Brain toxoplasmosis: typical and atypical imaging features.

Transcription

1 Brain toxoplasmosis: typical and atypical imaging features. Poster No.: C-1661 Congress: ECR 2011 Type: Educational Exhibit Authors: N. G. Macías, A. D. Sotomayor, J. berenguer, M. T. PUJOL FARRE, M. Olondo, L. Oleaga ; Barcelona/ES, Barcelona, 3 4 Barcelona/ES, BARCELONA/ES, barcelona 08036/ES Keywords: AIDS, Infection, Education, MR-Spectroscopy, MR-Diffusion/ Perfusion, MR, Neuroradiology brain DOI: /ecr2011/C-1661 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 51

2 Learning objectives 1- To present a spectrum of imaging features in Central Nervous System toxoplasmosis. 2- To identify imaging findings to differentiate cerebral toxoplasmosis from other intracranial space occupying lesions. Background Toxoplasmosis is caused by an obligate intracellular protozoan, Toxoplasma gondii. Human beings can be infected with Toxoplasmosis by ingestion of oocyst excreted in the feces of infected cats and also by ingestion of undercooked or raw meat containing tissue cyst. Other ways of infections is through organ transplantation and congenital 1 transmission. After an acute infection, the latent form (bradyzoites) remains in the tissues, reactivating the disease when the immune mechanism is altered, as occur in human immunodeficiency virus (HIV) infection, organ transplantation, malignancies, collagen vascular disease, corticosteroids, chemotherapy and radiotherapy. 2 Toxoplasmosis 3 is described as the most common cause of brain focal lesion in HIV patients. In addition, it is the most common central nervous system infection following bone marrow 4 transplantation and peripheral stem cell transplantation. Diagnosis of cerebral toxoplasmosis is mostly based on 1) Clinical features, 2) Neuroimaging findings and characteristics, 3) Elevated antitoxoplasma antibody titers in cerebrospinal fluid, 4) Direct detection of the parasite by staining or quantitative polymerase chain reaction (PCR) from brain tissue, blood and cerebrospinal fluid, and 5) 5 Clinical and radiological improvement with specific antitoxoplasma treatment. Common 6 toxoplasmosis focal neurological findings are hemiparesis and speech abnormalities. Once encephalitis toxoplasmosis is suspected in at-risk patients, studies suggest 7 treatment should be started empirically awaiting confirmation of the diagnosis. Page 2 of 51

3 Without treatment, cerebral toxoplasmosis is usually progressive and fatal. For this reason, the early diagnosis and high index of suspicion of this entity is critical for an adequate patient management. Imaging findings OR Procedure details Radiological studies of cerebral toxoplasmosis in inmunocompromised patients show typical and atypical imaging findings, both in computed tomography (CT) and magnetic resonance imaging (MRI). Typical imaging features of cerebral toxoplasmosis Cerebral toxoplasmosis usually presents as multiple brain lesions commonly located in the basal ganglia and the corticomedullary junction. 8 In the detection of brain toxoplasmosis, MRI is considered a better diagnostic tool than CT. 9 8,3 Typical CT findings described in the literature are the following: Usually multiple hypodense lesions. Usually with surrounding edema and mass effect. Follow up CT: Complete resolution of lesions, residual lucencies or hyperdense calcifications. Thin, smooth rim or solid nodular enhancement. In patients with acquired immunodeficiency syndrome (AIDS), necrotizing encephalitis has been described caused by Toxoplasma. The histological features on page 28 reported three well-defined zones without capsule formation. The zones described are 1) an avascular necrotic center, surrounded by 2) an intermediate zone with remarkable inflammatory reaction and finally 3) a peripheral area where necrosis was rare and vascular lesion minimal. These areas correlate with the typical imaging features on CT previously described: the necrotic center is the hypodense area, the inflammatory surrounded area is the rim enhancement and the periferic zone is the edema. 10 Page 3 of 51

