Discrimination of capsular stage brain abscesses from necrotic or cystic neoplasms using diffusion-weighted magnetic resonance imaging

European society of Clinical Microbiology and Infectious Diseases guidelines on diagnosis and treatment of brain abscess in children and adults

SCOPE

These European Society of Clinical Microbiology and Infectious Diseases guidelines are intended for clinicians involved in diagnosis and treatment of brain abscess in children and adults.

METHODS

Key questions were developed, and a systematic review was carried out of all studies published since 1 January 1996, using the search terms 'brain abscess' OR 'cerebral abscess' as Mesh terms or text in electronic databases of PubMed, Embase, and the Cochrane registry. The search was updated on 29 September 2022. Exclusion criteria were a sample size <10 patients or publication in non-English language. Extracted data was summarized as narrative reviews and tables. Meta-analysis was carried out using a random effects model and heterogeneity was examined by I2 tests as well as funnel and Galbraith plots. Risk of bias was assessed using Risk Of Bias in Non-randomised Studies - of Interventions (ROBINS-I) (observational studies) and Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) (diagnostic studies). The Grading of Recommendations Assessment, Development and Evaluation approach was applied to classify strength of recommendations (strong or conditional) and quality of evidence (high, moderate, low, or very low).

QUESTIONS ADDRESSED BY THE GUIDELINES AND RECOMMENDATIONS

Magnetic resonance imaging is recommended for diagnosis of brain abscess (strong and high). Antimicrobials may be withheld until aspiration or excision of brain abscess in patients without severe disease if neurosurgery can be carried out within reasonable time, preferably within 24 hours (conditional and low). Molecular-based diagnostics are recommended, if available, in patients with negative cultures (conditional and moderate). Aspiration or excision of brain abscess is recommended whenever feasible, except for cases with toxoplasmosis (strong and low). Recommended empirical antimicrobial treatment for community-acquired brain abscess in immuno-competent individuals is a 3rd-generation cephalosporin and metronidazole (strong and moderate) with the addition of trimethoprim-sulfamethoxazole and voriconazole in patients with severe immuno-compromise (conditional and low). Recommended empirical treatment of post-neurosurgical brain abscess is a carbapenem combined with vancomycin or linezolid (conditional and low). The recommended duration of antimicrobial treatment is 6-8 weeks (conditional and low). No recommendation is offered for early transition to oral antimicrobials because of a lack of data, and oral consolidation treatment after ≥6 weeks of intravenous antimicrobials is not routinely recommended (conditional and very low). Adjunctive glucocorticoid treatment is recommended for treatment of severe symptoms because of perifocal oedema or impending herniation (strong and low). Primary prophylaxis with antiepileptics is not recommended (conditional and very low). Research needs are addressed.

Clinical diagnosis and management of multiple cerebral ring-enhancing lesions-study of 50 patients at a tertiary healthcare center

AIM OF THE STUDY

Multiple ring-enhancing lesions are commonly experienced group of brain pathologies which we come across in day-to-day practice. Clinical symptoms in these lesions are quite non-specific, and hence, it is difficult to reach a final diagnosis. However, these lesions have a varied group of differential diagnosis and it is sometimes difficult to have an accurate diagnosis on conventional MRI. This article was written with the objective of discussing the demographical study and etiology, clinical diagnosis and management for these patients.

MATERIALS AND METHODS

It is a prospective study carried out at the Department of Neurosurgery, Dr. D Y Patil Medical College and Hospital, Pune, from September 2019 to August 2022 and included 50 patients who presented to us multiple ring-enhancing brain lesions.

