MRI of CNS Fungal Infections: Review of Aspergillosis to Histoplasmosis and Everything in Between

Case 334: Cryptococcal Meningitis

HISTORY

A 30-year-old female patient who was 25 weeks pregnant presented to the emergency department with a 1-month history of mild headache and 2 weeks of progressive somnolence and photophobia accompanied by binocular horizontal diplopia and right gaze deviation. The patient also described new neck pain with passive head movements, without neck stiffness. Overall, the pregnancy was uncomplicated, with no high-risk features. Fever, chills, cough, shortness of breath, and abdominal or chest pain were denied. The patient had no history of rash, intravenous drug use, immunosuppressive medication use, or documented congenital abnormalities. She had not traveled recently, although she lived in Vancouver, British Columbia, Canada, 2 years prior to presentation. There was no recent or recurrent bacterial or viral illness. At clinical examination, the patient exhibited a decreased level of alertness and appeared tired. Vital signs were unremarkable, with a normal temperature (37.1 °C). Cranial nerve assessment revealed mild right abducens nerve palsy; neurologic examination was otherwise normal. Fundoscopic examination showed moderate grade 3 papilledema, left greater than right, with obscuration of some of the vessels leaving the disk. A CT scan of the head at admission was interpreted as normal. MRI of the brain performed 5 days later, due to persistent symptoms, revealed infratentorial and supratentorial imaging abnormalities. Lumbar puncture revealed high cerebral spinal fluid (CSF) opening pressure (32 cm H2O; upper limit of normal, 25 cm H2O). The CSF was clear, and analysis revealed an elevated total nucleated cell count (136 ×106/L; reference range, 0-5 ×106/L), with predominant lymphocytic moderate pleocytosis (100 ×106/L; reference range, 0-5 ×106/L) (59% lymphocytes) and normal glucose (3.3 mmol/L; reference range, 2.2-3.9 mmol/L) and normal total protein (0.27 g/L; reference range, 0.16-0.49 g/L) levels. Blood culture results for mycobacteria and anaerobic and aerobic microorganisms showed no growth. Findings from extensive additional diagnostic workup, including serologic testing for herpes simplex virus, varicella-zoster virus, enterovirus, Brucella, Coccidioides, Histoplasma, and mycobacteria, were negative. The HIV test result was negative, and the CD4 lymphocyte count and complement and immunoglobulin levels were within normal range. Autoimmune screening results were also negative.

MRI differentiation of CNS fungal infections: correlating imaging features with microbiological and histopathological findings

PURPOSE

The study aims to evaluate the magnetic resonance (MR) features of central nervous system (CNS) fungal infections and determine the associations between these findings and the type of fungus. Our main objective was to assess whether imaging can serve as a predictor for identifying the specific group of fungi responsible for the infection using microbiology and histopathology as a benchmark.

MATERIALS AND METHODS

A retrospective analysis was done on 50 patients with proven CNS fungal infections. Fungal type was determined and grouped according to microbial classifications into four subtypes: hyalohyphomycetes, mucorales, yeasts and dematiaceous molds. MR findings were compared with histopathology/microbiology and associations between fungal groups were sought.

RESULTS

A total of 37 males and 13 females with a mean age of 39.3 years were included in the study. Aspergillus spp. infection (48%) was the most common. Most patients (54%) had an underlying risk factor for the infection. Pseudo-tumoral mass-like behavior was observed with Aspergillus, and the presence of meningitis was associated with yeast infections (p < 0.001). Of the 19 abscesses, 9 (47.3%) showed a dual rim sign on susceptibility-weighted imaging (SWI), and 10 (52.6%) showed intracavitary dot-like foci of dropouts on SWI. Both findings were statistically significant with dematiaceous molds (p = 0.04 and p = 0.009, respectively).

CONCLUSION

Although radiological characteristics are non-specific and can overlap with each type of fungi, our study shows that certain MR features can help radiologists point towards the causative type. More specifically, dot-like foci of susceptibility point towards abscesses caused by dematiaceous molds possibly owing to melanin pigment and metal chelation properties.

Review of neuroimaging findings of intracranial angioinvasive fungal infections

With increasing use of broad-spectrum antibiotics, advances in organ and stem-cell transplant therapy, and the continued diabetes mellitus II epidemic, as well as other risk factors, reports of fungal infections of the CNS have been increasing. The most lethal subset is the angioinvasive fungal infection. Aspergillus fumigatus, Mucor, and Fusarium tend to affect immunocompromised individuals depending on their risk factors. Exserohilum rostratum and Cladophialaphora species tend to infect immunocompetent individuals. Early diagnosis and treatment are imperative for improved outcomes and reduced morbidity and mortality. Clinical presentation is often nonspecific, while neuroimaging can be helpful for accurate diagnosis. CT of the head and/or the maxillofacial structures is the primary imaging modality. Once the infection begins to proliferate, areas of vasogenic and cytotoxic edema, with regional mass effect and shift of the midline structures may be seen. These findings, however, are often nonspecific and may also be seen in underlying neoplasm, inflammatory processes, and other intracranial infections. Characteristic findings on T1, T2, diffusion-weighted imaging (DWI), and gradient echo sequences (GRE) may help to further narrow the differential diagnoses. We present a review of neuroimaging findings that will aid the neuroradiologist in distinguishing intracranial angioinvasive fungal infections and lead to improved patient outcomes.

Trends in Clinico-radiological and Laboratory Characteristics of All-Cause Meningoencephalitis in Western Rajasthan

BACKGROUND AND OBJECTIVES

Meningoencephalitis encompasses the coexistence of meningitis and encephalitis in different proportions. This study aimed to delineate the clinical profile, laboratory parameters, radiological features, and outcome predictors of patients with meningoencephalitis.