4 Fig.: 41-years-old woman with HIV infection. Basal CT images show hypodense areas in the left temporal lobe and in the right basal ganglia. A and B: axial images. C: coronal image. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 4 of 51

5 Fig.: Cerebral toxoplasmosis in 41-years-old woman with HIV infection. Contrast enhanced CT images show a temporal left lesion with rim nodular enhancement. Another lesion is perceived in the right basal ganglia with nodular enhancement. Both lesions are surrounded by hypodense areas corresponding to perilesional edema. A and B: axial images. C: sagital image. D and E: coronal images. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 5 of 51

6 Fig.: Histological images from toxoplasmic encephalitis. A: It shows the necrotic tissue generally found in the core of toxoplasmic brain lesion. C: In this figure, the inflammatory reaction that generally surrounds the necrotic tissue (shown in the figure A) can be observed. B: Cysts of Toxoplasma gondii. Usually its range in size is 5-50 µm in diameter. Cysts are usually spherical in the brain. D: Brain tissue with multiple cysts of Toxoplasma gondii. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN 8,3 Typical MR findings described in the literature are the following: T1-weighted imaging: Hypointense. T2-weighted imaging: Hyperintense lesions (hypo-isointense or mixed pattern also found). Diffusion-weighted imaging (DWI): Hyperintense on DWI. It is described that the core of a rim-enhancing toxoplasma abscess does not exhibit restricted 11 water diffusion. Gadolinium contrast material-enhanced T1-weighted imaging: Ringenhancing lesions, often with surrounding hypointensity (edema). Page 6 of 51

7 "Eccentric target sign" on page 32 in gadolinium contrast materialenhanced T1-weighted images. This sign is considered highly suggestive of cerebral toxoplasmosis, although present in less than 30 % of cases. 12 Fig.: Cerebral toxoplasmosis in 44-years-old man with HIV infection. MRI images. A: Axial T1-weighted image shows a hypointense area in the left basal ganglia associated with mass effect affecting the surrounded structures. B: Axial FLAIR image shows a hyperintense lesion in the left basal ganglia. Some areas are iso-hypointense, mainly in the center of the lesion. C and D: Axial and coronal gadolinium contrast material-enhanced T1-weighted images show a ring-enhancing lesion in the left basal ganglia. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 7 of 51

8 Fig.: Cerebral toxoplasmosis in 41-years-old woman with HIV infection. MRI images. A: Axial T1-weighted image shows a hypointense area in the left temporal lobe. B: Axial FLAIR image shows a mainly hyperintense area, with some areas being isohypointense, located in the left temporal lobe (in the same location of hypointense zone of the figure A). C: Axial gadolinium contrast material-enhanced T1-weighted image shows a ring-enhancing lesion in the left temporal lobe. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 8 of 51

9 Fig.: Cerebral toxoplasmosis in 41-years-old woman with HIV infection. MRI images. A: Axial T1-weighted image shows a hypointense area in the right basal ganglia associated with mass effect. B: Axial FLAIR image shows a hyperintense lesion in the right basal ganglia. C: Axial gadolinium contrast material-enhanced T1-weighted image shows a ring-enhancing lesion in the right basal ganglia. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 9 of 51

10 Fig.: Cerebral toxoplasmosis in-37-years old man. MRI image. Axial gadolinium contrast material-enhanced T1-weighted image shows a lesion located in the right parietal lobe presenting "eccentric target sign" enhancement. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Magnetic resonance spectroscopy pattern described in the bibliography for cerebral toxoplasmosis is: 13 Decreased N-acetylaspartate. Moderately decreased choline. Markedly increased lactate and lipid. on page 33 Absent myoinositol peak. Page 10 of 51

