Viral Infections and White Matter Lesions

Into the Unknown: Diagnosing Mysterious Brain Lesions

The case discussed involves a 49-year-old male with simultaneous pancreas-kidney transplant who presented with fever, headache and was found to have multifocal brain lesion on brain imaging. This article is protected by copyright. All rights reserved.

Early life exposure to poly I:C impairs striatal DA-D2 receptor binding, myelination and associated behavioural abilities in rats

Early-life viral infections critically influence the brain development and have been variously reported to cause neuropsychiatric diseases such as Schizophrenia, Parkinson's diseases, demyelinating diseases, etc. To investigate the alterations in the dopaminergic system, myelination and associated behavioral impairments following neonatal viral infection, the viral immune activation model was created by an intraperitoneal injection of Poly I:C (5 mg/kg bw/ip) to neonatal rat pups on PND-7. The DA-D2 receptor binding was assessed in corpus striatum by using ³H-Spiperone at 3, 6 and 12 weeks of age. MOG immunolabelling was performed to check myelination stature and myelin integrity, while corpus callosum calibre was assessed by Luxol fast blue staining. Relative behavioral tasks i.e., motor activity, motor coordination and neuromuscular strength were assessed by open field, rotarod and grip strength meter respectively at 3, 6 and 12 weeks of age. Following Poly I:C exposure, a significant decrease in DA-D2 receptor binding, reduction in corpus callosum calibre and MOG immunolabelling indicating demyelination and a significant decrease in locomotor activity, neuromuscular strength and motor coordination signify motor deficits and hypokinetic influence of early life viral infection. Thus, the findings suggest that early life poly I:C exposure may cause demyelination and motor deficits by decreasing DA-D2 receptor binding affinity.

Intracranial Abnormalities with Diffusion Restriction

Multiple pathologic conditions can cause changes in the random movement of water, which can be detected with diffusion-weighted imaging (DWI). DWI plays a powerful clinical role in detecting restricted diffusion associated with acute brain infarction. Other disorders can also result in restricted diffusion. This article focuses on showing examples of common and uncommon disorders that have restricted diffusion secondary to cytotoxic and/or intramyelinic edema. These disorders include ischemia, infection, noninfectious demyelinating diseases, genetic mutations affecting metabolism, acquired metabolic disorders, toxic or drug exposures, neoplasms and tumorlike lesions, radiation treatment, trauma, and denervation.

Relapsing Demyelinating Syndromes in Children: A Practical Review of Neuroradiological Mimics

Relapsing demyelinating syndromes (RDS) in children encompass a diverse spectrum of entities including multiple sclerosis (MS) acute disseminated encephalomyelitis (ADEM), aquaporin-4 antibody associated neuromyelitis optica spectrum disorder (AQP4-NMOSD) and myelin oligodendrocyte glycoprotein antibody disease (MOG-AD). In addition to these, there are “antibody-negative” demyelinating syndromes which are yet to be fully characterized and defined. The paucity of specific biomarkers and overlap in clinical presentations makes the distinction between these disease entities difficult at initial presentation and, as such, there is a heavy reliance on magnetic resonance imaging (MRI) findings to satisfy the criteria for treatment initiation and optimization. Misdiagnosis is not uncommon and is usually related to the inaccurate application of criteria or failure to identify potential clinical and radiological mimics. It is also notable that there are instances where AQP4 and MOG antibody testing may be falsely negative during initial clinical episodes, further complicating the issue. This article illustrates the typical clinico-radiological phenotypes associated with the known pediatric RDS at presentation and describes the neuroimaging mimics of these using a pattern-based approach in the brain, optic nerves, and spinal cord. Practical guidance on key distinguishing features in the form of clinical and radiological red flags are incorporated. A subsection on clinical mimics with characteristic imaging patterns that assist in establishing alternative diagnoses is also included.

