Neuroimaging in encephalitis: analysis of imaging findings and interobserver agreement

Diagnosing infectious encephalitis: a narrative review

BACKGROUND

Diagnosing infectious encephalitis can be challenging as it can be caused by a wide range of pathogens, with viruses being the most common cause. In a substantial number of patients, no pathogen is identified despite a clinical diagnosis of infectious encephalitis. Recent advancements in diagnostic testing have introduced new methods to address this diagnostic challenge and improve pathogen detection.

OBJECTIVES

The objective of this study is to provide a comprehensive clinical approach for diagnosing infectious encephalitis and explore novel diagnostic methods.

SOURCES

We searched PubMed to identify relevant literature on diagnosing encephalitis in English up to 1 September 2024, as well as included articles known by the authors.

CONTENT

Clinical characteristics may suggest a specific cause of infectious encephalitis, but are insufficient to guide treatment decisions. Therefore, cerebrospinal fluid (CSF) examination remains the cornerstone of the diagnostic process, with CSF leucocyte count being the most reliable predictor for central nervous system infections. CSF features can be normal, however, in a proportion of patients presenting with infectious encephalitis. A definite diagnosis of infectious encephalitis is established by microbiological or histopathological tests in ∼50% of patients. Additional investigations, including neuroimaging or electroencephalography, can provide evidence for encephalitis or help to identify alternate conditions, although their role is primarily supportive. Emerging diagnostic techniques, including next-generation sequencing metagenomics and unbiased serology (Phage ImmunoPrecipitation Sequencing), have the potential to increase the proportion of patients with a confirmed diagnosis. However, these techniques are not yet practical because of their complex analysis, long turnaround times and high costs.

IMPLICATIONS

Microbiological confirmation is paramount in the diagnosis of infectious encephalitis, but it is currently established in about half of cases. Although novel techniques show promise to increase the proportion of cause-specific diagnoses, they are not yet suitable for routine use. This highlights the ongoing need for advancements in diagnostic methods.

Seronegative herpes simplex virus (HSV) encephalitis causing temporal lobe epilepsy resulting in new-onset psychosis: a case report and literature review

Background

Herpes simplex virus (HSV) encephalitis is the most common nonepidemic encephalitis and can result in temporal lobe necrosis. Inflammation of the temporal lobe can result in temporal lobe epilepsy which is known to cause psychiatric symptoms.

Case Description

We describe the case of a geriatric male patient who was admitted for new-onset visual hallucinations and other neuropsychiatric symptoms which began five days prior to admission. His lab work was unremarkable, and a computed tomography (CT) scan of the brain demonstrated small vessel ischemic disease. There was clinical suspicion for seizures, and electroencephalogram (EEG) monitoring showed focal seizure activity in the right hemisphere. He received a brain magnetic resonance imaging (MRI) which was suspicious for encephalitis. Various etiologies were considered, and he received an extensive workup including cerebrospinal fluid evaluation. Ultimately, he improved with empiric antiviral treatment added alongside multiple antiepileptic agents. The seizure control and resolution of symptoms with antiviral treatment, in addition to the findings of his central nervous system (CNS) workup, confirmed the presumptive diagnosis of HSV encephalitis.

Conclusions

Understanding the multifactorial causes of neuropsychiatric symptoms is important in determining an appropriate workup. The acute onset of specific symptoms in our patient increased suspicion for a structural neurological process. His initial presentation could largely be explained by the vascular dementia and epileptiform activity that were discovered during hospitalization. However, his refractory seizures were suggestive of another underlying etiology. The localization of his seizures and MRI findings were suggestive of HSV encephalitis despite negative HSV polymerase chain reaction (PCR). A patient may benefit from antiviral treatment when the clinical picture is consistent with HSV encephalitis even in the setting of negative serological studies. Clinicians should also be mindful of false negatives on serological tests.