METHODS

This prospective, observational, and descriptive study was conducted from July 2021 to March 2023. Patients satisfying the case definition of "meningitis" and "encephalitis" were enrolled. Mortality and morbidity (by modified Rankin Score [mRS]) were noted at discharge and at 1 and 3 months post-discharge.

RESULTS

Of 102 patients recruited, among infectious meningoencephalitis cases, 28 (27.5%) were viral, 11 (10.8%) were pyogenic, 32 (31.4%) were tubercular, four (3.9%) each were rickettsial, atypical bacterial, and fungal, and three (2.9%) were parasitic. Among noninfectious etiologies, 12 (11.8%) were antineuronal antibody mediated, three (2.9%) had systemic inflammatory etiology, and one (1%) had carcinomatous meningitis. Cerebrospinal fluid (CSF) analysis showed the highest protein content (336.82 ± 251.26 mg/dL) and cell count (476.73 ± 999.16/mm 3 ) in pyogenic followed by tubercular (200.29 ± 174.28/mm 3 ) meningoencephalitis. CSF glucose was lowest in tubercular group (38.30 ± 20.29 mg/dL). Imaging showed leptomeningeal enhancement predominantly in tubercular group (89.7%) and limbic involvement in viral etiology (38.5%). Overall mortality was highest in fungal and rickettsial groups (three out of four patients died at 1 month in each group). Pyogenic, atypical bacterial, and systemic inflammatory meningoencephalitis had maximum temporal improvement in mRS at 1 month, while tubercular, viral, and antineuronal antibody-mediated meningoencephalitis had decrease of at least 1 mRS at 3 months. Fever, altered sensorium, speech disturbances, neck stiffness, albumin, total leukocyte count, erythrocyte sedimentation rate, C-reactive protein, kidney and liver function tests showed significant association with mortality.

CONCLUSIONS

Tubercular, followed by viral meningoencephalitis, was the most common cause in our center in western India. Pyogenic, atypical bacterial, and systemic inflammatory groups had the best recovery at discharge, while fungal and rickettsial meningoencephalitis groups had worst mRS at 3 months.

Cerebritis, optic ischemia, and cavernous sinus thrombosis arising from sinonasal mucormycosis

Brain and ocular infections can be the worst and fatal consequences of sinonasal infections in immunomodulated or immunocompromised patients. We report a case of a 35-year-old female who received an allogenic hematopoietic stem cell transplantation for acute myeloid leukemia, suffering from maxillo-spheno-ethmoidal rhinosinusitis which was complicated by cavernous sinus thrombosis, orbital cellulitis, optic ischemia and cerebritis.

Infectious Diseases of the Brain and Spine: Fungal Diseases

Advances in treatments of autoimmune diseases, acquired immunodeficiency syndrome, organ transplantation, and the use of long-term devices have increased the rates of atypical infections due to prolonged immune suppression. There is a significant overlap in imaging findings of various fungal infections affecting the central nervous system (CNS), often mimicking those seen in neoplastic and noninfectious inflammatory conditions. Nonetheless, there are imaging characteristics that can aid in distinguishing certain atypical infections. Hence, familiarity with a wide range of infectious agents is an important part of diagnostic neuroradiology. In this article, an in-depth review of fungal diseases of the CNS is provided.

Overview of the Current Knowledge and Conventional MRI Characteristics of Peri- and Para-Vascular Spaces

Brain spaces around (perivascular spaces) and alongside (paravascular or Virchow-Robin spaces) vessels have gained significant attention in recent years due to the advancements of in vivo imaging tools and to their crucial role in maintaining brain health, contributing to the anatomic foundation of the glymphatic system. In fact, it is widely accepted that peri- and para-vascular spaces function as waste clearance pathways for the brain for materials such as ß-amyloid by allowing exchange between cerebrospinal fluid and interstitial fluid. Visible brain spaces on magnetic resonance imaging are often a normal finding, but they have also been associated with a wide range of neurological and systemic conditions, suggesting their potential as early indicators of intracranial pressure and neurofluid imbalance. Nonetheless, several aspects of these spaces are still controversial. This article offers an overview of the current knowledge and magnetic resonance imaging characteristics of peri- and para-vascular spaces, which can help in daily clinical practice image description and interpretation. This paper is organized into different sections, including the microscopic anatomy of peri- and para-vascular spaces, their associations with pathological and physiological events, and their differential diagnosis.

Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation

A diverse spectrum of pathologically distinct, nonneoplastic, proliferative conditions of the kidneys and urinary tract demonstrate a expansile growth pattern similar to that of neoplasms. The renal pseudotumors include myriad causes of infections as well as rare noninfectious causes such as sarcoidosis, amyloidosis, and immunoglobulin G4-related disease (IgG4-RD). Rare entities such as cystitis cystica, endometriosis, nephrogenic adenoma, and pseudosarcomatous myofibroblastic proliferation and distinct types of prostatitis comprise tumefactive nontumorous disorders that affect specific segments of the urinary tract. The pseudotumors of the kidneys and urinary tract demonstrate characteristic histopathologic and epidemiologic features, as well as protean clinical manifestations, natural history, and imaging findings. Many patients present with genitourinary tract-specific symptoms or systemic disease. Some cases may be incidentally discovered at imaging. Some entities such as perinephric myxoid pseudotumors, IgG4-RD, fibroepithelial polyp, and nephrogenic adenoma display specific anatomic localization and disease distribution. Imaging features of multisystem disorders such as tuberculosis, sarcoidosis, and IgG4-RD provide supportive evidence that may allow precise diagnosis. Fungal pyelonephritis, xanthogranulomatous pyelonephritis, IgG4-RD, actinomycosis, and endometriosis show markedly low signal intensity on T2-weighted MR images. Although some pseudotumors exhibit characteristic imaging findings that permit correct diagnosis, laboratory correlation and histopathologic confirmation are required for definitive characterization in most cases. A high index of suspicion is a prerequisite for diagnosis. Accurate diagnosis is critical for instituting optimal management while preventing use of inappropriate therapies or interventions. Surveillance CT and MRI are frequently used for monitoring the response of pseudotumors to therapy. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Differential Diagnosis of Tumor-like Brain Lesions

