Radiofrequency Mapping Prior to Dorsal Root Ganglion Stimulation in a Patient with CRPS and Transitional Vertebral Anatomy: A Case Report

Abstract

Dorsal root ganglion (DRG) stimulation is an effective treatment for chronic, refractory complex regional pain syndrome (CRPS). Routinely, the placement of a DRG stimulator lead is based on established anatomical knowledge of dermatomes. In patients with lumbosacral transitional vertebral anatomy, dermatome maps are not dependable due to dermatomal variance. This can make correct placement of stimulator leads challenging as the supposed target may not actually be responsible for sensing the painful area. We present a case of a 60-year-old woman with CRPS and lumbarization of the S1 vertebral body (presence of 6 lumbar vertebrae and 4 sacral vertebrae) who failed a DRG stimulator trial after using conventional dermatome maps to identify target DRGs assuming that the nerve exiting below L6 corresponded to the S1 dermatome. Following the failed trial, sensory stimulation of the DRG via radiofrequency stimulation was used to accurately map dermatomes leading to a successful DRG stimulation implant at a DRG level that differed from expected based on traditional dermatome maps. Thus, DRG stimulation may guide decisionmaking in regard to target stimulation in patients with abnormal vertebral anatomy. Key words: Dorsal root ganglion stimulation, dermatome mapping, radiofrequency stimulation, spinal anomaly, lumbosacral transitional vertebrae, complex regional pain syndrome, neuromodulation, dermatomal variance