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Advanced Diffusion Imaging in The Hippocampus of Rats with Mild Traumatic Brain Injury
Published on: August 14, 2019
Diffusion-weighted imaging of fungal cerebral infection
Paola Gaviani1, Richard B Schwartz, E Tessa Hedley-Whyte
1Stephen E. and Catherine Pappas Center for Neuro-oncology Unit, Massachusetts General Hospital, Boston, MA 02114, USA.
Background And Purpose:
Diffusion-weighted imaging (DWI) is useful in diagnosing bacterial brain abscesses, but DWI features of fungal brain abscesses have not been characterized. Because fungal abscesses are not purulent, we hypothesized that their DWI characteristics are distinct from those of bacterial abscesses.
Methods:
We reviewed clinical, neuropathologic and neuroimaging findings of patients with fungal brain infections due to Aspergillus (n = 6), Rhizopus (n = 1), or Scedosporium (n = 1) species. DWI and apparent diffusion coefficient (ADC) maps were obtained before definitive diagnosis and antifungal therapy. ADC ratios (lesion/contralateral white matter) were calculated.
Results:
Two patients had a rapidly progressive, fatal course, with cerebritis and acute inflammation; fungal organisms were largely restricted to vessels. Lesions were predominantly nonenhancing and had heterogeneous foci of restricted diffusion. Six patients with subacute neurologic presentations had acute or chronic inflammation, capsule formation, focal necrosis, and fungal organisms disseminated throughout the lesion. Their abscesses were ring enhancing. In five, lesions had restricted diffusion in the central nonenhancing portions. The sixth patient had a lesion with a peripheral rim of restricted diffusion but elevated central diffusion; histopathology showed early abscess formation. Mean ADC for all lesions was 0.33 +/- 0.06 x 10(-3) mm(2)/s, with an average ADC ratio of 0.43.
Conclusion:
Fungal cerebral abscesses may have central restricted diffusion similar to that of bacterial abscesses but with histologic features of acute or chronic inflammation and necrosis rather than suppuration. Altered water diffusion in these lesions likely reflects highly proteinaceous fluid and cellular infiltration.
Insights
Diffusion-weighted imaging (DWI) can help diagnose fungal brain abscesses, showing restricted diffusion similar to bacterial types but with distinct inflammation patterns. These findings aid in differentiating fungal infections from bacterial ones.
Area of Science:
- Neuroradiology
- Infectious Diseases
- Neuroscience
Background:
- Diffusion-weighted imaging (DWI) is valuable for diagnosing bacterial brain abscesses.
- DWI characteristics of fungal brain abscesses remain largely uncharacterized.
- Fungal abscesses differ from bacterial abscesses due to their non-purulent nature.
Purpose of the Study:
- To characterize the DWI features of fungal brain abscesses.
- To determine if DWI findings can distinguish fungal from bacterial brain abscesses.
Main Methods:
- Retrospective review of clinical, neuropathologic, and neuroimaging findings in 8 patients with fungal brain infections (Aspergillus, Rhizopus, Scedosporium).
- Analysis of DWI and apparent diffusion coefficient (ADC) maps obtained before treatment.
- Calculation of ADC ratios (lesion/contralateral white matter).
Main Results:
- Two patients with rapid progression showed nonenhancing lesions with heterogeneous restricted diffusion.
- Six patients with subacute presentations had ring-enhancing abscesses.
- Five of these six showed central restricted diffusion; one had peripheral restricted diffusion with central elevated diffusion, indicating early abscess formation. Mean ADC was 0.33 ± 0.06 x 10⁻³ mm²/s.
Conclusions:
- Fungal cerebral abscesses can exhibit central restricted diffusion, mimicking bacterial abscesses.
- Histologic features of acute/chronic inflammation and necrosis, rather than suppuration, differentiate fungal abscesses.
- Altered water diffusion in fungal abscesses is likely due to proteinaceous fluid and cellular infiltration.
