High Frequency Spinal Cord Stimulation as Treatment for Neuropathic Pain Related to Restless Leg Syndrome

Introduction: Restless leg syndrome (RLS) is a sensorimotor dysesthesia characterized as uncomfortable leg sensations and uncontrollable urge to move, especially at rest or sleep. Medical therapy is ineffective or poorly tolerated in about one-third of patients. Limited case series have been reported, suggesting improvement in RLS symptoms and function with low- and high-frequency (HF) spinal cord stimulation (SCS).1 This first prospective case series reports pain, RLS symptom, and functional outcomes using 10 kHz-HF-SCS, which may offer an advantage over paresthesia-producing low-frequency SCS for sleep-related disorders.

Methods: We prospectively identified patients undergoing SCS implantation for chronic low back pain who also met the study inclusion criteria for RLS [International Restless Legs Syndrome Study (IRLS) Group Rating Scale score > 20]. Patient-reported outcomes were recorded at baseline and at one, three, six, and 12-month follow-up including Visual Analogue Scale (VAS), Oswestry Disability Index, EQ-5D-5L, IRLS, and the Clinical Global Impression of Improvement. Paired t-tests compared baseline and 12-month outcomes, and Pearson correlation was used to assess correlation between pain relief and RLS symptom reduction.

Results: Seven patients were identified and screened per inclusion criteria – one failed SCS trial and 1 patient withdrew. In the 5 patients that were successfully implanted, VAS leg pain decreased from 6.3cm at baseline to 4.1cm at 12 months, a mean reduction of 2.2cm (95% CI −0.2-4.6; p=0.06), an average 35% (range:0–71%) decrease. Importantly, RLS scores improved from 24.4 to 13.0 at 12 months, a mean reduction of 11.4 points (95% CI 4.4–18.3; p=0.01), averaging a 49% decrease (range 19–73%). The RLS symptom improvement was not correlated with pain relief (r =-0.72, 95% CI -0.98-0.45, p=NS). Lastly, ODI score improved in all patients with an average reduction of 18% (range:11-58%).

Conclusion: This small feasibility study suggests that 10kHz-HF-SCS may provide clinically significant improvement in RLS symptoms as demonstrated by an improvement of > 3X the minimum clinically important difference on IRLS.2 In addition, 80% patients also experienced reduction in pain with some improvement in function. Interestingly, the pain and IRLS improvements were not correlated, suggesting different underlying mechanisms. This pilot study aimed for 15 patients but enrolled only 5, likely due to challenges meeting dual diagnostic criteria for chronic back pain and RLS required for SCS insurance approval. A large randomized controlled trial is needed to confirm these findings, and further research may clarify the mechanisms by which SCS relieves medically refractory RLS symptoms.