Metabolic Syndrome and Cardiovascular Disease Impacts on the Pathophysiology and Phenotype of HIV-Associated Neurocognitive Disorders

Evidence from epidemiological studies on the general population suggests that midlife cardiovascular disease (CVD) and/or metabolic syndrome (MetS) are associated with an increased risk of cognitive impairment and dementia later in life. In the modern combined antiretroviral therapy (cART) era, as in the general population, CVD and MetS were strongly and independently associated with poorer cognitive performances of sustained immunovirologically controlled persons living with human immunodeficiency viruses (PLHIVs). Those findings suggest that CV/metabolic comorbidities could be implicated in the pathogenesis of HIV-associated neurocognitive disorders (HAND) and might be more important than factors related to HIV infection or its treatment, markers of immunocompetence, or virus replication. The association between CVD/MetS and cognition decline is driven by still not well-understood mechanisms, but risk might well be the consequence of increased brain inflammation and vascular changes, notably cerebral small-vessel disease. In this review, we highlight the correspondences observed between the findings concerning CVD and MetS in the general population and virus-suppressed cART-treated PLHIVs to evaluate the real brain-aging processes. Indeed, incomplete HIV control mainly reflects HIV-induced brain damage described during the first decades of the pandemic. Given the growing support that CVD and MetS are associated with HAND, it is crucial to improve early detection and assure appropriate management of these conditions.

[Panencephalitis in children in modern conditions: clinical, etiological and mri-aspects]

AIM

To characterize the clinical picture, infectious etiology and MRI results of panencephalitis (PANE) in children, depending on the duration of the disease.

MATERIAL AND METHODS

Children (n=32) with PANE at the age from 3 months up to 17 years were examined for a group of actual viral and bacterial infections. The inclusion criterion was a diffuse lesion of white matter hemispheres on MRI. MRI of the brain and spinal cord, CSF study (pleocytosis, oligoclonal IgG, the main myelin protein (MBP) were performed. The follow-up was 5-10 years. The complex therapy included etiotropic (antiviral) and pathogenetic agents, with priority given to cytoflavin as a drug with a multimodal effect.

RESULTS

In 84.4% of cases, PANE in children are recorded under the age of 3 years and in 71.9% of cases, are associated with congenital infections with the prevalence of herpes viruses, especially cytomegalovirus (37,8%) and herpes type 6 (21.9%). In 78.3% of cases, PANE have chronic gradual development more often with a delay in the formation of motor and speech/prespeech skills, and manifested with pyramidal, cerebellar and other symptoms in the future. PANE is accompanied by a lesion of the white matter of the hemispheres in ¹/₂ cases with periventricular localization, less often in infratentorial structures (46.9%) and spinal cord (21.9%). With the duration of symptoms up to 3 months (n=22) PANE are characterized by inflammatory-demyelinating changes, signs of mass effect, contrast+, pleocytosis in CSF and the increase in MBP (average 4.2±0.8 ng/ml), and, with the duration of more than 3 months, by degenerative-sclerosing changes (n=10) and CSF oligoclonal IgG in 90% of cases.

CONCLUSION

In almost ²/₃ of cases, PANE are associated with congenital infections, accompanied by extensive symmetrical foci of demyelination in the CNS, and their clinical and laboratory parameters and outcomes depend on the start of treatment, with the positive dynamics in 75% of cases.

Human immunodeficiency virus-related cerebral white matter disease in children

The human immunodeficiency virus (HIV) epidemic seems largely controlled by anti-retroviral treatment with resultant large numbers of children growing up with the disease on long-term treatment, placing them at higher risk to develop HIV-related brain injury, ongoing cognitive impairment and treatment-related neurological complications. Cerebral white matter involvement is a common radiologic finding in HIV infection and the causes of this have overlapping appearances, ranging from diffuse widespread involvement to focal lesions. The varied pathophysiology is broadly grouped into primary effects of HIV, opportunistic infection, vascular disease and neoplasms. White matter changes in children can be different from those in adults. This review provides guidance to radiologists with the diagnostic dilemma of nonspecific cerebral white matter lesions in children with HIV. The authors discuss common causes of HIV-related cerebral white matter disease as well as the role of neuroimaging in the management of these children.

