The Use of Rechargeable Spinal Cord Stimulators for the Treatment of Neuropathic Pain (STIMREC)

Observational, Prospective, Monocentric Study, Assessing the Use of Rechargeable Spinal Cord Stimulators for the Treatment of Neuropathic Pain. Quantitative and Qualitative Evaluation Protocol

Neuropathic pain occurs due to one or several lesions of the central or peripheral nervous system. Spinal cord stimulation is now recommended in France by the Haute Autorité de Santé (HAS) to relieve chronic refractory neuropathic pain (HAS 2014) in the trunk, upper and lower limbs. Spinal cord stimulation can be done either through a standard spinal cord stimulator or with a rechargeable spinal cord stimulator. In this study, the investigators aim at assessing the recharge procedure and their constraints for consecutive patients operated for spinal cord stimulation with a rechargeable stimulator for the treatment of chronic neuropathic pain at the site by the same surgeon between 2019 and 2020.

Neuropathic pain occurs due to one or several lesions of the central or peripheral nervous system. The estimated prevalence in the general population in France was 31.7% in the STOPNEP study (Study of Prevalence of Neuropathic Pain). In general, neuropathic pain becomes rapidly resistant to even specific medical treatment, and treatment by neurostimulation is increasingly common. Spinal cord stimulation is now recommended in France by the Haute Autorité de Santé (HAS) to relieve chronic refractory neuropathic pain in the trunk, upper and lower limbs. The technique involves percutaneous or surgical placement of one or several electrodes in the epidural space to stimulate the dorsal columns of the spinal cord. The electrode is linked to a pacemaker-type stimulator which is usually placed in the subcutaneous abdominal area. Stimulation of the dorsal columns of the spinal cord is supposed to interrupt the transmission of pain messages to the areas of the brain involved in pain regulation. The average estimated lifespan of batteries of standard stimulators is 3.7 years. This is highly dependent on the way the stimulator is used. A battery may last between 1 and 2 years in patients who use the stimulator continuously at high intensities and frequencies (above 5 volts and 60 Hz). In these cases, the stimulators must be frequently, and surgically replaced. Besides the inconvenience of repeated surgeries, the risk of infection increases with each procedure. This risk has been confirmed in patients with deep brain stimulation while the results are similar, but less clear, with spinal cord stimulation. To prevent these problems, rechargeable stimulators have been developed and provide real medical progress for the reasons mentioned above. Rechargeable stimulators have been used in routine clinical practice since 2010. Certain rechargeable stimulators have a lifespan of 9 years, while others have a theoretically unlimited lifespan. Thus, after more than 10 years of use of rechargeable spinal cord stimulators, the choice between a standard and rechargeable stimulator must be evaluated. The cost benefit is clear with rechargeable stimulators. However, the choice of device must also consider facility of use during daily life. The use of the rechargeable device is more complicated, mainly due to the fact that the stimulator must be recharged on a regular basis. To recharge the batteries, the patient places an antenna on the skin where the stimulator is located. The recharge (the patient is advised to fully recharge the battery when it is at 50% capacity) can take 2 hours. When a "normal" intensity of stimulation is used (< 5 volts), the patient must charge the battery once a week, which is compatible with basically normal day to day activities. Management becomes more complicated, and even impossible in the intermediate and long term if a recharge takes longer and must be repeated more frequently, which occurs in about 25% of patients. In addition, with the most common rechargeable stimulators, the stimulator must remain constantly charged, because if it is completely empty it usually becomes impossible to recharge, requiring an intervention to replace the stimulator. This study, observational, will consider patients for whom a rechargeable implantable spinal cord stimulator was placed as part of standard of care, at least one year ago. The main goal is to determine the proportion of patients who are dissatisfied with the recharge procedure after at least one year of use, and to evaluate their experience to determine the causes of their dissatisfaction.

This F-SUS questionnaire uses a Likert scale including 5 possible responses ranging from " I do not agree at all" to " I completely agree " (Celenza A 2011, Croasmun JT 2011). The F-SUS is a short questionnaire with 10 questions (Brooke J 2013). In its original version half of the questions express strong agreement and the other half disagreement. Thus, all the even-numbered items (2, 4, 6, 8, 10) allow the participant to express a very negative opinion (disagreement). On the other hand, the odd-numbered items allow the participant to express a very positive opinion (strong agreement).

Patients that are dissatisfied with the recharge procedure (Score F-SUS < 70/100) will be invited to a so-called complementary information interview (an interview after the questionnaire has been completed). The corpus (the study group that will be interviewed) will naturally be diverse men/women, patients who were improved or not by stimulation, implanted with a rechargeable stimulator directly/replacing a stimulator, different brands of stimulator… The patient must agree to the interview and the way it will be performed (signature of consent form). The interview may be face-to -face at the site or by remote videoconference depending on the wishes and availability of the patient. There is no payment for these interviews but travelling or videoconference expenses are reimbursed All interviews will be audio- taped for further qualitative analysis.

F-SUS Questionnaire. This questionnaire uses a Likert scale including 5 possible responses ranging from " I do not agree at all" to " I completely agree ". The F-SUS is a short questionnaire with 10 questions. The total maximum score is 100. The total score will be used for the different analyses because the F-SUS is considered to be a unidimensional score. Satisfaction will be considered to be good with a score of 70 and excellent with 90. Satisfaction is correct between 50 and 70 (indicating that the system needs to be improved). At a score below 50 the system is unusable.

Comparison of numerical pain scale before spinal cord stimulator surgery and at least one year after the surgery.

The analgesic result of the spinal cord stimulation will be evaluated with a numerical pain scale ranging from 0 ("No pain") to 10 ("Maximum imaginable pain"). The value that will be compared to the preoperative numerical pain scale will be the mean of 3 measurements obtained on the day (morning, noon, night) before the questionnaire is filled out.

The brand of rechargeable stimulator will be collected for the study. The satisfaction level will be established with the F-SUS questionnaire. This questionnaire uses a Likert scale including 5 possible responses ranging from " I do not agree at all" to " I completely agree ". The F-SUS is a short questionnaire with 10 questions. The total maximum score is 100. The total score will be used for the different analyses because the F-SUS is considered to be a unidimensional score. Satisfaction will be considered to be good with a score of 70 and excellent with 90. Satisfaction is correct between 50 and 70 (indicating that the system needs to be improved). At a score below 50 the system is unusable.

Inclusion Criteria: Men or women implanted with a rechargeable spinal cord stimulator in 2019 and 2020, Implantation carried out more than one year before the date of inclusion in the study, Primary implantation of a rechargeable spinal cord stimulator or replacement of a non-rechargeable spinal cord stimulator with a rechargeable spinal cord stimulator, Dorsal or cervical spinal cord stimulation, Patient operated by the same surgeon, Patient informed of the study and consented to take part. Exclusion Criteria: Pregnant or breastfeeding woman Patient whose cognitive abilities, as assessed by the investigator, do not allow them to complete the F-SUS questionnaire or the numerical pain scale. Patient covered by legal protection measures

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