Cefepime-Induced Encephalopathy in Patients Treated for Urinary Tract Infection

Cefepime is a fourth-generation cephalosporin antibiotic administered intravenously used to treat various bacterial infections, including urinary tract infections. Administering cefepime to patients should be done with caution, understanding both potential risks and side effects. A 74-year-old female presented to the family medicine clinic with abdominal pain and a history of urinary tract infections. The workup included a CT scan that showed bowel obstruction and bladder wall thickening. Due to a history of urinary tract infections, three days following the presentation, the patient underwent an explorative laparotomy. Following the laparotomy, the patient was started on cefepime, a fourth-generation cephalosporin antibiotic. Five days following the initial presentation, the patient became confused and was nonverbal. An encephalopathy workup showed a negative MRI, but an EEG was consistent with encephalopathy. Cefepime was discontinued. Forty-eight hours after cefepime was discontinued, the patient returned to baseline with normal cognitive function. It is crucial that clinicians understand the different classifications of antibiotics, as well as the drugs and potential side effects of prescriptions. Cefepime can be used in gram-negative infections with resistance to more generic antibiotics. It has the ability to cross the blood-brain barrier, making it effective in treating meningitis. It has also been shown to cause encephalopathy as a side effect. It is important that clinicians understand the different generations of cephalosporins, as well as the cross-reactions and potential side effects of prescriptions. These factors must be considered when prescribing broad-spectrum antibiotics, such as cefepime.

Navigating diagnostic challenges: imaging strategies for herpes simplex encephalitis in resource limited settings: A case report

Encephalitis refers to the inflammatory condition affecting the brain parenchyma, leading to various neurological impairments. It can have various causes: infectious, postinfectious, and noninfectious origins. In this case, we present a 76-year-old man who presented to the emergency room with complaints of headache and behavioral changes. Initially, a Computed Tomography (CT) scan raised suspicion of herpes simplex encephalitis and prompted the initiation of treatment. Subsequently, Magnetic Resonance Imaging (MRI) and Cerebrospinal fluid (CSF) culture confirmed the diagnosis. However, despite medical intervention, the patient's condition unexpectedly deteriorated, and he unfortunately passed away after spending 2 weeks in the Intensive Care Unit (ICU). Possible factors contributing to this outcome include delayed presentation to medical care, viral resistance, or the inherent nature of the infection itself, particularly in elderly patients.

Viral meningoencephalitis in pediatric solid organ or hematopoietic cell transplant recipients: a diagnostic and therapeutic approach

Neurologic complications, both infectious and non-infectious, are frequent among hematopoietic cell transplant (HCT) and solid organ transplant (SOT) recipients. Up to 46% of HCT and 50% of SOT recipients experience a neurological complication, including cerebrovascular accidents, drug toxicities, as well as infections. Defects in innate, adaptive, and humoral immune function among transplant recipients predispose to opportunistic infections, including central nervous system (CNS) disease. CNS infections remain uncommon overall amongst HCT and SOT recipients, compromising approximately 1% of total cases among adult patients. Given the relatively lower number of pediatric transplant recipients, the incidence of CNS disease amongst in this population remains unknown. Although infections comprise a small percentage of the neurological complications that occur post-transplant, the associated morbidity and mortality in an immunosuppressed state makes it imperative to promptly evaluate and aggressively treat a pediatric transplant patient with suspicion for viral meningoencephalitis. This manuscript guides the reader through a broad infectious and non-infectious diagnostic differential in a transplant recipient presenting with altered mentation and fever and thereafter, elaborates on diagnostics and management of viral meningoencephalitis. Hypothetical SOT and HCT patient cases have also been constructed to illustrate the diagnostic and management process in select viral etiologies. Given the unique risk for various opportunistic viral infections resulting in CNS disease among transplant recipients, the manuscript will provide a contemporary review of the epidemiology, risk factors, diagnosis, and management of viral meningoencephalitis in these patients.

Anaplasma phagocytophilum Encephalitis: A Case Report and Literature Review of Neurologic Manifestations of Anaplasmosis

Anaplasma phagocytophilum is an obligate intracellular, Gram-negative pathogen, causative agent of Human Granulocytic Anaplasmosis (HGA). HGA usually manifests as a non-specific febrile illness, accompanied by evidence of leucopenia, thrombocytopenia, and an alteration in liver enzymes. Neurologic manifestations of anaplasmosis are rare and rarely reported. We describe a 62-year-old man who developed encephalitis due to an Anaplasma phagocytophilum infection. The patient favorably responded to intravenous doxycycline and recovered without neurological sequela. In the tick endemic area, clinicians should have a high index of suspicion for tick-borne diseases in patients presenting with neurological deficits. A prompt diagnosis and treatment lead to improvements in morbidity and mortality.

