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  • Structural and Functional MRI Characterization of Trial Spinal Cord Stimulation Responders in Failed Back Surgery Syndrome

    Final Number:

    Peter A. Pahapill MD, PhD, FACS, FRCSC; Guangyu Chen; Andrew Nencka; Hao Shu; Shekar N. Kurpad MD PhD; Shi-Jiang Li PhD

    Study Design:
    Laboratory Investigation

    Subject Category:

    Meeting: 2016 ASSFN Biennial Meeting

    Introduction: Chronic back pain is a burden to society and difficult to treat. Chronification of pain may involve structural and brain network connectivity changes that include transitions from somatomotorsensory to more emotionally-related brain networks. Spinal cord stimulation (SCS) can be effective in treating failed back surgery syndrome (FBSS) patients. Despite having a successful response to a brief SCS trial (SCSr), 30-50% of implanted patients fail to achieve satisfactory long-term pain relief. Improved pain control may be achieved with alternative, bursting patterns of SCS which may preferentially affect emotional components of chronic pain. Our goal is to begin to utilize functional imaging to help guide SCS management.

    Methods: Prior to SCS permanent implant, anatomical and resting state fcMRI were performed on 10 SCSr FBSS patients, and on 16 age-matched controls. Gray matter density (GMD)(1), brain inter-network function connection strengths (FCS) were calculated amongst motor (MTN), default model (DMN), salience (SAN), striatum (STM), temporal (TEP), hippocampus (HIP) and dorsal attention (DAN) networks. Two sample t-test with 5000 random permutation (2) and Bonferroni correction were performed for GMD and FCS respectively. A linear regression was used to test the clinical significance of FCS.

    Results: Significantly decreased GMD in bilateral precentral gyri (Fig 1A,B) and increased GMD in HIP/PHG areas (Fig 1A,C) were found in the SCSr FBSS group. The inter-network FCS of STM-MTN, STM-DMN, STM-TEP, STM-HIP and STM-DAN were significantly decreased in this group (Fig.2). The FCS of STM was negatively correlated with pain scores (Fig. 3).

    Conclusions: This is the first ever report in SCSr FBSS patients of decreased FCS between striatum and other functional networks that was also inversely correlated with pain scores, which may reflect mechanisms of pain chronification. The finding of increased HIP GMD in these patients is consistent with previous reports in animals (3) and humans (4), of hippocampal neurogenesis with persistent pain.

    Patient Care: Functional imaging data on chronic pain patients that are potential candidates for spinal cord stimulation may ultimately represent a non-invasive imaging tool that can help in 1) the selection of patients for SCS; and 2) the selection of the best SCS parameters so as too optimize SCS therapies.

    Learning Objectives: By the conclusion of this session, participants should be able to describe the potential emerging role of functional imaging in the anatomical and functional characterization of chronic pain patients that are potential candidates for spinal cord stimulation which may, in turn, help optimize SCS therapies.

    References: 1. Ashburner J (2009) Computational anatomy with the SPM software. Magn Reson Imaging 27(8):1163-1174. 2. Winkler AM, Ridgway GR, Webster MA, Smith SM, & Nichols TE (2014) Permutation inference for the general linear model. Neuroimage 92:381-397. 3. Apkarian AV, et al. (2016). Role of adult hippocampal neurogenesis in persistent pain. Pain 157: 418–428. 4. Smallwood RF, et al. (2013). Structural brain anomalies and chronic pain; a quantitative meta-analysis of gray matter volume. J. of Pain 14 (7): 663-675.

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