Persistent extra-axial post-surgical collections and Propionibacterium acnes infection. Presentation of two cases and literature review.

Objectives: It is common to observe the persistence of extra-axial collections after craniotomies. Most of these disappear in weeks or months but some remain. The onset of focal symptoms or the growth of these persistent collections months or years after surgery may indicate the presence of a chronic and latent infection by germs of low virulence such as Propionibacterium acnes (P. acnes).

Methods: We present two clinical cases with persistent extra-axial collections, which required surgery years after diagnosis, in which P. acnes was isolated as an aetiological agent and we reviewed the literature published in this regard.

Results: These are two patients who, following surgical procedures (decompressive craniectomy for severe TBI and craniotomy for right parietal meningioma) and extra-axial collections were kept, which were monitored over time and then were infected and required emergency evacuation. In these collections P. acnes grew as a causal agent and required targeted antibiotics.

Conclusions: We must consider P. acnes as an infectious agent of post-surgical collections of long evolution. Atypical presentation and radiological changes may be helpful in diagnosis.