Selective nerve root blocks: a new technique using electrical stimulation.

Selective nerve root blocks (SNRB) have been used for many years as a diagnostic tool in patients with low back pain with radicular symptoms. However the accuracy, specificity, and sensitivity of these blocks has been questioned as a screening tool for spine surgery. The utility of current SNRB techniques relies primarily on the relief of pain when local anesthetic is injected. However, patient responses are often non specific, and pain relief after injecting local anesthetic is often difficult to interpret. A new technique for performing SNRB using electrical stimulation is described in this article. The technique has been developed in order to reproduce radicular pain by stimulation with electrical current rather than to rely on a response to local anesthetic injection. The technique decreases the reliance on spread of local anesthetic for interpretation, and can therefore reduce false positive results from too much anesthetic (epidural spread affecting more than one nerve root) or not enough anesthetic (block peripheral to the area of inflammation or the "pain generator"). By stimulating several nerve roots in random order in a blind fashion to the patient, the technique can also eliminate placebo responders.