Cerebral Toxoplasmosis in a Patient with AIDS on F-18 FDG PET/CT

The distinction between primary central nervous system (CNS) lymphoma and nonmalignant lesions due to opportunistic infections, in particular cerebral toxoplasmosis, is important because of the different treatments involved. A 32-year-old patient with AIDS was hospitalized for intermittent headaches. Brain magnetic resonance imaging (MRI) showed a small well-enhanced nodular lesion in the right frontal lobe. A fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET)/computed tomography (CT) scan showed moderate FDG uptake in the nodular lesion of the right frontal lobe. We present a case of cerebral toxoplasmosis in a patient with acquired immunodeficiency syndrome (AIDS) and the usefulness of F-18 FDG PET/CT in the differential diagnosis of the cerebral toxoplasmosis will be discussed.     

Ga-67 citrate myocardial uptake in a patient with AIDS, toxoplasmosis, and myocarditis

A 38-year-old man with AIDS presented with fever of unknown origin, splenomegaly, anemia, and thrombocytopenia. Admission laboratory data revealed a positive toxoplasmosis titer in the blood. The initial chest x-ray showed small bilateral pleural effusions, a normal cardiac silhouette, no infiltrates, and no interstitial edema. Ga-67 imaging revealed markedly abnormal uptake in the myocardium. A diagnosis of toxoplasmosis myocarditis was made based on laboratory and imaging data. The patient was treated for toxoplasmosis. No myocardial uptake of tracer was demonstrated on a follow-up Ga-67 scan, performed after completion of treatment for toxoplasmosis.     

Differentiation of toxoplasmosis and lymphoma in AIDS patients by using apparent diffusion coefficients

BACKGROUND AND PURPOSE: Distinguishing between toxoplasmosis and lymphoma brain lesions in AIDS patients is difficult but clinically relevant. This study was performed to test the hypothesis that diffusion-weighted (DW) imaging with apparent diffusion coefficient (ADC) maps can be used to distinguish these two lesions. METHODS: The ADC values were calculated in regions of interest placed in 13 brain toxoplasmosis lesions and eight brain lymphoma lesions in patients with AIDS. These values were compared with those of normal white matter. ADC ratios in lymphoma lesions then were compared with those in toxoplasmosis lesions by using a two-sample two-tailed t test. RESULTS: Toxoplasmosis lesions demonstrated significantly greater diffusion than that of lymphoma lesions (P =.004). ADC ratios were 1.63 +/- 0.41 (mean +/- standard deviation) in the 13 toxoplasmosis lesions and 1.14 +/- 0.25 in the eight lymphoma lesions. While considerable overlap was present for ADC ratios between 1.0 and 1.6, ADC ratios greater than 1.6 were associated solely with toxoplasmosis, accounting for seven of 13 toxoplasmosis lesions. CONCLUSION: ADC values are helpful in differentiating toxoplasmosis from lymphoma in patients with AIDS.     

Analysis of the utility of diffusion-weighted MRI and apparent diffusion coefficient values in distinguishing central nervous system toxoplasmosis from lymphoma

Introduction Toxoplasmosis and lymphoma are common lesions of the central nervous system in patients with AIDS. It is often difficult to distinguish between these lesions both clinically and radiographically. Previous research has demonstrated restricted diffusion within cerebral lymphomas and bacterial abscesses. However, little work has been done to evaluate the diffusion characteristics of toxoplasmosis lesions. This study was designed to explore further the utility of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps and values in making the distinction between toxoplasmosis and lymphoma.Methods The magnetic resonance imaging (MRI) studies of 36 patients, including 22 with toxoplasmosis (all of whom had AIDS) and 14 with lymphoma (8 of whom had AIDS), at two institutions were reviewed retrospectively. The characteristics of the lesions on DWI were evaluated, and the ADC ratios of the lesions were calculated and compared.Results There was significant overlap of the ADC ratios of toxoplasma and lymphoma, most notably in the intermediate (1.0–1.6) range. There was variability in ADC ratios even among different lesions in the same patient. In only a minority of the lymphoma patients were the ADC ratios low enough to suggest the correct diagnosis.Conclusion Our study showed that toxoplasmosis exhibits a wide spectrum of diffusion characteristics with ADC ratios which have significant overlap with those of lymphoma. Therefore, in the majority of patients, ADC ratios are not definitive in making the distinction between toxoplasmosis and lymphoma.     

