Single S1 Dorsal Root Ganglia Stimulation for Intractable Complex Regional Pain Syndrome Foot Pain After Lumbar Spine Surgery: A Case Series.

Introduction: Intractable complex regional pain syndrome (CRPS)-related chronic foot pain, is a common therapeutic challenge for interventional pain management physicians and patients alike. Dorsal root ganglia (DRG) stimulation is a very target specific dorsal column stimulation technique with very promising clinical outcomes. Patients with CRPS foot pain and previous back surgery can benefit from DRG stimulation but also run a significant risk of epidural trauma from the DRG sheath advancement. Most sensory innervation to the foot is from L5 and S1 dermatomes. Although there is dual modulation from L5 and S1 DRG, significant "cross talk" exists between these structures such that a DRG lead solely at S1 could provide pain relief for the entire foot. In this case series, we examined the outcomes obtained from placement of solely S1 DRG stimulating electrodes in patients with CRPS-related chronic foot pain, and examine whether this may provide a reduced risk of dural injury. Furthermore, we describe the technical aspects of a S1 DRG placement and discuss relevant anatomical issues pertaining to this approach.

Materials And Methods: Five patients (four female, one male) with chronic foot pain participated. The oldest was 71 and the youngest 49. Three patients were diagnosed with foot CRPS-1, and two patients with foot CRPS-2. All patients had back surgery in the past and all underwent a trial and subsequent S1 DRG implantation. The patients were evaluated with a numeric rating score (NRS) for pain and function before the procedure and one, two, three, and six months after the procedure. The first patient underwent an L5 and S1 trial and developed CSF leak and postdural puncture headache. Two months later, the patient was re-trialed and implanted with a single S1 electrode. The other four patients were trialed and implanted with single S1 DRG electrodes.

Results: All five patients had severe pain (8-10 NRS) and significant loss of function and quality of life (2-4 NRS) before the procedure. All five patients had excellent (0-3 NRS) pain relief and functional restoration (8-10 NRS) with a single S1 electrode trial, and all five proceeded with permanent implantation. The pain relief from the S1 DRG stimulation extended to the entire foot without any sparing. All patients were able to discontinue or significantly reduce their oral pain medications. The one-, two-, three-, and six-month follow-up showed preservation of therapeutic efficacy.

Conclusions: A single S1 DRG electrode placement in patients diagnosed with CRPS of the foot and who had previous back surgery is therapeutically effective and can minimize the risk of dural trauma and CSF leak.