Imaging description

Brain abscesses are uncommon compared to primary and secondary brain tumors in the developed countries. The imaging features of brain abscesses can be very similar to glioblastoma multiforme (GBM) and metastases, however. The typical brain abscess in an immunocompetent individual has a cystic/necrotic center, an enhancing wall, and surrounding edema with mass effect. Brain abscesses are usually of hematogenic origin and located in the deep white matter. They can be solitary or multiple. On MRI, abscesses show markedly restricted diffusion in their cystic regions and decreased perfusion in their walls (Fig. 36.1). These features allow differentiation of abscesses from GBM and metastases with greater than 95% accuracy (Fig. 36.2) [1–3]. Essentially all pyogenic abscesses show restricted diffusion on DWI, but non-pyogenic abscesses such as tuberculomas and toxoplasmomas have variable DWI signal [4]. However, GBMs rarely show restricted diffusion centrally, which may lead to erroneous diagnosis of abscess.

Importance

Prompt diagnosis of brain abscess allows prompt treatment, which can be life-saving and negates expensive and time-consuming work-up for metastatic and primary tumors.