Concordant Pressure Paresthesia During Interlaminar Lumbar Epidural Steroid Injections Correlates with Pain Relief in Patients with Unilateral Radicular Pain

Background: Transforaminal and interlaminar epidural steroid injections are commonly used interventionalpain management procedures in the treatment of radicular low back pain. Even though several studies haveshown that transforaminal injections provide enhanced short-term outcomes in patients with radicularand low back pain, they have also been associated with a higher incidence of unintentional intravascularinjection and often dire consequences than have interlaminar injections.Objectives: We compared 2 different approaches, midline and lateral parasagittal, of lumbar interlaminarepidural steroid injection (LESI) in patients with unilateral lumbosacral radiculopathic pain. We also tested therole of concordant pressure paresthesia occurring during LESI as a prognostic factor in determining the efficacyof LESI.Study Design: Prospective, randomized, blinded study.Setting: Pain management center, part of a teaching-community hospital in a major metropolitan US city.Methods: After Institutional Review Board approval, 106 patients undergoing LESI for radicular low back painwere randomly assigned to one of 2 groups (53 patients each) based on approach: midline interlaminar (MIL)and lateral parasagittal interlaminar (PIL). Patients were asked to grade any pressure paresthesia as occurringipsilaterally or contralaterally to their “usual and customary pain,” or in a distribution atypical of their daily pain.Other variables such as: the Oswestry Disability Index questionnaire, pain scores at rest and during movement, useof pain medications, etc. were recorded 20 minutes before the procedure, and on days 1, 7, 14, 21, 28, 60, 120,180 and 365 after the injection.Results: Results of this study showed statistically and clinically significant pain relief in patients undergoing LESIby both the MIL and PIL approaches. Patients receiving LESI using the lateral parasagittal approach had statisticallyand clinically longer pain relief then patients receiving LESI via a midline approach. They also had slightly betterquality of life scores and improvement in everyday functionality; they also used less pain medications than patientsreceiving LESI using a midline approach. Furthermore, patients in the PIL group described significantly higher ratesof concordant moderate-to-severe pressure paresthesia in the distributions of their “usual and customary pain”compared to the MIL group. In addition, patients who had concordant pressure paresthesia and no discordantpressure paresthesia (i.e., “opposite side or atypical”) during interventional treatment had better and longer painrelief after LESI. Two patients from each group required discectomy surgery in the one-year observation period.Limitations: The major limitation of this study is that we did not include a transforaminal epidural steroidinjection group, since that is one of the approaches still commonly used in contemporary pain practices forthe treatment of low back pain with unilateral radicular pain.Conclusions: This study showed that the lateral parasagittal interlaminar approach was more effectivethan the midline interlaminar approach in targeting low back pain with unilateral radicular pain secondaryto degenerative lumbar disc disease. It also showed that pressure paresthesia occurring ipsilaterally duringan LESI correlates with pain relief and may therefore be used as a prognostic factor.Key words: lumbar epidural steroid injection, interlaminar injection, low back pain, unilateral radicularpain, midline interlaminar approach, lateral parasagittal interlaminar approach, pressure paresthesia, qualityof life, everyday functionality