Restoration of sensory feedback after lower limb amputation using stimulation of the dorsal root ganglia and spinal cord: a case report

Lower limb amputations are approximately three times more common than upper limb amputations, yet sensory feedback restoration methods, including sensory mapping, have historically been developed mainly for the upper limb. In patients with lower limb amputation, the lack of information about the interaction between the prosthesis and the ground increases cognitive load and the risk of falls. Dorsal root ganglion stimulation (DRG-S) and spinal cord stimulation (SCS) are considered as means of delivering an artificial sensory signal; however, comparative data on the perceptual patterns and motor side effects they evoke, and on their use in closed-loop biofeedback in such patients, are lacking.We report a male patient with a right lower leg amputation at the level of the distal third following a mine-blast injury sustained 4 years before the observation, and phantom limb pain (background pain of 3–6 points on the visual analogue scale with paroxysms of 8–10 points occurring 15–20 times a day). DRG (L5–S1) and SCS (L4–L5) test electrodes were implanted electively. During sensory mapping with concurrent surface electromyography, S1 DRG stimulation evoked focal sensations in the phantom phalanges without motor responses across the entire amplitude range (up to 8 mA), whereas SCS projected to the heel area and was accompanied by pronounced muscle contractions and contralateral radiation. In closed-loop testing with a sensory insole, stimulus recognition accuracy with the DRG electrode and the prosthesis worn was 87% with both electrical and sham stimulation. With the SCS electrode and the prosthesis removed, accuracy increased from 80% to 97% (sensitivity 100%) after a 30-minute sensorimotor adaptation period. The protocol was completed in full, and no serious adverse events were recorded.This case shows that sensory mapping and biofeedback techniques can be adapted for patients with lower limb amputation. DRG-S provides focal sensations without motor artifacts, SCS requires a sensorimotor adaptation period, and the evaluation of feedback systems requires control of mechanical pressure transmission through the prosthetic socket. These conclusions are based on a single case with different electrode testing conditions and need to be verified in a larger sample.