Introduction: The use of surgical intervention to manage chronic lower back pain with spinal fusion is not successful in all patients. Identifying patients that will not respond to treatment will save them from the procedure and allow for alternative treatment plans to be explored. Atrophy in the brain has been previously shown to relate to chronic pain, and in this study we aim to identify neuroimaging markers of pain in patients prior to undergoing spinal fusion surgery.
Methods: Eight patients with chronic back pain (37-63 yo; one female) and eight age- and gender-matched controls with no pain participated in an MRI scanning session that included T1-weighted anatomical imaging and single-voxel MR spectroscopy. Volumes of the left and right thalami (LT and RT) were quantified from the anatomical images using FreeSurfer after correcting for total intracranial volume. N-acetylaspartate in the LT was quantified as a ratio with creatine (NAA/Cr) from spectroscopy data. LT and RT volumes and NAA/Cr were compared across groups and with pain level reported using the visual scale (1-10).
Results: Using ANOVA, with age and gender as covariates, we found that LT volume was significantly lower in the pain group vs. controls (8.13 cc vs. 8.83 cc; p = 0.029). We found a similar group relationship in the RT, but it only met trend-level significance (p = 0.065). Further, we found a significant linear correlation between NAA/Cr and pain level in the pain group (r = -0.79; p = 0.037).
Conclusions: We report on two imaging indices of thalamic neurodegeneration in patients with chronic back pain: decreased volume, which indicates atrophy, and lower NAA, which is a marker of neuronal loss. Together, these findings can form the basis of future studies aimed at discriminating patients based on suspected pain outcomes before spinal fusion surgery, and thus allow for alternative treatment options.
Patient Care: This work represents the first step in identifying neuroimaging correlates with chronic pain, which can be ultimately be used to explore specific markers that predict success in spinal fusion. Discriminating patients based on suspected pain outcomes before spinal fusion surgery will allow for more effective treatment options.
Learning Objectives: By the conclusion of this session, participants will have learned about: 1) atrophy of the thalamus in patients with chronic back pain; 2) MR spectroscopy correlates with pain level; and 3) neuroimaging biomarkers pain and how they can be used to plan appropriate therapy and surgical intervention.