Diffusion-weighted imaging and proton MR spectroscopy in the characterization of acute disseminated encephalomyelitis

Pediatric Neuroimaging of Multiple Sclerosis and Neuroinflammatory Diseases

Using a pediatric-focused lens, this review article briefly summarizes the presentation of several demyelinating and neuroinflammatory diseases using conventional magnetic resonance imaging (MRI) sequences, such as T1-weighted with and without an exogenous gadolinium-based contrast agent, T2-weighted, and fluid-attenuated inversion recovery (FLAIR). These conventional sequences exploit the intrinsic properties of tissue to provide a distinct signal contrast that is useful for evaluating disease features and monitoring treatment responses in patients by characterizing lesion involvement in the central nervous system and tracking temporal features with blood-brain barrier disruption. Illustrative examples are presented for pediatric-onset multiple sclerosis and neuroinflammatory diseases. This work also highlights findings from advanced MRI techniques, often infrequently employed due to the challenges involved in acquisition, post-processing, and interpretation, and identifies the need for future studies to extract the unique information, such as alterations in neurochemistry, disruptions of structural organization, or atypical functional connectivity, that may be relevant for the diagnosis and management of disease.

The Role of MRI in Differentiating Demyelinating and Inflammatory (not Infectious) Myelopathies

Demyelinating and inflammatory myelopathies represent a group of diseases with characteristic patterns in neuroimaging and several differential diagnoses. The main imaging patterns of demyelinating myelopathies (multiple sclerosis, neuromyelitis optica spectrum disorder, acute disseminated encephalomyelitis, and myelin oligodendrocyte glycoprotein antibody-related disorder) and inflammatory myelopathies (systemic lupus erythematosus-myelitis, sarcoidosis-myelitis, Sjögren-myelitis, and Behçet's-myelitis) will be discussed in this article, highlighting key points to the differential diagnosis.

Toxic leukoencephalopathy versus delayed post-hypoxic leukoencephalopathy after oral morphine sulphate overdose

Toxic leukoencephalopathy (TLE) is a rare pathology caused by various substances including opioids (notably heroin), immunosuppressants, chemotherapy agents, cocaine, alcohol and carbon monoxide. However, although heroin is metabolised by the body into morphine, there is a striking paucity in cases of primary oral morphine-induced TLE, especially in the adult population. We present the case of a man in his 40s admitted to hospital in respiratory depression with a Glasgow Coma Scale (GCS) score of 6 after taking an overdose of oral morphine sulphate. Following a complete recovery to baseline, he was then readmitted with an acute deterioration in his neurobehavioural condition. Initial investigations returned normal but MRI showed changes characteristic for TLE.In cases of opioid toxicity such as ours, TLE is difficult to differentiate from delayed post-hypoxic leukoencephalopathy, due to their similar clinical presentation, disease progression and radiological manifestation. We explore how clinicians can approach this diagnostic uncertainty.

Acute disseminated encephalomyelitis (ADEM) after SARS- CoV-2 vaccination: A case report

Acute disseminated encephalomyelitis (ADEM) is an acute demyelinating disorder of the central nervous system that is ordinarily monophasic. ADEM can develop following infection or vaccination. Here, we present a 37 y/o male patient with progressive muscle weakness in all limbs along with dysphagia following COVID-19 vaccination. Brain magnetic resonance imaging (MRI) revealed typical imaging findings which presented as multifocal T2-FLAIR signal changes in the corticospinal tract, pons, and temporal lobe with diffusion restriction. Magnetic resonance spectroscopy (MRS) further confirmed the diagnosis by the typical elevation of the Choline and Myoinositol peaks. Neurologic impairments have been reported as the potential side effects of COVID-19 vaccines. Appropriate imaging modalities together with a thorough clinical examination are essential for making a correct diagnosis.

Rapidly progressive dementia in a nonagenarian with acute disseminated encephalomyelitis

We describe a case of rapidly progressive dementia (RPD) in a nonagenarian. Dementia was caused by an acute disseminated encephalomyelitis (ADEM). Although not frequently diagnosed in the very elderly acute disseminated encephalomyelitis should not be overlooked for it is a treatable condition. A recent infection followed by rapid cognitive deterioration and multifocal neurologic signs should raise the attention to curable autoimmune diseases. Although the cause of ADEM is still unclear, immune suppression is the mainstay of treatment. Most patients improve on high-dose glucocorticoids and eventually immune globulin treatment or plasma exchange if steroid-unresponsive.

Proton and Multinuclear Spectroscopy of the Pediatric Brain

Magnetic resonance spectroscopy (MRS) is a valuable adjunct to structural brain imaging. State-of-the-art MRS has benefited greatly from recent technical advancements. Neurometabolic alterations in pediatric brain diseases have implications for diagnosis, prognosis, and therapy. Herein, the authors discuss MRS technical considerations and applications in the setting of various pediatric disease processes including tumors, metabolic diseases, hypoxic/ischemic encephalopathy/stroke, epilepsy, demyelinating disease, and infection.

