MRI of intracranial toxoplasmosis after bone marrow transplantation

Toxoplasma Encephalitis following Tandem Autologous Hematopoietic Stem Cell Transplantation: A Case Report and Review of the Literature

Infection with Toxoplasma gondii is a rare but often fatal complication in hematopoietic stem cell transplantation (HSCT) recipients. Most cases have been reported in allogeneic (allo-) HSCT recipients, with only narrative reports following autologous HSCT (ASCT). We report the case of a 58-year-old Caucasian male presenting with toxoplasma encephalitis following tandem ASCT for myeloma and successfully treated with diagnosis by polymerase chain reaction analysis of cerebrospinal fluid. He was treated with sulfadiazine and pyrimethamine (with leucovorin) followed by pyrimethamine and atovaquone as secondary prophylaxis while receiving subsequent therapy for progressive multiple myeloma. Toxoplasmosis is a potential complication in allo-HSCT as well as ASCT recipients and should be considered in any post-HSCT patient with neurological dysfunction. Rapid diagnosis and immediate antimicrobial treatment are essential to avoid morbidity and mortality.

Intracranial Toxoplasma gondii granuloma in a cat

An 8-year-old cat with recent-onset generalized seizures was diagnosed with a right forebrain mass using magnetic resonance imaging. The mass was excised and upon histologic and immunohistochemical examination shown to be a Toxoplasma gondii granuloma. Serology supported active T gondii infection. The cat was treated with phenobarbital to control seizures. After definitive diagnosis of toxoplasma granuloma, clindamycin was administered for approximately 1 month. Seizures recurred 8 months after initial presentation, and the cat was euthanased at the owner's request. This is a previously unreported manifestation of feline central nervous system toxoplasmosis. When a mass lesion is present in the brain of a cat and serologic test results support active infection with T gondii, toxoplasma granuloma must be a differential diagnosis. If the patient is suffering from clinical disease, surgical resection of the mass (if possible) can be complimented with medical treatment until definitive diagnosis is obtained. Immunocompromising factors should be identified and addressed if possible.

T1-Hypersignal Foci in Cerebral Toxoplasmosis after Stem Cell Transplantation

We present here the unique image of toxoplasma encephalitis in a transplant recipient, characterized by the finding of T1-hypersignal foci. It is emphasized that cerebral toxoplasmosis after stem cell transplantation may show a high signal on T1-weighted images even without any hemorrhagic or calcified lesions.

Parasites

Parasites are an important cause of human disease worldwide. The clinical severity and outcome of parasitic disease is often dependent on the immune status of the host. Specific parasitic diseases discussed in this chapter are amebiasis, giardiasis, cryptosporidiosis, cyclosporiasis, cystoisosporiasis, microsporidosis, granulomatous amebic encephalitis, toxoplasmosis, leishmaniasis, Chagas disease, malaria, babesiosis, strongyloidiasis, and scabies.

Central nervous system infections in cancer patients and hematopoietic stem cell transplant recipients

Central nervous system (CNS) infections in cancer patients present a diagnostic and therapeutic challenge for clinicians. While CNS infections are not frequent complications of cancer, its therapies, or hematopoietic stem cell transplantation, the importance of CNS infections lies in their propensity to result in profound morbidity and substantial mortality in this vulnerable patient population. With an expanding population of patients with malignant disease undergoing more potent and aggressive therapies and with the advent of newer immunomodulatory agents, the incidence of CNS infectious complications is likely to rise. This chapter will summarize the clinical and diagnostic evaluation of potential infections of the CNS in these patients and will discuss particular pathogens of interest with regard to this at-risk patient population.

[Case of toxoplasma encephalopathy with specific MRI findings, diagnosed by IgG avidity index and nested PCR]

We report a 60-year-old woman with toxoplasma encephalopathy. She was being treated with prednisolone and methotrexate for rheumatoid arthritis that was diagnosed at the age of 40. In a preoperative examination of her left fifth finger ganglion, pericardial effusions, cardiomegaly, and a right atrial mass were detected. In addition, brain MRI showed nodular shadows in the right thalamus, bilateral globus pallidus, and left dentate nucleus of the cerebellum. T1 and T2 weighted images showed high intensities within those shadows; however, a T1 gadolinium enhancement image showed no contrast enhancement in the lesions. There were no positive neurological findings. Examination of the cerebrospinal fluid and cultivation tests showed nothing particular. The right atrial mass was subsequently diagnosed as malignant lymphoma and treated with radiation therapy. Toxoplasma gondii antibody titers were increased in both serum and cerebrospinal fluid. Based on IgG avidity index and nested PCR, we diagnosed toxoplasma encephalopathy with chronic T. gondii infection. The T. gondii gene product was also detected in cerebrospinal fluid by nested PCR. We consider that IgG avidity index and nested PCR were useful for the diagnosis of toxoplasma encephalopathy.

