Clinical evaluation for spinal epidural abscess in patients with Staphylococcus aureus bacteraemia: a diagnostic...

Spinal epidural abscess (SEA) is a serious complication of Staphylococcus aureus bacteraemia (SAB) that can be difficult to diagnose. We aimed to describe the proportion of SAB cases with SEA and evaluate useful history or physical exam findings to help diagnose SEA.

This single-centre retrospective cohort study included consecutive SAB patients from 2021 to 2023. The index tests included risk factors, symptoms and signs of SEA as documented in patient charts. The reference standard was diagnosis of SEA based on spinal MRI or intra-operative finding during 90-day follow-up.

Of 357 SAB patients, 29 (8.1%) patients had a SEA. Saddle anaesthesia, radicular pain, numbness or paresthaesia, and spine tenderness were most useful to rule in SEA based on positive likelihood ratio (PLR) of 22.6, 13.8, 9.9 and 7.5 respectively. Absence of acute back pain, no objective limb weakness, no subjective limb weakness and no spine tenderness were most useful to rule out SEA based on negative likelihood ratio (NLR) of 0.19, 0.46, 0.57, and 0.62 respectively. A clinical prediction rule based on these findings had a sensitivity of 97% (95% CI 83%-100%), specificity of 77% (95% CI 73%-82%), PLR of 4.3 (95% CI 3.5-5.3) and NLR of 0.05 (95% CI 0.01-0.31).

All SAB patients should undergo systematic neurologic evaluation for SEA as we found SEA is not an uncommon complication of SAB. A clinical prediction rule may be helpful to identify high-risk patients needing an urgent spinal MRI to assess for SEA.