Patterns of chronic inflammation in extensively treated patients with arachnoiditis and chronic intractable pain.

OBJECTIVE To use biomarkers to gain insight into and gauge the residual (post-treatment) level of inflammation in two groups of intensively treated patients with severe chronic pain. METHODS Three study groups were analyzed, and included: (i) patients (n = 90) with chronic intractable pain (CIP), (ii) patients (n = 26) with chronic pain and MRI-documented arachnoiditis (ARC) and (iii) normal subjects without a diagnosis of chronic pain (n = 86). We determined and compared the serum concentrations of Alpha-1 Antitrypsin (A1AT), Myeloperoxidase (MPO) and soluble Tumor Necrosis Factor receptor type 2 (sTNFR2) in each of the patient populations studied. RESULTS Patients treated for ARC or CIP had higher serum levels of A1AT and MPO than normal untreated subjects without a diagnosis of chronic pain. ARC patients had an A1AT mean serum concentration of 167.9 ± 41.9 mg/dL as compared to 148.9 ± 35.2 mg/dL for normal subjects (p = 0.023). CIP patients had the highest mean serum A1AT level 183.6 ± 39.2 mg/dL with p values of <0.0001 or 0.08 when compared to normal subjects or ARC patients respectively. ARC patients had an MPO mean serum concentration of 344.6 ± 227.9 ng/mL as compared to 188.2 ± 107.5 ng/mL for normal subjects (p = < 0.0001). CIP patients had a similar mean serum MPO level of 352.3 ± 164 ng/mL with p values of <0.0001 or 0.85 when compared to normal subjects or ARC patients respectively. In addition, we noted a difference in the pattern of MPO expression in patients with ARC in that 34% had levels of MPO at normal or below and 31% had levels 2-fold or greater than normal. CONCLUSION This data supports the concept that in centralized pain, sites of neuroinflammation elaborate MPO and other inflammatory factors which may not be completely cleared from the system despite extensive and complex treatment regimens.