Transient disruption of functional connectivity and depression of neural fluctuations in a mouse model of acute septic encephalopathy

Septic encephalopathy leads to major and costly burdens for a large percentage of admitted hospital patients. Elderly patients are at an increased risk, especially those with dementia. Current treatments are aimed at sedation to combat mental status changes and are not aimed at the underlying cause of encephalopathy. Indeed, the underlying pathology linking together peripheral infection and altered neural function has not been established, largely because good, acutely accessible readouts of encephalopathy in animal models do not exist. Behavioral testing in animals lasts multiple days, outlasting the time frame of acute encephalopathy. Here, we propose optical fluorescent imaging of neural functional connectivity (FC) as a readout of encephalopathy in a mouse model of acute sepsis. Imaging and basic behavioral assessment were performed at baseline, Hr8, Hr24, and Hr72 following injection of either lipopolysaccharide or phosphate buffered saline. Neural FC strength decreased at Hr8 and returned to baseline by Hr72 in motor, somatosensory, parietal, and visual cortical regions. Additionally, neural fluctuations transiently declined at Hr8 and returned to baseline by Hr72. Both FC strength and fluctuation tone correlated with neuroscore indicating this imaging methodology is a sensitive and acute readout of encephalopathy.

Empirical intravenous aciclovir therapy in a suspected case of acute encephalitis

Herpes simplex encephalitis is the most common cause of sporadic viral encephalitis worldwide but presents as a diagnostic challenge at many settings due to its non-specific symptoms, which can be easily mistaken for systemic infection or metabolic encephalopathy. It has diverse range of presentations from fever, altered sensorium, nausea, vomiting, meningismus to seizures, neurological deficits and coma in advanced stages. It is associated with significant morbidity and mortality if treatment is delayed or inadequate. We here discuss a case of Herpes simplex virus (HSV) encephalitis which rapidly progressed to result in irreversible neurological insult due to delayed diagnosis and treatment.

Increased volume of cerebral oedema is associated with risk of acute seizure activity and adverse neurological outcomes in encephalitis - regional and volumetric analysis in a multi-centre cohort

BACKGROUND

Seizures can occur unpredictably in patients with acute encephalitis syndrome (AES), and many suffer from poor long-term neurological sequelae. Establishing factors associated with acute seizures risk and poor outcomes could support clinical care. We aimed to conduct regional and volumetric analysis of cerebral oedema on magnetic resonance imaging (MRI) in patients with AES. We assessed the relationship of brain oedema with acute seizure activity and long-term neurological outcome.

METHODS

In a multi-centre cohort study, adults and children presenting with an AES were recruited in the UK. The clinical and brain MRI data were retrospectively reviewed. The outcomes variables were inpatient acute seizure activity and neurological disability at six-months post-discharge. A poor outcome was defined as a Glasgow outcome score (GOS) of 1-3. We quantified regional brain oedema on MRI through stereological examination of T2-weighted images using established methodology by independent and blinded assessors. Clinical and neuroimaging variables were analysed by multivariate logistic regression to assess for correlation with acute seizure activity and outcome.

RESULTS

The study cohort comprised 69 patients (mean age 31.8 years; 53.6% female), of whom 41 (59.4%) had acute seizures as inpatients. A higher Glasgow coma scale (GCS) score on admission was a negative predictor of seizures (OR 0.61 [0.46-0.83], p = 0.001). Even correcting for GCS on admission, the presence of cortical oedema was a significant risk factor for acute seizure activity (OR 5.48 [1.62-18.51], p = 0.006) and greater volume of cerebral oedema in these cortical structures increased the risk of acute seizures (OR 1.90 [1.12-3.21], p = 0.017). At six-month post-discharge, 21 (30.4%) had a poor neurological outcome. Herpes simplex virus encephalitis was associated with higher risk of poor outcomes in univariate analysis (OR 3.92 [1.08-14.20], p = 0.038). When controlling for aetiology, increased volume of cerebral oedema was an independent risk factor for adverse neurological outcome at 6 months (OR 1.73 [1.06-2.83], p = 0.027).

CONCLUSIONS

Both the presence and degree of cerebral oedema on MRIs of patients with AES may help identify patients at risk of acute seizure activity and subsequent long-term morbidity.

