A 57-year-old man with cerebral palsy had been suffering for 9 years from severe neuropathic pain around the right lower abdomen and right pubic area after colostomy for ileus. Medications including maximum dose of nonsteroidal anti-inflammatory drugs, tricyclic antidepressant, selective serotonin reuptake inhibitor, calcium channel α2-δ ligands, and opioids failed to provide sufficient pain relief. The pain intensity was consistently 9 or 10 on the visual analog scale (VAS), regardless of the type of medication. We finally performed traditional SCS and placed two 8-electrode leads (1 × 8 Standard test lead model 3873; Medtronic Inc, Minneapolis, MN) at the level of the T12 vertebra (Figure 1). After this intervention, electrical stimulation relieved the lower right abdominal, but not the right pubic pain. Subsequently, the pain intensity decreased from 10 to 6 on the VAS for 1 year. However, pain gradually returned to maximum intensity despite reprogramming of stimulation parameters. Additionally, transcutaneous electrical peripheral nerve stimulation and direct injection of lidocaine into the pubic symphysis failed to provide any analgesic benefit. Because direct nerve root block via transforaminal L1-2 injection of lidocaine resulted in pain relief, we decided to perform L1 nerve root stimulation. We planned to introduce the electrical lead toward the right L1 nerve root through the epidural space, because DRG stimulation is not approved in Japan. An 8-electrode lead (1 × 8 Compact test lead model 3874; Medtronic Inc, Minneapolis, MN) was inserted between L2/3 and 3/4 via a parasagittal approach under local anesthesia. However, because the electrical lead could not be advanced to the targeted location, possibly because of epidural space adhesions, a fresh lead was placed at the middle of the L1 vertebra (Figure 2). Subsequent electrical stimulation only caused unpleasant paresthesia and lower limb muscle twitching. We, therefore, decided to remove the epidural leads placed during the second intervention under local anesthesia and directly stimulate the extraforaminal L1 nerve root site. We advanced a 14-gauge Tuohy needle (Medtronic Inc, Minneapolis, MN) from the right side of the back at the level of L1 toward the right L1 root via transforaminal approach after test insertion of a 22-gauge needle under fluoroscopic guidance. The tip of the electrical lead used during the second intervention was placed just lateral to the right L1 nerve root (Figure 3). The leads were anchored to the fascia using the accessory anchor tool provided by Medtronic. Intraoperative and postintervention electrical stimulation via the first and second electrodes elicited paresthesia and pain relief in the pubic area. Whereas stimulating at 7 V caused weak twitching of the external abdominal oblique muscle, this effect disappeared when the voltage was decreased to below 5 V. Our final stimulation parameters were 3.1 V, 5 Hz, and 700 μs pulse duration, using the first electrode as cathode and the second as anode. Although the stimulation effects fluctuated with the position of the patient, continuous stimulation reduced the pubic pain from 10 to 5 on the VAS score. Because the patient was satisfied with the therapeutic effect, we implanted an additional pulse generator (RestoreSensor SureScan MRI; Medtronic Inc, Minneapolis, MN) in the left abdomen 5 days later. During the follow-up period of 6 months, the VAS score fluctuated around 5, which was less than that before surgery. We radiologically confirmed absence of lead migration during the follow-up period (Figure 4). Although the patient considered the therapeutic effect acceptable at that time, the chronic medications were continued unchanged because of the patient’s anxiety for the recurrence of the pain.
Traditional SCS remains the gold standard for the treatment of neuropathic pain that is resistant to oral medication, spinal surgery, and other analgesic techniques. However, the recently developed DRG stimulation technique that selectively stimulates the nerve root corresponding to the dermatomal distribution of the pain has been shown to be even more efficacious than SCS and is an attractive option when traditional SCS fails.2 However, adhesions in the epidural space or scarring around a previously implanted electrical lead can make insertion of an electrical lead into the epidural space difficult.3 While a reported alternative electrode placement technique involved the epidural space,4 our technique allows placement of an electrode next to the nerve root via an extraforaminal approach. Falco et al5 reported a single case of successful treatment of chronic cervical radicular pain with extraforaminal nerve root stimulation. Their technique of targeting the nerve root located peripherally from the intervertebral foramen was the same as ours. This approach can also be effective when canal stenosis makes placement of the electrode difficult. Furthermore, the stimulation effect can be predicted before the intervention by nerve root block that is less invasive than a SCS trial.6 Lead migration is a major problem of this technique. It can be reduced by using an anchoring tool.7 We anchored the leads to the fascia, and radiological control during the follow-up confirmed lack of lead migration. The limited mobility of our patient possibly reduced the potential of lead migration. Other risks include nerve and vascular injuries. Muscle twitching caused by motor fiber stimulation can be reduced by decreasing the stimulation energy. The mechanism of this treatment is unknown, but we presume that it is similar to that of DRG stimulation.
In conclusion, this is the first report of extraforaminal electrical lead implantation for the management of neuropathic pain. Our experience suggests that this may be a valid alternative when insertion of an electrode lead through the epidural space proves difficult. The approach is off-label and not approved by Medtronic for this particular device. We, nevertheless, feel that it was acceptable in our case because standard techniques had failed and we reused the initially placed leads. As we have assessed the treatment effect for only a relatively short time period in a single patient, clinical trials will be necessary to document the long-term efficacy of extraforaminal nerve root stimulation in the management of neuropathic pain.
The authors acknowledge Dr Hiroshi Fujioka for his contribution to the primary diagnosis and treatment of this patient.
Name: Shunsuke Ishizaka, MD, PhD.
Contribution: This author helped treat the patient and write the manuscript.
Name: Mami Tsuda, ME.
Contribution: This author helped adjust the parameter of the stimulation after surgery.
Name: Eiichirou Urasaki, MD, PhD.
Contribution: This author helped decide the strategy of the treatment and prepare the manuscript.
This manuscript was handled by: Hans-Joachim Priebe, MD, FRCA, FCAI.
1. Geurts JW, Smits H, Kemler MA, Brunner F, Kessels AG, van Kleef MSpinal cord stimulation for complex regional pain syndrome type I: a prospective cohort study with long-term follow-up. Neuromodulation. 2013;16:523529.
2. Deer TR, Levy RM, Kramer JDorsal root ganglion stimulation yielded higher treatment success rate for complex regional pain syndrome and causalgia at 3 and 12 months: a randomized comparative trial. Pain. 2017;158:669681.
3. Dam-Hieu P, Magro E, Seizeur R, Simon A, Quinio BCervical cord compression due to delayed scarring around epidural electrodes used in spinal cord stimulation. J Neurosurg Spine. 2010;12:409412.
4. van Helmond N, Kardaszewski CN, Chapman KBCervical retrograde spinal cord stimulation lead placement to treat failed back surgery syndrome: a case report. A A Case Rep. 2017;8:334336.
5. Falco FJ, Kim D, Onyewu COCervical nerve root stimulation: demonstration of an extra-foraminal technique. Pain Physician. 2004;7:99102.
6. Kim DH, Lim CH, Heo JY, Jang YJ, Choi YSFeasibility of nerve stimulator as a supplemental aid for lumbar transforaminal epidural block. Clin Orthop Surg. 2014;6:324328.
Copyright © 2018 International Anesthesia Research Society
7. Weiner RL, Yeung A, Montes Garcia C, Tyler Perryman L, Speck BTreatment of FBSS low back pain with a novel percutaneous DRG wireless stimulator: pilot and feasibility study. Pain Med. 2016;17:19111916.