Persistent Spinal Pain Syndrome: A Study of Contact Heat-Evoked Potentials

Persistent spinal pain syndrome (PSPS) type 2 is a chronic condition characterized by low back pain, with or without radiating limb pain, persisting after spinal surgery. The underlying pathophysiology remains unclear, with potential contributions from altered central pain processing mechanisms.

This study investigates the role of central sensitization in PSPS using contact heat-evoked potentials (CHEPs), an electrophysiological tool for assessing spinothalamic tract integrity and central pain processing.

The study included 36 healthy controls and 15 PSPS patients with neuropathic pain (NP) localized to the L4, L5, and S1 dermatomes, stimulated at the L1 dermatome. CHEP parameters, including N2-P2 amplitude, N2 latency, and P2 latency, were compared between groups.

Significant differences were identified, with PSPS patients demonstrating prolonged N2 and P2 latencies (p=0.008 and p=0.005, respectively) and reduced N2-P2 amplitude (p=0.025). Receiver-operating characteristic (ROC) analyses revealed N2 latency as the most reliable diagnostic parameter (AUC=0.81, sensitivity 67%, specificity 80%). Approximately 68% of PSPS patients exhibited abnormal CHEP values, suggesting spinothalamic tract dysfunction.

These findings support the hypothesis of altered central pain processing in PSPS, consistent with previous studies on NP and central sensitization. However, no statistically significant correlation was observed between pain intensity (verbal rating scale) and CHEP parameters (p=0.06), potentially due to the limited sample size. CHEP is a valuable non-invasive tool for exploring central pain mechanisms in PSPS with potential diagnostic and therapeutic implications. Limitations include the small sample size and potential confounders, such as subclinical polyneuropathy in controls. Further research is recommended to complement these findings and explore the broader implications of central sensitization in PSPS and other chronic pain conditions.