Conus medullaris and cauda equina syndrome as complications of non-imaging guided epidural steroid injection: two case reports with comprehensive interdisciplinary work-up.

Introduction: Epidural steroid injection (ESI) is commonly performed in the outpatient setting for relieving lumbosacral radicular pain, i.e., sciatica. Neurological and neuro-urological adverse events are rare but devastating when occurring. This led to a warning of the U.S. Food and Drug Administration about the use of corticosteroids in the spine. Reviews on causes and numbers of complications are lacking.

Case presentation: Two cases from our tertiary spine center who sustained conus medullaris and cauda equina syndrome following ESI in a secondary care setting not affiliated with our institution. Both patients received ESI for the treatment of chronic lower back pain without sciatica and any reported neurological impairment prior to the injection. In both Case 1 (F, 72yrs) and Case 2 (F, 72yrs), ESI was administered without imaging-guidance and without pre-interventional lumbar MRI. We assessed both patients by thorough neurological examination, comprehensive neuroimaging, neurophysiology, and neuro-urological assessments. Case 1 had cauda equina syndrome, arachnoiditis was diagnosed from lumbar MRI. Case 2 had conus medullaris syndrome probably related to a reported accidental dura puncture. Symptoms of lumbosacral sensory impairment partly recovered, motor symptoms recovered, but neurogenic lower urinary tract and bowel dysfunction persisted. One patient still requires intermittent self-catheterization, while the other patient suffers from bowel dysfunction at 2-yr follow up.

Discussion: Although neurological complications from ESI are rarely reported they can be associated with serious long-term impairments. Comprehensive diagnostic work-up is required to discern potential underlying pathomechanisms and to quantify neural damage load. Neuro-urological diagnostics is required to reveal bladder-bowel dysfunction, install proper management and to prevent secondary complications. We advocate imaging-guidance in ESI to reduce the rate of neurological complications.