Heart Rate Variability: A Novel Modality for Diagnosing Neuropathic Pain after Spinal Cord Injury

Abstract

Background: Heart rate variability (HRV), the physiological variance in the heart's R-R interval length, can be analyzed to produce various parameters reflective of one's autonomic balance. HRV analysis may be used to capture those autonomic aberrations associated with chronic neuropathic pain (NP) in spinal cord injury (SCI). This study assesses the capacity of HRV parameters to diagnose NP in an SCI cohort.Methods: An electrocardiogram (ECG) was collected at rest from able bodied participants (AB, n = 15), participants with SCI only (SCI-NP, n = 11), and those with SCI and NP (SCI+NP, n = 20). HRV parameters were analyzed using conventional time and frequency analysis.Results: At rest, there were no heart rate differences amongst groups. However, SCI+NP participants demonstrated lower overall HRV, as determined by the SDNN time domain parameter, compared to either AB (p < 0.01) or SCI-NP (p < 0.05) groups. Moreover, AB and SCI-NP participants were statistically comparable for all HRV time and frequency domain parameters. Additional analyses demonstrated no differences in HRV parameters between T4, above vs. T5, below SCI groups (for all parameters: p > 0.15) or between C8, above vs. T1, below SCI groups (p > 0.30).Conclusions: Participants with SCI and NP exhibit a lower overall HRV, which can be determined by HRV time domain parameter SDNN. HRV analysis is an innovative modality with the capacity for objective quantification of chronic NP in participants with SCI.

Neuropathic pain modulation after spinal cord injury by breathing-controlled electrical stimulation (BreEStim) is associated with restoration of autonomic dysfunction

“…We recently published an innovative study that evidenced the capacity of baseline HRV parameters, namely time domain variables, to differentiate chronic SCI subjects with and without NP. 24 Additionally, we demonstrated that those HRV differences were unlikely to be influenced by the neurologic level or severity of the SCI itself. 24 …”

“… 24 Additionally, we demonstrated that those HRV differences were unlikely to be influenced by the neurologic level or severity of the SCI itself. 24 …”

Targeting the Autonomic Nervous System Balance in Patients with Chronic Low Back Pain using Transcranial Alternating Current Stimulation: A Randomized, Crossover, Double-Blind, Placebo-Controlled Pilot Study

“…Many studies within chronic pain have found decreased SDNN within clinical populations compared to healthy controls (12) and HRV suppression has been correlated with pain severity or disability perception (59,65,66). One study (67) measured SDNN in patients with spinal cord injury (SCI) with and without neuropathic pain and found significant lower resting SDNN in SCI patients with pain compared to SCI without pain and healthy controls. Since SDNN includes input from both the parasympathetic and sympathetic input, few conclusions on the increase of specific ANS branches can be drawn (12), but SDNN has been hypothesized to provide objective quantification of analgesic response to pain treatment (67).…”

“…One study (67) measured SDNN in patients with spinal cord injury (SCI) with and without neuropathic pain and found significant lower resting SDNN in SCI patients with pain compared to SCI without pain and healthy controls. Since SDNN includes input from both the parasympathetic and sympathetic input, few conclusions on the increase of specific ANS branches can be drawn (12), but SDNN has been hypothesized to provide objective quantification of analgesic response to pain treatment (67). Therefore, increasing overall HRV (SDNN) may be beneficial in patients with CLBP, and HRV intervention studies have shown increases in total HRV (24).…”

Combined transcranial direct current stimulation and breathing-controlled electrical stimulation for management of neuropathic pain after spinal cord injury

“…Neuropathic pain after SCI is probably due to maladaptive plastic cortical reorganization and sensitization of the central nervous system (CNS), although this is poorly understood (3,(47)(48)(49)(50). As a result of SCI and partial/complete denervation of spinal neurones, communication between the brain and the periphery is partially or completely interrupted.…”