Anatomical and morphological variations in the dorsal root ganglion: Technical implications for chronic pain treatment with neuromodulation—A systematic review

Objectives: In the last 20 years, we have seen the flourishing of multiple treatments targeting the dorsal root ganglion (DRG) for pain. However, there is concern regarding the variation in the location of the DRG, which could influence the long-term clinical outcomes. The aim of this work was to determine the exact position of the DRG in the spine and propose a pre-surgical planning. Materials and Methods: A systematic search was conducted following the principles recommended by PRISMA. Search terms “ganglia,” “DRG,” “dorsal root ganglia, anatomy,” “radiological,” “neuromodulation,” “dorsal root ganglion stimulation” (PubMed, Scopus, Medline, Web of Science, and Embase) were identified 177 articles and subjected to the selection criteria (inclusion/exclusion) based on the independent review of the abstracts. Results: Eighteen articles were selected (seven anatomical dissections on cadavers, five radiological studies, and six narrative reviews). Discussion: Percutaneous procedure targeting the DRG for the treatment of chronic pain requires preoperative planning independent to the study of the etiology of pain. The DRG should be typified using magnetic resonance imaging. We propose a preoperative evaluation scale based on four specific items: A—position in the vertebral canal, B—position of the DRG within the foramen, C—number of ganglia in the root, and D—ratio (proportion) of foramen/DRG. Conclusion: Percutaneous treatments for chronic pain directed at the DRG are effective. Clinical outcomes depend of good preoperative planning that allows for optimizing its effects. We propose a DRG morphology evaluation scale useful for the planning process prior to any treatment directed at the ganglion.