To the Editor: Cauda equina injury (CEI), a severe neurological disorder, is frequently associated with intractable neuropathic pain (NP). Dorsal root entry zone (DREZ) lesioning, which disrupts pain signaling pathways and suppresses dorsal horn neuron hyperactivity, is an effective surgical treatment for post-CEI NP.1,2 Spinal cord stimulation (SCS), the most widely used invasive neuromodulation technique, is a surgical intervention for chronic pain that is refractory to medical management. Both SCS and DREZ lesioning are established treatments for intractable post-CEI NP, but their comparative effectiveness is unclear. A study was therefore conducted to compare the surgical outcomes between the two treatments. The indications were as follows: (1) aged 20–70 years, (2) NP secondary to CEI, (3) fixed pain distribution, (4) disease duration >1 year, (5) a numerical rating scale (NRS) score ≥5 with pain that significantly impairs activities of daily living, and (6) inadequate response after ≥6 months of standard therapy. The contraindications were as follows: (1) cognitive impairment, (2) severe cardiac, hepatic, pulmonary, or renal disease, (3) severe opioid dependence, (4) surgical field or systemic infection, and (5) other potential etiologies of NP. After the indications were confirmed and the contraindications were excluded, treatment selection was guided primarily by cauda equina function, with pain laterality considered as a secondary metric. Patients with completely intact cauda equina function were treated with SCS, whereas those with complete loss of function underwent DREZ lesioning. With respect to partial impairment, patients with bilateral pain favored SCS, those with unilateral pain favored DREZ lesioning, and those with bilateral pain after failed SCS warranted cautious consideration of DREZ lesioning. The spine segment corresponding to the conus medullaris was determined from lumbar magnetic resonance imaging before SCS. A paddle lead (Medtronic, Minneapolis, USA) was placed in the epidural space along the midline through an interlaminar approach at the conus level. Intraoperatively, the lead was adjusted, and stimulation parameters were programmed to ensure that paresthesia overlapped with the pain territory. Following lead implantation, the trial SCS phase continued for 7–14 days using an external stimulator to assess short-term efficacy. The stimulation parameters included a frequency of 40–60 Hz, a pulse width of 210 μs, and a voltage marginally exceeding the sensory threshold. If satisfactory pain relief was achieved, a permanent implantable pulse generator was placed. The DREZ lesioning range was guided by painful dermatomes. The spinal cord was caudally exposed to the conus medullaris. Severe prior trauma often results in root avulsion or atrophy of the dorsolateral sulcus. In some patients, arachnoid calcification was observed, possibly due to a previous subarachnoid hemorrhage spread within the spinal canal. The pia mater covering the dorsolateral sulcus was incised laterally from the residual rootlets. The dorsolateral sulcus was gently separated from the dorsal horn at a 35°–45° angle to the midline. The dorsal horn appeared darker, with fine vessels entering the region. The goal of DREZ lesioning was to ablate Rexed laminae I–IV in the dorsal horn of the spinal gray matter at a depth of approximately 3–4 mm. Continuous low-power lesioning was performed using sharp-pointed bipolar forceps for coagulation. Following lesioning, the dura mater was sutured, and the laminae were restabilized with titanium plates Supplementary Figure 1, https://links.lww.com/CM9/C840. Baseline and intraoperative data were recorded. The last follow-up was conducted by an interviewer independent of the operating surgeons. At follow-up, the NRS score, global impression of change (GIoC), and long-term complications were assessed. The last follow-up was completed in March 2025. Two-sided P 0.05) Table 1. Table 1 - Comparison between SCS and DREZ lesioning groups in patients with post-CEI NP. Variables SCS (n = 16) DREZ lesioning (n = 13) Statistics P values Baseline and intraoperative data Age (years) 51.8 ± 13.7 52.3 ± 7.6 –0.139* 0.897 Sex (female/male) 6/10 3/10 0.186† 0.666 Laterality (left/right/bilateral) 5/0/11 3/3/7 3.697† 0.176 Etiology (trauma/iatrogenic injury) 9/7 12/1 3.038† 0.044 Lower-limb motor function 17.472† 70% retention (>35 points) indicated