Neuroinvasive disease due to West Nile virus: Clinical and imaging findings associated with a re-emerging pathogen

The West Nile virus (WNV) is an arbovirus than can infect human beings and cause severe neuroinvasive disease. Taking the outbreak that occurred in Spain in 2020 as a reference, this article reviews the clinical and imaging findings for neuroinvasive disease due to WNV. We collected demographic, clinical, laboratory, and imaging (CT and MRI) variables for 30 patients with WNV infection diagnosed at our center. The main clinical findings were fever, headache, and altered levels of consciousness. Neuroimaging studies, especially MRI, are very useful in the diagnosis and follow-up of these patients. The most common imaging findings were foci of increased signal intensity in the thalamus and brainstem in T2-weighted sequences; we illustrate these findings in cases from our hospital.

Herpes Simplex Virus Type 2 Encephalitis in an Immunocompetent Adult: A Case Report on an Unusual but Relevant Cause of Significant Neurological Morbidity

Encephalitis refers to inflammation of the brain that is most frequently caused by viral infection (particularly herpes simplex virus type 1 [HSV-1]). In some instances, it may be associated with substantial neurological mortality and long-term morbidity. Although HSV-1 is the most common agent involved in producing neurological infections and disorders, herpes simplex virus type 2 (HSV-2) can occasionally affect the central nervous system, particularly in immunocompromised patients. We discuss the case of an immunocompetent male patient with a history of well-controlled diabetes who presented with symptoms of encephalitis. Our patient did not have a history of herpes infection, indicating the presence of subclinical infections. His initial magnetic resonance imaging was inconclusive, but the diagnosis was established following a lumbar puncture and subsequent cerebrospinal fluid analyses.

Neurology of Acute Viral Infections

As specialists in acute neurology, neurohospitalists are often called upon to diagnose and manage acute viral infections affecting the nervous system. In this broad review covering the neurology of several acute viral infections, our aim is to provide key diagnostic and therapeutic pearls of practical use to the busy neurohospitalist. We will review acute presentations, diagnosis, and treatment of human herpesviruses, arboviruses, enteroviruses, and some vaccine-preventable viruses. The neurological effects of coronaviruses, including COVID-19, are not covered in this review.

Case Report: HSV-2 Encephalitis Presenting With Chorea; Effects of Infection Alone or Combination of Infection and Autoimmunity?

Background: Chorea as a symptom of late-onset post-infectious autoimmune encephalitis has been reported with HSV-1 but not HSV-2 encephalitis. Extrapyramidal symptoms are typically associated with the presence of anti-NMDA receptor antibodies but may also exist in antibody-negative individuals.

Case: This case highlights a patient who presented with mental status changes and chorea as the initial manifestation of HSV-2 encephalitis. The choreiform movements failed to respond to antiviral medications but were rapidly responsive to plasmapheresis, which, together with abnormal intrathecal immunoglobulin synthesis, suggests a potential contribution of parainfectious immune-mediated process. The patient made a full recovery and a complete resolution of the chorea.

Discussion: This is the first case associating HSV-2 encephalitis presentation with chorea. The neurological complications, including chorea, are largely related to active CNS HSV-2 infection, possibly together with triggered CNS autoimmunity despite undetectable CSF neuronal autoantibodies and normal neuroimaging. Early diagnosis and treatment with antiviral agent and immune therapies might be pivotal to optimize the clinical outcome.

Encephalitis as a neurological complication of COVID-19: A systematic review and meta-analysis of incidence, outcomes, and predictors

BACKGROUND AND PURPOSE

Although COVID-19 predominantly affects the respiratory system, recent studies have reported the occurrence of neurological disorders such as stroke in relation to COVID-19 infection. Encephalitis is an inflammatory condition of the brain that has been described as a severe neurological complication of COVID-19. Despite a growing number of reported cases, encephalitis related to COVID-19 infection has not been adequately characterised. To address this gap, this systematic review and meta-analysis aims to describe the incidence, clinical course, and outcomes of patients who suffer from encephalitis as a complication of COVID-19.

METHODS

All studies published between 1 November 2019 and 24 October 2020 that reported on patients who developed encephalitis as a complication of COVID-19 were included. Only cases with radiological and/or biochemical evidence of encephalitis were included.

RESULTS

In this study, 610 studies were screened and 23 studies reporting findings from 129,008 patients, including 138 with encephalitis, were included. The average time from diagnosis of COVID-19 to onset of encephalitis was 14.5 days (range = 10.8-18.2 days). The average incidence of encephalitis as a complication of COVID-19 was 0.215% (95% confidence interval [CI] = 0.056%-0.441%). The average mortality rate of encephalitis in COVID-19 patients was 13.4% (95% CI = 3.8%-25.9%). These patients also had deranged clinical parameters, including raised serum inflammatory markers and cerebrospinal fluid pleocytosis.