Primary central nervous system lymphoma versus toxoplasmosis in AIDS

The imaging studies of 16 patients with acquired immunodeficiency syndrome (AIDS) and proved primary central nervous system (CNS) lymphoma were reviewed. All studies included computed tomography (CT); six also included magnetic resonance (MR) imaging. A periventricular lesion was seen in 50% of patients. At least one such lesion exhibited subependymal spread or ventricular encasement in 38%. One-third of lesions in three of five patients who underwent nonenhanced CT were hyperattenuating. Five lesions were at least in part hypointense on T2-weighted MR images. The specificity of these findings was evaluated with a similar review of the imaging studies in 28 patients with AIDS and proved toxoplasmosis. Only 3% of lesions were periventricular. None exhibited subependymal spread or encasement. None were hyperattenuating on nonenhanced CT scans. Similar findings in other CNS lesions in AIDS patients could not be found in the literature. A focal enhancing mass with subependymal spread on CT or MR images and hyperattenuation at nonenhanced CT were the most reliable features in distinguishing between primary CNS lymphoma and toxoplasmosis in AIDS patients.     

艾滋病弓形体虫脑炎的影像诊断价值分析

目的:评价艾滋病脑弓形体虫脑炎影像学表现的诊断价值。方法:回顾分析17例艾滋病脑弓形体虫脑炎的影像学表现。结果:病变多为双侧多发,可单发,侵犯基底核12例,丘脑3例,皮髓质连接区1例;累及小脑及脑干1例;CT呈低密度,MRI呈长T1长T2信号;周围水肿效应明显;增强扫描,小环状、螺旋状或靶形增强12例;巨大环形增强1例;多发病灶15例,单发2例。结论:位于基底节区的多发小环状、螺旋状或靶形增强,高度提示脑弓形体虫脑炎。CT和MRI对弓形体虫脑炎是有效的诊断方法。MRI对病灶检出率明显高于CT。     

Focal brain lesions on computed tomography in patients with acquired immune deficiency syndrome

Neurologic involvement is common in patients with acquired immune deficiency syndrome (AIDS). To assess the computed tomographic findings in AIDS, the authors reviewed 12 consecutive patients found to have focal brain lesions representing AIDS complications on computed tomography and having histologic or clinical proof of the diagnosis. Five patients had toxoplasmosis, six had lymphoma and one had both conditions sequentially. The finding of multiple lesions and mass effects with edema was more common with toxoplasmosis. In six patients who had toxoplasmosis 33 nodules were observed compared with only 8 in seven patients who had lymphoma. Disease extending linearly along the ventricular wall was typically seen in patients who had lymphoma.     

Atypical imaging appearance of toxoplasmosis in an HIV patient as a butterfly lesion

In acquired immunodeficiency syndrome (AIDS) patients, differentiating toxoplasmosis and primary central nervous system (CNS) lymphoma remains a clinical and radiographic dilemma. The presence of butterfly lesions crossing the corpus callosum is customarily used to exclude the possibility of toxoplasmosis. We present an AIDS patient who had Epstein‐Barr virus (EBV) polymerase chain reaction (PCR) ‐positive cerebrospinal fluid studies with a butterfly toxoplasmosis lesion confirmed by multiple methods signifying the importance of including toxoplasmosis in the differential diagnosis of butterfly lesions. J. Magn. Reson. Imaging 2009;30:873–875. © 2009 Wiley‐Liss, Inc.     