The importance of toxoplasma gondii infection in diseases presenting with headaches. Headaches and aseptic meningitis may be manifestations of the Jarisch-Herxheimer reaction

Worldwide, approximately 2 billion people are chronically infected with T. gondii with largely unknown consequences. This review presents clinical symptoms, differential diagnosis, triggering factors, treatment, and pathomechanisms responsible for idiopathic intracranial hypertension, pseudotumor cerebri, and aseptic meningitis. Literature cited in this work illustrates that immune state and other biologic mediator imbalances due to various endogenous and exogenous triggering factors may markedly affect latent central nervous system T. gondii infection/inflammation intensity, and cause reactivation of cerebral toxoplasmosis (CT). Irregularities in pro- and anti-inflammatory processes may markedly disturb the host and/or T. gondii defense mechanisms important for immune control of the parasite thereby manifesting as a wide range of neurologic symptoms and signs observed in some patients with migraine, epilepsy, celiac disease, Henoch-Schönlein purpura, and other brain disorders. This is consistent with reactivation of CT in mice after treatment with dexamethasone associated with depression of type T(H)1 immune response, and development of CT after administration of etanercept or other bioproducts. It seems that various types of headaches, epilepsy, aseptic meningitis, systemic adverse reactions to drugs or other substances represent the Jarisch-Herxheimer reaction due to apoptosis of T. gondii tachyzoites. Also development of some brain tumors, such as ependymoma and glioma may be associated with a chronic course of CT. Thus, all these patients should be tested for T. gondii infection.

Detection of toxoplasmic lesions in mouse brain by USPIO-enhanced magnetic resonance imaging

The objective of this study was to examine the feasibility of detecting toxoplasmic brain lesions in a mouse model of cerebral toxoplasmosis by ultrasmall superparamagnetic particles of iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI). Toxoplasmosis encephalitis was induced in Kunming mice by intracerebral injection of Toxoplasma gondii tachyzoites. T2- and T2*--weighted MRI was performed 1, 3, 4, 5 and 6 days after infection before USPIO injection; immediately after USPIO injection; and 24 h later. A comparison of USPIO enhancement and Gd-DTPA enhancement was made in three toxoplasmic mice 4 days after infection. Hematoxylin and eosin staining and Prussian blue staining were performed to detect inflammatory reactions and presence of iron in and around the toxoplasmic brain lesions. Nonenhanced T2-/T2*-weighted imaging detected few abnormalities in the brain up to 5 days. Most mice developed prominent hydrocephalus at 6 days. Gd-DTPA-enhanced imaging showed prominent enhancement of the cerebral ventricles but revealed only few space-occupying lesions in the parenchyma. USPIO-enhanced T2*-weighted imaging showed improved detection of toxoplasmic brain lesions that were invisible to nonenhanced T2-/T2*-weighted imaging and gadolinium-enhanced imaging. Most of the enhancing lesions showed nodular enhancement immediately after USPIO injection, some of which changed appearance 24 h later, having a ring enhancement at the outer rim. It can be concluded that USPIO enhancement of the toxoplasmic lesions may reflect blood-brain barrier impairment and/or inflammatory reactions associated with these lesions. USPIO-enhanced imaging may be used in combination with gadolinium-enhanced imaging to provide better characterization of toxoplasmic brain lesions and, potentially, improve the differential diagnosis of toxoplasmosis encephalitis.

Neuroimaging and neurologic complications after organ transplantation

Neurologic complications are common after transplantation and affect 30-60% of transplant recipients. The etiology of most of the posttransplant neurologic disorders is related to the opportunistic infections, both systemic and involving central nervous system (CNS), toxicity of immunosuppressive medications, and the metabolic insult created by the underlying primary disease and the transplant procedure. Neuroimaging studies are one of the key tools in the evaluation and enable early diagnosis of neurologic complications in transplant patients, especially posterior reversible leukoencephalopathy syndrome, central pontine myelinolysis, intracerebral hemorrhage, and fungal and bacterial abscesses. Magnetic resonance imaging (MRI) is the preferred technique, but each of the available neuroimaging techniques offers a unique insight into the pathophysiologic mechanisms underlying neurologic complications of transplantation. The role of neuroimaging in this population includes early detection of calcineurin inhibitor neurotoxicity, opportunistic infections, neoplasia, metabolic disorders, or cerebrovascular diseases. In addition, we can monitor longitudinal progression of disease and treatment response.

