Fast-Acting Sub-perception Spinal Cord Stimulation for a Case of Painful Diabetic Polyneuropathy. Just an Antalgic Treatment or Even a Therapy?

Introduction: Painful diabetic polyneuropathy (P-DPN) occurs in 20% - 30% of diabetic patients. Currently, therapeutic strategies include lifestyle modifications, good glycemic control, and neuropathic pain drugs. Spinal cord stimulation (SCS) has been shown to be successful in patients who have not responded to other treatments. The American Diabetes Association strongly recommends early screening and diagnosis for this condition through clinical tests and nerve conduction study (NCS). In recent years, high-resolution ultrasonography (HRUS) with the analysis of cross-sectional area (CSA) has shown an increasingly important role in detecting changes in the nervous structures, blood vessels, echo, and mobility of the nerve. Cross-sectional area is frequently enlarged in these patients, even those with normal NCS. We aimed to use SCS with fast-acting sub-perception therapy (FAST) modality to treat P-DPN. We also evaluated the CSA of the involved nerves before and after treatment. Case Presentation: A 58-year-old female patient was referred to our hospital in 2020 (Civitavecchia, Italy). She suffered from P-DPN for 3 years and did not respond to conventional medical treatments. Preoperative electromyography (EMG) was negative for radiculopathy, while electroneurography (ENG) showed a reduction in sensory conduction velocity (SCV) in the sural nerve (SN) bilaterally. Clinical tests on perceived pain and quality of life showed high severity. The report was confirmed by HRUS with enlargement of the CSA of the posterior tibial nerve (PTN), external popliteal nerve (EPN), and SN. The patient was successfully subjected to all-in-one SCS implantation in the FAST modality. She obtained immediate pain relief that remained unaltered at the 3-month follow-up. The patient completely discontinued drug therapy. One month after implantation, ENG highlighted an increased SN SCV, and the HRUS of PTN EPN and SN showed a significant reduction in CSA in all 3 nerves involved. Conclusions: Early diagnosis and treatment are crucial in improving the clinical outcome of P-DPN, but there is still no gold standard therapy. Spinal cord stimulation in the new FAST modality was effective in this clinical case. The pain relief was supported by a significant reduction in the CSA of the studied nerves observed on HRUS 1 month after SCS implantation. The results and the improvement of a pathological nervous pattern, albeit with a short follow-up of only 3 months, could suggest not only a symptomatic but perhaps also a therapeutic role of SCS in P-DPN.