Answer for BIR CoW 27 Jul 2025
Cerebral abscess due to fungal etiology
Findings
Evidence of multiple (2) ill defined T1 hypointense/ T2 hyperintense lesion with hypointense wall and peripheral crenated margins noted in the right frontal lobe showing peripheral areas of diffusion restriction and internal foci of gradient blooming. There is extensive perilesional edema noted causing mass effect in the form of effacement of ipsilateral sulcal spaces and ipsilateral lateral ventricle. The perilesional edema is also noted extending up to right midbrain. Midline shift to left of about 8mm noted. On MR spectroscopy, there is increased lipid and lactate integral values within the lesion. Chronic lacunar infarct noted in left corona radiata region.
Discussion
Most CNS fungal infections are opportunistic. Terminology CNS fungal infections are also called cerebral mycosis. A focal "fungus ball" is also called a mycetoma or fungal granuloma. Etiology The most common are Coccidioides immitis, Aspergillus fumigatus, Cryptococcus neoformans, Histoplasma capsulatum, Candida albicans, and Blastomyces dermatitidis. Pathology CNS mycoses have four basic pathologic manifestations: diffuse meningeal disease (most common), solitary or multiple focal parenchymal lesions (common), disseminated nonfocal parenchymal disease (rare), and focal dura-based masses (rarest). Location - The meninges are the most common site, followed by the brain parenchyma and spinal cord. Size and Number -Parenchymal mycetomas vary in size from tiny (a few millimeters) to 1 or 2 cm. Large lesions are rare although multiple lesions are common. Imaging General Features. Findings vary with the patient's immune status. Well-formed fungal abscesses are seen in immunocompetent patients. Imaging early in the course of a rapidly progressive infection in an immunocompromised patient may show diffuse cerebral edema more characteristic of encephalitis than fungal abscess. MR Findings. Fungal meningitis appears as "dirty" CSF on T1WI. Parenchymal lesions are typically hypointense on T1WI but demonstrate T1 shortening if subacute hemorrhage is the cavity are typical. T2/FLAIR scans in patients with fungal cerebritis show bilateral but asymmetric cortical/subcortical white matter and basal ganglia hyperintensity. Focal lesions (mycetomas) show high signal foci that typically have a peripheral hypointense rim, surrounded by vasogenic edema. T2* scans may show "blooming" foci caused by hemorrhages or Calcification. Focal paranasal sinus and parenchymal mycetomas usually restrict on DWI. T1 C+ FS scans usually show diffuse, thick, enhancing basilar leptomeninges. Angioinvasive fungi may erode the skull base, cause plaque-like dural thickening, and occlude one or both carotid arteries. Parenchymal lesions show punctate, ring-like, or irregular enhancement. MRS shows mildly elevated Cho and decreased NAA. A lactate peak is seen in 90% of cases, whereas lipid and amino acids are identified in approximately 50%. Multiple peaks resonating between 3.6 and 3.8 ppm are common and probably represent trehalose. Differential diagnosis includes - cerebral abscess due to pyogenic and tuberculous etiology.
Findings
Evidence of multiple (2) ill defined T1 hypointense/ T2 hyperintense lesion with hypointense wall and peripheral crenated margins noted in the right frontal lobe showing peripheral areas of diffusion restriction and internal foci of gradient blooming. There is extensive perilesional edema noted causing mass effect in the form of effacement of ipsilateral sulcal spaces and ipsilateral lateral ventricle. The perilesional edema is also noted extending up to right midbrain. Midline shift to left of about 8mm noted. On MR spectroscopy, there is increased lipid and lactate integral values within the lesion. Chronic lacunar infarct noted in left corona radiata region.
Discussion
Most CNS fungal infections are opportunistic. Terminology CNS fungal infections are also called cerebral mycosis. A focal "fungus ball" is also called a mycetoma or fungal granuloma. Etiology The most common are Coccidioides immitis, Aspergillus fumigatus, Cryptococcus neoformans, Histoplasma capsulatum, Candida albicans, and Blastomyces dermatitidis. Pathology CNS mycoses have four basic pathologic manifestations: diffuse meningeal disease (most common), solitary or multiple focal parenchymal lesions (common), disseminated nonfocal parenchymal disease (rare), and focal dura-based masses (rarest). Location - The meninges are the most common site, followed by the brain parenchyma and spinal cord. Size and Number -Parenchymal mycetomas vary in size from tiny (a few millimeters) to 1 or 2 cm. Large lesions are rare although multiple lesions are common. Imaging General Features. Findings vary with the patient's immune status. Well-formed fungal abscesses are seen in immunocompetent patients. Imaging early in the course of a rapidly progressive infection in an immunocompromised patient may show diffuse cerebral edema more characteristic of encephalitis than fungal abscess. MR Findings. Fungal meningitis appears as "dirty" CSF on T1WI. Parenchymal lesions are typically hypointense on T1WI but demonstrate T1 shortening if subacute hemorrhage is the cavity are typical. T2/FLAIR scans in patients with fungal cerebritis show bilateral but asymmetric cortical/subcortical white matter and basal ganglia hyperintensity. Focal lesions (mycetomas) show high signal foci that typically have a peripheral hypointense rim, surrounded by vasogenic edema. T2* scans may show "blooming" foci caused by hemorrhages or Calcification. Focal paranasal sinus and parenchymal mycetomas usually restrict on DWI. T1 C+ FS scans usually show diffuse, thick, enhancing basilar leptomeninges. Angioinvasive fungi may erode the skull base, cause plaque-like dural thickening, and occlude one or both carotid arteries. Parenchymal lesions show punctate, ring-like, or irregular enhancement. MRS shows mildly elevated Cho and decreased NAA. A lactate peak is seen in 90% of cases, whereas lipid and amino acids are identified in approximately 50%. Multiple peaks resonating between 3.6 and 3.8 ppm are common and probably represent trehalose. Differential diagnosis includes - cerebral abscess due to pyogenic and tuberculous etiology.
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!