MR spectroscopy in brain infections

Brain metabolic profile assessed by magnetic resonance spectroscopy in ‎‎children with Down syndrome: Relation to intelligence quotient

BACKGROUND

Down syndrome (DS) is one of the most common causes of intellectual disability. Children with DS have varying intelligence quotient (IQ) that can predict their learning abilities.

AIM

To assess the brain metabolic profiles of children with DS and compare them to standard controls, using magnetic resonance spectroscopy (MRS) and correlating the results with IQ.

METHODS

This case-control study included 40 children with DS aged 6-15 years and 40 age and sex-matched healthy children as controls. MRS was used to evaluate ratios of choline/creatine (Cho/Cr), N-acetyl aspartic acid/creatine (NAA/Cr), and myoinositol/creatine (MI/Cr (in the frontal, temporal, and occipital lobes and basal ganglia and compared to controls and correlated with IQ.

RESULTS

Children with DS showed significant reductions in NAA/Cr and MI/Cr and a non-significant reduction in Cho/Cr in frontal lobes compared to controls. Additionally, we observed significant decreases in NAA/Cr, MI/Cr, and Cho/Cr in the temporal and occipital lobes and basal ganglia in children with DS compared to controls. Furthermore, there was a significant correlation between IQ and metabolic ratios in the brains of children with DS.

CONCLUSION

Brain metabolic profile could be a good predictor of IQ in children with DS.

Neuro-ophthalmic manifestations of tuberculosis

Neuro-ophthalmic features are a known association in tuberculosis, especially common in central nervous system tuberculosis (CNS-TB). They are mostly the result of the visual pathway and/or ocular motor and other cranial nerve involvement. Furthermore, toxic optic neuropathy and paradoxical response to anti-tubercular drugs (ATT) are also not uncommon. The etiopathogenesis is by the complex interplay of various factors like exudates, vasculitis, arachnoiditis, presence of tuberculomas, hydrocephalus, brain infarcts and/or immune-mediated reaction. The entity often poses a diagnostic dilemma for the ophthalmologists/neuro-ophthalmologists and may lead to irreversible vision loss. The presence of neuro-ophthalmic features not only affect the visual outcome but are also predictors of systemic morbidity of the disease. Therefore, understanding and knowledge about this entity are necessary for the comprehensive management of the disease. While various forms of TB including CNS-TB have been well-dealt with in literature, little is discussed specifically about the neuro-ophthalmic manifestations of tuberculosis. Therefore, the purpose of this review is to highlight current understanding of the types of neuro-ophthalmic involvement in tuberculosis, its etiopathogenesis, diagnosis and management.

Multiple brain abscesses presented with monoparesis in a patient with lung abscess mimicking lung cancer

Multiple brain abscesses associated with the lung mass require differential diagnosis from cancerous diseases. Here, we report a rare case of multiple brain abscesses originating from a lung abscess. A 65-year-old man presented with a 2-day history of motor weakness during antibiotic treatment for pneumonia. Brain magnetic resonance imaging (MRI) revealed multiple enhanced lesions of various sizes in the whole brain. Diffusion-weighted MRI showed high signal intensity in several lesions, and magnetic resonance (MR) spectroscopy showed reduced N-acetyl-aspartate (NAA) and high lactate-lipid complex levels. Positron emission tomography/computed tomography revealed a hypermetabolic mass-like lesion (size: 5 × 3 cm) in the right lower lobe. The patient was diagnosed with organizing pneumonia by bronchoscopy and was successfully treated with empirical antibiotics for multiple brain abscesses and lung abscesses. If new neurological deficits occur during the treatment of inflammatory diseases such as pneumonia, the possibility of brain abscesses and cancerous conditions should be considered. Appropriate diagnosis and antibiotic treatment should be performed to ensure favorable outcomes.

Role of MRI in Differentiating Various Posterior Cranial Fossa Space-Occupying Lesions Using Sensitivity and Specificity: A Prospective Study

BACKGROUND

Any abnormal space-occupying posterior fossa lesion may directly involve the vital structures like the brain stem, cranial nerves, cerebellum, vertebrobasilar artery, and venous sinuses, which makes the surgical approach and total excision very difficult. Hence for these reasons, precise evaluation of posterior fossa lesion with MRI is a must to visualize the vital structures, which helps in planning and safe surgery.  Objective: This study aimed to evaluate the added value of diffusion-weighted imaging and magnetic resonance spectroscopy in the localization, extension, characterization, differentiation of various posterior fossa space-occupying lesions, and correlating with the histopathological result.