Purpose of Review

Tumor-like brain lesions are rare and commonly suggest a neoplastic etiology. Failure to rapidly identify non-neoplastic causes can lead to increased morbidity and mortality. In this review, we describe 10 patients who presented with atypical, non-neoplastic tumor-like brain lesions in which brain biopsy was essential for a correct diagnosis and treatment.

Recent Findings

There has been increasing recognition of autoimmune conditions affecting the nervous system, and many of those diseases can cause tumor-like brain lesions. Currently available reports of non-neoplastic tumor-like brain lesions are scarce. Most case series focus on tumefactive demyelinating lesions, and a comprehensive review including other neuroimmunological conditions such as CNS vasculitis, neurosarcoidosis, histiocytic and infectious etiologies is lacking.

Summary

We review the literature on tumor-like brain lesions intending to increase the awareness and differential diagnosis of non-neoplastic brain tumor mimics. We advocate for earlier brain biopsies, which, in our case series, significantly changed diagnosis, management, and outcomes.

Construction of Candida albicans Adhesin-Exposed Synthetic Cells for Preventing Systemic Fungal Infection

The development of efficient fungal vaccines is urgent for preventing life-threatening systemic fungal infections. In this study, we prepared a synthetic, cell-based fungal vaccine for preventing systemic fungal infections using synthetic biology techniques. The synthetic cell EmEAP1 was constructed by transforming the Escherichia coli chassis using a de novo synthetic fragment encoding the protein mChEap1 that was composed of the E. coli OmpA peptide, the fluorescence protein mCherry, the Candida albicans adhesin Eap1, and the C-terminally transmembrane region. The EmEAP1 cells highly exposed the mChEap1 on the cell surface under IPTG induction. The fungal vaccine was then prepared by mixing the EmEAP1 cells with aluminum hydroxide gel and CpG. Fluorescence quantification revealed that the fungal vaccine was stable even after 112 days of storage. After immunization in mice, the vaccine resided in the lymph nodes, inducing the recruitment of CD11c+ dendritic cells. Moreover, the vaccine strongly activated the CD4+ T splenocytes and elicited high levels of anti-Eap1 IgG. By the prime-boost immunization, the vaccine prolonged the survival time of the mice infected by the C. albicans cells and attenuated fungal colonization together with inflammation in the kidneys. This study sheds light on the development of synthetic biology-based fungal vaccines for the prevention of life-threatening fungal infections.

ß-D-Glucan Assay in the Cerebrospinal Fluid for the Diagnosis of Non-cryptococcal Fungal Infection of the Central Nervous System: A Retrospective Multicentric Analysis and a Comprehensive Review of the Literature

BACKGROUND

Except for cryptococcosis, fungal infection of the central nervous system (FI-CNS) is a rare but severe complication. Clinical and radiological signs are non-specific, and the value of conventional mycological diagnosis is very low. This study aimed to assess the value of β1,3-D-glucan (BDG) detection in the cerebrospinal fluid (CSF) of non-neonatal non-cryptococcosis patients.

METHODS

Cases associated with BDG assay in the CSF performed in 3 French University Hospitals over 5 years were included. Clinical, radiological, and mycological results were used to classify the episodes as proven/highly probable, probable, excluded, and unclassified FI-CNS. Sensitivity and specificity were compared to that calculated from an exhaustive review of the literature.

RESULTS

In total, 228 episodes consisting of 4, 7, 177, and 40 proven/highly probable, probable, excluded, and unclassified FI-CNS, respectively, were analysed. The sensitivity of BDG assay in CSF to diagnose proven/highly probable/probable FI-CNS ranged from 72.7% [95% confidence interval {CI}: 43.4%‒90.2%] to 100% [95% CI: 51%‒100%] in our study and was 82% in the literature. For the first time, specificity could be calculated over a large panel of pertinent controls and was found at 81.8% [95% CI: 75.3%‒86.8%]. Bacterial neurologic infections were associated with several false positive results.

CONCLUSIONS

Despite its sub-optimal performance, BDG assay in the CSF should be added to the diagnostic armamentarium for FI-CNS.

[COVID-19: Neurological manifestations and complications during the acute phase of the disease]

The neurological manifestations and complications of the acute phase of COVID-19 are numerous. They mainly concern the central nervous system in the frequent forms of encephalopathy, encephalitis and neurovascular pathologies. Peripheral neurological manifestations mainly include acute polyneuropathies such as Guillain-Barré syndrome and intensive care neuromyopathies. Most of these manifestations were described during the first wave of the pandemic. The epidemiological, clinical, paraclinical, pathophysiological and therapeutic aspects are addressed in this general review of the literature published from 2020 to early 2023.

