Figure 1
Abscess
Clinical History
Headaches, and fever.
Imaging Findings
The patient had left-sided mastoid infection. Medical therapy was commenced. However, two months later he presented with severe headaches, and high fever. On MRI, T1 and T2-weighted images, images after intravenous administration of contrast medium, and diffusion-weighted images were acquired.
Discussion
Evolution of brain abscess has mainly four stages: early cerebritis, late cerebritis, early capsule formation, and late capsule formation. The stages associated with capsule formation usually begin about the end of second week of following the initial infection, and lasts several weeks and months. During these stages imaging appearance is mainly a ring-enhancing lesion with surrounding edema. Differential dignosis covers some primary and metastatic brain tumors, resolving hematoma, granuloma, infarct, trombosed vascular malformations, and focal demyelinating disease. Diffusion MRI appears to be a sensitive method in disriminating necrotic-cystic tumors from abscesses. Usually, abscesses demonstrate high signal on heavily diffusion weighted (i.e. b=1000 sec/mm2) images, and low signal and low ADC values on ADC maps. These findings are usually opposite for necrotic-cystic tumors. However, it should be remembered that recently a metastatic adenocarcinoma has been reported with diffusion MRI features similar to abscess. The current patient was operated, and the laboratory evidence was consistent with pyogenic abscess.
Differential Diagnosis List
Brain abscess secondary to mastoiditis
Final Diagnosis
Brain abscess secondary to mastoiditis
References
[1] Osborn AG. Diagnostic Neuroradiology. Mosby, St. Louis (1994).
[2]
Ketelslegers E, Duprez T, Ghariani S, Thauvoy C, Cosnard G. Time dependence of serial diffusion-weighted imaging features in a case of pyogenic brain abscess.
J Comput Assist Tomogr. 2000 May-Jun;24(3):478-81. (PMID: 10864089)
[3]
Okamoto K, Ito J, Ishikawa K, Sakai K, Tokiguchi S. Diffusion-weighted echo-planar MR imaging in differential diagnosis of brain tumors and tumor-like conditions.
Eur Radiol. 2000;10(8):1342-50. (PMID: 10939505)
[4]
Desprechins B, Stadnik T, Koerts G, Shabana W, Breucq C, Osteaux M. Use of diffusion-weighted MR imaging in differential diagnosis between intracerebral necrotic tumors and cerebral abscesses.
AJNR Am J Neuroradiol. 1999 Aug;20(7):1252-7. (PMID: 10472982)
[5]
Holtas S, Geijer B, Stromblad LG, Maly-Sundgren P, Burtscher IM. A ring-enhancing metastasis with central high signal on diffusion-weighted imaging and low apparent diffusion coefficients.
Neuroradiology. 2000 Nov;42(11):824-7. (PMID: 11151689)
Case information
| URL: | https://eurorad.org/case/1079 |
| DOI: | 10.1594/EURORAD/CASE.1079 |
| ISSN: | 1563-4086 |
Figure 2
Diffusion MRI
b=0 (T2-weighted) image reveals the mass, rim, and edema.
b=500 sec/mm2 (with partial T2 information referred to as T2 shine through) image reveals the mass with high signal. Peripheral edema is also seen with some high signal.
b=1000 sec/mm2 (heavily diffusion-weighted or true diffusion) image reveals the mass with high signal. Presence of high signal on this true diffusion image is consistent with restricted movement of water molecules in the contents of the mass. This appearance, coupled with ring enhancement, is usually characteristic for an abscess, however it should be noted that necrotic tumors may sometimes present with a similar appearance. Note that perilesional edema is not seen on this image.
Apparent diffusion coefficient (ADC) map reveals an ADC value of 0.67 X10-3 mm2/sec in the abscess, a value which indeed falls within the normal ranges of the brain parenchyma (= 0.60 to 1.05 X10-3 mm2/sec). Vasogenic edema has a high ADC value: 1.74 X10-3 mm2/sec. Normal parenchymal ADC values are shown: 0.73 and 0.73 X10-3 mm2/sec.
Diffusion MRI
b=0 (T2-weighted) image reveals the mass, rim, and edema.
b=500 sec/mm2 (with partial T2 information referred to as T2 shine through) image reveals the mass with high signal. Peripheral edema is also seen with some high signal.
b=1000 sec/mm2 (heavily diffusion-weighted or true diffusion) image reveals the mass with high signal. Presence of high signal on this true diffusion image is consistent with restricted movement of water molecules in the contents of the mass. This appearance, coupled with ring enhancement, is usually characteristic for an abscess, however it should be noted that necrotic tumors may sometimes present with a similar appearance. Note that perilesional edema is not seen on this image.
Apparent diffusion coefficient (ADC) map reveals an ADC value of 0.67 X10-3 mm2/sec in the abscess, a value which indeed falls within the normal ranges of the brain parenchyma (= 0.60 to 1.05 X10-3 mm2/sec). Vasogenic edema has a high ADC value: 1.74 X10-3 mm2/sec. Normal parenchymal ADC values are shown: 0.73 and 0.73 X10-3 mm2/sec.