MATERIALS AND METHODS

This prospective study comprised of 40 patients who were suspected with posterior fossa space-occupying lesions on basis of clinical features or on CT scan. All patients were evaluated using conventional as well as newer MRI techniques using Siemens 1.5 Tesla MRI scanner (Siemens Medical System, Erlangen, Germany). Diffusion-weighted imaging (DWI) was done in all patients and magnetic resonance spectroscopy (MRS) was done in 27 patients. Based on the MRI findings, various posterior fossa lesions were classified as neoplastic or non-neoplastic. The neoplastic lesions were further classified as benign and malignant. The MRI findings were correlated with histopathological findings or follow-up.

STATISTICAL ANALYSIS

Independent sample t-test was used to compare the mean apparent diffusion coefficient (ADC) values of various posterior fossa space-occupying lesions. Receiver operating characteristic (ROC) curve analysis was done to determine the optimal cut-off mean ADC values and choline/creatinine (Cho/cr) ratios for various benign and malignant posterior fossa tumors.

RESULTS

Of 40 patients with posterior fossa lesions, 23 were males and 17 were females with a mean age of 34.67±1.93[SD] years. Metastases were the most common posterior fossa lesions in our study sample and found in seven patients (17.5%) followed by vestibular schwannomas and brainstem gliomas in five patients (12.5%) each, demyelinating lesion in four patients (10%), tubercular abscess in three patients (7.5%), hemangioblastoma, tuberculoma, arachnoid cyst, epidermoid cyst, pilocytic astrocytoma, low-grade glioma in two patients (5%) each, meningioma, medulloblastoma, pyogenic abscess and high-grade glioma in one patient (2.5%) each. The mean ADC value of benign tumors was higher than that of malignant tumors and this difference was found to be significant (p = 0.019). The cut-off ADC value 1.022 x 10^-3mm²/s had a sensitivity of 78.6% and specificity of 66.7%. MRS played important role in differentiating neoplastic from non-neoplastic lesions and benign from malignant tumors. The cut-off Cho/cr ratio of 1.25 had a sensitivity of 66.7%, specificity of 85.7% to differentiate benign from malignant tumors.

CONCLUSION

Conventional MRI sequences able to diagnose most of the benign-appearing lesions of posterior fossa, however, adding advanced MRI sequences like diffusion-weighted imaging and MR spectroscopy helps us to differentiate and diagnose various posterior fossa lesions even closer to the actual histopathological diagnosis.

MR spectroscopy in pediatric neuroradiology

Magnetic resonance spectroscopy (MRS), being able to identify and measure some brain components (metabolites) in pathologic lesions and in normal-appearing tissue, offers a valuable additional diagnostic tool to assess several pediatric neurological diseases. In this review we will illustrate the basic principles and clinical applications of brain proton (H¹; hydrogen) MRS (H¹MRS), by now the only MRS method widely available in clinical practice. Performing H¹MRS in the brain is inherently less complicated than in other tissues (e.g., liver, muscle), in which spectra are heavily affected by magnetic field inhomogeneities, respiration artifacts, and dominating signals from the surrounding adipose tissues. H¹MRS in pediatric neuroradiology has some advantages over acquisitions in adults (lack of motion due to children sedation and lack of brain iron deposition allow optimal results), but it requires a deep knowledge of pediatric pathologies and familiarity with the developmental changes in spectral patterns, particularly occurring in the first two years of life. Examples from our database, obtained mainly from a 1.5 Tesla clinical scanner in a time span of 15 years, will demonstrate the efficacy of H¹MRS in the diagnosis of a wide range of selected pediatric pathologies, like brain tumors, infections, neonatal hypoxic-ischemic encephalopathy, metabolic and white matter disorders.

Trehalose as quantitative biomarker for in vivo diagnosis and treatment follow-up in cryptococcomas

Brain lesions caused by Cryptococcus neoformans or C. gattii (cryptococcomas) are typically difficult to diagnose correctly and treat effectively, but rapid differential diagnosis and treatment initiation are crucial for good outcomes. In previous studies, cultured cryptococcal isolates and ex vivo lesion material contained high concentrations of the virulence factor and fungal metabolite trehalose. Here, we studied the in vivo metabolic profile of cryptococcomas in the brain using magnetic resonance spectroscopy (MRS) and assessed the relationship between trehalose concentration, fungal burden, and treatment response in order to validate its suitability as marker for early and noninvasive diagnosis and its potential to monitor treatment in vivo. We investigated the metabolites present in early and late stage cryptococcomas using in vivo ¹H MRS in a murine model and evaluated changes in trehalose concentrations induced by disease progression and antifungal treatment. Animal data were compared to ¹H and ¹³C MR spectra of Cryptococcus cultures and in vivo data from 2 patients with cryptococcomas in the brain. In vivo MRS allowed the noninvasive detection of high concentrations of trehalose in cryptococcomas and showed a comparable metabolic profile of cryptococcomas in the murine model and human cases. Trehalose concentrations correlated strongly with the fungal burden. Treatment studies in cultures and animal models showed that trehalose concentrations decrease following exposure to effective antifungal therapy. Although further cases need to be studied for clinical validation, this translational study indicates that the noninvasive MRS-based detection of trehalose is a promising marker for diagnosis and therapeutic follow-up of cryptococcomas.

