Motor corticospinal excitability abnormalities differ between distinct chronic low back pain syndromes

Area of Science:

• Neuroscience
• Pain Research
• Clinical Medicine

Background:

• Low-back pain (LBP) is a prevalent condition with diverse etiologies.
• Previous research suggests cortical plastic changes in non-specific LBP (ns-LBP).
• It remains unclear if these changes are consistent across all LBP types, including neuropathic pain.

Purpose of the Study:

• To investigate and compare cortical excitability (CE) profiles in patients with three distinct LBP conditions: ns-LBP, failed back surgery syndrome (FBSS), and sciatica (Sc).
• To determine if observed CE differences are solely attributable to neuropathic pain characteristics.

Main Methods:

• A cohort of 60 LBP patients (20 per group: ns-LBP, FBSS, Sc) underwent clinical pain assessment.
• Conditioned pain modulation (CPM) and transcranial magnetic stimulation (TMS)-based CE measures (SICI, ICF, MEPs) were evaluated.
• Patient data were compared with normative data from healthy volunteers.

Main Results:

• Neuropathic pain groups (FBSS, Sc) reported higher pain intensity, interference, disability, and catastrophism than ns-LBP.
• CPM was reduced in FBSS and Sc patients compared to ns-LBP patients.
• Defective ICF was more prevalent in FBSS (80.0%) than ns-LBP (52.5%) or Sc (52.5%).
• Low MEPs were significantly higher in FBSS (50.0%) and Sc (15.0%) compared to ns-LBP (20.0%).
• In FBSS, higher MEPs correlated with mood and lower neuropathic pain symptoms.

Conclusions:

• Distinct clinical, CPM, and CE profiles are associated with different LBP etiologies.
• These neurophysiological differences are not exclusively linked to the presence of neuropathic pain.
• Further characterization of LBP patients using psychophysical and neurophysiological approaches is warranted.