Impact of Serum Magnesium Levels on Outcomes After Transforaminal Epidural Steroid Injections for Lumbar Radicular Pain: A Retrospective Study.

BACKGROUND

Transforaminal epidural steroid injections (TFESIs) are a commonly used intervention for the management of lumbar radicular pain. While anatomical predictors of pain conditions like nerve compression severity, are well-known, the role of patient-specific metabolic factors has received comparatively less attention. Meanwhile, magnesium (Mg), a natural N-methyl-D-aspartate (NMDA) receptor antagonist, plays a major role in pain modulation and the prevention of central sensitization.

OBJECTIVES

To investigate the association between pre-procedural serum magnesium levels and the clinical success of TFESIs.

STUDY DESIGN

A retrospective observational cohort study.

SETTING

A tertiary referral center, Istanbul, Türkiye.

METHODS

Data from 121 patients undergoing single-level TFESIs were analyzed. The severity of each patient's radiological nerve root compression was graded using magnetic resonance imaging (MRI)-based criteria. With the use of an evidence-based cutoff value of 0.85 mmol/L to identify subclinical deficiency, the patients were categorized into groups labeled Low-Mg (< 0.85 mmol/L, n = 29) and Normal-Mg (≥ 0.85 mmol/L, n = 92). Clinical progress was tracked using the Numeric Rating Scale (NRS) and Oswestry Disability Index (ODI) at baseline, one month, and 3 months. Treatment success was defined as ≥ 50% pain relief and ≥ 40% functional improvement.

RESULTS

Despite comparable radiological nerve compression grades, patients in the low-Mg group reported significantly higher baseline pain intensity than did those in the normal-Mg group (9.65 vs. 8.15, P < 0.001). Post-procedural outcomes were significantly better in patients with normal Mg levels. Success rates differed significantly between the groups: 71.7% vs. 20.7% at one month (P < 0.001), and 66.3% vs. 34.5% at 3 months (P = 0.002). Correlation analysis suggested a possible threshold effect, with outcomes deteriorating below the defined Mg cutoff rather than following a linear dose-response relationship.

LIMITATIONS

Limitations include the study's retrospective design, the lack of dietary intake data, and the reliance on serum rather than ionized Mg measurements.

CONCLUSION

Low serum Mg levels (< 0.85 mmol/L) are associated with higher baseline pain intensity and a poor therapeutic response to TFESIs. Screening patients for their Mg levels represents a simple and potentially modifiable factor that may help improve injection outcomes, warranting consideration for supplementation in borderline cases.

Copyright: 2026, American Society of Interventional Pain Physicians.