Dysregulated Pain-Autonomic Responses in Patients With Nonspecific Chronic Low Back Pain

Neurophysiological assessments might advance the understanding of nonspecific chronic low back pain (nsCLBP) by quantifying altered pain processing and associated autonomic responses. Contact heat-evoked potentials (CHEPs) and sympathetic skin responses (SSRs) were compared between nsCLBP patients and healthy controls (HCs), and their relationships with experimental and clinical pain ratings were explored.

A total of 56 nsCLBP patients and 40 age- and sex-matched HCs were included in this study. All participants underwent simultaneous recordings of CHEPs and SSRs in response to two blocks of 15 heat stimuli applied at the back (i.e., the patients' clinical pain area) and the hand (nonpainful control area). Participants rated the perceived pain intensity of each contact heat stimulus using a numerical rating scale (0-10). The change of pain ratings, CHEP, and SSR amplitudes between blocks was calculated as habituation index.

SSR latencies were prolonged in patients compared to HCs (F = 9.5, p = 0.003) and were shorter after back stimulation compared to hand stimulation (F = 9.6, p < 0.001). No other group differences were observed. Clinical pain intensities in patients correlated (1) with contact heat pain ratings in both areas (back: rho = 0.27, p = 0.041, control area: rho = 0.272, p = 0.042) and (2) inversely with CHEP P2 latencies after hand stimulation (current pain: rho = -0.324, p = 0.019; average 4 weeks: rho = -0.320, p = 0.022).

Prolonged SSR latencies in nsCLBP might indicate a dysregulated pain-autonomic response.

Clinicaltrials.gov_identifier: NCT04433299.