Imaging of Invasive Fungal Infections- The Role of PET/CT

Over the last decades, the population at risk for invasive fungal disease (IFD) has increased because of medical therapy advances and diseases compromising patients' immune systems. The high morbidity and mortality associated with invasive fungal disease in the immunocompromised present the challenge of early diagnosis of the IFD and the need to closely monitor the infection during treatment. The definitive diagnosis of invasive fungal disease based on culture or histopathological methods often has reduced diagnostic accuracy in the immunocompromised and may be very invasive. Less invasive and indirect evidence of the fungal infection by serology and imaging has been used for the early diagnosis of fungal infection before definitive results are available or when the definitive methods of diagnosis are suboptimal. Imaging in invasive fungal disease is a non-invasive biomarker that helps in the early diagnosis of invasive fungal disease but helps follow-up the infection during treatment. Different imaging modalities are used in the workup to evaluate fungal disease. The different imaging modalities have advantages and disadvantages at different sites in the body and may complement each other in the management of IFD. Positron emission tomography integrated with computed tomography with [18F]Fluorodeoxyglucose (FDG PET/CT) has helped manage IFD. The combined functional data from PET and anatomical data from the CT from almost the whole body allows noninvasive evaluation of IFD and provides a semiquantitative means of assessing therapy. FDG PET/CT adds value to anatomic-based only imaging modalities. The nonspecificity of FDG uptake has led to the evaluation of other tracers in the assessment of IFD. However, these are mainly still at the preclinical level and are yet to be translated to humans. FDG PET/CT remains the most widely evaluated radionuclide-based imaging modality in IFD management. The limitations of FDG PET/CT must be well understood, and more extensive prospective studies in uniform populations are needed to validate its role in the management of IFD that can be international guidelines.

Intracranial manifestations of rhinocerebral mucormycosis: a pictorial essay

Rhinocerebral mucormycosis has emerged as a common coinfection in coronavirus disease 2019 (COVID-19) patients during the convalescence period. Frequent spread of disease from sinonasal mucosa to bone, neck spaces, orbit, and brain occurs along the perivascular/perineural routes or through direct invasion. Brain involvement represents severe manifestation and is often associated with poor functional outcomes and high mortality rates. Magnetic resonance imaging (MRI) is the modality of choice for the intracranial assessment of disease severity in mucormycosis. Early and accurate identification of intracranial extension is imperative to improve survival rates. With this pictorial essay, we aim to familiarize the readers with the cross-sectional imaging features of intracranial complications of mucormycosis. The radiological details in this essay should serve as a broad checklist for radiologists and clinicians while dealing with this fulminant infection.

Differentiating central nervous system infection from disease infiltration in hematological malignancy

Hematological malignancies place individuals at risk of CNS involvement from their hematological disease and opportunistic intracranial infection secondary to disease-/treatment-associated immunosuppression. Differentiating CNS infection from hematological disease infiltration in these patients is valuable but often challenging. We sought to determine if statistical models might aid discrimination between these processes. Neuroradiology, clinical and laboratory data for patients with hematological malignancy at our institution between 2007 and 2017 were retrieved. MRI were deep-phenotyped across anatomical distribution, presence of pathological enhancement, diffusion restriction and hemorrhage and statistically modelled with Bayesian-directed probability networks and multivariate logistic regression. 109 patients were studied. Irrespective of a diagnosis of CNS infection or hematological disease, the commonest anatomical distributions of abnormality were multifocal-parenchymal (34.9%), focal-parenchymal (29.4%) and leptomeningeal (11.9%). Pathological enhancement was the most frequently observed abnormality (46.8%), followed by hemorrhage (22.9%) and restricted diffusion (19.3%). Logistic regression could differentiate CNS infection from hematological disease infiltration with an AUC of 0.85 where, with OR > 1 favoring CNS infection and < 1 favoring CNS hematological disease, significantly predictive imaging features were hemorrhage (OR 24.61, p = 0.02), pathological enhancement (OR 0.17, p = 0.04) and an extra-axial location (OR 0.06, p = 0.05). In conclusion, CNS infection and hematological disease are heterogeneous entities with overlapping radiological appearances but a multivariate interaction of MR imaging features may assist in distinguishing them.

Case report: MRI findings with CNS blastomycosis in three domestic cats

Blastomycosis is a systemic mycotic infection caused by dimorphic fungi. The disease is rare in cats, and reports on imaging findings with central nervous system (CNS) involvement are limited. Magnetic resonance imaging (MRI) was performed antemortem in three feline patients. Imaging findings that may allow prioritization of intracranial blastomycosis over other differential diagnoses included focal or multifocal intra-axial mass lesions with dural contact, lesion hypointensity on T2-weighted images and diffusion-weighted imaging/apparent diffusion coefficient map (DWI/ADC), strong and homogeneous contrast enhancement of the lesion(s), concurrent meningeal enhancement, marked perilesional edema and mass-effect, and ocular abnormalities. One cat was managed successfully and had a recurrence of CNS blastomycosis more than 4.5 years after the initial diagnosis. Repeat MRI at that point revealed both new and persistent (chronic) abnormalities.

Muerte cerebral debida a aspergilosis cerebral en un paciente de COVID-19

Las coinfecciones entre SARS-CoV-2 y otros patógenos son una cuestión importante para el tratamiento de los pacientes con COVID-19. Las infecciones por Aspergillus forman parte de esta consideración, ya que presentan elevada morbimortalidad. Presentamos el caso de un paciente con coinfección de COVID-19 y Aspergillus fumigatus que evolucionó a muerte cerebral debido a múltiples lesiones heterogéneas en el cerebro donde, tras biopsia post-mórtem, se encontraron lesiones patológicas compatibles con Aspergillus.

Systemic Aspergillosis: Radiological Findings in a Case With Diffuse Large B Cell Lymphoma Treated by Ibrutinib

Herein, we present a case of systemic aspergillosis with a fatal outcome in a case with diffuse large B cell lymphoma (DLBCL) treated by ibrutinib. Aspergillosis was suspected clinically and proven microbiologically. Radiological findings were compatible with aspergillosis. We aim to review radiological findings in a case with DLBCL treated with ibrutinib, which is an important tyrosine kinase inhibitor used in lymphoid neoplasias.

