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Restricted diffusion within ring enhancement is not pathognomonic for brain abscess
M Hartmann1, O Jansen, S Heiland
1Department of Neuroradiology, University of Heidelberg Medical School, Heidelberg, Germany.
Background And Purpose:
Recent experience suggests that diffusion-weighted MR imaging may be decisive in the differential diagnosis of ring-enhancing cerebral lesions. Whether restricted diffusion within a ring-enhancing cerebral mass lesion is pathognomonic for abscess was studied.
Methods:
Seventeen patients with ring-enhancing cerebral lesions (three abscesses, six glioblastomas, eight metastases) on conventional contrast-enhanced T1-weighted images were examined with echo-planar diffusion-weighted MR imaging. Apparent diffusion coefficient (ADC) maps and the ADCs were calculated for all lesions. Lesions with signs of intralesional hemorrhage on unenhanced T1-weighted images were excluded.
Results:
The central portion of all six glioblastomas and seven of eight metastases showed unrestricted diffusion, whereas two of three abscesses showed restricted diffusion (low ADC values) in their cavity. However, restricted diffusion also was found in one metastasis, and one abscess within a postoperative cavity showed unrestricted diffusion within a larger nondependent portion.
Conclusion:
In patients with ring-enhancing cerebral mass lesions, restricted diffusion might be characteristic but is not pathognomonic for abscess, as low ADC values also may be found in brain metastases.
Insights
Restricted diffusion on MRI is not always indicative of brain abscesses. While common in abscesses, low apparent diffusion coefficient (ADC) values can also occur in brain metastases, complicating differential diagnosis.
Area of Science:
- Neuroradiology
- Medical Imaging
- Neuro-oncology
Background:
- Diffusion-weighted MR imaging (DW-MRI) shows promise in differentiating ring-enhancing brain lesions.
- The diagnostic value of restricted diffusion in ring-enhancing lesions requires further investigation.
Purpose of the Study:
- To determine if restricted diffusion within a ring-enhancing cerebral mass lesion is pathognomonic for abscess.
- To evaluate the utility of apparent diffusion coefficient (ADC) values in distinguishing brain abscesses from other ring-enhancing lesions.
Main Methods:
- Seventeen patients with ring-enhancing lesions (abscesses, glioblastomas, metastases) underwent echo-planar DW-MRI.
- Apparent diffusion coefficient (ADC) maps were calculated for all lesions.
- Cases with intralesional hemorrhage on T1-weighted images were excluded.
Main Results:
- Restricted diffusion was observed in two of three abscesses.
- Glioblastomas and most metastases showed unrestricted diffusion.
- One metastasis and one abscess (in a postoperative cavity) exhibited unusual diffusion patterns.
Conclusions:
- Restricted diffusion is characteristic but not pathognomonic for brain abscesses.
- Low ADC values can be present in brain metastases, necessitating careful interpretation.
- DW-MRI findings should be considered alongside clinical and other imaging data for accurate diagnosis.