Effects of neuromodulation on the management of chronic low back pain

Abstract

Chronic pain is one of the commonest health complaints that creates significant morbidity and impairs quality of life. Considered as the prototype of neuromodulation, spinal cord stimulation (SCS) exerts its analgesic effect by the delivery of electrical stimulation to specific areas of the spinal cord. The growing popularity of SCS for the treatment of chronic refractory pain can be attributed to its superior pain relief over conventional medical management. However, given the relative novelty of SCS in Hong Kong, it remains unknown whether local chronic pain patients can also reap the benefits of SCS for pain control. Furthermore, to date, there is still a lack of understanding of the therapy outcome predictive factors, knowledge of which is deemed essential as it informs patient selection and facilitates clinical decision-making. In the current study, we aim to evaluate (i) the analgesic efficacy of SCS among local chronic pain patients; (ii) the effectiveness of SCS in improving physical functioning, health-related quality of life and emotional functioning; (iii) the safety of SCS in terms of adverse event and explant rate; and (iv) the predictive factors of SCS trial success. Hence, a retrospective study was conducted involving all chronic pain patients that underwent SCS trial and/or permanent implants at a tertiary teaching hospital in Hong Kong from 2014 to 2022. In total, 51 chronic pain patients were included (mean age 55.6 years; 52.9% female). 29 (56.9%) patients underwent a successful trial (defined as greater than or equal to 50% reduction in pain intensity upon trial lead insertion) and proceeded to a permanent implant. Meanwhile, those with trial failure were excluded from permanent lead insertion. In terms of the long-term outcomes of SCS, our results showed a significant reduction in pain intensity and analgesic consumption, together with a significant improvement in health-related quality of life, over the 12-month follow-up period. Concerning the predictors of SCS trial success, higher preoperative NRS (Numeric Rating Scale) and lower pre-trial SF-36 MCS (Short Form-36 Quality of Life Measure Mental Component Summary) scores were associated with a successful SCS trial. Subsequent plotting of the Receiver Operating Characteristic (ROC) curve showed that NRS ≥7.5 and SF-36 MCS ≤36.72 were independent determinants of a successful trial stimulation. The current study demonstrated that SCS was effective in relieving pain, improving health-related quality of life, and reducing analgesic consumption. Together with the relatively low complication and explant rate, SCS was considered safe for use, rendering SCS a favourable alternative for patients with chronic intractable pain. In terms of the predictors of trial success, preoperative pain intensity and mental health were significant factors influencing trial outcome. This suggests that both NRS and SF-36 scores can be employed in the preoperative assessment to help identify optimal candidates for SCS therapy.