Drug-enhanced spinal stimulation for pain: a new strategy

Neuropathic pain is notoriously difficult to manage and only a few classes of drugs may provide adequate benefits. Thus, in many cases spinal cord stimulation (SCS) is considered; however, in this group of patients, between 30-50% of the cases offered a percutaneous SCS trial may fail to obtain a satisfactory effect. Additionally, a certain number of patients with a good initial effect, report that after a period the benefits are reduced necessitating additional peroral drug therapy. Based on animal studies of transmitters and receptors involved in the effects of SCS in neuropathic pain, the GABA-B receptor seems to play a pivotal role for the effect and, moreover, the agonist baclofen injected intrathecally in rats potentiated the SCS effect in animals not responsive to SCS per se. Based on these and further studies, 48 patients with neuropathic pain and inadequate response to SCS were given intrathecal (i.t.) baclofen (ITB) in bolus doses as an adjuvant. In this group 7 patients enjoyed such a good effect that they were implanted with both SCS and drug delivery systems for ITB. Four additional cases received baclofen pumps alone. Some other patients were given intrathecal (i.t.) adenosine in combination with SCS and initially preferred this to baclofen. The chronic use of this drug in a pump however proved to be technically problematic and all the adenosine cases were eventually terminated. At follow-ups, in average 32 and 67 months after start of SCS + baclofen therapy, more than 50% still enjoy a very good effect. The daily dose of baclofen needed to maintain the effects was approximately doubled during the observation period. There were few and mild side-effects. However, in a group of three patients with peroral baclofen therapy and SCS, complaints of side-effects were common and this therapy was terminated. Informal reports from collegues support the negative experience with additional peroral baclofen. In conclusion, in patients with neuropathic pain demonstrating inadequate response to SCS (small VAS reduction; short duration) a trial of intrathecal baclofen in combination with SCS may be warranted.