BackgroundSpinal cord stimulation (SCS) is a standard treatment option for chronic neuropathic pain. However, some anatomical pain distributions are known to be difficult to cover with traditional SCS-induced paresthesias and/or may also induce additional, unwanted stimulation. We present the results from a retrospective review of data from patients with groin pain of various etiologies treated using neuromodulation of the dorsal root ganglion (DRG).MethodsData from 29 patients with neuropathic groin pain were reviewed. Patients underwent trial therapy where specifically designed leads were implanted at the target DRGs between T12 and L4. Patients who had a successful trial (>50% improvement) received the fully implantable neuromodulation system. Pain scores were captured on a visual analog scale (VAS) at baseline and at regular follow-up visits.ResultsTwenty-five patients (86.2%) received fully implantable neurostimulators, and the average follow-up period was 27.84.3 (standard error of the mean, SEM) weeks. The average pain reduction was 71.4 +/- 5.6%, and 82.6% (19/23) of patients experienced a>50% reduction in their pain at the latest follow-up. Individual cases showed improvement with a variety of etiologies and pain distributions; a subanalysis of postherniorrhaphy cohort also showed significant improvement.ConclusionsEarly findings suggest that neuromodulation of the DRG may be an effective treatment for chronic neuropathic pain conditions in the groin region. This technique offers a useful alternative for pain conditions that do not always respond optimally to traditional SCS therapy. Neuromodulation of the DRG provided excellent cross-dermatomal paresthesia coverage, even in cases with patients with discrete pain areas. The therapy can be specific, sustained, and independent of body position.

ObjectivesPhantom limb pain (PLP) is a neuropathic condition in which pain is perceived as arising from an amputated limb. PLP is distinct from, although associated with, pain in the residual limb and nonpainful phantom sensations of the missing limb. Its treatment is extremely challenging; pharmaceutical options, while commonly employed, may be insufficient or intolerable. Neuromodulatory interventions such as spinal cord stimulation have generated mixed results and may be limited by poor somatotopic specificity. It was theorized that dorsal root ganglion (DRG) neuromodulation may be more effective.Materials and MethodsPatients trialed a DRG neurostimulation system for their PLP and were subsequently implanted if results were positive. Retrospective chart review was completed, including pain ratings on a 100-mm visual analogue scale (VAS) and patient-reported outcomes.ResultsAcross eight patients, the average baseline pain rating was 85.5mm. At follow-up (mean of 14.4 months), pain was rated at 43.5mm. Subjective ratings of quality of life and functional capacity improved. Some patients reduced or eliminated pain medications. Patients reported precise concordance of the paresthesia with painful regions, including in their phantom limbs; in one case, stimulation eliminated PLP as well as nonpainful phantom sensations. Three patients experienced a diminution of pain relief, despite good initial outcomes.ConclusionsDRG neuromodulation may be an effective tool in treating this pain etiology. Clinical outcomes in this report support recent converging evidence suggesting that the DRG may be the site of PLP generation and/or maintenance. Further research is warranted to elucidate mechanisms and optimal treatment pathways.

ObjectivesElectrical peripheral nerve stimulation (PNS) is discussed as an effective neuromodulatory treatment in chronic pain. This human experimental study hypothesized a rightward shift of stimulus-response function as a marker of antinociceptive and analgesic PNS effects.Materials and MethodsInnocuous electrical PNS of the left superficial radial nerve trunk evoked paresthesia on the left hand dorsum in 29 healthy volunteers. In this innervation area, laser stimulation was performed before, during, and after PNS. Ten different laser intensities ranging between perception and tolerance thresholds were applied. Cortical laser-evoked potentials (LEP) were recorded, and perceptual ratings were documented. Data were analyzed in low, medium, and high laser intensity categories. Stimulus-response functions were calculated. Laser detection and pain thresholds were interpolated.ResultsInterpolated laser thresholds after logarithmic regression were not different from measured thresholds. Laser pain threshold increased during and after PNS. LEP amplitude decreased at medium and high intensities under PNS. Ratings transiently decreased during PNS at medium and high laser intensities.ConclusionsModulation of laser pain threshold, perceptual ratings, and LEP indicates a rightward shift of stimulus-response function under PNS. These data emphasize antinociceptive and analgesic effects of PNS in an experimental human model and support its clinical neuromodulative relevance.

BACKGROUND:The authors investigated the possibility of improving positioning of stimulation leads in patients with chronic neuropathic peripheral nerve pain and good pain relief from implantation of a peripheral nerve stimulator (PNS).METHODS:This pilot study includes four patients suffering from Chronic Regional Pain Syndrome type II (CRPS II) or neuropathic mononeuropathy treated with PNS therapy. The affected extremities and corresponding implantation sites were examined using computer tomographic scans (CT), additional CT angiography (CTA), reconstruction techniques and postprocessing procedures.RESULTS:It was possible to prove a close relation between the implanted device and the neurovascular bundle in each of these cases. Thus, indirect lead position control was obtained.CONCLUSIONS:Computer tomographic techniques represent a reliable method for the position control of implanted peripheral nerve electrodes. Hence, this procedure should surpass general radiographies in detecting lead displacements.

CASE REPORT:The reported female patient underwent sub-total resection of an intra-medullary cervicothoracic astrocytoma classified as WHO grade II in 1984 at the age of 18 months and received local irradiation. In 1989, a local recurrence was diagnosed and a partial resection was performed. Sixteen years later, a small recurrent cervicothoracic tumour was found and spinal seeding to the equine nerve roots and the left cerebellar cortex was apparent on MRI. The patient was implanted with a ventriculoperitoneal shunt for a pseudo-tumour cerebri producing papilloedema, which eventually lead to amaurosis. After an extended biopsy, the invasive lumbosacral tumour was classified as glioblastoma multiforme. Two months later, the patient died after rapid progression of the caudal cranial nerve dysfunction.DISCUSSION AND CONCLUSION:Anaplastic progression and dissemination of spinal astrocytomas even two decades after initial diagnosis and treatment are rare. Therapies and diagnostic follow-up strategies are discussed.