PET/MRI in paediatric disease

Nuclear medicine and molecular imaging have a small but growing role in the management of paediatric and neonatal diseases. During the past decade, combined PET/MRI has emerged as a clinically important hybrid imaging modality in paediatric medicine due to diagnostic advantages and reduced radiation exposure compared to alternative techniques. The applications for nuclear medicine, radiopharmaceuticals and combined PET/MRI in paediatric diagnosis is broadly similar to adults, however there are some key differences. There are a variety of clinical applications for PET/MRI imaging in children including, but not limited to, oncology, neurology, cardiovascular, infection and chronic inflammatory diseases, and in renal-urological disorders. In this article, we review the applications of PET/MRI in paediatric and neonatal imaging, its current role, advantages and disadvantages over other hybrid imaging techniques such as PET/CT, and its future applications. Overall, PET/MRI is a powerful imaging technology in diagnostic medicine and paediatric diseases. Higher soft tissue contrasts and lower radiation dose of the MRI makes it the superior technology compared to other conventional techniques such as PET/CT or scintigraphy. However, this relatively new hybrid imaging has also some limitations. MRI based attenuation correction remains a challenge and although methodologies have improved significantly in the last decades, most remain under development.

Approach to Neurologic Complications in the Immunocompromised Patient

Neurologic complications are common in immunocompromised patients, including those with advanced human immunodeficiency virus, transplant recipients, and patients on immunomodulatory medications. In addition to the standard differential diagnosis, specific pathogens and other conditions unique to the immunocompromised state should be considered in the evaluation of neurologic complaints in this patient population. A thorough understanding of these considerations is critical to the inpatient neurologist in contemporary practice, as increasing numbers of patients are exposed to immunomodulatory therapies. In this review, we provide a chief complaint-based approach to the clinical presentations and diagnosis of both infectious and noninfectious complications particular to immunocompromised patients.

Invasive sinus aspergillosis with mycotic aneurysm of the vertebral artery and subarachnoid hemorrhage - Case report

Invasive sinus aspergillosis is a rare life-threatening condition usually found in immunocompromised patients. The fungus spreads from paranasal sinuses into the central nervous system by direct extension or through blood vessels. Perineural spread is an uncommon mechanism of spread in invasive aspergillosis. A mycotic aneurysm is a dangerous complication of invasive sinus aspergillosis because of its insidious development and is often diagnosed only post-mortem after causing fatal intracranial hemorrhage. Intracranial vascular complications of invasive sinus aspergillosis require prompt recognition and treatment and should always be considered when a diagnosis of CNS aspergillosis is made. We present a case of invasive sinus aspergillosis in an apparently immunocompetent patient that manifested with a brain abscess, perineural spread of the infection, and mycotic aneurysm of the vertebral artery with subsequent rupture and fatal subarachnoid hemorrhage. This case highlights the possibility of perineural spread and hemorrhagic complications in invasive cerebral aspergillosis.

Central nervous system blastomycosis clinical characteristics and outcomes

Blastomycosis is a local or systemic infection, caused by Blastomyces dermatitidis (B. dermatitidis) or B. gilchristii. Blastomycosis has been described as "the great pretender," alluding to the fact that it manifests in a wide range of symptoms and disease severity. Central nervous system (CNS) involvement, although rare, carries significant mortality. Due to the limited published reports of CNS blastomycosis, we present an updated cohort with eight cases of proven or probable CNS blastomycosis describing presentation, diagnosis, treatment and outcomes. Headache was the most common presenting symptom. Magnetic resonance imaging (MRI) proved to be the superior imaging study. All patients in our cohort were diagnosed by histopathological staining or cultures of tissue or fluid obtained from CNS or extra-CNS lesions. All patients that received treatment with Liposomal amphrotericin B for at least 10 days followed by a prolonged azole therapy did not have relapse. Two patients with late diagnoses died during hospitalization. Our findings confirm the importance of timely diagnosis and treatment of CNS blastomycosis to improve outcomes especially with an azole that have a high CNS penetration and a good intrinsic activity for B. dermatitidis such as voriconazole.

Cerebral mucormycosis: neuroimaging findings and histopathological correlation

INTRODUCTION

Mucormycosis are infections caused by molds of the order Mucorales. These opportunistic infections are rare, difficult to diagnose, and have a poor prognosis. We aimed to describe common radiographic patterns that may help to diagnose cerebral mucormycosis and search for histopathological correlations with imaging data.

METHODS

We studied the radiological findings (CT and MRI) of 18 patients with cerebral mucormycosis and four patients' histopathological findings.

RESULTS

All patients were immunocompromised and/or diabetic. The type of lesions depended on the infection's dissemination pathway. Hematogenous dissemination lesions were most frequently abscesses (59 lesions), cortical, cortical-subcortical, or in the basal ganglia, with a halo aspect on DWI for lesions larger than 1.6 cm. Only seven lesions were enhanced after contrast injection, with different presentations depending on patients' immune status. Ischemia and hemorrhagic areas were also seen. Vascular lesions were represented by stenosis and thrombosis. Direct posterior extension lesions were bi-fronto basal hypodensities on CT and restricted diffusion without enhancement on MRI. A particular extension, perineural spread, was seen along the trigeminal nerve. Histopathological analysis found endovascular lesions with destruction of vessel walls by Mucorales, microbleeds around vessels, as well as acute and chronic inflammation.