RESULTS

In our study, 50 patients between age (1-70 years) with multiple ring-enhancing lesions were analyzed. Majority of the patients were between age group 30-39 years. Males (76%) were majority in our study than females (24%). Most common pathology was primary neoplasm (glioma) and metastasis, followed by nine patients of pyogenic abscess and tuberculosis each. Neurocysticercosis was seen in eight patients and three patients were diagnosed with CNS lymphoma. Most of our patients presented with headache (38 patients) and a subset of patients had associated seizures (28 patients). Two patients with primary neoplasm were diagnosed to have WHO grade 3 glioma and seven patients were diagnosed to have WHO grade 4 glioma. Glioblastoma multiforme presented as multifocal and multicentric lesions. Among the patients with primary neoplasm, three patients underwent stereotactic biopsy for diagnosis and the rest of seven patients underwent maximum safe resection followed by chemotherapy and radiotherapy. Ten patients were diagnosed with metastatic lesions, among them six patients underwent stereotactic biopsy for histopathological diagnosis and immunohistochemistry, and rest of the patients were managed on the basis of the primary lesion. Five patients were immune-compromised, among them two patients presented with abscess and three patients presented with primary neoplastic lesion. Thirty-six patients underwent biopsy, among them seven patients underwent frameless, seven patients underwent frame stereotactic biopsy, and the rest 22 patients underwent excision biopsy.

CONCLUSION

Multiple ring-enhancing lesions of brain pose a challenge in terms of achieving an accurate diagnosis and planning further treatment. It is of utmost importance to have a diagnosis in mind based on radiological investigations, so that surgical intervention can be planned accordingly be it by invasive or minimal invasive techniques. An idea toward the diagnosis also helps in prognosticating these patients which could avoid costly whole-body scans and unnecessary surgical intervention.

Advances in the application of neuroinflammatory molecular imaging in brain malignancies

The prevalence of brain cancer has been increasing in recent decades, posing significant healthcare challenges. The introduction of immunotherapies has brought forth notable diagnostic imaging challenges for brain tumors. The tumor microenvironment undergoes substantial changes in induced immunosuppression and immune responses following the development of primary brain tumor and brain metastasis, affecting the progression and metastasis of brain tumors. Consequently, effective and accurate neuroimaging techniques are necessary for clinical practice and monitoring. However, patients with brain tumors might experience radiation-induced necrosis or other neuroinflammation. Currently, positron emission tomography and various magnetic resonance imaging techniques play a crucial role in diagnosing and evaluating brain tumors. Nevertheless, differentiating between brain tumors and necrotic lesions or inflamed tissues remains a significant challenge in the clinical diagnosis of the advancements in immunotherapeutics and precision oncology have underscored the importance of clinically applicable imaging measures for diagnosing and monitoring neuroinflammation. This review summarizes recent advances in neuroimaging methods aimed at enhancing the specificity of brain tumor diagnosis and evaluating inflamed lesions.

Intracranial peripherally enhancing lesions in cardiac transplant recipients: A rare case series and literature review

Intracranial peripherally enhancing lesions in immunosuppressed solid organ transplant recipients represent a unique diagnostic and management dilemma due to the vast array of differentials that demand consideration. Diagnosis of the underlying pathology is often guided by the use of magnetic resonance imaging (MRI). We present the first published case series of three cardiac transplant recipients with significantly atypical neuroradiological findings contrary to the tenets of contemporary literature. Our rare case series consists of: (1) A sterile Mycobacterium pyogenic abscess mimicking glioblastoma multiforme due to an immunosuppressed state (2) Epstein Barr Virus encephalitis masquerading as Central Nervous System Post-Transplant Lymphoproliferative Disorder (3) An unusual case of partially treated disseminated Nocardiosis warning of the need to consider the immunosuppressed state and partial treatment response obfuscating classical MRI appearances. We utilise these unprecedented cases as the basis of a literature review to understand the pathophysiology behind the peculiar imaging findings in this rarefied cohort of transplant recipients, and rationalise why the MRI findings in each instance contradicts the accepted imaging patterns. In the setting of potential unreliability of neuroradiology in this immunosuppressed unique subgroup, we hope to impart to clinicians that definitive diagnosis obtained by emergent neurosurgical intervention may be necessary to accurately and expediently guide further medical management.

