New Clues About Chronic Pain and the Immune System
Researchers at the University of Arizona are exploring a potential connection between chronic pain and a relatively uncommon immune condition, eosinophilia. In a small study examining medical records, investigators found that 12% of chronic pain patients treated with spinal cord stimulation or an implanted pain medicine pump had eosinophilia. While this does not prove causation, the finding opens the door to investigating whether immune biomarkers could help predict treatment responses or illuminate the biology of chronic pain.
The Study and What It Found
The study was led by Julie Pilitsis, MD, PhD, professor and chair of the Department of Neurosurgery at the U of A College of Medicine – Tucson. Pilitsis and colleagues reviewed the records of 212 patients who underwent either spinal cord stimulation or intrathecal drug pump implantation for high-impact chronic pain. Of the 114 patients who had routine blood tests within a month before their procedures, 14—roughly 12%—showed eosinophilia, a higher rate than seen in the general population (typically under 1%).
Eosinophilia is defined by an elevated number of eosinophils, a type of white blood cell involved in defending against allergens and certain infections, and it has been linked to a range of autoimmune and inflammatory conditions. However, Pilitsis noted that in this study, inflammatory diseases such as rheumatoid arthritis did not correlate with eosinophilia, suggesting a more nuanced relationship between eosinophils and chronic pain itself.
Why This Might Matter for Chronic Pain Treatment
Chronic pain affects a substantial portion of the U.S. adult population. The Centers for Disease Control and Prevention reports that about 24.3% of adults live with chronic pain, and roughly 8.5% experience high-impact chronic pain that disrupts daily life. For many patients, interventions like spinal cord stimulation (SCS) or intrathecal pain pumps can significantly reduce pain—often by a notable margin. In this study, about 70% of SCS patients experienced some pain relief, underscoring the potential value of refining patient selection and treatment strategies.
So why does eosinophilia matter here? The researchers are exploring whether immune profiles could serve as biomarkers to predict who will respond best to neuromodulation therapies, or to identify patients who may benefit from additional anti-inflammatory approaches. The idea is not to label eosinophilia as a cause of chronic pain, but to examine whether immune system activity interacts with pain signaling in a way that could guide personalized care.
What Questions Remain—and What Comes Next?
Several important questions arise from these preliminary findings. Does eosinophilia predispose someone to chronic pain, or does chronic pain treatment influence eosinophil levels? Could tracking eosinophil counts before and after neuromodulation help clinicians predict outcomes or tailor therapies? And might anti-inflammatory strategies prove beneficial for patients showing eosinophilia who do not respond fully to standard pain treatment?
Pilitsis emphasizes that these results are exploratory. The team’s work is limited by its retrospective design and the relatively small sample size. Still, it provides a clear rationale for prospective studies that monitor immune markers alongside pain outcomes over time. As the field of neuromodulation continues to evolve, integrating immunology with pain management could yield new biomarkers and treatment pathways.
Expert Insight and Collaboration
Co-authors from the University of Arizona include Dr. Martin Weinand, a professor of neurosurgery, and medical students Hanna Johnson and Avantika Mitbander. The research also involved colleagues from outside the university, including Emma Sargent of Florida Atlantic University and Dr. Henry Skelton, a pre-residency fellow at the College of Medicine – Tucson. Their collaboration reflects a broader interest in how immune biology intersects with pain and its treatment.
Bottom Line
The discovery that eosinophilia occurred in a notable share of chronic pain patients undergoing neuromodulation procedures is intriguing but preliminary. It raises the possibility that immune biomarkers could someday help scientists and clinicians better understand who will benefit most from spinal cord stimulation or intrathecal drug delivery—and whether additional anti-inflammatory strategies might improve outcomes for a subset of patients. More research is needed to confirm the link and translate it into clinically useful tools.