CONCLUSIONS

MRI is the critical exam for cerebral mucormycosis. Weak ring enhancement and reduced halo diffusion suggest the diagnosis of fungal infections. Involvement of the frontal lobes should raise suspicion of mucormycosis (along with aspergillosis). The perineural spread can be considered a more specific extension pathway of mucormycosis.

Central nervous system infection: imaging findings suggestive of a fungus as the cause

Fungal infections of the central nervous system (CNS) are rare. However, because of the increase in the number of immunocompromised individuals, they have been gaining prominence in the differential diagnosis of CNS infections. Imaging techniques are sensitive for detecting and localizing an abnormality, in many cases allowing the origin of a lesion to be categorized as infectious, inflammatory, neoplastic, or vascular. This essay illustrates the magnetic resonance imaging and computed tomography findings of the most common fungal infections of the CNS, based on the experience of the Radiology Department of the Hospital de Clínicas de Porto Alegre, in the city of Porto Alegre, RS, Brazil.

Neuroimaging of CNS infection in haematological malignancy: important signs and common diagnostic pitfalls

Patients with haematological malignancy are at increased risk of developing central nervous system (CNS) infections, which are associated with significant morbidity and mortality. Neuroimaging plays a pivotal role in the diagnostic pathway of these patients; however, layers of complexity are added to image interpretation by the heterogeneity in imaging manifestations of haematological malignancies in the CNS, overlapping imaging features of CNS infection, treatment-related parenchymal changes and the presence of intracranial comorbidity. In this article, we review important intracranial findings of CNS infection cases accrued in 1,855 studies over more than a decade at a specialist tertiary centre. We offer schema to identify common and important neuroimaging features, discuss key differential diagnoses and frequent diagnostic pitfalls.

Johnson E, Littlechild J, Winlove CP, Vollmer F, Gow NAR. Biosensors and Diagnostics for Fungal Detection

Early detection is critical to the successful treatment of life-threatening infections caused by fungal pathogens, as late diagnosis of systemic infection almost always equates with a poor prognosis. The field of fungal diagnostics has some tests that are relatively simple, rapid to perform and are potentially suitable at the point of care. However, there are also more complex high-technology methodologies that offer new opportunities regarding the scale and precision of fungal diagnosis, but may be more limited in their portability and affordability. Future developments in this field are increasingly incorporating new technologies provided by the use of new format biosensors. This overview provides a critical review of current fungal diagnostics and the development of new biophysical technologies that are being applied for selective new sensitive fungal biosensors to augment traditional diagnostic methodologies.

MR Target Sign in Cerebral Aspergillosis

Magnetic resonance (MR) is an effective imaging modality in the evaluation of infectious brain disease, yet findings are often nonspecific. The presence of a diagnostic feature can facilitate early treatment, particularly where mortality is high. We highlight MR apparent diffusion coefficient/T2-weighted target sign in the diagnosis of cerebral aspergillosis.

Brain miliary enhancement

PURPOSE

Miliary enhancement refers to the presence of multiple small, monomorphic, enhancing foci on T1-weighted post-contrast MRI images. In the absence of a clear clinical presentation, a broad differential diagnosis may result in invasive procedures and possibly brain biopsy for diagnostic purposes.

METHODS

An extensive review of the literature is provided for diseases that may present with miliary enhancement on T1-weighted brain MR images. Additional disease-specific findings, both clinical and radiological, are summarized and categorized by the presence or absence of perivascular space involvement.

RESULTS

Miliary pattern of enhancement may be due to a variety of underlying causes, including inflammatory, infectious, nutritional or neoplastic processes. The recognition of disease spread along the perivascular spaces in addition to the detection or exclusion of disease-specific features on MRI images, such as leptomeningeal enhancement, presence of haemorrhagic lesions, spinal cord involvement and specific localisation or systemic involvement, allows to narrow the potential differential diagnoses.

CONCLUSION

A systematic approach to disease-specific findings from both clinical and radiological perspectives might facilitate diagnostic work-up, and recognition of disease spread along the perivascular spaces may help narrowing down differential diagnoses and may help to minimize the use of invasive diagnostic procedures.

A Case of Histoplasma duboisii Brain Abscess and Review of the Literature

Histoplasmosis is a fungal disease caused by Histoplasma capsulatum var. capsulatum (Hcc) and H. capsulatum var. duboisii (Hcd). Central nervous system (CNS) involvement is rare. So far, the few cases reported having Histoplasmosis associated brain abscesses were caused by H. capsulatum var. capsulatum. Herein, we report a unique case of brain abscess caused by H. capsulatum var. duboisii occurring in a 42-year-old immunocompromised woman with HIV. Initially, she presented with hypothermia, vomiting, frontal headache, evolving over one month. She then progressed to have a generalized seizure. Brain MRI showed multifocal brain abscesses and a frontal osteitis. The frontal osteitis was biopsied and confirmed the diagnosis of H. capsulatum var. duboisii. She was successfully treated with liposomal amphotericin B (150 mg daily) for the first four weeks and itraconazole (200mg twice daily) for six months.

