There is a lack of clinically relevant measures for quantification of maladaptive mechanisms of the nociceptive system leading to chronic pain. Recently, we developed a method that tracks nociceptive detection thresholds (NDTs) using intraepidermal electrical stimulation. In this study, we explored the feasibility of using this NDT method in patients with persistent spinal pain syndrome type 2 (PSPS-T2) and its potential to enable observation of altered nociceptive processing induced by dorsal root ganglion (DRG) stimulation. In addition, we compared NDTs with quantitative sensory testing (QST) measurements and numeric rating scale (NRS).
Materials and Methods
A total of 12 patients with PSPS-T2 (seven men; 60.4 ± 12.3 years) experiencing chronic unilateral lower limb pain treated with DRG stimulation were included in the study. Both the NDT method and electrical and pressure QST methods were performed twice in the L5 dermatome on both the affected and the unaffected foot, once with the DRG stimulator turned off and, subsequently, once with the DRG stimulator turned on.
The NDT method can be applied to patients with PSPS-T2. With the DRG stimulator turned off, NDTs on the affected side were significantly higher than on the unaffected side. This difference was no longer present once the DRG stimulator was turned on. Furthermore, DRG stimulation affected QST (electrical and pressure) values and NRS scores. Finally, NDTs showed larger contrasts between the sides than QST measures.
The NDT method permitted observation of altered nociceptive function. The effect of DRG stimulation also was reflected in QST outcomes and NRS scores. The larger contrast between the sides for NDTs suggests that the NDT method might be valuable for future quantification of nociceptive dysfunction in chronic pain.