Intracerebral microbleeds in sepsis: susceptibility-weighted MR imaging findings

Brain magnetic resonance imaging findings six months after critical COVID-19: A prospective cohort study

BACKGROUND

COVID-19 patients suffered from neurological symptoms in the acute phase. Whether this led to long-term consequences was unknown. We studied long-term brain MRI findings in ICU-treated COVID-19 patients and compared them with findings in groups with less severe acute disease.

MATERIALS AND METHODS

In this prospective cohort study, 69 ICU-treated, 46 ward-treated, and 46 home-isolated patients, as well as 53 non-COVID-19 controls, underwent brain MRI six months after acute COVID-19. Plasma neurofilament light chain (NfL), a biomarker of neuroaxonal injury, was measured simultaneously.

RESULTS

Ischaemic infarctions existed in 5.8% of ICU-treated patients. Cerebral microbleeds (CMBs) existed in 27 (39.1%) ICU-treated, 13 (28.3%) ward-treated, 8 (17.4%) home-isolated COVID-19 patients, and 12 (22.6%) non-COVID controls. Patients with CMBs were older (p < 0.001), had a higher level of plasma NfL (p = 0.003), and higher supplementary oxygen days (p < 0.001). In multivariable analysis, age (OR 1.06, 95% CI 1.02-1.09) and supplementary oxygen days (OR 1.07, 95% CI 1.02-1.13) were associated with CMBs. The ICU group showed prevalent distribution of CMBs in deep regions.

CONCLUSION

Age and supplementary oxygen days were independently associated with CMBs; COVID-19 status showed no association. Accumulation of risk factors in the ICU group may explain the higher prevalence of CMBs.

TRIAL REGISTRATION

ClinicalTrials.govNCT04864938, registered February 9, 2021.

Neuroimaging of Infectious Vasculopathy

Vasculitis is a complication of several infectious diseases affecting the central nervous system, which may result in ischemic and/or hemorrhagic stroke, transient ischemic attack, and aneurysm formation. Infectious agents may directly infect the endothelium causing vasculitis or indirectly affect the vessel wall through an immunological cascade. Clinical manifestations usually overlap with those of noninfectious vascular diseases, making diagnosis challenging. Neuroimaging enables the identification of inflammatory changes in intracranial vasculitis. In this article, we review the imaging features of infectious vasculitis of bacterial, viral, fungal and parasitic causes.

Cerebral microbleeds. Utility of SWI sequences

OBJECTIVES

Define the concept of cerebral microbleeds (CMBs) and describe the most useful MRI sequences for detecting this finding. Review the entities that most frequently present with CMBs and that may benefit from the use of susceptibility-weighted imaging (SWI) sequences.

CONCLUSIONS

SWI is a useful MRI sequence for the detection and characterization of microhemorrhages, venous structures and other sources of susceptibility in imaging. SWI is particularly sensitive to local magnetic field inhomogeneities generated by certain substances and is superior to T2* GRE sequences for this assessment. CMBs may be seen in different neurologic conditions, in certain infrequent clinical contexts and have a key role as a biomarker status in gliomas (ITTS) and as a marker of inflammatory activity in multiple sclerosis.

Risk Assessment of Cnm-Positive Streptococcus mutans in Stroke Survivors (RAMESSES): Protocol for a Multicenter Prospective Cohort Study

Introduction

The role of commensal microbiota in systemic diseases, including brain diseases, has attracted increasing attention. Oral infectious diseases, such as dental caries and periodontitis, are also involved in cerebrovascular diseases and cognitive impairment. Cerebral microbleeds (CMBs) and intracerebral hemorrhage due to small vessel disease (SVD), are presumably associated with a high risk of vascular cognitive impairment and stroke. We previously reported that Streptococcus mutans (S. mutans, the main pathogen of dental caries), harboring the cnm gene that encodes the collagen-binding protein Cnm, is associated with the development of hypertensive intracerebral hemorrhage and aggravation of CMBs. We also proposed a mechanism by which the circulating Cnm-expressing S. mutans causes intracerebral hemorrhage or CMBs; it binds to denuded basement membranes mainly composed of collagen IV through damaged tight junctions or it directly invades endothelial cells, resulting in blood-brain barrier injury. In November 2018, we initiated a multicenter, prospective cohort study (RAMESSES: Risk Assessment of Cnm-positive S. mutans in Stroke Survivors; UMIN Clinical Trials Registry: UMIN000045559) to explore the longitudinal association between Cnm-positive S. mutans and CMBs with comprehensive dental findings, which should determine the effect of Cnm-positive S. mutans in the oral cavity on the risk of CMB development and cognitive decline.

