Altered Sensory Insular Connectivity in Chronic Postsurgical Pain Patients.

Yin Ying Ching,Terence Tay,Phua Hwee Tang,Ban Leong Sng,Juan Zhou,Chenhao Wang,Yng Miin Loke

doi:10.3389/fnhum.2018.00483

Abstract

Chronic postsurgical pain (CPSP) occurs in up to 50% of individuals after surgeries and 32% after hysterectomy, leading to major adverse effects on quality of life and socioeconomic burden. Little is known about whether and how large-scale neural networks being affected in CPSP, particularly with regard to the functional connectivity (FC) of insula which is known to be the hub of the intrinsic neural network playing a critical role in pain processing. Here, we sought to examine the dynamics of insular FC in the context of noxious stimuli in CPSP patients. To this aim, resting state fMRI data were acquired, before and after acute heat pain stimulation, from 11 individuals with chronic post-hysterectomy pain (CPHP) and 22 age-matched healthy controls (HCs) who had a hysterectomy but without chronic post-surgical pain. We examined whole-brain FC were mapped by seeding at the sensorimotor and chemosensory subfields of the insula and found significant group × stimulation interaction effects. Specifically, the HC group had increased FC between the left sensorimotor insula and right angular and middle occipital gyrus (MOG) and increased FC between the left chemosensory insula and bilateral angular and MOG following pain stimulation. In contrast, such pain stimulation related FC changes were absent in the CPHP group. Furthermore, higher insular FC at baseline and smaller increased insular FC after pain stimulation correlated with clinical pain scores in CPHP patients. Our findings suggest that CPSP is associated with altered dynamics of large-scale functional networks anchored in the insula.

Highlights

Chronic postsurgical pain (CPSP) is a potential adverse outcome after surgery
We found that lower increase in insula functional connectivity (FC) after stimulation was associated with higher pre-operative temporal summation scores in chronic post-hysterectomy pain (CPHP) patients (r2 = 0.563; p < 0.05, Figure 2 bottom right)
We examined the insular FC in CPHP using resting state functional magnetic resonance imaging (fMRI) approach

Summary

Introduction

Chronic postsurgical pain (CPSP) is a potential adverse outcome after surgery. It has been described in patients after common surgical procedures and with an estimated incidence as high as 32% after hysterectomy (Perkins and Kehlet, 2000; Kehlet et al, 2006; Brandsborg et al, 2007; Fletcher et al, 2015; Pokkinen et al, 2015; Beyaz et al, 2016; Weibel et al, 2016). The development of chronic pain is thought to be multifactorial. In addition to peripheral persistent noxious stimuli (Li et al, 2007), the transition from acute to persistent postsurgical pain involves maladaptive neuroplastic changes in neurological pathways (Zeilhofer et al, 2012) and neural remodeling in brain connectivity (Chapman and Vierck, 2017). It has been postulated that persistent aberrant nociceptive activity causes neuroplastic changes in central nervous system networks that subserve pain and attention/cognition functions, leading to a chronic pain state (Davis and Moayedi, 2013).

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