CONCLUSIONS

Although encephalitis is an uncommon complication of COVID-19, when present, it results in significant morbidity and mortality. Severely ill COVID-19 patients are at higher risk of suffering from encephalitis as a complication of the infection.

Neuroinvasive disease due to West Nile virus: clinical and imaging findings associated with a re-emerging pathogen

The West Nile virus (WNV) is an arbovirus than can infect human beings and cause severe neuroinvasive disease. Taking the outbreak that occurred in Spain in 2020 as a reference, this article reviews the clinical and imaging findings for neuroinvasive disease due to WNV. We collected demographic, clinical, laboratory, and imaging (CT and MRI) variables for 30 patients with WNV infection diagnosed at our center. The main clinical findings were fever, headache, and altered levels of consciousness. Neuroimaging studies, especially MRI, are very useful in the diagnosis and follow-up of these patients. The most common imaging findings were foci of increased signal intensity in the thalamus and brainstem in T2-weighted sequences; we illustrate these findings in cases from our hospital.

Assessment of Magnetic Resonance Imaging Changes and Functional Outcomes Among Adults With Severe Herpes Simplex Encephalitis

Importance

Current guidelines recommend brain magnetic resonance imaging (MRI) for clinical management of patients with severe herpes simplex encephalitis (HSE). However, the prognostic value of brain imaging has not been demonstrated in this setting.

Objective

To investigate the association between early brain MRI data and functional outcomes of patients with HSE at 90 days after intensive care unit (ICU) admission.

Design, Setting, and Participants

This multicenter cohort study was conducted in 34 ICUs in France from 2007 to 2019 and recruited all patients who received a clinical diagnosis of encephalitis and exhibited cerebrospinal fluid positivity for herpes simplex virus DNA in the polymerase chain reaction analysis. Data analysis was performed from January to April 2020.

Exposures

All patients underwent a standard brain MRI during the first 30 days after ICU admission.

Main Outcomes and Measures

MRI acquisitions were analyzed by radiologists blinded to patients' outcomes, using a predefined score. Multivariable logistic regression and supervised hierarchical classifiers methods were used to identify factors associated with poor outcome at 90 days, defined by a score of 3 to 6 (indicating moderate-to-severe disability or death) on the Modified Rankin Scale.

Results

Overall, 138 patients (median [interquartile range {IQR}] age, 62.6 [54.0-72.0] years; 75 men [54.3%]) with an admission median (IQR) Glasgow Coma Scale score of 9 (6-12) were studied. The median (IQR) delay between ICU admission and MRI was 1 (1-7) days. At 90 days, 95 patients (68.8%) had a poor outcome, including 16 deaths (11.6%). The presence of fluid-attenuated inversion recovery MRI signal abnormalities in more than 3 brain lobes (odds ratio [OR], 25.71; 95% CI, 1.21-554.42), age older than 60 years (OR, 7.62; 95% CI, 2.02-28.91), and the presence of diffusion-weighted MRI signal abnormalities in the left thalamus (OR, 6.90; 95% CI, 1.12-43.00) were independently associated with poor outcome. Machine learning models identified bilateral diffusion abnormalities as an additional factor associated with poor outcome (34 of 39 patients [87.2%] with bilateral abnormalities had poor outcomes) and confirmed the functional burden of left thalamic lesions, particularly in older patients (all 11 patients aged >60 years had left thalamic lesions).

Conclusions and Relevance

These findings suggest that in adult patients with HSE requiring ICU admission, extensive MRI changes in the brain are independently associated with poor functional outcome at 90 days. Thalamic diffusion signal changes were frequently observed and were associated with poor prognosis, mainly in older patients.

