Jennifer Padwal (University of California, San Diego, La Jolla, USA) and others report in the Journal of NeuroInterventional Surgery that “with sufficient clinical skills and knowledge, trained interventional radiologists may safely perform [neuromodulation procedures] in an outpatient setting.”
The retrospective study, examining patient charts and medical records over a four-year period, involved a total of 45 patients with a median age of 47. The selected patients had failed all types of conservative treatment for chronic back or neck pain, including physical therapy, epidural steroid injections and pain medication therapy. The primary diagnoses for the study included 23 cases of failed back or neck surgery syndrome, 12 cases of spinal stenosis, four cases of axial pain, three cases of reflex sympathetic dystrophy, one case of peripheral vascular disease, one case of phantom limb and one case of post-concussion syndrome and occipital neuralgia.
The trial period of the study ranged from three days to one week. Electrical leads were fed under the skin to the point of pain. All but three patients required a second lead to ensure adequate coverage of painful areas, which was placed parallel or staggered in relation to the first lead. The leads were then connected to an external pulse generator. In the trial period, the patient manipulated the different programmes and recorded their pain level, activity and use of pain medications. At the end of the trial, a discussion was held with the patient regarding these three points.
A trial was successful if it saw a reduction in the patient’s pain level of ≥50%, calculated on the Visual Analogue Scale. In this event, the electrical leads, or an electrical paddle placed via a mini-laminectomy in the epidural space at the desired level, were attached to a generator which was then placed in a prepared subcutaneous pocket, usually located in the buttocks.
The trials were conducted in an outpatient clinic (34) or in hospital outpatient settings (11). Of the 45 trials, 27 progressed to permanent implantation – a trial-to-implant ratio of 60%. The authors said that this ratio of their study was “only slightly below the average trial-to-implant ratio reported in the literature of 65-83%. With a larger sample size, the trial-to-implant ratio would most likely rise.” Four of the implants were subcutaneous and 23 were epidural. An interventional neuroradiologist performed 17 implantations, while spinal surgeons performed 10. Of the 18 patients to fail the trial process, 17 reported <50% pain relief and one patient did not like the feeling of the leads in his back.
In terms of complications, two (8%) patients presented with evidence of lead migration, lower than the reported rate in the literature of 11–21%. Three patients (13%) went on to have infections necessitating the removal of the device, which was higher than the rate reported in the literature of 4.5%. However, the authors explain: “One patient was found to be an intravenous drug abuser who developed an infection after six months of the implantation, and another patient who developed an infection after three months was found to have previously undiscovered leukaemia.” There was one case of uncontrollable bleeding during placement of one of the trial leads, resulting in the removal of the lead and the continuation of the trial with one lead.
The authors conclude that this study will “provide an appropriate foundation for the design and implementation of future controlled prospective studies.”