Diagnostic value of alternative techniques to gadolinium-based contrast agents in MR neuroimaging-a comprehensive overview

Gadolinium-based contrast agents (GBCAs) increase lesion detection and improve disease characterization for many cerebral pathologies investigated with MRI. These agents, introduced in the late 1980s, are in wide use today. However, some non-ionic linear GBCAs have been associated with the development of nephrogenic systemic fibrosis in patients with kidney failure. Gadolinium deposition has also been found in deep brain structures, although it is of unclear clinical relevance. Hence, new guidelines from the International Society for Magnetic Resonance in Medicine advocate cautious use of GBCA in clinical and research practice. Some linear GBCAs were restricted from use by the European Medicines Agency (EMA) in 2017.

This review focuses on non-contrast-enhanced MRI techniques that can serve as alternatives for the use of GBCAs. Clinical studies on the diagnostic performance of non-contrast-enhanced as well as contrast-enhanced MRI methods, both well established and newly proposed, were included. Advantages and disadvantages together with the diagnostic performance of each method are detailed. Non-contrast-enhanced MRIs discussed in this review are arterial spin labeling (ASL), time of flight (TOF), phase contrast (PC), diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS), susceptibility weighted imaging (SWI), and amide proton transfer (APT) imaging.

Ten common diseases were identified for which studies reported comparisons of non-contrast-enhanced and contrast-enhanced MRI. These specific diseases include primary brain tumors, metastases, abscess, multiple sclerosis, and vascular conditions such as aneurysm, arteriovenous malformation, arteriovenous fistula, intracranial carotid artery occlusive disease, hemorrhagic, and ischemic stroke.

In general, non-contrast-enhanced techniques showed comparable diagnostic performance to contrast-enhanced MRI for specific diagnostic questions. However, some diagnoses still require contrast-enhanced imaging for a complete examination.

Pyogenic cerebral abscesses demonstrating facilitated diffusion

OBJECTIVE

Pyogenic cerebral abscesses are associated with high morbidity and mortality when treatment is delayed. Benign clinical presentation, as well as absence of restricted diffusion on MRI may contribute to missed diagnoses and delays. The authors sought to elucidate characteristics associated with facilitated diffusion on the MRIs of patients with pyogenic abscesses.

PATIENTS AND METHODS

The authors performed a 10-year retrospective review of prospectively attained data for patients undergoing mass resection by a single surgeon.

RESULTS

Our findings show that 3/33 (9%) patients with microbiological diagnoses of cerebral abscesses with a thin ring of contrast enhancement but minimal or no restricted diffusion MRI imaging. All causative organisms were hemolytic streptococci and none of the subjects received antibiotic therapy prior to specimen collection. A trend in these patients was the presence of diabetes and in conjunction with other studies that cite incomplete treatment as being associated with facilitated diffusion, we conjecture that impaired inflammatory responses in some patients may be associated with the absence of restricted diffusion.

CONCLUSION

With this in mind, clinicians must maintain a high index of suspicion when assessing patients with cystic, contrast enhancing masses. A prospective multicenter study to compile imaging along with other patient characteristics may help refine the non-invasive diagnostic criteria for brain abscesses.

Neuroimaging

Imaging is integral to the management of patients with brain tumors. Conventional structural imaging provides exquisite anatomic detail but remains limited in the evaluation of molecular characteristics of intracranial neoplasms. Quantitative and physiologic biomarkers derived from advanced imaging techniques have been increasingly utilized as problem-solving tools to identify glioma grade and assess response to therapy. This chapter provides a comprehensive overview of the imaging strategies used in the clinical assessment of patients with gliomas and describes how novel imaging biomarkers have the potential to improve patient management.

Abscess formation within a cerebellar metastasis: Case report and literature review

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We experienced a patient with a brain abscess within a cerebellar metastasis.

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A brain abscess within a brain neoplasm is a small entity, and only five cases harboring an abscess within a metastatic brain tumor have been reported to date.

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Surgical procedures for brain abscesses and brain tumors are completely different; however, even today, it is difficult to differentiate a brain abscess from a necrotic brain tumor in advance.

