Answer for BIR CoW 05 Dec 2021
Fungal abscess ( aspergillus)
Findings
Evidence of multiple T2 mixed intense lesions noted in right frontal region with surrounding perilesional edema and involving midbody of corpus callosum as well .The The lesion shows peripheral enhancement with crenated margins The lesion shows mass effect over the right lateral ventricle and midline shift to left of 8mm. Similar few smaller lesions also noted in left perisylvian and occipital region. MR spectroscopy shows large lipid lactate peak. ASL PERFUSION revealed no significantly increased cerebral blood flow
Discussion
CNS aspergillosis results from angioinvasive infection of the central nervous system by the fungus Aspergillus spp. Along with CNS cryptococcosis, it is one of the most common fungal opportunistic infections of the central nervous system.The disease predominates in immunocompromised individuals, such as those with: AIDS prolonged high-dose corticosteroid use neutropenia graft-vs-host disease after allogenic bone marrow transplantation There are two mechanisms of spread of Aspergillus spp to the CNS . Firstly, as per the pathogenesis of angioinvasive aspergillosis, spores of a variety of Aspergillus spp, most commonly Aspergillus fumigatus, are inhaled and proliferate in the alveoli, where the hyphae invade pulmonary arteries and gain access to the systemic circulation in 25-50% of cases . Once in the systemic circulation, spores can hematogenously spread to the CNS Aspergillosis can also directly spread to the CNS via the paranasal sinuses, where it may manifest as invasive fungal rhinosinusitis . Once in the CNS, the Aspergillus hyphae invade the walls of both small and large blood vessels . This either results in initial thrombosis leading to infarction, often followed by hemorrhage (in 25%), or development of mycotic aneurysms which can hemorrhage This hemorrhage may lead to further parenchymal seeding of Aspergillus, resulting in infectious cerebritis and eventual brain abscess formation, often multiple in nature. CT findings can be often non-specific but in keeping with at least one of the main three aforementioned findings that are characteristic of CNS aspergillosis 1-2. Detecting multiple such lesions in an immunosuppressed patient should prompt further investigation with MRI. Abscesses (and prior regions of cerebritis) are often multiple, present in a random distribution, and appear radiologically identical to other brain abscesses as classic ring-enhancing lesions with striking high signal intensity on DWI 1-3,5. However, Aspergillus abscesses may also have peripheral low signal intensity on T2-weighted images 2. This is better appreciated on GRE or SWI images, and is likely due to hemorrhage around the abscess Pyogenic abscess - T1 hypointense T2 hyperintense well defined smooth hypointense wall ,with central diffusion restriction and peripheral ring abscess and MRS showing amino acid peak(0.9ppm) Tuberculoma - T1 hypointense T2 hyperintense well defined smooth hypointense wall ,with central diffusion restriction and peripheral ring abscess and MRS showing lipid lactate peak ( 1.9ppm) Toxoplasmosis – eccentric Target sign On post contrast images , concentric Tatget appearance in T2 weighted images ,multiple abscess in varing stages With no central diffusion restriction .Predominantly in basal ganglia location Primary CNS lymphoma - typically T2 hypointense and shows increased choline peak and decreased NAA levels , however in immunocompromised patient it may show peripheral ring enhancement which will require MRS to differentiate
References
Tempkin AD, Sobonya RE, Seeger JF, Oh ES. Cerebral aspergillosis: radiologic and pathologic findings. Radiographics : a review publication of the Radiological Society of North America, Inc. 26 (4): 1239-42. doi:10.1148/rg.264055152 - Pubmed 2. Almutairi BM, Nguyen TB, Jansen GH, Asseri AH. Invasive aspergillosis of the brain: radiologic-pathologic correlation. Radiographics : a review publication of the Radiological Society of North America, Inc. 29 (2): 375-9. doi:10.1148/rg.292075143 - Pubmed
Findings
Evidence of multiple T2 mixed intense lesions noted in right frontal region with surrounding perilesional edema and involving midbody of corpus callosum as well .The The lesion shows peripheral enhancement with crenated margins The lesion shows mass effect over the right lateral ventricle and midline shift to left of 8mm. Similar few smaller lesions also noted in left perisylvian and occipital region. MR spectroscopy shows large lipid lactate peak. ASL PERFUSION revealed no significantly increased cerebral blood flow
Discussion
CNS aspergillosis results from angioinvasive infection of the central nervous system by the fungus Aspergillus spp. Along with CNS cryptococcosis, it is one of the most common fungal opportunistic infections of the central nervous system.The disease predominates in immunocompromised individuals, such as those with: AIDS prolonged high-dose corticosteroid use neutropenia graft-vs-host disease after allogenic bone marrow transplantation There are two mechanisms of spread of Aspergillus spp to the CNS . Firstly, as per the pathogenesis of angioinvasive aspergillosis, spores of a variety of Aspergillus spp, most commonly Aspergillus fumigatus, are inhaled and proliferate in the alveoli, where the hyphae invade pulmonary arteries and gain access to the systemic circulation in 25-50% of cases . Once in the systemic circulation, spores can hematogenously spread to the CNS Aspergillosis can also directly spread to the CNS via the paranasal sinuses, where it may manifest as invasive fungal rhinosinusitis . Once in the CNS, the Aspergillus hyphae invade the walls of both small and large blood vessels . This either results in initial thrombosis leading to infarction, often followed by hemorrhage (in 25%), or development of mycotic aneurysms which can hemorrhage This hemorrhage may lead to further parenchymal seeding of Aspergillus, resulting in infectious cerebritis and eventual brain abscess formation, often multiple in nature. CT findings can be often non-specific but in keeping with at least one of the main three aforementioned findings that are characteristic of CNS aspergillosis 1-2. Detecting multiple such lesions in an immunosuppressed patient should prompt further investigation with MRI. Abscesses (and prior regions of cerebritis) are often multiple, present in a random distribution, and appear radiologically identical to other brain abscesses as classic ring-enhancing lesions with striking high signal intensity on DWI 1-3,5. However, Aspergillus abscesses may also have peripheral low signal intensity on T2-weighted images 2. This is better appreciated on GRE or SWI images, and is likely due to hemorrhage around the abscess Pyogenic abscess - T1 hypointense T2 hyperintense well defined smooth hypointense wall ,with central diffusion restriction and peripheral ring abscess and MRS showing amino acid peak(0.9ppm) Tuberculoma - T1 hypointense T2 hyperintense well defined smooth hypointense wall ,with central diffusion restriction and peripheral ring abscess and MRS showing lipid lactate peak ( 1.9ppm) Toxoplasmosis – eccentric Target sign On post contrast images , concentric Tatget appearance in T2 weighted images ,multiple abscess in varing stages With no central diffusion restriction .Predominantly in basal ganglia location Primary CNS lymphoma - typically T2 hypointense and shows increased choline peak and decreased NAA levels , however in immunocompromised patient it may show peripheral ring enhancement which will require MRS to differentiate
References
Tempkin AD, Sobonya RE, Seeger JF, Oh ES. Cerebral aspergillosis: radiologic and pathologic findings. Radiographics : a review publication of the Radiological Society of North America, Inc. 26 (4): 1239-42. doi:10.1148/rg.264055152 - Pubmed 2. Almutairi BM, Nguyen TB, Jansen GH, Asseri AH. Invasive aspergillosis of the brain: radiologic-pathologic correlation. Radiographics : a review publication of the Radiological Society of North America, Inc. 29 (2): 375-9. doi:10.1148/rg.292075143 - Pubmed
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!