Abscess and Subdural Empyema

Patient previously operated for bilateral Subdural Hematomas (SDH) presented in febrile state with seizures. CT revealed peripherally enhancing cavity with surrounding edema parieto-temporally. Also noted were hyperdense SDH frontally and parietally with suspected leptomeningeal enhancement (arrows).
MRI confirmed CT findings showing enhancing, fluid filled cavity with surrounding edema and subdural fluid collections showing high signal on FLAIR (last image) and leptomeningeal enhancement (third image). Note mass effect on the coronal image.
Diffusion Weighted Imaging presented restricted diffusion of the fluid in the cavity showing high signal on DWI sequence and low signal on ADC map. This type of diffusion restriction in the fluid cavity is very suggestive for abscess.
More cranially has DWI shown also restricted diffusion in the subdural fluid collections that indicate empyemas. With note that hematoma can also show restricted diffusion, high signal on FLAIR and leptomeningeal enhancement, the whole spectrum of findings in this patient have been evaluated. Conclusion from the radiology and clinical investigation was: Brain Abscess with Infected Subdural Hematomas - Empyemas. Patient was operated using stereotactic neurosurgery based on MRI T1 MPRAGE sequence (not shown). During operation a flow of pus under pressure was noted from the abscess cavity. This case presents value of Diffusion Weighted Imaging in distinguishing between abscess and tumor. Tumor with necrotic fluid cavity generally shows no restriction on DWI.

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