Methods

Fifteen domestic institutes will be enlisted to enroll 230 patients who have at least one CMB in the deep brain area and develop a stroke within the past year. The prevalence of Cnm-positive S. mutans based on oral specimens and dental hygiene will be examined. The primary outcome is the number of newly developed deep CMBs. The secondary outcomes include the new development of lobar, subtentorial, or any type of CMBs; symptomatic intracerebral hemorrhage or ischemic stroke; changes in cognitive function or frailty; major bleeding; all-cause mortality; and antibody titers against periodontal pathogens. The observation period will be 2 years.

Discussion

The 2-year longitudinal prospective cohort study is expected to establish the role of Cnm-positive S. mutans in SVD including CMBs and intracerebral hemorrhage from the perspective of the “brain-oral axis” and provide guidance for novel prophylactic strategies against Cnm-positive S. mutans-induced SVD.

Treating the body to prevent brain injury: lessons learned from the coronavirus disease 2019 pandemic

PURPOSE OF REVIEW

We aim to provide the current evidence on utility and application of neuromonitoring tools including electroencephalography (EEG), transcranial Doppler (TCD), pupillometry, optic nerve sheath diameter (ONSD), cerebral near-infrared spectroscopy (cNIRS), somatosensory-evoked potentials (SSEPs), and invasive intracranial monitoring in COVID-19. We also provide recent evidence on management strategy of COVID-19-associated neurological complications.

RECENT FINDINGS

Despite the common occurrence of neurological complications, we found limited use of standard neurologic monitoring in patients with COVID-19. No specific EEG pattern was identified in COVID-19. Frontal epileptic discharge was proposed to be a potential marker of COVID-19 encephalopathy. TCD, ONSD, and pupillometry can provide real-time data on intracranial pressure. Additionally, TCD may be useful for detection of acute large vessel occlusions, abnormal cerebral hemodynamics, cerebral emboli, and evolving cerebral edema at bedside. cNIRS was under-utilized in COVID-19 population and there are ongoing studies to investigate whether cerebral oxygenation could be a more useful parameter than peripheral oxygen saturation to guide clinical titration of permissive hypoxemia. Limited data exists on SSEPs and invasive intracranial monitoring.

SUMMARY

Early recognition using standardized neuromonitoring and timely intervention is important to reduce morbidity and mortality. The management strategy for neurological complications is similar to those without COVID-19.

Multiple cerebral hemorrhages in sepsis-disseminated intravascular coagulation versus septic embolism: An image report

Background:

Septic emboli are commonly attributed to infective endocarditis and can present with a variety of symptoms including altered mental status and focal neurological deficits. Here, we reviewed images of septic emboli with hemorrhagic conversion in a patient with sepsis and a psoas abscess. We aim to show the classical image findings in septic embolism to brain, which is sparsely described in literature and the report differentiates the septic embolism from disseminated intravascular coagulation which can present with almost identical image findings.

Case Description:

A 53-year-old male patient who was operated on for a right inguinal hernia developed a postoperative wound infection 2 weeks after surgery and was started on IV antibiotics. Despite medical management, his infection did not improve, prompting a computed tomography (CT) scan which revealed a psoas abscess. The abscess was drained, and antibiotics continued. A few days later, he developed altered sensorium prompting a head CT which revealed septic emboli and hemorrhage at the gray-white junction. Cultures grew multidrug-resistant Escherichia coli; the patient was treated with IV tigecycline and improved over the following 4 weeks.

Conclusion:

In patients with a known ongoing infectious process with hemodynamic stability who develop altered mental status in the setting of a normal coagulation profile, D-dimer, positive blood cultures, and absent signs of multiorgan failure, a diagnosis of septic emboli should be entertained. Although CT can reveal macrobleeds, MRI is more sensitive in confirming cerebral microbleeds. Thus, patients in sepsis with unexplained altered sensorium should undergo an MRI of the brain to rule out septic emboli and microbleeds.

