The Dorsal Root Ganglion as a Novel Neuromodulatory Target to Evoke Strong and Reproducible Motor Responses in Chronic Motor Complete Spinal Cord Injury: A Case Series of Five Patients

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Abstract

Objectives: Current strategies for motor recovery after spinal cord injury (SCI) aim to facilitate motor performance through modulation of afferent input to the spinal cord using epidural electrical stimulation (EES). The dorsal root ganglion (DRG) itself, the first relay station of these afferent inputs, has not yet been targeted for this purpose. The current study aimed to determine whether DRG stimulation can facilitate clinically relevant motor response in motor complete SCI. Materials and Methods: Five patients with chronic motor complete SCI were implanted with DRG leads placed bilaterally on level L4 during five days. Based on personalized stimulation protocols, we aimed to evoke dynamic (phase 1) and isotonic (phase 2) motor responses in the bilateral quadriceps muscles. On days 1 and 5, EMG-measurements (root mean square [RMS] values) and clinical muscle force measurements (MRC scoring) were used to measure motor responses and their reproducibility. Results: In all patients, DRG-stimulation evoked significant phase 1 and phase 2 motor responses with an MRC ≥4 for all upper leg muscles (rectus femoris, vastus lateralis, vastus medialis, and biceps femoris) (p < 0.05 and p < 0.01, respectively), leading to a knee extension movement strong enough to facilitate assisted weight bearing. No significant differences in RMS values were observed between days 1 and 5 of the study, indicating that motor responses were reproducible. Conclusion: The current paper provides first evidence that bilateral L4 DRG stimulation can evoke reproducible motor responses in the upper leg, sufficient for assisted weight bearing in patients with chronic motor complete SCI. As such, a new target for SCI treatment has surfaced, using existing stimulation devices, making the technique directly clinically accessible.

Original languageEnglish
Pages (from-to)779-793
Number of pages15
JournalNeuromodulation
Volume24
Issue number4
DOIs
Publication statusPublished - Jun 2021

Bibliographical note

Acknowledgements:
The authors would like to express great gratitude to Marjan Scheltens-de Boer, Venny Pires, and Karla Biesheuvel at the Department of Clinical Neurophysiology of the Erasmus MC, for their role in the EMG-data acquisition. The authors would also like to express gratitude to Arjan Melger at the Center for Pain Medicine for his important contribution in the development of the DRG-stimulation protocol. Lastly, the authors would like to thank Wichor Bramer, biomedical information specialist at Erasmus MC, for creating the search string as used for the literature review.

Funding Information:
Source(s) of financial support: This study was funded by “Stichting Erasmus Fonds Pijnbestrijding.” Chris I. De Zeeuw was supported by the Dutch Organization for Medical Sciences (ZonMw) Life Sciences (Grant no. 854.10.004), the Neurotime, ERC‐advanced and ERC‐PoC programs of the European Community (Grant nos. 294,775, 768,914).

Publisher Copyright: © 2020 The Authors. Neuromodulation: Technology at the Neural Interface published by Wiley Periodicals LLC. on behalf of International Neuromodulation Society.

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