Acute Disseminated Encephalomyelitis: A rare form of COVID-19's neurotropism

Introduction

the COVID-19 pandemic still accounts for thousands of cases every day. It's neurological involvement has been well documented most likely due to auto-immune mechanisms than the virus itself.

Case report

we report the case of a 38 years old women who developed an Acute Disseminated Encephalomyelitis following a COVID-19 infection, with a favorable outcome after immunosuppressive therapy.

Discussion

In this chapter, we discuss ADEM's pathogenesis as well as its clinical and radiological features before detailing its relationship with infectious and vaccination episodes. We also discuss how our patient disease evolved.

Conclusion

Acute Disseminated Encephalomyelitis is an immune-mediated disorder in which the widespread inflammation of the brain and spinal cord is responsible for a variety of symptoms. The novel COVID-19 virus and its vaccine are both a newly incriminated etiologies of this demyelinating disorder.

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COVID-19 neurotropism has been well established and its neurological manifestations are varied.

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Demyelinating disorders are immune-induced disease most likely due to an antigenic analogy between the virus and myelin constituents.

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COVID-19 induced ADEM is extremely rare, only a dozen cases have been reported worldwide, and ours is the only case reported in our country.

Demyelinating Disease of the Central Nervous System Concurrent With COVID-19

Neurological diseases related to coronavirus disease-2019 (COVID-19) are increasingly reported. We report here three cases that presented with subtle neurologic findings manifesting within a range of 15 days to four months after their COVID-19 diagnoses. Magnetic resonance imaging showed acute multifocal periventricular and subcortical demyelinating lesions. Some of the lesions showed contrast enhancement and diffusion restriction. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) PCR was found in the cerebrospinal fluid of just one patient. All patients received intravenous methylprednisolone therapy. In this report, we aim to discuss the aspects of possible COVID-19-related demyelination that support a diagnosis of multiple sclerosis (MS) or acute disseminated encephalomyelitis (ADEM).

Spine MRI: A Review of Commonly Encountered Emergent Conditions

Over the last 2 decades, the proliferation of magnetic resonance imaging (MRI) availability and continuous improvements in acquisition speeds have led to significantly increased MRI utilization across the health care system, and MRI studies are increasingly ordered in the emergent setting. Depending on the clinical presentation, MRI can yield vital diagnostic information not detectable with other imaging modalities. The aim of this text is to report on the up-to-date indications for MRI of the spine in the ED, and review the various MRI appearances of commonly encountered acute spine pathology, including traumatic injuries, acute non traumatic myelopathy, infection, neoplasia, degenerative disc disease, and postoperative complications. Imaging review will focus on the aspects of the disease process that are not readily resolved with other modalities.

Covid-19 systemic infection exacerbates pre-existing acute disseminated encephalomyelitis (ADEM)

Acute disseminated encephalomyelitis (ADEM) is an uncommon diagnosis in adults. It is known to be due to an abnormal immune response to a systemic infection rather than direct viral invasion to the central nervous system. There have been few reports of ADEM diagnosed in the setting of COVID-19 systemic infection. However, we report a case of Coxsackie induced ADEM that remitted but got exacerbated by COVID-19 infection. The patient contracted the COVID-19 infection shortly after being discharged to a rehabilitation facility. Direct COVID-19 neuroinvasion was ruled out via CSF PCR testing for the virus. The patient responded well to pulse steroid therapy and plasmapheresis in both occasions. We hypothesize that COVID-19 infection can flare-up a recently remitted ADEM via altering the immune responses. It is known now that COVID-19 infection can produce cytokine storming. Cytokine pathway activation is known to be involved in the pathology of ADEM. Caution regarding discharging immune suppressed patient to the inpatient rehabilitation facility should be made in the era of COVID-19 pandemic.

Posterior reversible encephalopathy syndrome in scrub typhus fever

The clinical course of a 40-year-old female patient, who presented with acute febrile illness due to scrub typhus fever became complicated by seizures and posterior reversible encephalopathy syndrome (PRES), leading to a fatal outcome. She had normal blood pressure at admission; however, she later developed hypotension and shock. PRES is a syndrome of vasogenic cerebral oedema and accompanying neurological deficits resulting from the breakdown of blood-brain barrier due to high blood pressure or radical blood pressure changes. PRES is a clinico-radiographic diagnosis of heterogeneous aetiologies and is rare in the context of infections. Although there are many neurological manifestations in scrub typhus, to the best of our knowledge, PRES has never been reported.