Cerebral microbleeds: from depiction to interpretation

Cerebral microbleeds (CMBs) are defined as hypointense foci visible on T2*-weighted and susceptible-weighted MRI sequences. CMBs are increasingly recognised with the widespread use of MRI in healthy individuals as well as in the context of cerebrovascular disease or dementia. They can also be encountered in major critical medical conditions such as in patients requiring extracorporeal mechanical oxygenation. The advent of MRI-guided postmortem neuropathological examinations confirmed that, in the context of cerebrovascular disease, the vast majority of CMBs correspond to recent or old microhaemorrhages. Detection of CMBs is highly influenced by MRI parameters, in particular field strength, postprocessing methods used to enhance T2* contrast and three dimensional sequences. Despite recent progress, harmonising imaging parameters across research studies remains necessary to improve cross-study comparisons. CMBs are helpful markers to identify the nature and the severity of the underlying chronic small vessel disease. In daily clinical practice, presence and numbers of CMBs often trigger uncertainty for clinicians especially when antithrombotic treatments and acute reperfusion therapies are discussed. In the present review, we discuss those clinical dilemmas and address the value of CMBs as diagnostic and prognostic markers for future vascular events.

Oral Carriage of Streptococcus mutans Harboring the cnm Gene Relates to an Increased Incidence of Cerebral Microbleeds

Supplemental Digital Content is available in the text.

Cerebral microbleeds (CMB) are associated with stroke and cognitive impairment. We previously reported a high prevalence of CMB in people with Streptococcus mutans expressing Cnm, a collagen-binding protein in the oral cavity. S.mutans is a major pathogen responsible for dental caries. Repeated challenge with S.mutans harboring the cnm gene encoding Cnm induced cerebral bleeding in stroke-prone spontaneously hypertensive rats. The purpose of this longitudinal study is to examine the relationship of cnm-positive S.mutans to the development of CMB.

Annexin A2 depletion exacerbates the intracerebral microhemorrhage induced by acute rickettsia and Ebola virus infections

Intracerebral microhemorrhages (CMHs) are small foci of hemorrhages in the cerebrum. Acute infections induced by some intracellular pathogens, including rickettsia, can result in CMHs. Annexin a2 (ANXA2) has been documented to play a functional role during intracellular bacterial adhesion. Here we report that ANXA2-knockout (KO) mice are more susceptible to CMHs in response to rickettsia and Ebola virus infections, suggesting an essential role of ANXA2 in protecting vascular integrity during these intracellular pathogen infections. Proteomic analysis via mass spectrometry of whole brain lysates and brain-derived endosomes from ANXA2-KO and wild-type (WT) mice post-infection with R. australis revealed that a variety of significant proteins were differentially expressed, and the follow-up function enrichment analysis had identified several relevant cell-cell junction functions. Immunohistology study confirmed that both infected WT and infected ANXA2-KO mice were subjected to adherens junctional protein (VE-cadherin) damages. However, key blood-brain barrier (BBB) components, tight junctional proteins ZO-1 and occludin, were disorganized in the brains from R. australis-infected ANXA2-KO mice, but not those of infected WT mice. Similar ANXA2-KO dependent CMHs and fragments of ZO-1 and occludin were also observed in Ebola virus-infected ANXA2-KO mice, but not found in infected WT mice. Overall, our study revealed a novel role of ANXA2 in the formation of CMHs during R. australis and Ebola virus infections; and the underlying mechanism is relevant to the role of ANXA2-regulated tight junctions and its role in stabilizing the BBB in these deadly infections.

Microbleeds in the Corpus Callosum in Anoxic Brain Injury

Purpose

This study was performed to evaluate the relationship between callosal microbleeds and anoxic brain injury.

Materials and Methods

Twenty-seven patients with anoxic brain injuries were analyzed and retrospectively compared to the control group of patients without a history of anoxic brain injury using Fisher's exact test regarding comorbidities and cerebral microbleeds. The patient group was subdivided according to the presence of callosal microbleeds. Fisher's exact test was used to compare the presence of typical MRI findings of anoxic brain injury, use of cardiopulmonary resuscitation, and prognosis. The Mann-Whitney U test was used to compare the interval between the occurrence of anoxic brain injury to MRI acquisition.

Results

The prevalence of cerebral microbleeds in the patient group was 29.6%, which was significantly higher than that in the control group at 3.7% (p = 0.012). All cerebral microbleeds in the patient group were in the corpus callosum. Compared with the callosal microbleed-absent group, the callosal microbleed-present group showed a tendency of good prognosis (6/8 vs. 11/19), fewer typical MRI findings of anoxic brain injury (2/8 vs. 10/19), and more cardiopulmonary resuscitation (6/8 vs. 12/19), although these differences did not reach statistical significance (p = 0.35, p = 0.19, and p = 0.45, respectively).