Detection of the 'Big Five' mold killers of humans: Aspergillus, Fusarium, Lomentospora, Scedosporium and Mucormycetes

Fungi are an important but frequently overlooked cause of morbidity and mortality in humans. Life-threatening fungal infections mainly occur in immunocompromised patients, and are typically caused by environmental opportunists that take advantage of a weakened immune system. The filamentous fungus Aspergillus fumigatus is the most important and well-documented mold pathogen of humans, causing a number of complex respiratory diseases, including invasive pulmonary aspergillosis, an often fatal disease in patients with acute leukemia or in immunosuppressed bone marrow or solid organ transplant recipients. However, non-Aspergillus molds are increasingly reported as agents of disseminated diseases, with Fusarium, Scedosporium, Lomentospora and mucormycete species now firmly established as pathogens of immunosuppressed and immunocompetent individuals. Despite well-documented risk factors for invasive fungal diseases, and increased awareness of the risk factors for life-threatening infections, the number of deaths attributable to molds is likely to be severely underestimated driven, to a large extent, by the lack of readily accessible, cheap, and accurate tests that allow detection and differentiation of infecting species. Early diagnosis is critical to patient survival but, unlike Aspergillus diseases, where a number of CE-marked or FDA-approved biomarker tests are now available for clinical diagnosis, similar tests for fusariosis, scedosporiosis and mucormycosis remain experimental, with detection reliant on insensitive and slow culture of pathogens from invasive bronchoalveolar lavage fluid, tissue biopsy, or from blood. This review examines the ecology, epidemiology, and contemporary methods of detection of these mold pathogens, and the obstacles to diagnostic test development and translation of novel biomarkers to the clinical setting.

A consensus document for the clinical management of invasive fungal diseases in pediatric patients with hematologic cancer and/or undergoing hematopoietic stem cell transplantation in Brazilian medical centers

In the present paper we summarize the suggestions of a multidisciplinary group including experts in pediatric oncology and infectious diseases who reviewed the medical literature to elaborate a consensus document (CD) for the diagnosis and clinical management of invasive fungal diseases (IFDs) in children with hematologic cancer and those who underwent hematopoietic stem-cell transplantation. All major multicenter studies designed to characterize the epidemiology of IFDs in children with cancer, as well as all randomized clinical trials addressing empirical and targeted antifungal therapy were reviewed. In the absence of randomized clinical trials, the best evidence available to support the recommendations were selected. Algorithms for early diagnosis and best clinical management of IFDs are also presented. This document summarizes practical recommendations that will certainly help pediatricians to best treat their patients suffering of invasive fungal diseases.

CNS Infections in Immunoincompetent Patients : Neuroradiological and Clinical Features

In patients with immunodeficiency the pathogen spectrum of central nervous system (CNS) infections is broader and different from that of immunocompetent patients. Numerous opportunistic infections are characterized by a high prevalence of viral, bacterial and parasitic pathogens, and depend on the type of impaired immune defense, for example impaired T‑cell or monocyte function, monoclonal antibody treatment, and impaired granulocyte function. Neuroradiological features as well as laboratory findings are often different and versatile in comparison to immunocompetent individuals and pathognomonic imaging findings do not exist; however, knowledge of possible pathways of pathogens in the CNS and preferred tissue affection may help in narrowing down differential diagnoses. Therefore, knowledge of the type of patient and the performed immunomodulatory therapy is essential for the neuroradiological assessment and the differential diagnostic considerations. Moreover, parenchymal reactions in the sense of an immune reconstitution inflammatory syndrome (IRIS) can occur when immunocompetence is restored. This review focus on the most common pathologies in immunocompromised patients, and an overview of imaging features but also of pathology and clinical aspects is given. The synopsis of anamnestic information, clinical findings and structured analysis of the lesion pattern, its spread and short-term follow-up may increase the correct diagnostic classification; however, the gold standard is still determination of the pathogen in the cerebrospinal fluid (CSF), blood cultures or biopsies.

Central Nervous System Infections Due to Aspergillus and Other Hyaline Molds

Central nervous system infections due to Aspergillus spp and other hyaline molds such as Fusarium and Scedosporium spp are rare but fatal conditions. Invasion of the central nervous system (CNS) tends to occur as a result of hematogenous dissemination among immunocompromised patients, and by local extension or direct inoculation secondary to trauma in immunocompetent hosts. Efforts should be directed to confirm the diagnosis by image-guided stereotactic brain biopsy when feasible. Non-culture methods could be useful to support the diagnosis, but they have not been validated to be performed in cerebral spinal fluid. Treatment of these infections is challenging given the variable susceptibility profile of these pathogens and the penetration of antifungal agents into the brain.

Brain and Spinal Epidural Abscess

PURPOSE OF REVIEW

Brain abscesses and spinal epidural abscesses are serious, potentially life-threatening infections of the central nervous system. This article outlines the clinical presentation, evaluation, and management of brain abscesses and spinal epidural abscesses, with a specific focus on bacterial infections.

RECENT FINDINGS

The overall incidence of brain abscesses has declined, in part because of fewer brain abscesses associated with otogenic infections. However, emerging patient populations at high risk for brain abscess include those with a history of penetrating head trauma, neurosurgery, or immunodeficiency. Improved mortality rates for brain abscess are attributable to modern diagnostic imaging, stereotactic-guided aspiration, and newer antimicrobials that readily penetrate into the central nervous system and abscesses. Brain MRI is more sensitive than CT for brain abscess, particularly in the early stages, but CT remains more widely available and can adequately identify potential abscesses and confirm response to treatment. With the advent of minimally invasive neurosurgical techniques, surgical excision is often employed only for posterior fossa, multiloculated, or superficial well-circumscribed abscesses. In select clinical scenarios, conservative medical management may be a safe alternative to a combined surgical and medical approach. Unlike brain abscess, the incidence of spinal epidural abscess is on the rise and has been attributed to higher prevalence of predisposing factors, including spinal procedures and instrumentation.

SUMMARY

Successful diagnosis and management of brain abscess and spinal epidural abscess requires a collaborative approach among neurologists, neurosurgeons, radiologists, and infectious disease physicians. The foundation of management of brain abscess includes surgical intervention for diagnostic purposes if a pathogen has not been identified or for decompression of larger abscesses or those with mass effect and significant surrounding edema; appropriate dosing and adequate duration of an antimicrobial regimen tailored to the presumptive source of infection and available culture data, and eradication of the primary source of infection. For spinal epidural abscesses, neurologic status at the time of presentation is directly related to outcomes, underscoring the importance of prompt recognition and intervention.