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Differentiation between the two is important due to different methods of management; preoperative assumption of the possible coexistence of both types of lesions could lead to a good outcome when we encounter a lesion which has both the imaging characteristics.

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The preferred treatment of a case with both an abscess and a brain metastasis is complete surgical removal of the tumor and targeted antibiotic therapy for the abscess. The present case highlights the importance of considering coexisting diseases prior to surgery.

Introduction

The managements of brain abscesses and brain tumors including brain metastases differ greatly, especially in terms of surgical procedures. Therefore, differentiating between the two is essential for assuring optimal treatment. However, on rare occasion, these two lesions coexist. Only five cases with both a brain tumor and an abscess have thus, far been reported. We experienced a patient with a brain abscess within a cerebellar metastasis.

Case presentation

A middle-aged man receiving treatment for bile duct cancer presented with headache and nausea. Computed tomography (CT) and magnetic resonance (MR) imaging revealed two lesions, one in each cerebellar hemisphere. Although these lesions appeared to be brain metastases, the right lesion showed high intensity on diffusion-weighted images (DWI), and magnetic resonance spectroscopy (MRS) findings suggested an abscess. Surgical puncture of the lesion identified it as a brain abscess histologically, and we thus, administered antibiotics. However, since the lesion grew, we performed a second surgery for removal, which histopathologically the lesion to be a well-differentiated adenocarcinoma. The final diagnosis was an abscess within a cerebellar metastasis.

Discussion/conclusion

Modern diagnostic tools such as DWI and MRS are reportedly reliable for differentiating brain tumors from brain abscesses, though they are not specific in cases with both lesions. The present case highlights the importance of considering coexisting diseases prior to surgery when we encounter a lesion which has the imaging characteristics of both a tumor and an abscess. The patient may have a better outcome if, preoperatively, surgeons take into consideration the possibility of the coexistence of a brain tumor and a brain abscess.

Pyogenic and non-pyogenic spinal infections: emphasis on diffusion-weighted imaging for the detection of abscesses and pus collections

The incidence of spinal infections has increased in the past two decades, owing to the increasing number of elderly patients, immunocompromised conditions, spinal surgery and instrumentation, vascular access and intravenous drug use. Conventional MRI is the gold standard for diagnostic imaging; however, there are still a significant number of misdiagnosed cases. Diffusion-weighted imaging (DWI) with a b-value of 1000 and apparent diffusion coefficient (ADC) maps provide early and accurate detection of abscess and pus collection. Pyogenic infections are classified into four types of extension based on MRI and DWI findings: (1) epidural/paraspinal abscess with spondylodiscitis, (2) epidural/paraspinal abscess with facet joint infection, (3) epidural/paraspinal abscess without concomitant spondylodiscitis or facet joint infection and (4) intradural abscess (subdural abscess, purulent meningitis and spinal cord abscess). DWI easily detects abscesses and demonstrates the extension, multiplicity and remote disseminated infection. DWI is often a key image in the differential diagnosis. Important differential diagnoses include epidural, subdural or subarachnoid haemorrhage, cerebrospinal fluid leak, disc herniation, synovial cyst, granulation tissue, intra- or extradural tumour and post-surgical fluid collections. DWI and the ADC values are affected by susceptibility artefacts, incomplete fat suppression and volume-averaging artefacts. Recognition of artefacts is essential when interpreting DWI of spinal and paraspinal infections. DWI is not only useful for the diagnosis but also for the treatment planning of pyogenic and non-pyogenic spinal infections.