Conclusion

Callosal microbleeds may be an adjunctive MRI marker for anoxic brain injury.

Astroglia in Sepsis Associated Encephalopathy

Cellular pathophysiology of sepsis associated encephalopathy (SAE) remains poorly characterised. Brain pathology in SAE, which is manifested by impaired perception, consciousness and cognition, results from multifactorial events, including high levels of systemic cytokines, microbial components and endotoxins, which all damage the brain barriers, instigate neuroinflammation and cause homeostatic failure. Astrocytes, being the principal homeostatic cells of the central nervous system contribute to the brain defence against infection. Forming multifunctional anatomical barriers, astroglial cells maintain brain-systemic interfaces and restrict the damage to the nervous tissue. Astrocytes detect, produce and integrate inflammatory signals between immune cells and cells of brain parenchyma, thus regulating brain immune response. In SAE astrocytes are present in both reactive and astrogliopathic states; balance between these states define evolution of pathology and neurological outcomes. In humans pathophysiology of SAE is complicated by frequent presence of comorbidities, as well as age-related remodelling of the brain tissue with senescence of astroglia; these confounding factors further impact upon SAE progression and neurological deficits.

Cerebral microbleeds: Beyond the macroscope

While being increasingly recognized in clinical routine, brain microbleeds remain a puzzling finding for physicians. These small dot-like lesions are thought to be old perivascular collections of hemosiderin deposits. They can be found in different neurological settings such as cerebrovascular or neurodegenerative diseases. While their microscopic size would suggest considering these lesions as anecdotal, they are now regarded as biomarkers of severity of an underlying cerebrovascular disease. Their natural history and the interactions with surrounding brain cells remain unknown. However, their presence may impact therapeutic decisions. Deciphering the biological mechanisms leading to, or following microbleeds would enable us to address a key question: do microbleeds arise and impact the surrounding parenchyma like a miniature version of intracerebral hemorrhages or do they represent a different kind of injury? We hereby discuss, based on both clinical and experimental literature, the gap between the definition of microbleeds coming from neuroimaging and the pathophysiological hypotheses raised from histopathological and experimental data. Our analysis supports the need for a convergent effort from clinicians and basic scientists to go beyond the current “macro” view and disclose the cellular and molecular insights of these cerebral hemorrhagic microlesions.

Cerebral Microbleeds: Imaging and Clinical Significance

Cerebral microbleeds (CMBs), also referred to as microhemorrhages, appear on magnetic resonance (MR) images as hypointense foci notably at T2*-weighted or susceptibility-weighted (SW) imaging. CMBs are detected with increasing frequency because of the more widespread use of high magnetic field strength and of newer dedicated MR imaging techniques such as three-dimensional gradient-echo T2*-weighted and SW imaging. The imaging appearance of CMBs is mainly because of changes in local magnetic susceptibility and reflects the pathologic iron accumulation, most often in perivascular macrophages, because of vasculopathy. CMBs are depicted with a true-positive rate of 48%-89% at 1.5 T or 3.0 T and T2*-weighted or SW imaging across a wide range of diseases. False-positive "mimics" of CMBs occur at a rate of 11%-24% and include microdissections, microaneurysms, and microcalcifications; the latter can be differentiated by using phase images. Compared with postmortem histopathologic analysis, at least half of CMBs are missed with premortem clinical MR imaging. In general, CMB detection rate increases with field strength, with the use of three-dimensional sequences, and with postprocessing methods that use local perturbations of the MR phase to enhance T2* contrast. Because of the more widespread availability of high-field-strength MR imaging systems and growing use of SW imaging, CMBs are increasingly recognized in normal aging, and are even more common in various disorders such as Alzheimer dementia, cerebral amyloid angiopathy, stroke, and trauma. Rare causes include endocarditis, cerebral autosomal dominant arteriopathy with subcortical infarcts, leukoencephalopathy, and radiation therapy. The presence of CMBs in patients with stroke is increasingly recognized as a marker of worse outcome. Finally, guidelines for adjustment of anticoagulant therapy in patients with CMBs are under development. ^© RSNA, 2018.