11 Fig.: Cerebral toxoplasmosis in 37-years old man. Magnetic resonance spectroscopy image. Notice the lactate and lipid are increased, as is described in cerebral toxoplasmosis. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Atypical imaging features of cerebral toxoplasmosis Patients with cerebral toxoplasmosis can present neuroimaging features that differ from the typical imaging findings described above. Some of these atypical presentations are: Hyperintensity of the basal ganglia and the cerebral cortex on page 34 on Fluid-Attenuated Inversion Recovery sequence (FLAIR) and T2-weighted images on MRI. On gadolinium contrast material-enhanced T1-weighted images, an enhancement of the basal ganglia on page 34 could be demonstrated. Page 11 of 51

12 Fig.: Toxoplasmic encephalitis in 46-years-old man with HIV infection. MRI images. A and B: Axial FLAIR and T2-weighted images show hyperintensity that affects both basal ganglia and cerebral cortex. C and D: Axial and coronal gadolinium contrast material-enhanced T1-weighted images show enhancement of basal ganglia and diffuse leptomeningeal enhancement. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN On gadolinium contrast material-enhanced T1-weighted images, a leptomeningeal or ependymal enhancement. This finding could lead to misdiagnosis with cerebral tuberculosis, central nervous system lymphoma 14 and even viral ependymitis (cytomegalovirus or varicela zoster). Page 12 of 51

13 Fig.: Cerebral toxoplasmosis in 48-years-old man with myelodysplastic syndrome. A and B: Coronal and axial gadolinium contrast material-enhanced T1-weighted images show a leptomeningeal enhancement in the left frontal lobe, surrounded by hypointense area corresponding to edema. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 13 of 51

14 Fig.: A: Cerebral toxoplasmosis in 33-years-old man with HIV infection. Axial gadolinium contrast material-enhanced T1-weighted image shows ependymal enhancement in the left frontal horn. In this image, an irregular rim enhancement in the left basal ganglia can be observed, surrounded by a hypointense area corresponding to edema. Notice the mass effect associated. B: Cerebral toxoplasmosis in 25 years-old woman with HIV infection. Axial gadolinium contrast material-enhanced T1-weighted image shows ependymal enhancement that affect both frontal horns. Notice the partial ring enhancement at the left thalamus and the significant enhancement surrounding the left occipital horn. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN In the presentation of cerebral toxoplasmosis an acute hemorrhage on page 37 in the lesion could be found, show as a hyperdensity area in CT images and hypointensity in gradient-echo T2*-weighted MRI. In patients with AIDS, this is generally observed after the initiation of antitoxoplasmos therapy, whereas in bone marrow transplantation it is commonly seen at the 15 initial stages of therapy. Page 14 of 51

15 Fig.: Cerebral toxoplasmosis in 48-years old man with myelodysplastic syndrome. MRI images A: Axial FLAIR image shows hyperintensity area with some iso-hypodense zones, mainly in the center of the lesion, located in the left frontal lobe. B: Axial gradient-echo T2*-weighted image shows hypointense areas in the left frontal lobe that correspond to hemorrhagic areas. C: Axial T1-weighted image shows hypointense area in the left frontal lobe corresponding to edema surrounding the hemorrhagic area. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN In non-enhanced T1-weighted MRI images, hyperintensity on page 38 can be found in the affected areas instead of hypo-isointensity as is typical. In the literature, it has been described hypersignal intensity foci at bilateral basal ganglia in the early weeks after treatment, confirming through CT the 16 absence of hemorrhage or calcifications. Page 15 of 51

16 Fig.: Cerebral toxoplasmosis in 25-years-old woman with HIV infection. MRI images. A and C: Non-enhanced T1-weighted MRI images show multiple hyperintense areas that affect mainly the brain cortex and the left cerebellar hemisphere. B and D: Axial gradient-echo T2*weighted images show no presence of intensity alterations that suggest hemorrhagic areas or calcifications. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Single lesions. Porter et al. reported the presence of solitary lesions detected by MRI in only 14 % of patients. A paucity of enhancement and a scarce presence of mass effect and edema 17 13, 15 are described in the literature as an atypical presentation. The most common differential diagnosis of cerebral toxoplasmosis in inmunocompromised patients is the central nervous system lymphoma. It can also be tuberculosis, bacterial or fungal abscesses and metastasis. An accurate radiological differential diagnosis in inmunocompromised patiens between brain toxoplasmosis and central nervous system lymphoma is still a challenging Page 16 of 51

