Adhesive arachnoiditis following lumbar epidural steroid injections: a report of two cases and review of the literature

Abstract

Lumbar epidural steroid injections (LESIs) are commonly used for managing lower back pain (LBP) and radicular pain. LESIs are generally considered safe with only rare serious complication. One very rare complication that is frequently cited in the literature is adhesive arachnoiditis. However, a literature search failed to detect even one published manuscript, clearly documenting LESI induced arachnoiditis. This article presents two patients who received a transforaminal L5-S1 and two L3-L4 interlaminar LESIs. Although the presented patients developed clear radiological (MRI) findings of arachnoiditis, they were not accompanied by any improvement or deterioration in their clinical condition. The article also reviews the literature on the prevalence, pathogenesis, diagnosis, and clinical features of adhesive arachnoiditis. Literature suggests that adhesive arachnoiditis following LESIs is a rare entity, which - as seen in our patients - has clear radiological characteristics but uncertain pathogenesis. It has a large spectrum of clinical presentation, ranging from an incidental finding to a serious neurological sequela. In at least some patients with adhesive arachnoiditis following LESI, the radiological and clinical findings may fail to correlate with each other. In light of the fact that LESI is one of the most commonly performed procedures for managing LBP, clinicians should be aware of this rare yet existing entity.

Keywords: MRI; magnetic resonance imaging; radicular pain; sciatica; spinal stenosis.

Figure 1

T2W Sagittal and axial MRI studies of patient 1. Notes: Sagittal MRI studies before the ESI (A) showing discrete cauda equine nerve roots, and after the ESI (B) showing clumping of the nerve roots, mainly at the L4–L5 level (arrow). Axial study before the injection (C) shows a more or less symmetrical distribution of the nerve roots at the L4–L5 level, whereas after the injection (D), the caudal nerve roots create a mass-like structure in the center of the spinal canal (arrows) with no surrounding CSF. Abbreviations: CSF, cerebrospinal fluid; ESI, epidural steroid injection.

Figure 2

T2W Sagittal and axial MRI studies of patient 2. Notes: Sagittal MRI studies of patient 2 before the ESI (A) showing discrete cauda equine nerve roots along the entire lumbar spine. After the ESI (B), clumped nerve roots create an elongated single mass, mimicking “tethered cord” along the entire lumbar spine. Axial MRI study before the injection (C) shows symmetrical distribution of the nerve roots at L3 level. After the injection (D), the caudal nerve roots form a mass displaced posteriorly and to the left. Abbreviation: ESI, epidural steroid injection.