Magnetic resonance features of pyogenic brain abscesses and differential diagnosis using morphological and functional imaging studies: a pictorial essay

The aim of this paper is to illustrate the potential of magnetic resonance imaging (MRI) in diagnosis, differential diagnosis, treatment planning and evaluation of therapy effectiveness of pyogenic brain abscesses, through the use of morphological (or conventional) and functional (or advanced) sequences. Conventional MRI study is useful for the identification of lesions, to determine the location and morphology and allows a correct hypothesis of nature in the most typical cases. However, the differential diagnosis from other brain lesions, such as non-pyogenic abscesses or necrotic tumors (high-grade gliomas and metastases) is often only possible through the use of functional sequences, as the measurement of diffusion with apparent diffusion coefficient (DWI-ADC), proton magnetic resonance spectroscopy ((1)H-MRS) and perfusion weighted imaging (PWI), which complement the morphological sequences and provide essential information on structural, metabolic and hemodynamic characteristics allowing greater neuroradiological confidence. Modern diagnostic MRI of pyogenic brain abscesses cannot be separated from knowledge, integration and proper use of the morphological and functional sequences.

Can diffusion-weighted imaging be used to differentiate brain abscess from other ring-enhancing brain lesions? A meta-analysis

AIM

To explore the role of diffusion-weighted imaging (DWI) in the discrimination of brain abscess from other ring-enhancing brain lesions through meta-analysis.

MATERIALS AND METHODS

The PUMBED, OVID, and China National Knowledge Infrastructure (CNKI) databases, from January 1995 to March 2013, were searched for studies evaluating the diagnostic performance of DWI in the discrimination of brain abscess lesions. Using the data collected, pooled sensitivities and specificities across studies were determined, positive and negative likelihood ratios (LR) were calculated, and summary receiver operating characteristic (SROC) curves were constructed.

RESULTS

A total of 11 studies fulfilled all of the inclusion criteria and were considered for the analysis. The pooled sensitivity values and pooled specificity values including 95% confidence intervals (CI) were 0.95 (0.87-0.98) and 0.94 (0.88-0.97). The pooled positive LR (95% CI) was 4.13(2.55-6.7); the pooled negative LR (95% CI) was 0.01 (0-1.7); and the area under the curve of the symmetric SROC was 0.98.

CONCLUSIONS

DWI has high sensitivity and specificity for the differentiation of brain abscess from other intracranial cystic mass lesions.

The role of magnetic resonance imaging in the management of brain metastases: diagnosis to prognosis

This article reviews the different MRI techniques available for the diagnosis, treatment and monitoring of brain metastases with a focus on applying advanced MR techniques to practical clinical problems. Topics include conventional MRI sequences and contrast agents, functional MR imaging, diffusion weighted MR, MR spectroscopy and perfusion MR. The role of radiographic biomarkers is discussed as well as future directions such as molecular imaging and MR guided high frequency ultrasound.

Intracranial cysts: an imagery diagnostic challenge

Intracerebral cysts and cystic appearing intracerebral masses are common findings at routine cerebral imaging examination. We discuss here the most interesting aspects of some intracerebral cysts encountered in medical practice in terms of imaging, clinical and pathological description, and problems of differential diagnosis. On an almost routine basis, the neurologists have to deal with such differentials. Therefore, we aim to mention here some of the frequently encountered diagnosis problems when a patient presents with a cystic cerebral mass.

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.

A neurosurgical presentation of patent foramen ovale with atrial septal aneurysm

We describe a case of cerebral abscess in a 53-year-old lady with a background of congenital heart defect. She has an atrial septal defect with atrial septal aneurysm, which remained undiagnosed until this clinical presentation. She presented with a short history of right-sided hemiplaegia and neuroimaging revealed a heterogeneous lesion in the left frontoparietal region. Neuronavigation-guided left frontoparietal craniotomy was performed to debulk the lesion and preoperatively frank pus was drained, which grew Streptococcus constellatus. She was successfully treated with antibiotics for 6 weeks and her clinical condition improved. We believe that the patients' previous dental extraction has possibly resulted in a paradoxical embolism through the atrial septal defect bypassing the pulmonary circulation. The MRI scan picture was misleading, as it was initially thought to be a high-grade brain tumour.