17 task. Primary central nervous system lymphoma is typically a single or multicentric infiltrative lesion, larger than 30 mm in a periventricular distribution or found in the deep gray matter, posterior fosa or corpus callosum (butterfly like pattern), presenting less pronounced edema and mass effect in contrast to toxoplasmosis lesions. It is important to mention that additional studies have shown that the number of the lesions, their location, signal intensity and postcontrast images are not completely dependable to 21 define the final diagnosis in these cases. A number of studies report Thallium 201 brain SPECT could help distinguish these two entities, being suggestive of toxoplasmosis when negative uptake and possible central nervous system lymphoma diagnosis when 8 positive uptake. Some studies have demonstrated that ADC values are helpful in distinguishing toxoplasmosis from lymphoma. In the studies, Toxoplasmosis lesions showed significantly greater diffusion than that of lymphoma lesions and ADC greater 22 than 1.6 was associated with toxoplasmosis. Other studies report toxoplasmosis ADC ratios present a significant overlapping with those of lymphoma due to the wide 23 spectrum of diffusion characteristics of cerebral toxoplasmosis. In MRI perfusion imaging, toxoplasmosis usually present decreased perfusion (cerebral blood volume), in comparison with increased perfusion that appear in the central nervous system lymphoma, which could help to differentiate these entities. 24 Page 17 of 51

18 Fig.: Central nervous system lymphoma in 51 years-old man. MRI images. A: Axial FLAIR image shows a lesion located in the left caudate head with mixed pattern intensity. Notice it is surrounded by hyperintense area (edema) and the lesion presents mass effect. B: Axial gadolinium contrast material-enhanced T1weighted image shows enhancement of the lesion present in the figure A. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 18 of 51

19 Fig.: A,B and C: Central nervous system lymphoma in 56-year-old man. MRI images. A: Axial gadolinium contrast material-enhanced T1-weighted image shows a left frontal lesion with nodular enhancement. B: The lesion described in the figure A is hyperintense in the DWI image. C: ADC image shows restricted diffusion of the left frontal lesion described previously. D,E and F: Cerebral toxoplasmosis in 41-yearsold woman with HIV infection. D: Axial gadolinium contrast material-enhanced T1weighted image shows a lesion located in right basal ganglia with ring-enhancement. E: Notice the lesion described in the figure D presents hyperintensity in the DWI image. F: ADC image shows restricted diffusion of the lesion described in the figure D. Although diffusion images are considered useful to differentiate lymphoma from toxoplasmosis,there is a significant overlap between the two entities on imaging. Notice in these two cases, the DWI and ADC findings show similar features between lymphoma and toxoplasmosis, making difficult the differential diagnosis between these two entities. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 19 of 51

20 Fig.: A and B. Cerebral toxoplasmosis in 37-years-old man. MRI images. A: Axial gadolinium contrast material-enhanced T1-weighted image shows a lesion located in the right parietal lobe presenting "eccentric target sign" enhancement. B: MR perfusion image shows decreased perfusion of the lesion described in the figure A. C and D: Axial gadolinium contrast material-enhanced T1-weighted image shows a lesion located in the left frontal lobe with nodular enhancement. B: MR perfusion image shows increased perfusion of the lesion described in the image. C: Notice in some cases MR perfusion could be helpful in differentiating lymphoma from toxoplasmosis. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Typical radiological signs of central nervous system tuberculosis that help distinguish this entity from cerebral toxoplasmosis are: 1) multiloculated abscess, 2) cisternal enhancement, 3) infarction of the basal ganglia and 4) communicating hydrocephalus in inmunocompromised patients. 25 Page 20 of 51

