Examining Carryover Effect in Patients Treated witH Spinal cOrd Stimulation (ECHO)

Spinal cord stimulation is a minimally invasive surgical treatment for severe, chronic, neuropathic pain that is refractory to conventional treatment. The treatment consists of an electrode implanted in the epidural space of the spinal cord, either via a percutaneous approach (using the so-called percutaneous leads) or via a surgical (hemi-) laminectomy (using the so-called surgical leads or plate leads). It is a well-known clinical observation that when activating or deactivating SCS stimulation, there is a variable interval before the patient perceives a clinical effect of the change. This variation goes by different names (carryover, echo, after effect, etc.) and might be dependent on the clinical condition and treatment duration. To our knowledge only very little research has been published on the topic of carryover effects; a recent study showed that the interval is highly variable between patients. While patients may experience immediate pain relief at the onset of SCS treatment, the effect in patients with a long-term SCS treatment history may have different characteristics, possibly due to ongoing changes in the nervous system. The aim of this pilot study is to lay the foundation for investigating the carryover effects in spinal cord stimulation. This will be carried out in a mixed population of patients with different indications for SCS, and with different treatment durations. Patients will be asked to deactivate their device via their remote control or with a magnet in a standardized fashion. They will be asked to reactivate the device when specific parameters have been met, and the time is recorded.

In the post-hoc analysis the carryover and reverse carryover effect will be analyzed and correlated to a number of parameters including, but not limited to: Indication, treatment duration, symptom duration, preoperative pain score, stimulation paradigm, gender, age. Data will be collected and stored using a dedicated REDCap database under the auspices of Aarhus University.