Childhood acute disseminated encephalomyelitis: an Egyptian pilot study

Describing the variable clinical features, laboratory findings, neuroimaging findings, and treatments given to children who presented with ADEM and following them up both clinically and radiologically. 21 patients were recruited: 14 new cases, and 7 old ones presenting over the preceding 5 years (retrospective review of existing data). 11 males and 10 females, with a mean age of 4.4 years ± 2.7 SD, were included. All new patients were subject to full history, examination and a panel of investigations including MRI of the brain. Treatment was given in the form of pulsed methyl prednisolone or intravenous immunoglobulin (IVIG), followed by clinical and radiological follow-up every 3 months as needed. 11 cases occurred in spring, 8 post vaccine, of which 5 were after oral polio vaccine (OPV). MRI was done for all 21 patients and was abnormal in all of them, CT was done in only 10 patients as was normal in 9. Hyponatremia was seen in 11 patients. All patients who received corticosteroids showed prompt improvement. 6 out of 10 patients who received IVIG first failed treatment. Of the 17 treated patients, 10 had no sequelae and 10 had total lesion resolution on MRI at 3 months, versus 1 and 0 patients, respectively, in the untreated group. We found a disproportionately large number of post vaccination cases, especially after OPV. The association of ADEM with hyponatremia needs further study. MRI is central to diagnosis. Outcome is much better with treatment with steroids being far superior to IVIG. Excess use of IVIG should be discouraged.

COVID-19-associated acute disseminated encephalomyelitis (ADEM)

A 51-year-old woman with COVID-19 infection developed coma and an impaired oculocephalic response to one side. MRI of the brain demonstrated acute multifocal demyelinating lesions, and CSF testing did not identify a direct cerebral infection. High-dose steroids followed by a course of IVIG was administered, and the patient regained consciousness over the course of several weeks. As more patients reach the weeks after initial infection with COVID-19, acute disseminated encephalomyelitis should be considered a potentially treatable cause of profound encephalopathy or multifocal neurological deficits.

"CHOICES": An acronym to aid in delineating potential causes of non-metabolic, non-infectious acute toxic leukoencephalopathy

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Recognition the etiologies of ATL is important due to its potentially reversible nature after treatment or removal of the toxin.

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“CHOICES” is useful to memorize etiologies associated with PVWM injury in non-metabolic and non-infectious ATL patients.

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Reduced diffusion is an early and important imaging finding to evaluate patients with non-metabolic and non-infectious ATL patients.

Purpose

To describe non-metabolic, non-infectious etiologies of acute toxic leukoencephalopathy (ATL) on DWI MRI, and provide a useful acronym to remember them.

Material and Methods

Our PACS archive was reviewed, yielding 185 patients with suspected ATL per MRI reports and clinical follow up; infectious or metabolic causes were excluded.

Result/Discussion

The 87 included non-infectious, non-metabolic ATL patients' etiologies are represented by the acronym 'CHOICES': chemotherapy ('C',n = 34); heroin-induced ('H',n = 6), opioid analogues ('O',n = 14); immunosuppressant ('I',n = 11) or imidazole (n = 2); cocaine ('C',n = 1); environmental or ethanol abuse ('E',n = 5), splenial lesions ('S',n = 9), and 'other' (n = 5).

Conclusion

The "CHOICES" acronym delineates various toxic etiologies of ATL.

Management of Viral Central Nervous System Infections: A Primer for Clinicians

Viruses are a common cause of central nervous system (CNS) infections with many host, agent, and environmental factors influencing the expression of viral diseases. Viruses can be responsible for CNS disease through a variety of mechanisms including direct infection and replication within the CNS resulting in encephalitis, infection limited to the meninges, or immune-related processes such as acute disseminated encephalomyelitis. Common pathogens including herpes simplex virus, varicella zoster, and enterovirus are responsible for the greatest number of cases in immunocompetent hosts. Other herpes viruses (eg, cytomegalovirus, John Cunningham virus) are more common in immunocompromised hosts. Arboviruses such as Japanese encephalitis virus and Zika virus are important pathogens globally, but the prevalence varies significantly by geographic region and often season. Early diagnosis from radiographic evidence and molecular (eg, rapid) diagnostics is important for targeted therapy. Antivirals may be used effectively against some pathogens, although several viruses have no effective treatment. This article provides a review of epidemiology, diagnostics, and management of common viral pathogens in CNS disease.

Clinical Intravoxel Incoherent Motion and Diffusion MR Imaging: Past, Present, and Future

The concept of diffusion magnetic resonance (MR) imaging emerged in the mid-1980s, together with the first images of water diffusion in the human brain, as a way to probe tissue structure at a microscopic scale, although the images were acquired at a millimetric scale. Since then, diffusion MR imaging has become a pillar of modern clinical imaging. Diffusion MR imaging has mainly been used to investigate neurologic disorders. A dramatic application of diffusion MR imaging has been acute brain ischemia, providing patients with the opportunity to receive suitable treatment at a stage when brain tissue might still be salvageable, thus avoiding terrible handicaps. On the other hand, it was found that water diffusion is anisotropic in white matter, because axon membranes limit molecular movement perpendicularly to the nerve fibers. This feature can be exploited to produce stunning maps of the orientation in space of the white matter tracts and brain connections in just a few minutes. Diffusion MR imaging is now also rapidly expanding in oncology, for the detection of malignant lesions and metastases, as well as monitoring. Water diffusion is usually largely decreased in malignant tissues, and body diffusion MR imaging, which does not require any tracer injection, is rapidly becoming a modality of choice to detect, characterize, or even stage malignant lesions, especially for breast or prostate cancer. After a brief summary of the key methodological concepts beyond diffusion MR imaging, this article will give a review of the clinical literature, mainly focusing on current outstanding issues, followed by some innovative proposals for future improvements.