Disseminated toxoplasmosis resulting in graft failure in a cord blood stem cell transplant recipient

Toxoplasmosis is an infrequent infection with a high mortality rate in hematopoietic stem cell transplant recipients, and is usually caused by reactivation of prior, latent infection upon intensive immunosuppression. We report a case of fatal disseminated toxoplasmosis, diagnosed at autopsy, in a 7-year-old boy who received a cord blood graft for recurrent acute lymphoblastic leukemia. This case represents both the first reported case of toxoplasmosis in an engrafted cord blood recipient, and also of graft failure due to toxoplasmosis. Recommendations for toxoplasmosis diagnosis, treatment, and prophylaxis in stem cell transplant recipients are reviewed.

Toxoplasma meningoencephalitis in HIV-seronegative patients: clinical patterns, imaging features and treatment outcome

We evaluated the clinical and imaging features of cranial toxoplasmosis in patients without HIV infection. Between 1995 and 2005, 15 patients with serologically proven cranial toxoplasmosis were selected for clinical and imaging study from 233 patients with chronic meningitis and 364 patients with seizures/psychosis. All patients had poor immune status due to nutritional and metabolic causes. Neurological presentations included focal encephalitis, multifocal encephalitis and diffuse meningoencephalitis. The three groups had distinct symptoms and imaging features, with some overlap. Magnetic resonance imaging showed single or multiple nodular or ring-enhancing lesions often at the grey-white junction with subcortical white matter perifocal oedema. Within the large diffuse lesions there were discrete small haemorrhagic lesions and contrast medium administration showed fine-beaded parallel lines or small discrete nodules traversing the white matter suggesting perivenous spread. Complete clinical recovery was noted in 12 patients after several 6-week courses of pyrimethamine and sulfonamide/clindamycin. Five patients required two such courses, three patients required three courses, three patients required five courses and two patients required six courses for the final radiological healing, which was complete in nine patients. One patient was lost to follow-up and one patient died of cardiomyopathy. Knowledge of these three distinct initial presentations may help in the early diagnosis of cranial toxoplasmosis in HIV-seronegative patients. Prognosis in early cases is generally good but complete recovery may need several courses of treatment.

Results of magnetic resonance imaging in 14 cats with meningoencephalitis

Medical records and magnetic resonance (MR) images of 14 cats with inflammatory diseases affecting the central nervous system (CNS) were reviewed retrospectively. Cases included eight cats with feline infectious peritonitis and two cats with toxoplasmosis. Abnormalities affecting the CNS were observed in MR images in 10 (71%) cats. Intracranial lesions appeared as slightly hypointense foci in T1-weighted images in two (14%) cats, as hyperintense foci in T2-weighted images in seven (50%) cats and as hyperintense foci after intravenous administration of a gadolinium-based contrast medium in 10 (71%) cats. In six cats with lesions in T1- and/or T2-weighted images, additional lesions were visible in T1-weighted images obtained after gadolinium-based contrast medium administration. In three cats, lesions were visible only after contrast medium administration. In our study, MR imaging (MRI) did not appear to detect all cases of CNS inflammation in the population of cats with inflammatory cerebrospinal fluid (CSF); however, MRI adds information about the sites and morphology of intracranial lesions that should help to distinguish between neoplasia and inflammatory conditions and, possibly, between different inflammatory conditions.

AIDS-related cerebral toxoplasmosis with hyperintense foci on T1-weighted MR images: A case report

The neuroradiological findings are helpful for the diagnosis of toxoplasmic encephalitis. The T1 hypersignal intensity foci on brain magnetic resonance (MR) images without contrast enhancement are presented and can be a pathognomonic sign of this disease.

Imaging characteristics of toxoplasmosis encephalitis after bone marrow transplantation: report of two cases and review of the literature

Toxoplasmosis encephalitis is a severe, but often misdiagnosed complication in patients after bone marrow transplantation (BMT). We describe the unique computed tomography (CT) and magnetic resonance (MR) imaging features of cerebral toxoplasmosis in two bone marrow recipients and compare them to the cases in the literature. To our knowledge, this is the first report analyzing the appearance of cerebral toxoplasmosis on diffusion-weighted MR imaging (DWI).