21 Fig.: Cerebral tuberculosis in 36-years-old man. MRI images. Gadolinium contrast material-enhanced T1-weighted images show multiple lesions with nodular enhancement. A: axial B: coronal. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 21 of 51

22 Fig.: Cerebral tuberculosis in 46-years-old man. MRI images. Gadolinium contrast material-enhanced T1-weighted images show leptomeningeal enhancement, predominantly in the left hemisphere at the insular sulcus. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Pyogenic abscesses can present significant similarities with cerebral toxoplasmosis in the radiologic presentation. DWI has been described to be helpful in the differentiation of these entities because purulent abscess present markedly restricted water diffusion 26 while toxoplasmosis does not. Page 22 of 51

23 Fig.: Pyogenic abscess in 56 years-old man. A: Axial FLAIR image shows a left parietal hyperintense area. B, C and D: Axial, sagital and coronal gadolinium contrast material-enhanced T1-weighted image show a left parietal lesion with ring-enhancement. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 23 of 51

24 Fig.: Pyogenic abscess in 59-years-old man. A: Axial FLAIR images shows a left parietal lesion surrounded by hyperintense area (edema). B and C: Axial and coronal gadolinium contrast material-enhanced T1-weighted image show the lesion described previously with ring-enhancement. D and E: Notice the lesion shows hyperintense in the DWI image (D) and presents restricted diffusion in the ADC image (E). References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Page 24 of 51

25 Fig.: Pyogenic abscess by Nocardia in 49 years-old man. MRI images. A: Axial gadolinium contrast material-enhanced T1-weighted image shows a rim enhancing right parieto-occipital lesion. B: Axial non-enhanced T1 weighted image presents the lesion described previously hypointense. C: Axial FLAIR image shows the lesion described in A with a mixed pattern intensity surrounded by hyperintense area (edema). Notice the mass effect. D: Axial gadolinium contrast material-enhanced T1-weighted image shows a small ring-enhancing lesion located in the left temporal lobe. E: Axial gadolinium contrast materialenhanced T1-weighted image shows a small ring-enhancing lesion located in the right temporal lobe. F: Axial gadolinium contrast material-enhanced T1-weighted image shows leptomeningeal enhancement. Notice there are multiple lesions as is typically described in cerebral toxoplasmosis. References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Regarding fungal abscesses on page 47, cerebral aspergillosis in inmunocompromised patients could present multiple ring enhancing lesions, simulating cerebral toxplasmosis typical neuroimaging. In HIV patients, polymorphonuclear impairment is not typical, therefore invasive aspergillosis is relatively rare. Neutropenic 27 and under corticosteroids therapy patients are at major risk. Page 25 of 51

26 Fig.: Cerebral fungal abscess by Aspergillus in 27 years-old man patient. MRI images. A: Axial FLAIR image shows left frontal and parieto-occipital lesions, with mixed pattern intensity surrounded by hyperintense area. B: Axial gadolinium contrast materialenhanced T1-weighted image shows the lesion described in the figure A with ringenhancement. C and D: Notice the lesions described previously are hyperintense in the DWI image (C) and present restricted diffusion in ADC image (D). References: N. G. Macías; CDI, Clinic, Barcelona, SPAIN Cryptococcosis generally extends along the Virchow-Robin perivascular spaces, producing its dilatation without parenquima's brain involvement. Cryptococcoma is the only parenquimal form of this entity and it is produced by the direct invasion of the parenquima by the fungus, producing a granulomatous reaction. On CT, cryptococcomas are hypodense, presenting high signal on T2-weighted MRI, demonstrating ring like or nodular enhancement. By imaging alone, it cannot be distinguished from granulomas of other etiology. 8 Page 26 of 51

27 Cerebral toxoplasmosis could simulate primary brain tumors or metastasis due to its similar neuroimaging characteristics. For this reason, it is important to introduce these entities in the differential diagnosis. Images for this section: Fig. 1: 41-years-old woman with HIV infection. Basal CT images show hypodense areas in the left temporal lobe and in the right basal ganglia. A and B: axial images. C: coronal image. Page 27 of 51

