A Case of Spinal Cord Injury Caused By Electrical Stimulation of Thoracic Spinal Cord for Treatment of Diabetic Foot

Dear Editor

The thoracic Spinal Cord Stimulator (SCS) has been widely accepted as a treatment option for diabetic foot and is gaining acceptance. This case highlights a previously unreported potential complication of the SCS. A 66-year-old man had long-standing diabetes (30 years) and hypertension (10 years), accompanied by diabetic foot and generalized psoriasis. The patient reported pain in the bilateral lower extremities, especially in both feet, which was significant at night and when walking. His Visual Analog Scale (VAS) pain score was 10/10. The pain was accompanied by slight numbness without sensory disturbance. These symptoms gradually exacerbated over 2 months. His Quality of Life Scale (QOLS) score was 186, and the skin temperature of both his feet decreased at rest. Following conservative treatment elsewhere, the abovementioned symptoms remained refractory; the patient presented to our hospital for further treatment. SCS was implanted on June 6, 2021 for pain relief.

After admission, we completed preoperative examinations and scheduled surgery under C-arm guidance. Because of severe psoriasis on the skin surface of T11 and T12, the possibility of impaired incision healing was considered. The skin over T9 and T10 was incised after careful consideration (Figure 1). Conventional upward insertion of the electrode into the epidural space of T11 and T12 vertebral bodies was abandoned in favor of downward insertion of the electrode into the epidural space of T9 and T10 vertebral bodies (Figure 1); the same treatment outcome was eventually achieved. An electrode (model: 565 DEFINE 2 * 8; Medtronic, USA) was implanted, and the resistance was normal intraoperatively. A conventional initial voltage of 0.5 V, pulse width of 210μs, and frequency of 40 Hz were adopted for testing. The patient stated that the sensation of electricity passing through the lower limbs was significant and involved full coverage of both feet. We connected the SCS to a temporary, external stimulator. Once safely returned to ward, we conducted postoperative adjustment and set the stimulat or with the following parameters: voltage, 0.1 V; pulse width, 210μs, and frequency, 40 Hz. When the voltage was modulated to 0.5 V, the patient’s sensation of current stimulation in the lower limbs was un ideal; thus, we gradually increased the voltage to 1.5 V. At this point, the lower limbs could not be autonomously controlled, the feet were unresponsive to external stimulation, and with T12 as the transverse section, all spinal cord reflexes below disappeared, specifically manifesting as flaccid paralysis, reduced muscle tension, disappearance of knee and tendon reflexes, and failure to elicit pathological reflexes. Fecal and urinary incontinence was absent, consistent with “acutephase spinal cord shock.” The thoracic vertebra was examined by plain radiography after considering ongoing methylprednisolone for Spinal Cord Injury (SCI). After eliminating fractures or acute lesions, we switched off the external temporary stimulator, and the motor and sensory abnormalities of the lower limbs disappeared. On postoperative day 1, we attempted re-initiate the stimulator. When the voltage was adjusted to 1.15 V, the patient’s sensation of current in the lower limbs was satisfactory, and no abnormalities were found. The temperature of the patient’s feet was significantly higher postoperatively than in the preoperative period (Figure 1); the pain in the lower limbs resolved. The VAS pain score was 0/10, postoperatively. The patient’s condition remained stable throughout his hospital stay. Before discharge, his pain had significantly improved, with normal motor and sensory functions on both lower limbs. He returned to the hospital 2 weeks after discharge and was treated with an implantable pulse generator. During the 3-month follow-up period, the patient recovered well, and the QOLS score was 253.

    

    

    Figure 1: (A) Because of psoriasis on the skin surface at the T11 and T12 levels, the T9 and T10 levels were selected for incisions.
(B) The electrode is fixed in the epidural space of the T11 level. (C) Preoperative infrared thermography showing the
skin temperature of each part of both the lower limbs. (D) Postoperative infrared thermography showing the skin temperature
of each part of both the lower limbs.