Neuropathological correlate of the “concentric target sign” in MRI of HIV‐associated cerebral toxoplasmosis

Cerebral toxoplasmosis is a frequent cause of focal brain lesions in the setting of immunodeficiency states, particularly acquired immune deficiency syndrome (AIDS), and magnetic resonance imaging (MRI) is an important diagnostic modality to differentiate toxoplasmosis from tuberculoma, and primary central nervous system lymphoma with diverse therapeutic implications. Several imaging patterns have been described in cerebral toxoplasmosis. The “concentric target sign” is a recently described MRI sign on T2‐weighted imaging of cerebral toxoplasmosis that has concentric alternating zones of hypo‐ and hyperintensities. It is believed to be more specific than the well‐known “eccentric target sign” in the diagnosis of cerebral toxoplasmosis and hence more useful in differentiation from other focal brain lesions in the context of AIDS. The concentric target sign, seen in deep parenchymal lesions, is distinct from the surface‐based cortical “eccentric” target sign. The histopathological correlate of the latter has been recently described, but that of the concentric target sign is not known. In this study we describe the neuropathological correlate of this concentric target sign from the postmortem of a 40‐year‐old man with AIDS‐associated cerebral toxoplasmosis. The concentric alternating zones of hypo/hyper/iso/intensities corresponded to zones of hemorrhage/fibrin‐rich necrosis with edema/coagulative compact necrosis/inflammation with foamy histiocytes admixed with hemorrhage forming the outermost zone, respectively. The exclusive specificity of this sign in cerebral toxoplasmosis remains to be further elucidated. J. Magn. Reson. Imaging 2013;38:488–495. © 2013 Wiley Periodicals, Inc.     

艾滋病颅内机遇性感染及肿瘤病变的CT诊断

目的:探讨HIV/AIDS相关性颅内感染及肿瘤病变的CT表现特点,提高颅内感染性及肿瘤病变的诊断水平。方法:回顾分析在博茨瓦纳玛丽娜公主医院临床及病理检验证实的26例AIDS患者的头颅CT表现。全部病例均有完整的CT资料。结果:①AIDS合并脑弓形虫感染6例,典型表现为颅内单发或多发结节影,边缘不规则,中央见坏死灶,增强扫描病灶明显强化,4例坏死灶不均匀轻度强化,周围见明显水肿带;②脑结核3例,表现为颅内多发散在低密度区及小结节灶,增强扫描2例病灶强化,1例表现为多发散在钙化点;③病毒性脑炎4例,两侧大脑多发片状低密度区,增强CT无明显强化,1例见沿脑回线样强化,轻度脑肿胀;④结核性脑膜炎2例,增强扫描见两侧大脑外侧裂池、桥脑环池明显异常强化;⑤脑脓肿7例,表现为颅内厚壁空洞形成,增强后壁明显强化,病灶周围水肿明显;⑥淋巴瘤4例,表现为颅内团块状影,平扫呈等或稍高密度,密度较均匀,增强后中度或明显强化,周围轻中度水肿。结论:CT检查是AIDS所致颅内机遇性感染最基本的影像学检查方法,能很好地显示病变的部位、形态以及病灶周围水肿情况。但在临床定性诊断时需要结合实验室检测和组织活检。     

Computed tomographic findings in cerebral toxoplasmosis in adults

The clinical and computerized tomographic (CT) findings in 10 patients with cerebral toxoplasmosis are reviewed. All patients with cerebral toxoplasmosis were homosexuals and/or intravenous drug users, and all patients had other manifestations of AIDS. Two presented with focal seizures, 4 presented with focal neurological deficit which progressively worsened, and 4 had evidence of diffuse neurological dysfunction (altered consciousness, generalized seizures). CT showed a single lesion in 3 patients and multiple lesions in 7 patients. Two patients had hypodense nonenhancing lesions(s). Eight patients had hypodense lesions with peripheral or nodular enhancement. The lesions were more commonly located in the cerebral hemispheres and subcortical gray matter nuclear masses (thalamus, basal ganglia). The finding of a hypodense lesion with a central slightly hyperdense noncalcified region that showed dense nodular homogeneous enhancement was quite characteristic of cerebral toxoplasmosis, but this pattern may also be seen in other neurological conditions including brain lymphomas.     