Multiparametric magnetic resonance imaging for the differentiation between benign and malignant salivary gland tumors

PURPOSE

To evaluate the stepwise approach in differentiating between benign and malignant salivary gland tumors using time-intensity curves (TICs) and apparent diffusion coefficients (ADCs).

MATERIALS AND METHODS

TICs and ADCs were analyzed on the tumor-by-tumor (overall) and pixel-by-pixel (TIC and ADC maps) bases in patients with benign (n = 52) or malignant (n = 18) salivary gland tumor. TICs were categorized into Types 1 (<20% increment ratio), 2 (>or=20% increment ratio and >120 sec peak time), 3 (>or=20% increment ratio, <or=120 sec peak time, and <30% washout ratio), or 4 (>or=20% increment ratio, <or=120 sec peak time, and >or=30% washout ratio). ADCs were classified as extremely low (<0.6 x 10(-3) mm(2)/sec), low (<1.2), intermediate (<1.8), or high (>or=1.8).

RESULTS

Malignant tumors had small (<30%) areas with Type 1 TIC with one of the following magnetic resonance imaging (MRI) characteristics: Type 3 overall TIC patterns, Type 4 overall TIC patterns and extremely low (<0.60 x 10(-3) mm(2)/sec) overall ADCs, or Type 2 overall TIC patterns and large (>40%) areas with low or extremely low ADCs.

CONCLUSION

We propose a stepwise approach by using multiparametric MRI techniques as an effective tool for differentiating between benign and malignant salivary gland tumors.

Quantitative imaging biomarkers in neuro-oncology

Conventional structural imaging provides limited information on tumor characterization and prognosis. Advances in neurosurgical techniques, radiotherapy planning and novel drug treatments for brain tumors have generated increasing need for reproducible, noninvasive, quantitative imaging biomarkers. This Review considers the role of physiological MRI and PET molecular imaging in understanding metabolic processes associated with tumor growth, blood flow and ultrastructure. We address the utility of various techniques in distinguishing between tumors and non-neoplastic processes, in tumor grading, in defining anatomical relationships between tumor and eloquent brain regions and in determining the biological substrates of treatment response. Much of the evidence is derived from limited case series in individual centers. Despite their 'added value', the effect of these techniques as an adjunct to structural imaging in clinical research and practice remains limited.

A Challenging Picture of Cancer-and Inflammation-Related Changes

The authors describe a diagnostically challenging case where a patient with previous squamous cell carcinoma of the tonsil developed a putative second primary squamous cell carcinoma in the lung (stage IV with lung and bone metastases). During palliative chemotherapy several episodes of severe infection occurred, eventually resulting in abscess formation in the hip and brain. The dilemma of distinguishing between metastasis and abscess and the therapeutic implications are discussed.

Management of bacterial brain abscesses

✓ Brain abscesses are well-known lesions that have been reported from the beginning of the Hippocratic era. They continue, however, to be characterized by problematic and fatal features, even though there have been enormous developments in treatment and diagnostic technologies—especially in the areas of computed tomography (CT), surgery, anesthesia, bacterial isolation techniques, and new antibiotics. The predisposing factors may change according to patient age, geographic location, and socioeconomic conditions of the community, but patients frequently have a contiguous infection such as otitis or mastoiditis. The clinical signs and symptoms of brain abscesses are nonspecific. Patients typically present with signs and symptoms due to mass effects, accompanied by high fever and seizure. The main treatment is surgical, although medical therapy can be used for selected cases. The treatment of choice is aspiration, which may be performed with the aid of an endoscope or free hand, with or without stereotactic or intraoperative ultrasound guidance. Excision is valuable in some cases. The success of the treatment, whether surgical or medical, mostly depends on the success of isolation of the causative organism, which provides essential data for accurate medical treatment. Third-generation cephalosporins and metronidazole are the most commonly used antimicrobial agents in the treatment of brain abscesses. Use of corticosteroids may be acceptable when lesions are accompanied by edema. Prophylactic antiepileptic therapy is strongly recommended. The patient's Glasgow Coma Scale score at presentation is one of the most important factors predicting outcome.