Approach to an Intracranial Mass in Patients With HIV

PURPOSE OF REVIEW

Space-occupying lesions represent a diagnostic challenge among people with the human immunodeficiency virus, acquired immunodeficiency syndrome (HIV/AIDS). To determine the best diagnostic approach to the wide array of possible etiologies and provide a thorough interpretation of neuroimaging in order to narrow a hierarchical differential diagnosis among these patients. Given that there is no pathognomonic neuroimaging pattern in this clinical setting, we searched results from brain biopsies to best determine the etiology of commonly found lesions.

RECENT FINDINGS

Multimodal brain MRI and MRI spectroscopy (MRS) often provide the most valuable information in the study of focal masses among people with HIV/AIDS. Brain biopsy appears safe and provides high diagnostic yields in these patients. Among patients with HIV/AIDS who present with space-occupying intracranial lesions, brain MRI and MRS are useful tests. However, in cases of diagnostic uncertainty, brain biopsy is a safe procedure and should be performed. The role of metabolic studies like ²⁰¹Th-SPECT or PET is useful in the detection of primary central nervous system lymphoma.

Cerebral abscesses imaging: A practical approach

Brain abscesses (BAs) are focal infections of the central nervous system (CNS) that start as a localised area of weakening of the brain parenchyma (cerebritis) and develops into a collection of pus surrounded by a capsule. Pyogenic (bacterial) BAs represent the majority of all BAs; in some cases, the diagnostic and therapeutic management can be challenging. Imaging has a primary role in differentiating BAs from other lesions. Conventional magnetic resonance imaging (cMRI) is essential for the identification of the lesion, its localisation and its morphological features. However, cMRI does not allow to reliably differentiate BAs from other intracranial mass lesions such as necrotic tumours. Advanced sequences, such as diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI) and proton MR spectroscopy (¹H-MRS) are very useful in the differential diagnosis from other brain lesions, such as non-pyogenic abscesses or necrotic tumours, and provide essential information on structural, vascular and metabolic characteristics allowing greater neuroradiological confidence. The aim of this pictorial review is to provide a practical approach showing the added value of more advanced MRI techniques in their diagnostic management.

Effect of antibiotic therapy on proton MR spectroscopy findings in human pyogenicbrain abscesses

BACKGROUND

This work aims to determine how antibiotic therapy influences MR spectroscopic findings in patients undergoing treatment for pyogenic brain abscess.

METHODS

This prospective, single center study included all patients who received treatment for brain abscesses at the Neurosurgery Department of University Hospital Ostrava between 2012-2017. Pre-operative MR imaging was carried out on all patients including diffusion-weighted imaging and in vivo single-voxel proton spectroscopy with intermediate echo time. The following factors were evaluated: duration of antibiotic therapy, characteristics of MR imaging and spectra findings and culture results.

RESULTS

MR spectroscopy findings characteristic of brain abscesses, i.e. the resonances of at least one of the metabolites concerned (amino acids, acetate, alanine and succinate), were observed in 23 patients who had undergone antibiotic therapy for less than 72 hours beforehand (median 7 hours; IQR 30 hours). The 20 patients who underwent antibiotic therapy for longer than this (the median time was 336 hours with an IQR of 284 hours) showed no abscess-specific metabolites, only nonspecific lactate and/or lipid resonance (p <0.0005). These results were further compared with culture findings of pus samples taken intra-operatively: a significantly higher rate of positive culture (78,2%) was determined in cases where antibiotics were administered less than 72 hours before MRS (p <0.0005).

CONCLUSIONS

Prolonged antibiotic therapy can influence MRS findings in pyogenic brain abscesses - a fact which is certainly necessary to take into account in its differential diagnosis. The disappearance of the characteristic metabolites can be indirectly interpreted as an indicator of successful antibiotic therapy in cases where surgical intervention is not possible. Further study in this field is required to confirm the results of this study.

