Postoperative epidural fluid collection mimicking epidural abscess: illustrative cases

After craniotomy, fluid may accumulate in the surgical bed, raising suspicion for hemorrhage, abscess, or postoperative pseudomeningocele. Typically, peripheral contrast enhancement, internal restricted diffusion, and adjacent edema are consistent with infection.

The authors present 4 cases with postoperative epidural fluid collections mimicking epidural abscesses on MRI with restricted diffusion on diffusion-weighted imaging. Three of these cases were associated with adjacent brain edema. The fluid appeared 1-3 months after the surgery on routine follow-up MRI in the absence of clinical symptoms, and nearly resolved, either spontaneously without treatment or with conservative therapy alone. Given imaging findings concerning for infection in the absence of symptoms, diagnosis and management were challenging.

When there is increased epidural fluid collection after craniotomy, radiographic findings may mimic abscess, but they are not always clinically significant. Clinical assessment is a crucial component of the diagnosis to avoid unnecessary intervention, and follow-up imaging is recommended. The pathogenesis of this restricting, enhancing fluid collection remains unclear. https://thejns.org/doi/10.3171/CASE26757.