28 Fig. 2: Cerebral toxoplasmosis in 41-years-old woman with HIV infection. Contrast enhanced CT images show a temporal left lesion with rim nodular enhancement. Another lesion is perceived in the right basal ganglia with nodular enhancement. Both lesions are surrounded by hypodense areas corresponding to perilesional edema. A and B: axial images. C: sagital image. D and E: coronal images. Page 28 of 51

29 Fig. 3: Histological images from toxoplasmic encephalitis. A: It shows the necrotic tissue generally found in the core of toxoplasmic brain lesion. C: In this figure, the inflammatory reaction that generally surrounds the necrotic tissue (shown in the figure A) can be observed. B: Cysts of Toxoplasma gondii. Usually its range in size is 5-50 µm in diameter. Cysts are usually spherical in the brain. D: Brain tissue with multiple cysts of Toxoplasma gondii. Page 29 of 51

30 Fig. 4: Cerebral toxoplasmosis in 44-years-old man with HIV infection. MRI images. A: Axial T1-weighted image shows a hypointense area in the left basal ganglia associated with mass effect affecting the surrounded structures. B: Axial FLAIR image shows a hyperintense lesion in the left basal ganglia. Some areas are iso-hypointense, mainly in the center of the lesion. C and D: Axial and coronal gadolinium contrast materialenhanced T1-weighted images show a ring-enhancing lesion in the left basal ganglia. Page 30 of 51

31 Fig. 5: Cerebral toxoplasmosis in 41-years-old woman with HIV infection. MRI images. A: Axial T1-weighted image shows a hypointense area in the left temporal lobe. B: Axial FLAIR image shows a mainly hyperintense area, with some areas being iso-hypointense, located in the left temporal lobe (in the same location of hypointense zone of the figure A). C: Axial gadolinium contrast material-enhanced T1-weighted image shows a ringenhancing lesion in the left temporal lobe. Page 31 of 51

32 Fig. 6: Cerebral toxoplasmosis in 41-years-old woman with HIV infection. MRI images. A: Axial T1-weighted image shows a hypointense area in the right basal ganglia associated with mass effect. B: Axial FLAIR image shows a hyperintense lesion in the right basal ganglia. C: Axial gadolinium contrast material-enhanced T1-weighted image shows a ring-enhancing lesion in the right basal ganglia. Page 32 of 51

33 Fig. 7: Cerebral toxoplasmosis in-37-years old man. MRI image. Axial gadolinium contrast material-enhanced T1-weighted image shows a lesion located in the right parietal lobe presenting "eccentric target sign" enhancement. Page 33 of 51

34 Fig. 8: Cerebral toxoplasmosis in 37-years old man. Magnetic resonance spectroscopy image. Notice the lactate and lipid are increased, as is described in cerebral toxoplasmosis. Page 34 of 51

35 Fig. 9: Toxoplasmic encephalitis in 46-years-old man with HIV infection. MRI images. A and B: Axial FLAIR and T2-weighted images show hyperintensity that affects both basal ganglia and cerebral cortex. C and D: Axial and coronal gadolinium contrast material-enhanced T1-weighted images show enhancement of basal ganglia and diffuse leptomeningeal enhancement. Page 35 of 51

36 Fig. 10: Cerebral toxoplasmosis in 48-years-old man with myelodysplastic syndrome. A and B: Coronal and axial gadolinium contrast material-enhanced T1-weighted images show a leptomeningeal enhancement in the left frontal lobe, surrounded by hypointense area corresponding to edema. Page 36 of 51

