• Kaare Meier, Cecile C de Vos, Martine Bordeleau, Sharon van der Tuin, Bart Billet, Thomas Ruland, Morten Rune Blichfeldt-Eckhardt, Matthias Winkelmüller, Helga Angela Gulisano, Kliment Gatzinsky, Anne Lene Knudsen, Hedemann SørensenJens ChristianJCDepartment of Neurosurgery, Aarhus University Hospital, Aarhus, Denmark; Center for Experimental Neuroscience (CENSE), Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark., Ioanna Milidou, and CottinSylvine CarrondoSCDepartment of Neuroscience, CHU de Québec-Université Laval, Quebec City, Canada..
• Department of Neurosurgery, Aarhus University Hospital, Aarhus, Denmark; Department of Anesthesiology, Aarhus University Hospital, Aarhus, Denmark; Center for Experimental Neuroscience (CENSE), Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark. Electronic address: kaamei@rm.dk.
• Neuromodulation. 2024 Jul 1; 27 (5): 887898887-898.

ObjectivesSpinal cord stimulation (SCS) is a surgical treatment for severe, chronic, neuropathic pain. It is based on one to two lead(s) implanted in the epidural space, stimulating the dorsal column. It has long been assumed that when deactivating SCS, there is a variable interval before the patient perceives the return of the pain, a phenomenon often termed echo or carryover effect. Although the carryover effect has been problematized as a source of error in crossover studies, no experimental investigation of the effect has been published. This open, prospective, international multicenter study aimed to systematically document, quantify, and investigate the carryover effect in SCS.Materials And MethodsEligible patients with a beneficial effect from their SCS treatment were instructed to deactivate their SCS device in a home setting and to reactivate it when their pain returned. The primary outcome was duration of carryover time defined as the time interval from deactivation to reactivation. Central clinical parameters (age, sex, indication for SCS, SCS treatment details, pain score) were registered and correlated with carryover time using nonparametric tests (Mann-Whitney/Kruskal-Wallis) for categorical data and linear regression for continuous data.ResultsIn total, 158 patients were included in the analyses. A median carryover time of five hours was found (interquartile range 2.5;21 hours). Back pain as primary indication for SCS, high-frequency stimulation, and higher pain score at the time of deactivation were correlated with longer carryover time.ConclusionsThis study confirms the existence of the carryover effect and indicates a remarkably high degree of interindividual variation. The results suggest that the magnitude of carryover may be correlated to the nature of the pain condition and possibly stimulation paradigms.Clinical Trial RegistrationThe Clinicaltrials.gov registration number for the study is NCT03386058.Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.

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