Cytotoxic Lesions of the Corpus Callosum That Show Restricted Diffusion: Mechanisms, Causes, and Manifestations

Cytotoxic lesions of the corpus callosum (CLOCCs) are secondary lesions associated with various entities. CLOCCs have been found in association with drug therapy, malignancy, infection, subarachnoid hemorrhage, metabolic disorders, trauma, and other entities. In all of these conditions, cell-cytokine interactions lead to markedly increased levels of cytokines and extracellular glutamate. Ultimately, this cascade can lead to dysfunction of the callosal neurons and microglia. Cytotoxic edema develops as water becomes trapped in these cells. On diffusion-weighted magnetic resonance (MR) images, CLOCCs manifest as areas of low diffusion. CLOCCs lack enhancement on contrast material-enhanced images, tend to be midline, and are relatively symmetric. The involvement of the corpus callosum typically shows one of three patterns: (a) a small round or oval lesion located in the center of the splenium, (b) a lesion centered in the splenium but extending through the callosal fibers laterally into the adjacent white matter, or (c) a lesion centered posteriorly but extending into the anterior corpus callosum. CLOCCs are frequently but not invariably reversible. Their pathologic mechanisms are discussed, the typical MR imaging findings are described, and typical cases of CLOCCs are presented. Although CLOCCs are nonspecific with regard to the underlying cause, additional imaging findings and the clinical findings can aid in making a specific diagnosis. Radiologists should be familiar with the imaging appearance of CLOCCs to avoid a misdiagnosis of ischemia. When CLOCCs are found, the underlying cause of the lesion should be sought and addressed. ^©RSNA, 2017 An earlier incorrect version of this article appeared online. This article was corrected on February 13, 2017.

Structural and Ultrastructural Alterations in Human Olfactory Pathways and Possible Associations with Herpesvirus 6 Infection

Structural and ultrastructural alterations in human olfactory pathways and putative associations with human herpesvirus 6 (HHV-6) infection were studied. The olfactory bulb/tract samples from 20 subjects with an unspecified encephalopathy determined by pathomorphological examination of the brain autopsy, 17 healthy age-matched and 16 younger controls were used. HHV-6 DNA was detected in 60, 29, and 19% of cases in these groups, respectively. In the whole encephalopathy group, significantly more HHV-6 positive neurons and oligodendrocytes were found in the gray matter, whereas, significantly more HHV-6 positive astrocytes, oligodendrocytes, microglia/macrophages and endothelial cells were found in the white matter. Additionally, significantly more HHV-6 positive astrocytes and, in particular, oligodendrocytes were found in the white matter when compared to the gray matter. Furthermore, when only HHV-6 PCR⁺ encephalopathy cases were studied, we observed similar but stronger associations between HHV-6 positive oligodendrocytes and CD68 positive cells in the white matter. Cellular alterations were additionally evidenced by anti-S100 immunostaining, demonstrating a significantly higher number of S100 positive cells in the gray matter of the whole encephalopathy group when compared to the young controls, and in the white matter when compared to both control groups. In spite the decreased S100 expression in the PCR⁺ encephalopathy group when compared to PCR^- cases and controls, groups demonstrated significantly higher number of S100 positive cells in the white compared to the gray matter. Ultrastructural changes confirming the damage of myelin included irregularity of membranes and ballooning of paranodal loops. This study shows that among the cellular targets of the nervous system, HHV-6 most severely affects oligodendrocytes and the myelin made by them.

Infektionen des ZNS

Viren, Bakterien, Protozoen, Helminthen und Pilze können, sofern es ihnen gelingt, die Blut-Hirn-Schranke zu überwinden, ZNS und gelegentlich das periphere Nervensystem involvieren; Meningitis, Enzephalitis, Hirnabszess, Meningovaskulitis oder granulomatöse Prozesse sind potenzielle Folgen.