores at 36 months (P <.001) and in another study, TCSS improved by at least 2 points in more stem cell recipients at 3 years (84% vs 43%; P <.001).
Using autologous adipose tissue for lipofilling of the pudendal nerve, 10 out of 15 patients had improved VAS scores (P <.001) and short form 36 (SF-36) scores (P <.01) at 1 year. Similarly, 5 out of 9 patients with trigeminal neuropathic pain who received autologous adipose-derived stromal vascular fraction reported improved numeric rating scale scores at 6 months (P =.018).
There were no safety concerns reported in this systematic review; however, the review authors emphasized that uncontrolled of proliferation and differentiation of MSC has the potential to lead to tumor generation.
Overall, the quality of evidence was very low due to the indirectness of evidence, risk for bias, publication bias, imprecision, and inconsistency.
This systematic review was not able to draw any definitive conclusions about the use of biologic therapies for the treatment of neuropathic pain conditions.
“What is striking about the current review is the large overall number of studies investigating the use of biologics for neuropathic pain, particularly those evaluating the use of PRP for [carpal tunnel syndrome], but due to study design and risk of bias, an inability to draw definitive conclusions regarding the efficacy of these therapies for neuropathic pain conditions,” the study authors noted.
They note that based on the quality of current available evidence, the use of biologics for neuropathic pain should not be considered as standard alternatives to standard of care therapy.
Bies M, Ashmore Z, Qu W, Hunt C. Injectable biologics for neuropathic pain: A systematic review. Pain Med. 2022;pnac066. doi:10.1093/pm/pnac066