Anti-NMDAR encephalitis for psychiatrists: the essentials

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis predominantly presents with psychiatric symptoms. Psychiatrists need to be alert to this diagnostic possibility, especially in female adolescents and young adults, as exemplified by the real (de-identified) case outlined below. Earlier diagnosis and immunotherapy improves long-term outcomes. Collaboration with neurology colleagues is essential for optimal care. 'Red flags' for autoimmune encephalitis and 'diagnostic clues' act as helpful aide memoires for this uncommon condition. The gold standard for testing is the detection of NMDAR antibodies in cerebrospinal fluid, but serum can be tested as a more accessible (but less reliable) preliminary step. The results of routine blood tests, magnetic resonance imaging of the head and electroencephalograms can be normal or show non-specific changes. Diagnostic criteria exist to define probable and definite cases. Immunotherapy for anti-NMDAR encephalitis is effective for many patients, but recovery is prolonged and relapses can occur.

Varicella Zoster Virus Encephalitis in Denmark From 2015 to 2019-A Nationwide Prospective Cohort Study

BACKGROUND

Knowledge of the epidemiology and clinical characteristics of varicella zoster virus (VZV) encephalitis remains limited.

METHODS

Nationwide prospective cohort study of adults treated for microbiologically confirmed VZV encephalitis at Danish departments of infectious diseases from 2015 to 2019. Modified Poisson regression analysis was used to compute adjusted relative risks (RRs) of unfavorable outcome.

RESULTS

We identified 92 adults (49% female) with VZV encephalitis, yielding an incidence of 5.3/1 000 000 per year (95% CI, 4.2-6.6). Median age was 75 years (IQR, 67-83) and immunocompromising conditions were frequent (39%). Predominant symptoms were confusion (76%), headache (56%), nausea (45%), gait disturbance (42%), and personality changes (41%). Cranial imaging showed cerebral vasculitis (including infarction and hemorrhage) in 14 (16%) patients and encephalitic abnormalities in 11 (13%) with predilection for the brainstem and deep brain structures. Intravenous acyclovir treatment was initiated a median (IQR) of 13.4 hours (5.2-46.3) since admission, while cranial imaging and lumbar puncture were performed after 6.3 hours (2.5-31.0) and 18.5 hours (4.9-42.0). In-hospital, 1-month, and 3-month mortalities were 4%, 9%, and 11%, respectively. Unfavorable outcome (Glasgow Outcome Score of 1-4) was found in 69% at discharge, with age (adjusted RR [aRR], 1.02; 95% CI, 1.01-1.03), vasculitis (aRR, 1.38; 95% CI, 1.02-1.86), and Glasgow Coma Scale (GCS) <15 (aRR, 1.32; 95% CI, 1.01-1.73) identified as independent risk factors.

CONCLUSIONS

VZV encephalitis occurs primarily in elderly or immunocompromised patients with a higher incidence than previously estimated. The diagnosis is often delayed; risk factors for unfavorable outcome are age, cerebral vasculitis, and GCS <15.

Current perspectives on neuroimaging techniques used to identify stroke mimics in clinical practice

INTRODUCTION

Urgent clinical assessment and brain imaging are essential for differentiating stroke mimics from stroke and to avoid unnecessary initiation of reperfusion and other therapies in stroke mimic patients.

AREAS COVERED

In this article, the authors will review acute stroke imaging and then the imaging patterns of the most common stroke mimics. The authors have focused our review on brain CT scan, and more specifically CT perfusion, as this is the most commonly available and emerging tool in emergency settings. The authors also provide information on acute brain MRI and MR perfusion.

EXPERT OPINION

Imaging can contribute to the detection and diagnosis of acute stroke mimics. Knowledge of imaging findings in different stroke mimics can help distinguish these from patients with stroke who require timely reperfusion therapy. CT and MRI perfusion and diffusion-weighted imaging (DWI) MRI are useful imaging modalities for the assessment of acute stroke patients as they provide more accurate information than plain CT scan. Some of these modalities should be available in the emergency setting. The authors recommended CT perfusion as a useful tool for stroke management and differentiation with stroke mimics.

An adolescent with herpes simplex encephalitis, presenting with mild symptoms and rapid deterioration: A case report