Diffusion Weighted Imaging in Acute Attacks of Multiple Sclerosis

Background

Multiple sclerosis (MS) is one of the most common autoimmune disorders of the central nervous system. In spite of various imaging modalities, the definitive diagnosis of MS remains challenging.

Objectives

This study was designed to evaluate the usefulness of diffusion weighted imaging (DWI) in the diagnosis of acute MS attack and to compare its results with contrast enhanced MRI (CE-MRI).

Patients and Methods

In this cross sectional study, seventy patients with definite diagnosis of relapsing-remitting MS were included. CE-MRI using 0.1 mmol/kg gadolinium as well as DWI sequences were performed for all patients. The percentage of patients with positive DWI was compared with the results of CE-MRI and the consistency between the two imaging modalities was evaluated. Moreover, the relationship between the time of onset of patient’s symptoms and test results for both methods were investigated.

Results

CE-MRI yielded positive results for 61 (87%) patients and DWI yielded positive for 53 (76%) patients. In fifty patients (71.42%), both tests were positive and in six cases (8.57%), both were negative. The test results of three patients turned out to be positive in DWI, while they tested negative in CE-MRI. There was no significant relationship between the results of CE-MRI as well as DWI and the time of imaging from the onset of symptoms.

Conclusion

These data indicate that while CE-MRI will depict more positive results, there are cases in which DWI will show a positive result while CE-MRI is negative. We suggest that the combination of these two imaging modalities might yield more positive results in diagnosing acute MS attack giving rise to a more accurate diagnosis.

What to see when you are looking at confusion: a review of the neuroimaging of acute encephalopathy

Acute encephalopathy is a clinical conundrum in neurocritical care facing physicians with diagnostic and therapeutic challenges. Encephalopathy arises from several concurrent causes, and delayed diagnosis adds to its grim prognosis. Diagnosis is reached by melding clinical, neurophysiological and biochemical features with various neuroimaging studies. We aimed to compile the pathophysiology of acute encephalopathies in adults, and the contribution of cerebral CT, MRI, MR spectroscopy (MRS), positron emission tomography (PET) and single-photon emission CT (SPECT) to early diagnosis, treatment and prognostication. Reports from 1990 to 2013 were identified. Therefore, reference lists were searched to identify additional publications. Encephalopathy syndromes best studied by neuroimaging emerge from hypoxic-ischaemic injury, sepsis, metabolic derangements, autoimmune diseases, infections and rapidly evolving dementias. Typical and pathognomonic neuroimaging patterns are presented. Cerebral imaging constitutes an important component of diagnosis, management and prognosis of acute encephalopathy. Its respective contribution is dominated by rapid exclusion of acute cerebral lesions and further varies greatly depending on the underlying aetiology and the range of possible differential diagnoses. CT has been well studied, but is largely insensitive, while MRI appears to be the most helpful in the evaluation of encephalopathies. MRS may provide supplementary biochemical information and determines spectral changes in the affected brain tissue. The less frequently used PET and SPECT may delineate areas of high or low metabolic activity or cerebral blood flow. However, publications of MRS, PET and SPECT are limited only providing anecdotal evidence of their usefulness and sensitivity.

Imaging neuroinflammation? A perspective from MR spectroscopy

Neuroinflammatory mechanisms contribute to the brain pathology resulting from human immunodeficiency virus (HIV) infection. Magnetic resonance spectroscopy (MRS) has been touted as a suitable method for discriminating in vivo markers of neuroinflammation. The present MRS study was conducted in four groups: alcohol dependent (A, n = 37), HIV-infected (H, n = 33), alcohol dependent + HIV infected (HA, n = 38) and healthy control (C, n = 62) individuals to determine whether metabolites would change in a pattern reflecting neuroinflammation. Significant four-group comparisons were evident only for striatal choline-containing compounds (Cho) and myo-inositol (mI), which follow-up analysis demonstrated were due to higher levels in HA compared with C individuals. To explore the potential relevance of elevated Cho and mI, correlations between blood markers, medication status and alcohol consumption were evaluated in H + HA subjects. Having an acquired immune deficiency syndrome (AIDS)-defining event or hepatitis C was associated with higher Cho; lower Cho levels, however, were associated with low thiamine levels and with highly active antiretroviral HIV treatment (HAART). Higher levels of mI were related to greater lifetime alcohol consumed, whereas HAART was associated with lower mI levels. The current results suggest that competing mechanisms can influence in vivo Cho and mI levels, and that elevations in these metabolites cannot necessarily be interpreted as reflecting a single underlying mechanism, including neuroinflammation.