37 Fig. 11: A: Cerebral toxoplasmosis in 33-years-old man with HIV infection. Axial gadolinium contrast material-enhanced T1-weighted image shows ependymal enhancement in the left frontal horn. In this image, an irregular rim enhancement in the left basal ganglia can be observed, surrounded by a hypointense area corresponding to edema. Notice the mass effect associated. B: Cerebral toxoplasmosis in 25 yearsold woman with HIV infection. Axial gadolinium contrast material-enhanced T1-weighted image shows ependymal enhancement that affect both frontal horns. Notice the partial ring enhancement at the left thalamus and the significant enhancement surrounding the left occipital horn. Page 37 of 51

38 Fig. 12: Cerebral toxoplasmosis in 48-years old man with myelodysplastic syndrome. MRI images A: Axial FLAIR image shows hyperintensity area with some iso-hypodense zones, mainly in the center of the lesion, located in the left frontal lobe. B: Axial gradientecho T2*-weighted image shows hypointense areas in the left frontal lobe that correspond to hemorrhagic areas. C: Axial T1-weighted image shows hypointense area in the left frontal lobe corresponding to edema surrounding the hemorrhagic area. Page 38 of 51

39 Fig. 13: Cerebral toxoplasmosis in 25-years-old woman with HIV infection. MRI images. A and C: Non-enhanced T1-weighted MRI images show multiple hyperintense areas that affect mainly the brain cortex and the left cerebellar hemisphere. B and D: Axial gradientecho T2*-weighted images show no presence of intensity alterations that suggest hemorrhagic areas or calcifications. Page 39 of 51

40 Fig. 14: Central nervous system lymphoma in 51 years-old man. MRI images. A: Axial FLAIR image shows a lesion located in the left caudate head with mixed pattern intensity. Notice it is surrounded by hyperintense area (edema) and the lesion presents mass effect. B: Axial gadolinium contrast material-enhanced T1-weighted image shows enhancement of the lesion present in the figure A. Page 40 of 51

41 Fig. 15: A,B and C: Central nervous system lymphoma in 56-year-old man. MRI images. A: Axial gadolinium contrast material-enhanced T1-weighted image shows a left frontal lesion with nodular enhancement. B: The lesion described in the figure A is hyperintense in the DWI image. C: ADC image shows restricted diffusion of the left frontal lesion described previously. D,E and F: Cerebral toxoplasmosis in 41-years-old woman with HIV infection. D: Axial gadolinium contrast material-enhanced T1-weighted image shows a lesion located in right basal ganglia with ring-enhancement. E: Notice the lesion described in the figure D presents hyperintensity in the DWI image. F: ADC image shows restricted diffusion of the lesion described in the figure D. Although diffusion images are considered useful to differentiate lymphoma from toxoplasmosis,there is a significant overlap between the two entities on imaging. Notice in these two cases, the DWI and ADC findings show similar features between lymphoma and toxoplasmosis, making difficult the differential diagnosis between these two entities. Page 41 of 51

42 Fig. 16: A and B. Cerebral toxoplasmosis in 37-years-old man. MRI images. A: Axial gadolinium contrast material-enhanced T1-weighted image shows a lesion located in the right parietal lobe presenting "eccentric target sign" enhancement. B: MR perfusion image shows decreased perfusion of the lesion described in the figure A. C and D: Axial gadolinium contrast material-enhanced T1-weighted image shows a lesion located in the left frontal lobe with nodular enhancement. B: MR perfusion image shows increased perfusion of the lesion described in the image. C: Notice in some cases MR perfusion could be helpful in differentiating lymphoma from toxoplasmosis. Page 42 of 51

43 Fig. 17: Cerebral tuberculosis in 36-years-old man. MRI images. Gadolinium contrast material-enhanced T1-weighted images show multiple lesions with nodular enhancement. A: axial B: coronal. Page 43 of 51

44 Fig. 18: Cerebral tuberculosis in 46-years-old man. MRI images. Gadolinium contrast material-enhanced T1-weighted images show leptomeningeal enhancement, predominantly in the left hemisphere at the insular sulcus. Page 44 of 51

