Herniated disc morphology and outcome of selective nerve root block in acute sciatica.

Purpose: The clinical sequelae associated with acute sciatica have been traditionally attributed to mechanical compression of the spinal nerve root by a herniated disc (HD). More recent studies have demonstrated that the HD induces the release of inflammatory mediators and that a tumor necrosis factor alpha-inhibiting agent can resolve the symptoms.|Selective nerve root block (SNRB) involves the transforaminal application of steroid under fluoroscopic guidance adjacent to the selected nerve root. Well-defined criteria for patients that will most likely benefit from SNRB remain unclear. The goal of this study was to determine whether or not the morphology (i.e. posterolateral, sequestrated, foraminal, far lateral) of HD influences the therapeutic value of SNRB treatment. Methods: An observational cohort study of 37 patients with acute sciatica of less than 12 weeks duration, McCulloch scores of 4 or 5 and evidence of HD on MRI scan at the appropriate level was completed. Disc morphology was determined by blinded interpretation of the MRI scans by a Musculoskeletal Radiologist. Outcome measures included the Modified Roland-Morris Disability Questionnaire (RDQ), administered on the day of, and 6 weeks following, the SNRB procedure and the Visual Analogue Scale (VAS) filled out by the patient immediately before, 30 minutes after and 6 weeks after SNRB. Results: Of the 37 patients enrolled in this study, the HD morphology was classified as: posterolateral 20, sequestrated 9, foraminal 6, far lateral 2. 35 of 37 patients (95%) reported a 30 minute VAS score of less than 3/10. 14 of 20 patients (70%) with posterolateral HD reported > 3 point improvement in RDQ and > 5 point improvement in VAS at 6 weeks post procedure. 1 of 9 patients (11%) with sequestrated HD showed the same level of improvement in RDQ and VAS scores. None of the patients with foraminal or far lateral HD reported > 1 point improvement in RDQ or > 2 point improvement in VAS scores. Conclusions: Patients with posterolateral HD were found to have significantly more favorable outcomes from SNRB than those with sequestrated, foraminal or far lateral HD morphology.