|Ph.D Student||Samuelly Leichtag Gil|
|Subject||The Association between Proinflammatory Cytokines,|
Bacterial Infection, Imaging, Psychological
Factors and Clinical Manifestations in
Patients with Sciatica
|Department||Department of Medicine||Supervisor||PROF. Elon Eisnberg|
|Full Thesis text|
Background: The mechanisms of sciatica are thought to be associated with nerve root compression and inflammation, causing neuropathic pain and disability. Several pro inflammatory cytokines have been suggested as promotors of disc herniations and pain. Additionally, microbial pathogens have also been associated with disc herniations and sciatica. Despite the frequent occurrence of sciatica in the general population its underling mechanisms are obscure. Therefore, we aimed to assess the clinical manifestations and sensory profiles of patients with sciatica, and their relationship to disc microbial infection, levels of disc and blood cytokines, herniation size and location, and pain-related psychological factors.
Methods: Fifty-three adult subjects scheduled for lumbar spine surgery due to radicular pain were evaluated using experimental sensory tests (heat, cold and mechanical detection and pain thresholds, temporal summation and conditioned pain modulation(CPM)), Oswestry Low Back Pain Disability Index (ODI), Short-Form McGill Pain Questionnaire (SF-MPQ), Spielberger's Sate-Trait Anxiety Inventory (STAI), Pain Sensitivity Questionnaire (PSQ), Pain Catastrophizing Scale (PCS), DN4 questionnaire and neurological examination prior to surgery. Subjects' blood and disc samples were tested for levels of pro-inflammatory cytokines (interleukin (IL)-1b, IL-6, IL-8, IL-17, tumor necrosis factor alpha (TNFa) and interferon gamma (IFNg)) and microbial infections using ELISA and rt-PCT. Subjects' MRI scans were assessed for disc herniation size and place using the MSU classification and three-dimensional volumetric analysis.
Results: Complete data was available from 40 (75%) patients (15 female) age 44.8±16.3 years. Clinical pain (r=0.429, P=0.007) and SF-MPQ (r=0.459, P=0.003) were positively correlated with pain catastrophizing and negatively correlated to CPM (r=-0.437, P=0.006; r=-0.421, P=0.007; for average pain and affective SF-MPQ respectively). ODI was positively correlated with pain ratings (r=0.441, P=0.006) and SF-MPQ (r=0.635, P<0.001) and negatively correlated with painful leg strength (r=-0.358, P=0.023) and CPM (r=-0.369, P=0.019). No correlations were found between pain and disability with MRI assessments, disc and blood cytokine levels and bacterial infection. CPM (P=0.001), DN4 (P<0.001) and gender (P=0.029) variables predicted the average pain with adjusted R2 of 0.443, and the SF-MPQ (P<0.001) predicted the ODI score with adjusted R2 of 0.333.
Conclusion: Pain catastrophizing, CPM and gender rather than objective measures of inflammation and imaging seem to contribute to pain in patients with sciatica, although only the last two predict pain intensity. Disability in these patients is more likely attributed to pain and less to objective measures or psychological factors. The role of mechanical compression and inflammation in the generation of pain in patients with sciatica is still obscure.