Thalamic lesions in acute encephalopathy with biphasic seizures and late reduced diffusion

BACKGROUND

We aimed to assess the characteristics of thalamic lesions in children with acute encephalopathy with biphasic seizures and late reduced diffusion.

METHODS

Using the Tokai Pediatric Neurology Society database, we identified and enrolled 18 children with acute encephalopathy with biphasic seizures and late reduced diffusion from 2008 to 2010. Using diffusion-weighted images, we identified patients with thalamic lesions and compared their clinical factors with those of patients without thalamic lesions. We analyzed the time sequence of thalamic, sucortical, and cortical lesions. To study the topography of thalamic lesions, we divided the thalamus into five sections: anterior, medial, anterolateral, posterolateral, and posterior. Subsequently, we analyzed the relationship between the topography of thalamic lesions and the presence of central-sparing.

RESULTS

Seven children presented with symmetrical thalamic lesions associated with bilateral subcortical or cortical lesions. No statistical difference in the clinical features was observed between individuals with and without thalamic lesions. These lesions were observed only when subcortical or cortical lesions were present. In 5 children, thalamic lesions were present in bilateral anterior or anterolateral sections and were associated with subcortical or cortical lesions in bilateral frontal lobes with central-sparing. In the other two children, thalamic lesions were extensive and accompanied by diffuse subcortical and cortical lesions without central-sparing.

CONCLUSION

Thalamic lesions in patients with acute encephalopathy with biphasic seizures and late reduced diffusion involve the anterior sections. The thalamocortical network may play a role in development of thalamic lesions in patients with acute encephalopathy with biphasic seizures and late reduced diffusion.

Pneumococcal-meningitis associated acute disseminated encephalomyelitis (ADEM) - case report of effective early immunotherapy

Introduction

Unvaccinated patients with history of splenectomy are prone to fulminant courses of Streptococcus pneumoniae-associated bacterial meningitis. Besides direct brain damage those patients may additionally suffer from parainfectious syndromes, notably vasculitis and acute disseminated encephalomyelitis (ADEM). Differentiation and treatment of these immunological reactions is challenging.

Methods

Case report.

Results

A 61 year-old woman with history of splenectomy without vaccination for S. pneumoniae presented with progressive headache and meningism. CSF-analysis revealed pleocytosis with microbiological evidence for pneumococcal meningitis. After unsuspicious initial cranial CT imaging and initiation of appropriate antibiotic therapy, MRI two days later showed widespread FLAIR- and T2-hyperintense white matter lesions that further progressed upon follow-up MRI and that fulfilled imaging criteria of ADEM. Meanwhile the patient deteriorated and required mechanical ventilation. Cranial angiography showed no signs of vasculitis or vasospasms. Screening for autoimmune diseases remained negative, however oligoclonal bands turned positive. Brain biopsy mainly revealed perivascular CD4+ T-cells and demyelinated areas. Despite ongoing acute meningitis, a 10-day corticosteroid-pulse was initiated followed by steroid-tapering. Within 4 weeks, clinical and MRI findings ameliorated. In an one-year follow-up visit, the patient significantly recovered, MRI lesions were markedly reduced and no further relapses occurred.

Conclusion

Acute pneumococcal meningitis in unvaccinated splenectomized patients may be complicated by a monophasic course of parainfectious ADEM that can be controlled with high-dose corticosteroids. Parainfectious vasculitis or cerebritis are important differential diagnoses and exact differentiation of these entities is important to initiate early appropriate immunotherapy.

Diffusion-weighted imaging and demyelinating diseases: new aspects of an old advanced sequence

OBJECTIVE

The purpose of this article is to discuss classic applications in diffusion-weighted imaging (DWI) in demyelinating disease and progression of DWI in the near future.

CONCLUSION

DWI is an advanced technique used in the follow-up of demyelinating disease patients, focusing on the diagnosis of a new lesion before contrast enhancement. With technical advances, diffusion-tensor imaging; new postprocessing techniques, such as tract-based spatial statistics; new ways of calculating diffusion, such as kurtosis; and new applications for DWI and its spectrum are about to arise.

A pattern approach to focal white matter hyperintensities on magnetic resonance imaging

Evaluation of focal white matter hyperintensities on magnetic resonance imaging in any age group is always challenging because the cause of these hyperintensities varies extensively. Understanding the clinical presentation, pathophysiology, and associated imaging findings can allow the radiologist to limit the differential diagnosis. A specific imaging approach including age, pattern of distribution, signal characteristics on various sequences, enhancement pattern, and other ancillary findings helps to identify a correct cause for these hyperintensities. This article provides a pattern approach to differentiate various common and a few uncommon diseases presenting as focal white matter hyperintensities.

