Limitations of diffusion-weighted imaging in distinguishing between a brain tumor and a central nervous system histoplasmoma

Brain tumour? - Cerebellar histoplasmosis as a solitary mass lesion

A 50-year-old man who had been living in Thailand presented with a history of falls, deteriorating vision and weight loss over several months. He had been admitted to a hospital in Thailand where he was given a diagnosis of multiple sclerosis. Neurological examination revealed a mild ataxic gait and lateral nystagmus, but no other abnormalities. He tested positive for human immunodeficiency virus with a CD4 cell count of 16 cells/µL. Brain magnetic resonance imaging was suggestive of an intrinsic neoplasm and he underwent stereotactic brain biopsy which showed numerous yeast-like organisms. Panfungal polymerase chain reaction was positive for Histoplasma capsulatum. He received liposomal amphotericin B for six weeks, followed by itraconazole, and started antiretroviral therapy four weeks into treatment. He developed an immune reconstitution inflammatory syndrome which responded well to steroids. Six months after diagnosis, he has no neurological symptoms or signs and remains on itraconazole. Isolated bulky central nervous system histoplasmomas are exceedingly rare. A clinical suspicion of immunosuppression was key in making this diagnosis.

Histoplasmosis with Deep CNS Involvement: Case Presentation with Discussion and Literature Review

Central nervous system (CNS) histoplasmosis is rare and difficult to diagnose because it is often overlooked or mistaken for other pathologies due to its nonspecific symptoms. A 32-year-old Hispanic man with advanced acquired immunodeficiency virus presented with altered mental status and reported confusion for the past 3 months. He had a Glasgow Coma Scale of 12, repetitive nonfluent speech, and a disconjugate gaze with a right gaze preference. Lung computed tomography (CT) findings indicated a pulmonary histoplasmosis infection. Magnetic resonance imaging of the brain revealed a ring-enhancing lesion in the left caudate nucleus. A CT-guided left retroperitoneal node biopsy was performed and indicated a benign inflammatory process with organisms compatible with fungal yeast. Treatment with amphotericin B followed by itraconazole was initiated in spite of negative cerebrospinal fluid (CSF) cultures and proved effective in mitigating associated CNS lesions and resolving neurologic deficits. The patient was discharged 3 weeks later in stable condition. Six weeks later, his left basal ganglia mass decreased. Early recognition of symptoms and proper steps is key in improving outcomes of CNS histoplasmosis. Aggressive medical management is possible in the treatment of intracranial deep mass lesions, and disseminated histoplasmosis with CNS involvement can be appropriately diagnosed and treated, despite negative CSF and serology studies.

Applicable apparent diffusion coefficient of an orthotopic mouse model of gastric cancer by improved clinical MRI diffusion weighted imaging

In vivo imaging studies in animal models are hindered by variables that contribute to poor image quality and measurement reliability. As such we sought to improve the diffusion coefficient (ADC) of an orthotopic mouse model of gastric cancer in diffusion-weighted images (DWI) using alginate moulding and Ultrasonic coupling medium. BGC-823 human gastric cancer cells were subcutaneously injected into the abdomen of nude mice and 1 mm(3) primary tumour was orthotopically transplanted. Alginate and coupling medium were applied to the mice and MRI (T2 and DWI) was performed for 6 weeks. Regions of interest (ROI) were drawn and liver and tumour ADC were evaluated. Using alginate moulding, the mean quality total score of DW imaging was 8.53; however, in control animals this value was 5.20 (p < 0.001). The coefficient of variation of ADC of liver in experimental and control groups were 0.071 and 0.270 (p < 0.001), respectively, suggesting this method may be helpful for DWI studies of important human diseases such as gastric cancer.

Fungal infection of a ventriculoperitoneal shunt: histoplasmosis diagnosis and treatment

BACKGROUND

Histoplasmosis is a fungal disease caused by Histoplasma capsulatum, commonly found in the Americas, and Histoplasma duboisii, located in Africa. In the United States, H. capsulatum is prevalent in the Ohio and Mississippi river valleys. In rare circumstances, central nervous system (CNS) histoplasmosis infection can be caused by shunt placement. We present a case report of a 45-year-old woman in whom CNS histoplasmosis developed after having a ventriculoperitoneal (VP) shunt placed for communicating hydrocephalus. A review of the literature on fungal infections after CNS shunt placement as well as treatment options for this subset of patients was undertaken.

METHODS

The PubMed database current to 1958 was filtered and limited to English-language articles. Fifty-eight articles were selected for review based on evidence of information regarding the fungal organism responsible for shunt infection, symptoms, treatment, and/or outcomes. Also included in this review is our case study.

RESULTS

A thorough analysis of the PubMed database revealed 58 reported cases of CNS shunt-related fungal infections in the English-language medical literature as well as 7 therapeutic agents used to treat patients in whom postshunt fungal infections developed.

CONCLUSIONS

We describe the steps in diagnosis of histoplasmosis after shunt placement, provide an effective therapeutic regimen, and review the present understanding of CNS fungal infections. The medical literature was surveyed to compare and analyze various CNS fungal infections that can arise from shunt placement as well as treatments rendered.

Diffusion imaging in brain infections

Diffusion-weighted magnetic resonance imaging (DWI) provides image contrasts that are different from conventional magnetic resonance techniques. DWI is particularly sensitive for detecting acute ischemic stroke, but it also has many other clinical applications, including the evaluation of central nervous system (CNS) infections. This article addresses the role of DWI in the differential diagnosis of CNS infections, and discusses the most common DWI findings for each type of infection.

Diffusion weighted imaging in small rodents using clinical MRI scanners

Diffusion weighted imaging (DWI) has emerged as a unique and powerful non-invasive magnetic resonance imaging (MRI) technique with a major potential impact on imaging-based diagnosis in a variety of clinical applications including oncology and tissue viability assessment. In light of increasing demand for applying this technique in preclinical investigations using small animals, we have explored the potentials of a clinical magnet for acquiring the DWI in rats and mice with either cerebral ischemia or solid tumors. Through technical adaptation and optimization, we have been able to perform a series of clinically relevant animal studies with conclusions based on DWI quantification. Focusing more on practical aspects and cross-referencing with the current literature, this paper is aimed to summarize our ongoing DWI studies on small rodents with stroke and tumors, and to provide protocols for researchers to replicate similar techniques in their own preclinical and clinical studies.