Cerebral Abscess

Findings:
    Axial noncontrast and contrast CT images show a large ring enhancing mass involving the right frontal lobe, with internal low density and nondependent debris, associated with moderate surrounding edema and mass effect. There is moderate right to left midline shift.

Differential diagnosis:
    Glioma, metastasis, abscess, hematoma (less likely). Helpful distinguishing features: thin uniform wall with +/- mesial thinning.

Discussion:
    -direct vs. hematogenous(most common), anaerobes overall most common but may be S. aureus after surgery or trauma.
    -frontal and parietal lobes
    -lethargy, nausea, vomiting, fever(< 50%), meningeal signs(< 30%)
    -rapid progression helps distinguish from tumor

    Stages:
   1-early cerebritis 3-5 d
       -poorly defined area of necrosis- may be nl CT or hypodense, mild mass effect and patchy enhancement. MR nonspec hypo/hyper.
   2-late cerebritis 1-2 wks
       -thick, irregular wall enhancement with vasogenic edema. may have delayed fill in, may respond to Abx.
   3-early capsule
       -well defined rim enhancement, low T2.
   4-late capsule w
       -better defined rim with possible loculation, paramagnetic effect, possible mesial thinning.
 
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