Headaches in children are a common, but unspecific symptom that can have many underlying causes, ranging from unspecific tension headache through migraine and up to encephalitis and intracranial hypertension. We present the case of a 14-year-old boy who presented to our emergency department with headache, nausea as well as vomiting and developed seizures later on. The initial diagnosis was complicated by a magnetic resonance imaging which did not show any signs of inflammation, but was of limited informative value due to orthodontic appliances. Despite the unremarkable imaging, prophylactic antiviral and antibiotic treatment was started after lumbar puncture. Herpes simplex virus as well as human herpes virus 7 were confirmed in the cerebrospinal fluid. Although both viruses are ubiquitous, severe infections are a rare complication. Immunodeficiency syndromes are predisposing factors for serious complications and genetic analysis of UNC93B and TLR-3 might be helpful for decision-making. No genetic or immunologic predisposition was found in our patient. The patient’s condition deteriorated rapidly, so he had to be admitted to the pediatric intensive care unit, where he was intubated and his antiviral treatment with acyclovir was extended by foscarnet. After prolonged mechanical ventilation, he slowly improved. With intensive neurorehabilitation, he could finally return to his daily life activities 3 months after diagnosis. Despite headaches being an unspecific symptom, the possibility of a herpes simplex virus encephalitis should always kept in mind, especially in patients presenting with additional symptoms such as vomiting, altered mental status and/or focal neurological deficits. An initial magnetic resonance imaging might be misleading if orthodontic appliances are in place. Initiation of treatment without delay is crucial for neurologic outcome of herpes simplex virus encephalitis.

Concordance between a neuroradiologist, a consultant radiologist and trained reporting radiographers interpreting MRI head examinations: An empirical study

INTRODUCTION

This study assessed agreement between MRI reporting radiographers and a consultant radiologist compared with an index neuroradiologist when reporting MRI head (brain/internal auditory meati [IAMs]) examinations. The effect on patient management of any discordant reports was also examined.

METHODS

Two trained MRI reporting radiographers (RRs), a consultant radiologist (CR) and an index neuroradiologist (INR) reported on a random sample of 210 MRI examinations. The radiographers reported during clinical practice and the radiologists in clinical practice conditions. Two independent consultant physicians (neuro-rehabilitation and neuropsychiatry) compared these reports with the index neuroradiologist report for agreement and the clinical importance of discrepant reports.

RESULTS

Overall observer agreement between the RRs and CR was comparable in relation to agreement with the INR: RR; 93/210 (44.3%); and the CR; 83/210 (39.4%) for all head MRI examinations (p = 0.32). For brain examinations the difference was similar: RR; 64/180 (35.6%); and CR; 54/190 (30.0%), p = 0.26. Agreement rates for the IAMs examinations were identical, 29/30 (97.7%). For all head MRI examinations (n = 210) there was a very small observed difference of <0.5% in mean agreement between the reporting radiographers and the consultant radiologist (p = 0.92) for examinations where a major disagreement would have been likely to have led to a change in patient management.

CONCLUSION

MRI reporting radiographers reported during clinical practice on MRI head examinations to a level of agreement comparable with a consultant radiologist.

IMPLICATIONS FOR PRACTICE

This is an area in which radiographers could provide additional reporting roles to the reporting service to increase capacity. Wider potential benefits include cost-effectiveness and role development/retention of radiographers.

Acute Disseminated Encephalomyelitis: Current Perspectives

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated central nervous system (CNS) disorder, characterized by polyfocal symptoms, encephalopathy and typical magnetic resonance imaging (MRI) findings, that especially affects young children. Advances in understanding CNS neuroimmune disorders as well as the association of myelin oligodendrocyte glycoprotein antibody (MOG-Ab) with both monophasic and recurrent forms of ADEM have led to new insights into its definition, management and outcome. In this review, we aim to provide an update based on current epidemiologic, clinical, radiological and immunopathological aspects and clinical outcome of ADEM.

Neurological Disorders Identified during Treatment of a SARS-CoV-2 Infection

A 69-year-old man was admitted to our hospital under diagnosis of pneumonia due to severe acute respiratory syndrome-corona virus 2 (SARS-CoV-2) (Day 0). He underwent endotracheal intubation from Day 3. Although his respiratory condition improved and anesthetic drugs were discontinued, no cough reflex was observed despite intubation having been performed until Day 17. His tendon reflexes were also diminished. We suspected that he had developed Guillain-Barré syndrome (GBS), and administered intravenous immunoglobulin from Day 18. The absence of cough reflex improved and extubation was successfully performed on Day 23. Neurological disorders including GBS should be considered when intubated SARS-CoV-2 patients present with a loss of cough reflex during the treatment period.

Third time's a charm: diagnosis of herpes simplex encephalitis after two negative polymerase chain reaction results

Introduction

Polymerase chain reaction (PCR) testing of cerebrospinal fluid (CSF) is a sensitive and specific method in diagnosing herpes simplex virus (HSV) encephalitis. However there are increasing reports of false negative HSV PCR.

