Lumbar radicular pain constitutes only 5%-10% of low back pain conditions, but it accounts for 33% of the sick leave and 47% of the disability benefits due to back pain in Norway. Previous data show that the recovery from lumbar radicular pain may be influenced by physical, psychosocial, surgery-related and clinical factors. In addition, genetic factors can influence on the development of disc degeneration and the recovery after symptomatic disc herniation.
The fact that inflammation contributes to the pathogenesis of disc herniation and radicular pain is now well established. The inflammatory response, initiated from the annulus fibrosus in case of disc herniation, may lead to increased levels of pro-inflammatory interleukins (ILs) close to nerve roots. This inflammatory process could also promote Modic changes.
In this thesis, the role of such cytokines and genetic factors in recovery from lumbar radicular pain was addressed. The present data demonstrated a significant association between the inflammatory serum cytokine IL-6 and functional recovery from symptomatic disc herniation. Moreover, the genotype IL-1a C>T rs1800587 increased the risk of persistent pain 1-year after disc herniation. Regarding the radiological factors, we showed that type I Modic changes influences the short-term clinical outcome in patients with low back pain and radicular pain. A sex dependent effect of the opioid receptor mu 1 (OPRM1 A118G) rs1799971 genotype on recovery after disc herniation was also identified.
It is concluded that inflammatory, radiological and genetic factors may be important for the recovery after lumbar disc herniation.
List of papers. Paper II is removed from the thesis due to publisher restrictions.
Paper I. This is the pre-peer reviewed version of the following article: E.I. Schistad, A. Espeland, L.M. Pedersen, L. Sandvik, J. Gjerstad, and C. Røe. Association between baseline IL-6 and one-year recovery in lumbar radicular pain, Eur J Pain. 2014 Apr 2. which has been published in final form at doi:10.1002/j.1532-2149.2014.502.x
Paper II. Elina Iordanova Schistad, Line Melå Jacobsen, Cecilie Røe, and Johannes Gjerstad. The interleukin-1α gene C>T polymorphism rs1800587 is associated with increased pain intensity and decreased pressure pain thresholds in patients with lumbar radicular pain. The Clinical Journal of Pain. 2014 Oct;30(10):869-74. doi:10.1097/AJP.0000000000000048
Paper III. Elina Iordanova Schistad, Ansgar Espeland, Lars Jørgen Rygh, Cecilie Røe, and Johannes Gjerstad. The influence of Modic changes on pain during one-year follow-up in patients with lumbar radicular pain. Submitted version. Skeletal Radiol. 2014 Sep;43(9):1271-9. The final publication is available at Springer via doi:10.1007/s00256-014-1928-0
Paper IV. Maria Belland Olsen, Line Melå Jacobsen, Elina Iordanova Schistad, Linda Margareth Pedersen, Lars Jørgen Rygh, Cecilie Røe, and Johannes Gjerstad. Pain intensity the first year after lumbar disc herniation is associated with the A118G polymorphism in the opioid receptor mu 1 gene: evidence of a sex and genotype interaction. J Neurosci. 2012 Jul 18;32(29):9831-4. doi:10.1523/JNEUROSCI.1742-12.2012 This article is freely available online through the J Neurosci Open Choice option.