Extensive acute disseminated encephalomyelitis in a young girl responding to intravenous methylprednisolone

Acute disseminated encephalomyelitis (ADEM) is a monophasic clinical syndrome, characterised by immune-mediated demyelination of the central nervous system. Differentiating ADEM from acute viral encephalomyelitis may pose a difficult clinical challenge. We describe a 3-year-old girl who presented with fever, weakness in all four limbs, urinary retention, respiratory distress and altered sensorium. MRI of the brain showed multiple cerebral T2-hyperintense signals with bilateral thalamic and basal ganglia involvement. MRI of the spine showed extensive T2-hyperintensities from cervical to lumbar spinal cord. Cerebrospinal fluid examination was normal. The patient was diagnosed as ADEM and treated with intravenous methylprednisolone. She showed complete clinical and radiological improvement at the end of 1-month follow-up.

Fulminant demyelinating diseases

Fulminant demyelinating disease is a heading that covers acute disseminated encephalomyelitis and its variant acute hemorrhagic leukoencephalitis (Hurst disease), severe relapses of multiple sclerosis (MS), variants of MS (tumefactive MS, Marburg variant, Balo concentric sclerosis, myelinoclastic diffuse sclerosis), and neuromyelitis optica-spectrum disorders associated with aquaporin autoimmunity. These categories of inflammatory demyelinating disease often prompt hospital admission and many necessitate intensive care monitoring due to the aggressive nature of the illness and associated neurologic morbidity. In this review, we highlight the discriminating clinical, radiographic, and pathologic features of these disorders. Acute management is often accomplished with use of high-dose intravenous steroids and plasma exchange. Aggressive disease may respond to immunosuppression. Prognosis for recovery varies among the disorders but most patients improve. Factors influencing outcome are also discussed.

MR spectroscopy in brain infections

Infection of the central nervous system can be life-threatening and hence requires early diagnostic support for its optimal management. Routine definitive laboratory diagnostic tests can be time-consuming and delay definitive therapy. Noninvasive imaging modalities have established themselves in the diagnosis of various neurologic diseases. In this article, a pragmatic review of the current role of magnetic resonance spectroscopy in the diagnosis and management of intracranial infections is addressed.

1H magnetic resonance spectroscopy in multiple sclerosis and related disorders

Proton magnetic resonance spectroscopy ((1)H-MRS) is an unconventional technique that allows noninvasive characterization of metabolic abnormalities in the central nervous system. (1)H-MRS provides important insights into the chemical-pathologic changes that occur in patients with multiple sclerosis (MS). In this review article we present the main brain and spinal cord (1)H-MRS features in MS, their diagnostic value in differentiating pseudotumoral demyelinating lesions from primary brain tumors, and their relationship with clinical variables. Last, some data related to the use of (1)H-MRS in therapeutic trials is presented.

Acute disseminated encephalomyelitis

The advent of magnetic resonance imaging (MRI) has contributed to increase the interest and awareness in childhood white matter disorders. Pediatric inflammatory demyelinating diseases of the central nervous system (CNS) are clinically heterogeneous with respect to their mode of presentation, clinical severity, rate of progression, and prognosis. Acute disseminated encephalomyelitis (ADEM) is an immune-mediated inflammatory disorder of the CNS, typically transitory and self-limiting. The highest incidence of ADEM is observed during childhood. It is characterized by an acute encephalopathy with polyfocal neurological deficits. In the absence of specific biological markers the diagnosis of ADEM is still based on clinical features and MRI evidence of widespread demyelination, after ruling out other possible explanations for an acute encephalopathy. Over the past decade, many retrospective patient studies have focused on clinical and neuroimaging features, in an attempt to define specific diagnostic criteria. The occurrence of relapses in children with ADEM poses diagnostic difficulties in its differentiation from multiple sclerosis (MS) and neuromyelitis optica (NMO). With the widespread use of high-dose steroids, the long-term prognosis of ADEM with regard to functional and cognitive recovery is favorable. This chapter summarizes the available literature on ADEM in children, including the proposed consensus definitions for its monophasic and relapsing variants.

Acute disseminated encephalomyelitis

Acute disseminated encephalomyelitis is an immune-mediated inflammatory and demyelinating disorder of the central nervous system, commonly preceded by an infection. It principally involves the white matter tracts of the cerebral hemispheres, brainstem, optic nerves, and spinal cord. Acute disseminated encephalomyelitis mainly affects children. Clinically, patients present with multifocal neurologic abnormalities reflecting the widespread involvement in central nervous system. Cerebrospinal fluid may be normal or may show a mild pleocytosis with or without elevated protein levels. Magnetic resonance image (MRI) shows multiple demyelinating lesions. The diagnosis of acute disseminated encephalomyelitis requires both multifocal involvement and encephalopathy by consensus criteria. Acute disseminated encephalomyelitis typically has a monophasic course with a favorable prognosis. Multiphasic forms have been reported, resulting in diagnostic difficulties in distinguishing these cases from multiple sclerosis. In addition, many inflammatory disorders may have a similar presentation with frequent occurrence of encephalopathy and should be considered in the differential diagnosis of acute disseminated encephalomyelitis.