45 Fig. 19: Pyogenic abscess in 56 years-old man. A: Axial FLAIR image shows a left parietal hyperintense area. B, C and D: Axial, sagital and coronal gadolinium contrast material-enhanced T1-weighted image show a left parietal lesion with ring-enhancement. Page 45 of 51

46 Fig. 20: Pyogenic abscess in 59-years-old man. A: Axial FLAIR images shows a left parietal lesion surrounded by hyperintense area (edema). B and C: Axial and coronal gadolinium contrast material-enhanced T1-weighted image show the lesion described previously with ring-enhancement. D and E: Notice the lesion shows hyperintense in the DWI image (D) and presents restricted diffusion in the ADC image (E). Page 46 of 51

47 Fig. 21: Pyogenic abscess by Nocardia in 49 years-old man. MRI images. A: Axial gadolinium contrast material-enhanced T1-weighted image shows a rim enhancing right parieto-occipital lesion. B: Axial non-enhanced T1 weighted image presents the lesion described previously hypointense. C: Axial FLAIR image shows the lesion described in A with a mixed pattern intensity surrounded by hyperintense area (edema). Notice the mass effect. D: Axial gadolinium contrast material-enhanced T1-weighted image shows a small ring-enhancing lesion located in the left temporal lobe. E: Axial gadolinium contrast material-enhanced T1-weighted image shows a small ring-enhancing lesion located in the right temporal lobe. F: Axial gadolinium contrast material-enhanced T1weighted image shows leptomeningeal enhancement. Notice there are multiple lesions as is typically described in cerebral toxoplasmosis. Page 47 of 51

48 Fig. 22: Cerebral fungal abscess by Aspergillus in 27 years-old man patient. MRI images. A: Axial FLAIR image shows left frontal and parieto-occipital lesions, with mixed pattern intensity surrounded by hyperintense area. B: Axial gadolinium contrast materialenhanced T1-weighted image shows the lesion described in the figure A with ringenhancement. C and D: Notice the lesions described previously are hyperintense in the DWI image (C) and present restricted diffusion in ADC image (D). Page 48 of 51

49 Conclusion The knowledge of all possible brain toxoplasmosis presentations on MR in inmunocompromised patients is important in order to avoid misleading diagnosis, taking in consideration both the typical and atypical neuroimaging presentations of the disease. Personal Information References 1. Montoya JG, Liesenfeld O. Toxoplasmosis. Lancet Jun 12;363(9425): Post MJ, Chan JC, Hensley GT, et al. Toxoplasma encephalitis in Haitian adults with acquired immunodeficiency syndrome: a clinical-pathologic-ct correlation. AJR Am J Roentgenol May;140(5): Osborn AG, Blaser SI, Salzman KL, et al. Diagnostic imaging: brain. Salt Lake City, Utah: Amirsys, 2004; Cibickova L, Horacek J, Prasil P, et al. Cerebral toxoplasmosis in an allogeneic peripheral stem cell transplant recipient: case report and review of literature. Transpl Infect Dis Dec;9(4): Satishchandra P, Sinha S. Seizures in HIV-seropositive individuals: NIMHANS experience and review Epilepsia Aug;49 Suppl 6: Luft BJ, Hafner R, Korzun AH, et al. Toxoplasmic encephalitis in patients with the acquired immunodeficiency syndrome. N Engl J Med 1993; 329: Weenink JJ, Weenink AG, Geerlings SE, et al Severe cerebral toxoplasma infection cannot be excluded by a normal CT scan. Neth J Med Apr;67(4): Thurnher MM, Donovan Post MJ. Neuroimaging in the brain in HIV-1-infected patients. Neuroimaging Clin N Am Feb;18(1): Levy RM, Mills CM Posin JP, et al. The efficacy and clinical impact of brain imaging in neurologically symptomatic AIDS patients; a prospective CT/ MRI study. J Acquir Inmune Defic Syndr 1990;3:461. Page 49 of 51

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