Abscess, Left Temporal Lobe due to Mastoiditis


Findings:
Multiple MR images demonstrate a large irregular peripherally enhancing lesion within the left temporal lobe. The lesion demonstrates a rim of relative decreased T2 and increased T1 precontrast signal. There is extensive signal abnormality within the left mastoid air cells. Temporal bone CT demonstrates destruction of the left tegmen tympani. The diffusion weighted imaging demonstrates marked diffusion restriction within the core of the multiseptated lesion. There is surrounding edema and mass effect with partial effacement of the left lateral ventricle and midline shift.

 

Differential Diagnosis:

Abscess, high grade glial neoplasm, metastasis. Restricted diffusion and rim characteristics are key distinguishing features that indicate a diagnosis of abscess rather than the other possibilities. The presence of an obvious source in the left mastoid region also effectively eliminates the other possibilities.

 

Discussion:

Discussion of abscess is found in many other cases on this site. Importantly, 30% or more cases of abscess do not have an identifiable source. Headache and elevated ESR are fairly universal, but fever is found in only about 50%. Drainage is usually performed if greater than 2.5 cm. Any development of restricted diffusion in the previously drained cavity indicates recurrence. 

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