Selective nerve root blocks for the treatment of sciatica: Evaluation of injection site and effectiveness - A study with patients and cadavers

PURPOSE: To relate different types of radiographic contrast material distri butions to anatomic compartments by using cadaveric specimens and to relate the injection site to treatment-induced discomfort and therapeutic effect. MATERIALS AND METHODS: The contrast material distributions of selective ner ve root blocks (SNRBs) in 36 patients (13 women, 23 men; mean age, 52 years ; age range, 22-88 years) were graded by two radiologists in conference as type 1 (tubular appearance), type 2 (nerve root visible as filling defect), or type 3 (nerve root not visible). These patterns were correlated with pa in reduction after 15 minutes and 2 weeks (with a visual analogue scale of 100-mm length). In addition, 30 nerve roots were injected with Iodine-conta ining contrast material and blue dye in three cadaveric specimens. Radiogra phs were compared with anatomic sections. RESULTS: After 15 minutes and 2 weeks, 75% and 86% of the patients, respect ively, reported pain relief. Mean pain relief length after 15 minutes for t ype 1 distribution was 60 mm; for type 2, 44 mm; and for type 3, 22 mm; and after 2 weeks, it was 34 mm fortype 1, 31 mm fortype 2, and 57 mm fortype 3. There was no correlation between early and late response. Pain during in tervention was less pronounced in type 2 injection, compared with type 1 (P = .002). On the basis of anatomic sections, type 1 injection was intraepin eural; type 2, extraepineural; and type 3, paraneural. CONCLUSION: Therapeutic SNRB is effective in sciatica, but early response d oes not predict the effect after 2 weeks. Type 1 injections are more painfu l than type 2 injections.