126 Association of PAG Connectivity in SCI Subjects With Neuropathic Pain in a Resting-State FMRI Study

Abstract

INTRODUCTION: Neuropathic pain (NP) is estimated to be present in 61% of subjects with chronic spinal cord injury (SCI). Periaqueductal Grey (PAG) plays a crucial role in descending pain modulation system. Few studies assessed PAG’s functional connectivity (FC) in pain syndromes, however, it has not been studied in SCI. METHODS: 10 SCI subjects with NP were divided into two groups (moderate-severe n = 7, mild-no pain n = 3), and 10 healthy controls (HC) were enrolled. Resting-state fMRI was performed for subjects using a 3T Philips Ingenia scanner with a dedicated 32 channels head coil. Seed-to-voxel analysis was performed using CONN toolbox with the PAG as the seed region. Group-based analysis was performed between three groups with age and gender as confounding variables. A voxel threshold p-value of <0.05 was used, with the results corrected for multiple comparisons using fdr with a significance level of 0.05. RESULTS: Compared to HCs, SCI with NP demonstrated decreased FC between PAG and one cluster. SCI with pain compared to SCI without pain demonstrated Increased FC in one and decreased FC in two clusters. For each common anatomical region between pairwise analyses, FC alterations were compared to assess whether they are the result of SCI or NP. CONCLUSIONS: Altered FC was observed between PAG and regions involved in the pain modulation in SCI with NP compared with SCI without pain and HCs. We hypothesized that alterations between PAG and the Frontal cortex, Thalamus, Brain stem, and Cerebellum could be the result of NP sequela rather than the SCI itself. Further studies with more subjects will be needed to assess this hypothesis.