CNS complications of AIDS: CT and MR findings

AIDS is now a common disease, seen daily in large metropolitan medical centers. Neuroimaging techniques such as CT and MR are critical to the detection and diagnosis of CNS complications. Intracerebral infections are common. These infections frequently are caused by opportunistic organisms; less commonly, they are bacterial infections. The cranial imaging features on CT and MR are not pathognomonic, but their distribution or appearance (e.g., asymmetric target lesions of toxoplasmosis) may have predictive value in a known AIDS patient. The superior contrast resolution of MR makes it a more sensitive cross-sectional imaging tool for evaluating intracerebral abnormalities associated with a variety of infectious processes. Differential diagnoses still include metastatic disease, lymphoma, and infarcts. When MR is used as the initial cross-sectional imaging study, contrast-enhanced CT may still be necessary to further characterize a lesion. Currently, more experience exists with CT for follow-up of the AIDS patient with CNS manifestations. MR, particularly with gadolinium-DTPA as a contrast medium, will probably become the imaging method of choice.     

AIDS相关性脑病的18F-FDG PET/CT表现

目的:探讨18F-FDG PET/CT在AIDS相关性脑病中的应用价值.方法:对7例AIDS患者行PET/CT检查,并分析其影像学表现.结果:7例患者分别为弓形体病、弓形体病合并脑结核、胶质瘤、脑囊虫病、脑结核、进行性多灶性白质脑病和周皮细胞瘤.结论:18F-FDG PET/CT可以对AIDS颅内病变行定位、定量、定性...     

Acquired immunodeficiency syndrome: cerebral computed tomographic manifestations

CT examination of the central nervous system was performed in 19 patients with acquired immunodeficiency syndrome (AIDS). Eighteen patients were homosexuals, and five drug abusers. Parenchymal and meningeal inflammations were seen in patients with intracranial manifestations of the disease. The most common demonstrable lesion in the parenchyma was toxoplasmosis, which produced ring enhancement, solid enhancement, and nonenhancing focal edema. The most common meningeal inflammation was cryptococcosis, which was diagnosed by examination of the cerebrospinal fluid and did not show specific CT changes. It is concluded that toxoplasmosis and cryptococcosis should be the first diagnostic consideration in patients with neurologic findings who have a history of homosexuality and/or intravenous drug abuse and previous unusual infections or anergy. A delayed contrast scan, single or double dose, appears to be the most accurate method of outlining the total extent of disease thereby helping to locate the best biopsy site for pretreatment diagnosis. Empirical institution of toxoplasmosis therapy is recommended in those cases in which CT findings are consistent with toxoplasmosis and the biopsy shows only nonspecific encephalitis. A biopsy of every parenchymal lesion is not considered necessary.     

Neuroradiologic findings in AIDS: a review of 200 cases

The radiologic studies of 200 consecutive AIDS patients with neurologic symptoms were evaluated to determine their diagnostic specificity and prognostic value. Of 81 patients with initially normal CT scans, four (5%) later developed progressive neurologic illness. Of 75 patients with CT evidence of diffuse cerebral atrophy, 12 (16%) later developed CT abnormalities or had postmortem CNS disease. CT scans showed mass lesions initially in 44 patients and later in an additional seven patients. Although toxoplasma gondii infection was the most frequent cause of these lesions, the CT characteristics of cerebral toxoplasmosis are too nonspecific to warrant diagnosis without biopsy. Preliminary evidence suggests that MRI may be more sensitive than CT in detecting intracranial disease in patients with AIDS.     

Computed tomography aspects of cerebral toxoplasmosis in AIDS

We followed by CT 19 AIDS patients with cerebral toxoplasmosis. Diagnosis of cerebral toxoplasmosis was assessed on radiological and clinical basis, including the therapeutic response. CT allowed to confirm brain lesions (40 lesions in 19 patients) and to follow the evolution with treatment. Analysis of the CT features of these brain lesions permits to define some characteristic findings, though not pathognomonic. These lesions share common characteristics with other granulomatous diseases or with brain abscesses. The most frequently observed features are: target lesions (74%) with contrast enhancement (95%), frequently multiple (53%), associated with a hypodense area of oedema (100%), and responsible for a mass effect (79%). Under treatment, we observed improvement in 89%, resulting either in complete disappearance of the lesions (16%), disappearance of one or more contrast enhancing (46%) or hypodense (6%) areas, or volumetric regression of the hypodensities (50%). We conclude that CT is a good first-step examination for the detection and follow-up of cerebral toxoplasmosis in AIDS patients. MRI, a method with a higher sensitivity but still less accessible, may be considered at the present time as a second-step examination for those patients with solitary lesions on CT, or for symptomatic patients with normal CT.     