Diffusion-weighted imaging in the diagnosis of enterovirus 71 encephalitis

BACKGROUND

In the early phase of viral encephalitis, conventional MRI may appear normal. Diffusion-weighted imaging (DWI) is a sensitive tool for detecting early changes in cellular function in the central nervous system.

PURPOSE

To investigate the usefulness of DWI in the diagnosis of enterovirus 71 (EV71) encephalitis, and to determine whether DWI is superior to conventional MR sequences.

MATERIAL AND METHODS

MRI scans in 26 patients were retrospectively evaluated for distribution of lesions on T1-weighted images (T1WI), T2-weighted images (T2WI), fluid-attenuated inversion recovery (FLAIR), and DWI. Contrast-to-noise ratios (CNRs) were calculated for all regions on each sequence and differences in the four MRI sequences were assessed using CNRs. Apparent diffusion coefficient (ADC) values were measured for all regions to look for true restriction of diffusion.

RESULTS

Fifteen out of 26 cases showed positive findings on MR imaging. The brain stem was involved in 11 patients, cortex and subcortical white matter in four patients. DWI was more sensitive in detecting the abnormalities (89.7%) compared to T2WI (48.7%), FLAIR (41.0%), and T1WI (35.9%), and the positive ratio of DWI was significantly higher compared to other sequences. Furthermore, no significant difference was found between T2WI and FLAIR (P = 0.649). The corresponding mean CNRs were 8.73 ± 2.57, 83.59 ± 29.28, 24.22 ± 6.22, and 132.27 ± 78.32 on T1WI, T2WI, FLAIR, and DWI, respectively. The absolute values of CNRs of lesions on DWI were significantly greater than those on other sequences.

CONCLUSION

DWI appears to be more sensitive in detecting EV71 encephalitis than conventional MRI sequences. This capability may improve the accuracy in diagnosing EV71 encephalitis, especially at the early stage.

Immune mediated diseases and immune modulation in the neurocritical care unit

This chapter will review the spectrum of immune-mediated diseases that affect the nervous system and may result in an admission to the neurological intensive care unit. Immunomodulatory strategies to treat acute exacerbations of neurological diseases caused by aberrant immune responses are discussed, but strategies for long-term immunosuppression are not presented. The recommendations for therapeutic intervention are based on a synthesis of the literature, and include recommendations by the Cochrane Collaborative, the American Academy of Neurology, and other key organizations. References from recent publications are provided for the disorders and therapies in which randomized clinical trials and large evidenced-based reviews do not exist. The chapter concludes with a brief review of the mechanisms of action, dosing, and side effects of commonly used immunosuppressive strategies in the neurocritical care unit.

Advanced magnetic resonance imaging techniques in the evaluation of pediatric white matter diseases

This article aimed to describe the technical principles and clinical application of advanced magnetic resonance imaging techniques for the assessment of white matter diseases. The following techniques are going to be discussed: magnetization transfer, proton magnetic resonance spectroscopy, diffusion-weighted imaging, diffusion tensor imaging, as well as perfusion and postprocessing techniques such as tract-based spatial statistics. These techniques allow a better understanding of the physiopathology of the white matter diseases as well as have a significant impact on the definition of the differential diagnosis and treatment options.

Diffusion MR imaging for monitoring treatment response

The objective of this article was to emphasize the use of diffusion-weighted imaging in the diagnosis and follow-up of several major disease contexts, as established in recent literature. In some of these diseases the diffusion changes are correlated with the clinical deficit and are potentially useful for early diagnosis and longitudinal evaluation, as well as in the context of pharmacologic trials. Diffusion magnetic resonance is a major advance in the continuing evolution of MR imaging. It provides contrasts and characterization between tissues at a cellular level that may imply differences in function as well as framework and have contributed to a better understanding of the pathophysiological mechanisms of several diseases.

Neuropathologic correlates for diffusion tensor imaging in postinfectious encephalopathy

