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

Dorsal root ganglion (DRG) stimulation is an effectivetreatment for chronic, refractory complexregional pain syndrome (CRPS). Routinely, theplacement of a DRG stimulator lead is basedon established anatomical knowledge of dermatomes.In patients with lumbosacral transitionalvertebral anatomy, dermatome maps are notdependable due to dermatomal variance. Thiscan make correct placement of stimulator leadschallenging as the supposed target may not actuallybe responsible for sensing the painful area.We present a case of a 60-year-old woman withCRPS and lumbarization of the S1 vertebral body(presence of 6 lumbar vertebrae and 4 sacralvertebrae) who failed a DRG stimulator trial afterusing conventional dermatome maps to identifytarget DRGs assuming that the nerve exiting belowL6 corresponded to the S1 dermatome. Followingthe failed trial, sensory stimulation of the DRG viaradiofrequency stimulation was used to accuratelymap dermatomes leading to a successful DRGstimulation implant at a DRG level that differedfrom expected based on traditional dermatomemaps. Thus, DRG stimulation may guide decisionmakingin regard to target stimulation in patientswith 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