Study Finds Possible Link Between Chronic Pain and Eosinophilia

A small study of medical records led by Julie Pilitsis, MD, PhD, professor and chair of the department of neurosurgery at the University of Arizona College of Medicine in Tucson, unexpectedly found that 12 percent of chronic pain patients who were treated with spinal cord stimulation or an implanted pain medicine pump had a white blood cell condition called eosinophilia. The condition is often a result of something gone awry with the immune system and is typically seen in less than one percent of the general population. While patients with eosinophilia didn’t appear to fare any worse in their treatment, the findings suggest a possible link between chronic pain and the immune system.  

A spinal cord stimulator is an implanted device that sends low levels of electricity directly into the spinal cord to relieve pain. An intrathecal pain pump is surgically implanted and delivers pain medication directly into the fluid surrounding the spinal cord.

Dr. Pilitsis and her co-workers reviewed the medical records of 212 patients who underwent spinal cord stimulation or intrathecal drug pump implantation for high-impact chronic pain. They evaluated data from 114 patients who had routine blood tests done within the month prior to treatment to determine the incidence and clinical relevance of eosinophilia. 

“The condition typically affects fewer than one in 100 people, and we found 14 of 114, or roughly 12 percent, in this group had eosinophilia before treatment,” Dr. Pilitsis said. “Now we’re asking what is it about eosinophilia that might predispose someone to chronic pain? Should we be looking at this as a biomarker before and after treatment to see if the latter reduces the eosinophilia?”

Roughly 70 percent of spinal cord stimulation patients see some reduction in pain. “We don’t know if this could be a marker to help identify patients who might do better or worse with treatment, and if inflammation plays a role,” Dr. Pilitsis said. “Could spinal cord stimulation reduce inflammation at some point? It’s just speculation, but for those who don’t do well, we could think of adding an anti-inflammatory to the chronic pain treatment. We still have many questions.”