Central Nervous System Infections Complicating Immunosuppression and Transplantation

PURPOSE OF REVIEW

This article reviews infections associated with cancer treatments and immunosuppressive/immunomodulatory therapies used in both neoplastic and non-neoplastic conditions, including hematopoietic cell transplantation and solid organ transplantation. It provides a clinical approach to the most commonly affected patient groups based on clinicoanatomic presentation and disease-specific risks resulting from immune deficits and drugs received.

RECENT FINDINGS

The clinical presentations, associated neuroimaging findings, and CSF abnormalities of patients with central nervous system infections who are immunocompromised may differ from those of patients with central nervous system infections who are immunocompetent and may be confused with noninfectious processes. Triggering of brain autoimmunity with emergence of neurotropic antibodies has emerged as a recognized parainfectious complication. New unbiased metagenomic assays to identify obscure pathogens help clinicians navigate the increasing range of conditions affecting the growing population of patients with altered immunity.

SUMMARY

Despite evidence-based prophylactic regimens and organism-specific antimicrobials, central nervous system infections continue to cause significant morbidity and mortality in an increasing range of patients who are immunocompromised by their conditions and therapies. Multiple new drugs put patients at risk for progressive multifocal leukoencephalopathy, which has numerous imaging and clinical manifestations; patients at risk include those with multiple sclerosis, for whom infection risk is becoming one of the most important factors in therapeutic decision making. Efficient, early diagnosis is essential to improve outcomes in these often-devastating diseases.

Role of FDG PET/CT in monitoring treatment response in patients with invasive fungal infections

Introduction

Invasive fungal infections (IFIs) occur mostly in immunosuppressed patients and can be life-threatening. Inadequate treatment is associated with high morbidity and mortality. We examined the role of 2-fluorodeoxyglucose positron emission tomography integrated with CT (FDG-PET/CT) in monitoring IFIs and therapy decision-making, and evaluated the role of baseline metabolic parameters in predicting the metabolic response.

Methods

All patients between October 2009 and March 2018, diagnosed with IFIs, treated with antifungal drugs, and who underwent FDG-PET/CT at baseline and at one or more timepoints during treatment were retrospectively included. The electronic patient files were reviewed for pathology, microbiology, and laboratory findings. All FDG-PET/CT scans were performed according to standardized European Association of Nuclear Medicine/EANM Research Limited (EANM/EARL) protocols. For each scan, the global total lesion glycolysis (TLG) and metabolic volume (MV), highest maximum standardized uptake value (SUVmax), and peak standardized uptake value (SUVpeak) were determined. The role of FDG-PET/CT on monitoring antifungal therapy was assessed by looking at the clinical decision made as result of the scan. Furthermore, the added value of the baseline metabolic parameters in predicting metabolic response to the antifungal treatment was evaluated.

Results

Twenty-eight patients with in total 98 FDG-PET/CT scans were included with a mean age of 43 ± 22 years. FDG-PET/CT altered management in 14 out of the 28 patients (50%). At the final FDG-PET/CT scan, 19 (68%) had a complete metabolic response (CMR), seven a partial response and two patients were defined as having progressive disease. Using receiver operative analysis, the cut-off value, sensitivity, specificity, and significance for the baseline TLG and MV to discriminate patients with CMR were 160, 94%, 100%, p < 0.001 and 60, 84%, 75%, p = 0.001 respectively.

Conclusion

FDG-PET/CT is useful in the monitoring of IFIs resulting in management therapy change in half of the patients. Baseline TLG and MV were found to be able to predict the metabolic response to antifungal treatment.

Electronic supplementary material

The online version of this article (10.1007/s00259-018-4192-z) contains supplementary material, which is available to authorized users.

Fungal infections in pediatric neurosurgery

INTRODUCTION

Invasive mycosis of the central nervous system represent a diverse group of diseases that have gradually emerged as not only opportunistic infections in patients with immune susceptibility due to congenital and acquired deficiency, immunomodulation, solid organ and stem cell transplantation, hematological malignancies, and chronic steroid use but also in selected risk populations such as low weight preterm infants, patients with shunted hydrocephalus and external ventricular drainages, skull base surgery, and head injury.

OBJECTIVES

The purpose of this review is to familiarize the pediatric neurosurgeon with the most common mycosis and their clinical scenarios which can be encountered in the clinical practice, with special emphasis on clinical, radiological, and laboratory diagnosis beyond classical microorganism cultures as well as options in medical and surgical treatment given the high incidence of morbidity and mortality associated with these challenging entities.

METHODS

We conducted an online database review (Ovid, PubMed) gathering relevant English language literature published in the last 20 years with special emphasis on recent breakthroughs in the diagnosis and treatment of invasive mycosis of the CNS as well as reported cases within the pediatric neurosurgical literature and their surgical management.

RESULTS

Fungal agents capable of invading the CNS can behave as aggressive entities with rapid progression manifesting as overwhelming meningoencephalitis with vascular compromise or can lead to space-occupying lesions with abscess formation which require prompt diagnosis by either laboratory identification of the components of these biological agents and their host response or by obtaining tissue specimens for microbiological identification which may not be straightforward due to prolonged culture time.

CONCLUSION

Following a high degree of suspicion with prompt initiation of antifungal agents and reversal of potential immunosuppressant therapies along with neurosurgical evacuation of intracranial collections or removal of infected hardware (CSF shunts) can lead to more optimistic outcomes of these complex clinical scenarios.