Toxoplasmosis after renal transplantation: implications of a missed diagnosis

We describe a renal transplant patient with a primary Toxoplasma gondii infection presenting as pneumonitis, with subsequent chorioretinitis and encephalitis. The diagnostic challenges of T. gondii infection in immunocompromised patients are discussed.

Neuroimaging of infections

Neuroimaging plays a crucial role in the diagnosis and therapeutic decision making in infectious diseases of the nervous system. The review summarizes imaging findings and recent advances in the diagnosis of pyogenic brain abscess, ventriculitis, viral disease including exotic and emergent viruses, and opportunistic disease. For each condition, the ensuing therapeutic steps are presented. In cases of uncomplicated meningitis, cranial computed tomography (CT) appears to be sufficient for clinical management to exclude acute brain edema, hydrocephalus, and pathology of the base of skull. Magnetic resonance imaging (MRI) is superior in depicting complications like sub-/epidural empyema and vasculitic complications notably on FLAIR (fluid-attenuated inversion recovery)-weighted images. The newer technique of diffusion-weighted imaging (DWI) shows early parenchymal complications of meningitis earlier and with more clarity and is of help in differentiation of pyogenic abscess (PA) from ring enhancing lesions of other etiology. Proton magnetic resonance spectroscopy (PMRS) seems to produce specific peak patterns in cases of abscess. The presence of lactate cytosolic amino acids and absence of choline seems to indicate PA. Also in cases of suspected opportunistic infection due to toxoplasma DWI may be of help in the differentiation from lymphoma, showing no restriction of water diffusion. In patients with herpes simplex and more exotic viruses like West Nile and Murray Valley virus DWI allows earlier lesion detection and therapeutic intervention with virustatic drugs.

Parasitic central nervous system infections in immunocompromised hosts

Immunosuppression due to therapy after transplantation or associated with HIV infection increases susceptibility to various central nervous system (CNS) infections. This article discusses how immunosuppression modifies the presentation, diagnosis, and treatment of selected parasitic CNS infections, with a focus on toxoplasmosis, Chagas disease, neurocysticercosis, schistosomiasis, and strongyloidiasis.

Comparison of PCR-enzyme-linked immunosorbent assay and real-time PCR assay for diagnosis of an unusual case of cerebral toxoplasmosis in a stem cell transplant recipient

A PCR-enzyme-linked immunosorbent assay and a real-time PCR assay were compared for diagnosis and follow-up of cerebral toxoplasmosis in a stem cell transplant recipient. The sensitivity of detection was similar for both assays but was higher when the assays were performed on buffy coat rather than on whole blood or serum.

CT and MR imaging of central nervous system effects of therapy in patients treated for hematological malignancies

The purpose of this article is to present the imaging appearance of central nervous system effects of therapy that may occur in patients treated for hematological malignancies. Imaging in these patients relates to complications of high-dose therapy, bone marrow transplantation, infections occurring in immunocompromised patients, central nervous system dysfunction due to failure of other organ systems, or cerebral hemorrhages due to platelet refractoriness. Rapid and accurate diagnosis is essential but often difficult, as neurological manifestations are rarely disease specific. Neurological imaging, in combination with electrophysiological studies as well as blood and cerebrospinal fluid investigations, may be helpful for diagnosing most of these complications, as well as in differentiating between the manifestations of the underlying disease and complications of the treatment.

Cerebral toxoplasmosis after autologous peripheral blood stem cell transplantation

Toxoplasmosis appears to be a rare opportunistic protozoal infection following haematopoietic stem cell transplantation (HSCT). Most cases have been reported in allogeneic HSCT recipients, with only anecdotal reports of infection occurring after autologous transplantation. Reported here is the case of a patient who developed cerebral toxoplasmosis following autologous peripheral blood stem cell transplantation for non-Hodgkin's lymphoma.

Neurologic complications of bone marrow transplantation

The various forms of HSCT are or will soon be accepted treatments for an ever-increasing number of hematologic and solid cancers. Attempts to reduce the mortality and morbidity of HSCT and at the same time preserve or increase its efficacy in tumor control include development of nonmyeloablative allogeneic stem-cell transplant strategies [208] and allogeneic laboratory research-enhancing graft acceptance [209,210]. Eventually, these efforts will reduce complication rates of HSCT, including neurologic complications. In the interim, the consultant neuro-oncologist or neurologist with a specific inteest in this field is faced with complex clinical syndromes, neuroradiologic imaging studies and neurophysiologic tests, and generally poorly understood pathophysiologic mechanisms. Prospective studies of HSCT patients in large transplantation centers using clinical registries are needed.