Acute necrotizing encephalopathy and acute disseminated encephalomyelitis are 2 rare types of acute postinfectious encephalopathy in children. Acute necrotizing encephalopathy is characterized by multiple symmetric lesions in the thalami, putamena, cerebral and cerebellar white matter, and brainstem. Acute disseminated encephalomyelitis is an immune-mediated demyelinating central nervous system disorder that predominantly affects the white matter. Diffusion magnetic resonance imaging is sensitive to measuring water diffusion in the central nervous system in human and animal models. Recent studies have demonstrated that by using an analytical approach to directional diffusivity-derived parameters, the axial diffusivity and the radial diffusivity, one can assess the extent of axonal or myelin injury in the central nervous system white matter. We applied directional diffusivity to acute necrotizing encephalopathy, acute disseminated encephalomyelitis, and control subjects correlating with neuropathology findings. In acute necrotizing encephalopathy, axonal injury without demyelination, noted on biopsy samples of brain tissue, was suggested by a decreased apparent diffusion coefficient, unchanged fractional anisotropy, and decreased axial and radial diffusivity. In acute disseminated encephalomyelitis, an increased apparent diffusion coefficient, decreased fractional anisotropy, unchanged axial diffusivity, and markedly increased radial diffusivity compatible with active inflammatory demyelination were noted, consistent with tissue biopsy sample neuropathology. In conclusion, diffusion tensor parameters can potentially depict more microstructural changes than conventional magnetic resonance imaging in postinfectious encephalopathy in children.

Astrocytopathy in Balo's disease

Baló's disease is characterized by alternating rings of demyelination and preserved myelin. As additional multiple sclerosis (MS)-like lesions often coexist in Baló's cases, Baló's disease is regarded as a variant of MS. In demyelinated areas, many hypertrophic astrocytes are present in close contact with oligodendrocytes, which often show apoptotic features. In the outermost layer of preserved myelin, stress proteins involved in tissue preconditioning are abundant in oligodendrocytes. The peri-plaque perimeter is thus assumed resistant to subsequent attack, thereby leaving a layer of preserved myelin. In some cases, Baló's concentric rings develop step by step in a centrifugal direction, whereas many other cases show simultaneous enhancement of multiple rings. Therefore tissue preconditioning and successive ring formation does not fully describe the mechanism of the disease. We recently reported that in four Filipino Baló's patients, aquaporin-4 (AQP4) was extensively lost in glial fibrillary acidic protein-positive hypertrophic astrocytes, both in demyelinated and myelinated layers of all actively demyelinating lesions. None of six further patients with MRI-confirmed Baló's disease were seropositive for anti-AQP4 antibody. I propose that AQP4 astrocytopathy, in the absence of anti-AQP4 antibody, is characteristic of Baló's disease. This hypothesis should be tested in future experimental studies.

[Value of MR spectroscopy in infectious and inflammatory brain diseases]

Proton magnetic resonance spectroscopy (MRS) is a non-invasive method for measuring cerebral metabolite concentrations in various pathologic conditions. This review discusses the MRS findings in the most common infectious and inflammatory brain diseases.

Multiple sclerosis with initial stroke-like clinicoradiologic features: case report and literature review

A 17-year-old male presented with sudden onset of persistent focal neurological symptoms. Magnetic resonance imaging (MRI) demonstrated a nonenhancing white matter lesion that appeared hyperintense on fluid-attenuated inversion recovery sequence and diffusion-weighted imaging, while hypointense on apparent diffusion coefficient mapping corresponding to the patient's clinical features. A smaller subclinical lesion was also present. The patient's history, radiographic findings, and initial hospital course including response to treatment appeared supportive of a stroke diagnosis. However, a rapid recovery from his severe neurological deficits and results of subsequent serologic testing strongly indicated a demyelinating condition. The onset of adolescent multiple sclerosis can present diagnostic and therapeutic challenges, especially when the initial demyelinating event resembles an acute stroke in clinical and radiographic presentation. Every effort should be made to distinguish these diagnoses as early as possible to ensure timely and appropriate management.

Long-term prognosis of pediatric patients with relapsing acute disseminated encephalomyelitis

Although long-term follow-up data are available for cases with acute disseminated encephalomyelitis, the findings range widely because of the lack of consistent definitions. Using the International Pediatric Multiple Sclerosis Study Group definitions strictly, we determined the long-term prognosis of children with acute disseminated encephalomyelitis, especially concerning relapsing cases. In our cohort of 86 children who presented with a first event of inflammatory demyelinating disease of central nervous system, 33 patients (38%) met the Study Group criteria for acute disseminated encephalomyelitis of which 9 patients had relapses. The mean follow-up duration was 12.8 years for relapsing cases and 9.2 years for all patients with acute disseminated encephalomyelitis. The risk of developing relapses is 27% but the risk of developing multiple sclerosis from acute disseminated encephalomyelitis is low at 6%. All relapsing cases had a benign course on prolonged follow-up, in spite of multiple relapses in the first 3 years.

Diagnostic imaging in acute disseminated encephalomyelitis

Acute disseminated encephalomyelitis is an idiopathic inflammatory demyelinating disease of the CNS that is particularly difficult to differentiate from the first episode of multiple sclerosis, so called clinically isolated syndrome. Currently, no diagnostic criteria exist that could reliably differentiate these two diseases. More importantly no single clinical, neuroimaging or cerebrospinal fluid feature defines a disorder with absolute certainty. This review will summarize clinical and paraclinical characteristics of acute disseminated encephalomyelitis in adults, with special emphasis on diagnostic imaging.