Neuroimmune Axes of the Blood-Brain Barriers and Blood-Brain Interfaces: Bases for Physiological Regulation, Disease States, and Pharmacological Interventions

Central nervous system (CNS) barriers predominantly mediate the immune-privileged status of the brain, and are also important regulators of neuroimmune communication. It is increasingly appreciated that communication between the brain and immune system contributes to physiologic processes, adaptive responses, and disease states. In this review, we discuss the highly specialized features of brain barriers that regulate neuroimmune communication in health and disease. In section I, we discuss the concept of immune privilege, provide working definitions of brain barriers, and outline the historical work that contributed to the understanding of CNS barrier functions. In section II, we discuss the unique anatomic, cellular, and molecular characteristics of the vascular blood-brain barrier (BBB), blood-cerebrospinal fluid barrier, and tanycytic barriers that confer their functions as neuroimmune interfaces. In section III, we consider BBB-mediated neuroimmune functions and interactions categorized as five neuroimmune axes: disruption, responses to immune stimuli, uptake and transport of immunoactive substances, immune cell trafficking, and secretions of immunoactive substances. In section IV, we discuss neuroimmune functions of CNS barriers in physiologic and disease states, as well as pharmacological interventions for CNS diseases. Throughout this review, we highlight many recent advances that have contributed to the modern understanding of CNS barriers and their interface functions.

A murine model of inflammation-induced cerebral microbleeds

BACKGROUND

Cerebral microhemorrhages (CMH) are tiny deposits of blood degradation products in the brain and are pathological substrates of cerebral microbleeds. The existing CMH animal models are β-amyloid-, hypoxic brain injury-, or hypertension-induced. Recent evidence shows that CMH develop independently of hypoxic brain injury, hypertension, or amyloid deposition and CMH are associated with normal aging, sepsis, and neurodegenerative conditions. One common factor among the above pathologies is inflammation, and recent clinical studies show a link between systemic inflammation and CMH. Hence, we hypothesize that inflammation induces CMH development and thus, lipopolysaccharide (LPS)-induced CMH may be an appropriate model to study cerebral microbleeds.

METHODS

Adult C57BL/6 mice were injected with LPS (3 or 1 mg/kg, i.p.) or saline at 0, 6, and 24 h. At 2 or 7 days after the first injection, brains were harvested. Hematoxylin and eosin (H&E) and Prussian blue (PB) were used to stain fresh (acute) hemorrhages and hemosiderin (sub-acute) hemorrhages, respectively. Brain tissue ICAM-1, IgG, Iba1, and GFAP immunohistochemistry were used to examine endothelium activation, blood-brain barrier (BBB) disruption, and neuroinflammation. MRI and fluorescence microscopy were used to further confirm CMH development in this model.

RESULTS

LPS-treated mice developed H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. No surface and negligible H&E-positive CMH were observed in saline-treated mice (n = 12). LPS (3 mg/kg; n = 10) produced significantly higher number, size, and area of H&E-positive CMH at 2 days. LPS (1 mg/kg; n = 9) produced robust development of PB-positive CMH at 7 days, with significantly higher number and area compared with saline (n = 9)-treated mice. CMH showed the highest distribution in the cerebellum followed by the sub-cortex and cortex. LPS-induced CMH were predominantly adjacent to cerebral capillaries, and CMH load was associated with indices of brain endothelium activation, BBB disruption, and neuroinflammation. Fluorescence microscopy confirmed the extravasation of red blood cells into the brain parenchyma, and MRI demonstrated the presence of cerebral microbleeds.

CONCLUSIONS

LPS produced rapid and robust development of H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. The ease of development of both H&E- and PB-positive CMH makes the LPS-induced mouse model suitable to study inflammation-induced CMH.

[Formula: see text]evidence of neuropsychological dysfunction in Stevens-Johnson Syndrome and toxic epidermal necrolysis: case report

Stevens-Johnson Syndrome (SJS) and toxic epidermal necrolysis (TEN) is a potentially life-threatening critical illness affecting multiple organ systems including the peripheral and central nervous system. This case report involves a young man who was diagnosed with SJS/TEN at age 16 and underwent neuropsychological assessment at age 21. Results indicate a diffuse pattern of cerebral compromise and represent a decline from premorbid level of functioning. The etiology of the cognitive impairment in this patient is likely multifactorial with possible pathophysiologic mechanisms including hypoxemia, metabolic acid-base perturbations, hyperglycemia, and delirium, as well as sepsis and inflammation.