Introduction: Pain-related fear plays a substantial role in chronic low back pain (LBP) by amplifying the experienced disability. Related dysfunctional emotions and cognitions may also affect sensory aspects of pain through a modulatory pathway in which the periaqueductal gray (PAG) and the amygdala play key roles.
Objectives: We therefore hypothesized a differential amygdala-PAG functional connectivity (FC) in patients with chronic LBP that is modulated by the degree of pain-related fear.
Methods: We used data of a previously reported fMRI study where 20 chronic LBP patients (7 females, mean age = 39.35) and 20 healthy controls (12 females, mean age = 32.10) were asked to observe video clips showing potentially harmful and neutral activities for the back. Pain-related fear was assessed using the Tampa Scale of kinesiophobia (TSK) and Fear Avoidance Beliefs questionnaires (FABQ). Generalized psychophysiological interactions were used to reveal task-based FC.
Results: Compared to controls, patients exhibited a significant decrease in amygdala-PAG-FC (P = 0.022) during observation of harmful activities, but not of neutral activities. Furthermore, amygdala-PAG-FC correlated negatively with Tampa Scale of kinesiophobia scores in patients (R2 = 0.28, P = 0.01) but not with Fear Avoidance Beliefs questionnaires scores.
Discussion: Our findings might indicate a maladaptive psychobiological interaction in chronic LBP patients characterized by a disrupted amygdala-PAG-FC that is modulated by the degree of pain-related fear. These results shed new light on brain mechanisms underlying psychological factors that may have pronociceptive effects in chronic LBP.
Keywords: Amygdala; Chronic low back pain; Fear avoidance beliefs; Functional connectivity; Kinesiophobia; PAG; PPI; fMRI.