Magnetic Resonance Spectroscopy and its Clinical Applications: A Review

In vivo NMR spectroscopy is known as magnetic resonance spectroscopy (MRS). MRS has been applied as both a research and a clinical tool in order to detect visible or nonvisible abnormalities. The adaptability of MRS allows a technique that can probe a wide variety of metabolic uses across different tissues. Although MRS is mostly applied for brain tissue, it can be used for detection, localization, staging, tumour aggressiveness evaluation, and tumour response assessment of breast, prostate, hepatic, and other cancers. In this article, the medical applications of MRS in the brain, including tumours, neural and psychiatric disorder studies, breast, prostate, hepatic, gastrointestinal, and genitourinary investigations have been reviewed.

Cerebral cryptococcoma mimicking glioblastoma

Cryptococcus neoformans and C. gattii cause invasive fungal disease, with meningitis being the most common manifestation of central nervous system (CNS) disease. Encapsulated cryptococcomas occur rarely, predominantly in immunocompetent hosts, usually related to C. gattii Our patient was an immunocompetent man who presented with headache and a large cystic CNS lesion thought to be glioblastoma. Biopsy of a concomitant lung lesion confirmed cryptococcoma and empiric antifungal therapy was started for presumed CNS cryptococcoma. Antifungal therapy failed to shrink the CNS lesion, and surgical excision confirmed C. gattii CNS cryptococcoma. Following surgery he had complete resolution of symptoms. This case highlights that cryptococcoma cannot be distinguished from tumour on clinical or imaging findings. A combined medical and surgical approach is optimal for the management of large or surgically accessible cryptococcomas, as antifungal therapy alone is unlikely to penetrate large lesions sufficiently to lead to a cure.

Relapsing-Remitting Severe Bickerstaff's Brainstem Encephalitis - Case Report and Literature Review

BACKGROUND

Bickerstaff's brainstem encephalitis (BBE) is a very rare disease of the central nervous system. Aetiology of the disease is auto-immunological. However, it is not entirely understood. Clinically BBE manifests in progressive ophthalmoplegia, ataxia and consciousness disturbances. Clinical symptoms are usually preceded by an unidentified infection of the upper respiratory tract. Usually, the disease has one phase, but individual relapses have also been described. Despite quite severe clinical symptoms, the prognosis is usually good.

CASE REPORT

The article presents a case of a patient with relapsing-remitting severe BBE. The case is presented due to the relapsing-remitting clinical course of the disease that resulted in patient's death, rarely described in the literature. We also present the results of subsequent MR scans in the course of the disease, so far described only in individual reports. It is also the first report in the world's literature presenting the results of series of MR spectroscopy (MRS) examinations in the course of BBE.

CONCLUSIONS

MR examination is an important component in BBE diagnostics, allowing to differentiate atypical cases and place them under special supervision due to the possibility of the severe clinical course. MR also facilitates differentiation between Miller-Fisher Syndrome (MFS) and BBE in cases of diagnostic doubts. Adding MRS and MRI to the protocol allows us to define the nature of morphological changes more accurately in patients with suspected or diagnosed BBE.

Magnetic resonance imaging in neurocysticercosis

Cysticercosis in one of the most common parasitic infections in the central nervous system. The complex and unpredictable nature of the host immune reaction against cysticercosis as well as the pleomorphism of your injuries make the disease neurocysticercosis interesting and fascinating to study. Imaging studies play an important role in the diagnosis of this disease. Advanced imaging techniques have improved detection and visualization of scolex cysts extraparenchymal spaces.

Fungal central nervous system infections: prevalence and diagnosis

Fungal infections of the central nervous system (CNS) are rare but they pose a significant challenge. Their prevalence spans a wide array of hosts including immunosuppressed and immunocompetent individuals, patients undergoing neurosurgical procedures and those carrying implantable CNS devices. Cryptococcus neoformans and Aspergillus spp. remain the most common pathogens. Magnetic resonance imaging can help localize the lesions, but diagnosis is challenging since invasive procedures may be needed for the retrieval of tissue, especially in cases of fungal abscesses. Antigen and antibody tests are available and approved for use in the cerebrospinal fluid (CSF). PCR-based techniques are promising but they are not validated for use in the CSF. This review provides an overview on the differential diagnosis of the fungal CNS disease based on the host and the clinical syndrome and suggests the optimal use of diagnostic techniques. It also summarizes the emergence of Cryptococcus gatti and an unanticipated outbreak caused by Exserohilum rostratum.