Eccentric target sign in cerebral toxoplasmosis: Neuropathological correlate to the imaging feature

Cerebral toxoplasmosis remains one of the most common focal brain lesions in patients with acquired immune deficiency syndrome (AIDS). Diagnosis is a challenge because on cranial imaging it closely mimics central nervous system lymphoma, primary and metastatic central nervous system (CNS) tumors, or other intracranial infections like tuberculoma or abscesses. A magnetic resonance imaging (MRI) feature on postcontrast T1‐weighted sequences considered pathognomonic of toxoplasmosis is the “eccentric target sign.” The pathological correlate of this imaging sign has been speculative. Herein we correlate the underlying histopathology to the MR feature of eccentric target sign in a patient with autopsy‐proven HIV/AIDS‐related cerebral toxoplasmosis. The central enhancing core of the target seen on MRI was produced by a leash of inflamed vessels extending down the length of the sulcus that was surrounded by concentric zones of necrosis and a wall composed of histiocytes and proliferating blood vessels, with impaired permeability producing the peripheral enhancing rim. J. Magn. Reson. Imaging 2010;31:1469–1472. © 2010 Wiley‐Liss, Inc.     

Pulmonary toxoplasmosis in AIDS.

The chest radiographs obtained in nine patients with acquired immunodeficiency syndrome (AIDS) and pulmonary toxoplasmosis were reviewed. In three patients, a bilateral, diffuse, fine to medium reticulonodular pattern indistinguishable from that seen in Pneumocystis carinii pneumonia (PCP) was observed. In six patients, however, a bilateral, predominantly coarse, nodular pattern was observed. This type of abnormality is unusual with PCP, and its presence may help in distinguishing between pulmonary infections caused by Toxoplasma gondii and P carinii. Other opportunistic pneumonias occurring in patients with AIDS, including tuberculosis, histoplasmosis, and coccidioidomycosis, might show similar coarse, nodular opacities on chest radiographs and thus may not be differentiated from pulmonary toxoplasmosis. No hilar or mediastinal adenopathy was observed. Two patients had pleural fluid. Radiologists familiar with the chest radiographic appearance of T gondii pneumonia could be first to suggest this unusual complication of AIDS.     

Primary cerebral lymphoma in acquired immunodeficiency syndrome (AIDS)--CT manifestations

Primary lymphoma of the brain in AIDS is being observed with increased frequency; five pathologically proven cases are presented. Although the CT patterns may correlate well with patterns previously described in lymphoma, occasionally an irregular ring-like lesion may occur which is difficult to distinguish from toxoplasmosis or other inflammatory processes without appropriate pathological material.     

Brain SPECT with 201-thallium in AIDS patients

Brain lymphoma is a late complication in AIDS. Lymphoma incidence is increasing in AIDS patients due to the introduction of HAART and prolongation of these patients' life expectancy. This work aims to evaluate the usefulness of brain SPECT with 201Tl in patients with AIDS who present focal brain lesions in computed tomography (CT).Methods: Seventeen patients with neurologic symptoms and focal neurologic lesions in the CNS (central nervous system) were studied. The images were interpreted as positive when the intensity of the focal deposit of the tracer was greater than that of the adjacent tissue. The SPECT results were compared with serologic data, clinical evolution and/or radiologic follow-up and cerebral biopsy.Results: SPECT images showed focal uptake of radiotracer in 3 patients. All three died shortly after the SPECT was performed. All of them had negative serology for toxoplasmosis. Four patients were diagnosed of progressive multifocal leukoencephalopathy and the ten remaining cases had a good clinical and/or radiologic response.Conclusions: Brain SPECT with 201Tl is a very useful non-invasive technique for the differential diagnosis of cerebral focal lesions in AIDS patients.