preserved function, 30–70% (15–35 points) indicated partially preserved function, and <30% (<15 points) indicated loss of function. The pain-relief rate was calculated as (preoperative NRS–postoperative NRS)/(preoperative NRS) × 100%. The GIoC was measured on a 7-point scale (1 = very much improved, 2 = moderately improved, 3 = slightly improved, 4 = no change, 5 = slightly worsened, 6 = moderately worsened, and 7 = very much worsened). ASIA: American Spinal Injury Association; CEI: Cauda equina injury; CI: Confidence interval; DN4: Douleur neuropathique 4 questions; DREZ: Dorsal root entry zone; GIoC: Global impression of change; NRS: Numeric rating scale; NP: Neuropathic pain; SCS: Spinal cord stimulation. In this retrospective study involving 29 patients with post-CEI NP, DREZ lesioning achieved significantly better postoperative pain relief than SCS did, and both groups exhibited a decline in therapeutic efficacy during long-term follow-up. The mechanisms underlying SCS in pain modulation are complex. In addition to the classic gate control theory, these mechanisms involve modulation of the descending inhibitory system, including the noradrenergic and serotonergic pathways. Recent studies on higher-frequency stimulation and burst paradigms have revealed additional mechanisms, including the direct attenuation of hyperexcitability in wide dynamic range neurons within the dorsal horn and the direct stimulation of small-diameter fibers.3 Owing to its minimally invasive nature and effectiveness, SCS has become a staple of chronic pain management for patients with various conditions. Studies have shown that SCS is highly effective in patients with normal or partially preserved dorsal column-medial lemniscus function.4 The gradual decline in therapeutic efficacy over time has long been considered a major limitation of SCS, often described as tolerance or habituation. However, Mekhail et al5 reported that a physiological adherence to supra-evoked compound action potential (ECAP) threshold therapy that generates pain inhibition provided by ECAP-controlled closed-loop-SCS (CL-SCS) leads to durable improvements in pain intensity with no evidence of loss of therapeutic effect through 36-month follow-up. DREZ lesioning employs a direct mechanism by ablating hyperexcitable neurons in the dorsal horn of the spinal cord, thereby blocking the transmission of abnormal pain signals. Consistent with our findings, previous studies have demonstrated the efficacy of DREZ lesioning in managing post-CEI NP. However, many recent studies have included patients with concomitant spinal cord injury (SCI), and dedicated research focusing specifically on post-CEI NP remains limited. Sitthinamsuwan et al2 conducted a comparative analysis between CEI and SCI cohorts, and their results demonstrated that compared with the SCI group, the CEI group achieved significantly better long-term pain relief and superior surgical outcomes. DREZ lesioning at the conus medullaris can disrupt cauda equina afferents below L2, increasing the risk of postoperative bladder–bowel dysfunction. Accordingly, SCS is preferred for patients with normal or mildly reduced sensation and preserved lower-limb motor and bladder–bowel function, whereas DREZ lesioning is preferred for those with sensory loss and motor/bladder–bowel impairment. For patients with sensory loss but partially preserved motor or bladder–bowel function, management should be individualized. For unilateral, limited pain, unilateral DREZ lesioning should be considered. Bilateral DREZ lesioning is contraindicated due to the high risk of functional impairment. SCS should be attempted first and DREZ should be reserved for patients in whom the trial fails and who accept the potential trade-off of residual function for pain control. This study is prone to selection bias, as the choices between SCS and DREZ lesioning were influenced by residual function and economic factors. In conclusion, both SCS and DREZ lesioning show favorable efficacy for post-CEI NP management. DREZ lesioning achieves greater pain improvement postoperatively but is irreversible, warranting careful patient selection and risk–benefit assessment. Funding This study was supported by grants from the National Key Research and Development Program of China (No. 2022YFC3602203) and the Beijing Hospitals Authority’s Ascent Plan (No. DFL20240803).
Huang et al. (Mon,) studied this question.