Case description

We present a patient in the 9^th decade of life with abnormal behavior and focal seizures with MRI showing a right temporal T2 hyperintense non-enhancing lesion with electrographic evidence of right lateralized periodic discharges. CSF analysis and PCR for HSV-1 and 2 yielded negative results twice, and therefore acyclovir was discontinued. Patient initially improved following correction of hyponatremia. Patient however deteriorated and imaging revealed a new right parietal lesion. Third CSF sample showed lymphocytic pleocytosis with positive HSV-1 PCR. Patient improved following antiviral treatment.

Discussion

Acyclovir treatment should continue in high clinical suspicion scenarios despite negative HSV PCR. We further discuss causes of PCR false negatives and challenges it poses for patient care.

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

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

Therapeutic difficulties in vegetative epileptic seizures as a sign of acute viral encephalitis: case presentation

Acute encephalitis is a severe pathology represented by the inflammation of the brain parenchyma associated with neurological dysfunction. The etiology is predominantly viral or autoimmune, with different therapeutic approach. The typical manifestations include fever, epileptic seizures and neurological focal signs. The treatment consists in specific drug therapies regarding the etiology and rehabilitation therapies in case of incomplete recovery. We present a case of a 43-year-old woman with occipital cephalalgia and dizziness, associated with vesperal high blood pressure levels at the same hour daily. The brain MRI described possible acute encephalitis, with FLAIR and T2 hypersignal area on right parietal region and diffusion restriction. The lumbar puncture revealed no modifications and the EEG recordings showed irritative patterns. The acyclovir intravenous treatment and an antiepileptic drug were initiated. The repeated MRI revealed laminar necrosis which explained the vegetative epileptic seizures manifested with high blood pressure. The clinical status of the patient majorly improved due to specific treatment including rehabilitation interventions. Key words: acute viral encephalitis, vegetative epileptic seizures, laminar necrosis, cephalalgia, rehabilitation,

Incidence, Risk Factors and Outcomes Among Children With Acute Flaccid Myelitis: A Population-based Cohort Study in a California Health Network Between 2011 and 2016

BACKGROUND

Acute flaccid myelitis (AFM) is defined as an acute onset of limb weakness with longitudinal spinal gray matter lesions. Reporting bias and misdiagnosis confound epidemiologic studies of AFM. We mitigated these confounders by using a large data set to assess AFM incidence, risk factors and outcomes in a fixed population.

METHODS

A retrospective cohort study was conducted within Kaiser Permanente Northern California population among children 1-18 years. Cases met radiographic and clinical criteria for AFM and were confirmed by two clinicians. Clinical and demographic data were assessed.

RESULTS

A total of 28 patients met study criteria for AFM between January 1, 2011 and December 31, 2016, an overall rate of 1.46 per 100,000 person-years. Incidence increased from 0.30 to 1.43 cases/per 100,000 person-years between 2011 and 2016, respectively. Median age was 9 years. Risk factors included male sex, Asian ancestry and history of asthma, atopic dermatitis or head injury. Risk factors associated with poliomyelitis were absent. Prodromal illness was common; enterovirus was the most common pathogen detected (n = 5). Among the 27 patients with 12-month follow-up, most demonstrated some improvement, 11 (41.0%) had full recovery, but several had significant deficits with one death reported after the study period.

CONCLUSIONS

We employed a closed-population study to generate AFM incidence, risk and outcome data. Our findings support previous reports of male sex and atopy as risk factors. Interval increase in incidence, predisposing Asian ancestry and history of head injury were unique findings to this study. Overall prognosis was better than prior reports, but recovery was incomplete in several patients.

Hyponatremia Is Predictive of HSV-1 Encephalitis among Patients with Viral Encephalitis

Encephalitis is an inflammatory process involving the brain parenchyma associated with neurologic dysfunction. The main causes of infectious encephalitis are viruses, including Herpes simplex virus type 1 (HSV-1). As the mortality rate of HSV-1 encephalitis could be reduced with early acyclovir treatment, it is imperative to distinguish HSV-1 encephalitis from other type of viral encephalitis as early as possible. However, sophisticated methods for definitive diagnosis of HSV-1 encephalitis are not readily available. We aimed to explore distinctive clinical and laboratory features of HSV-1 encephalitis. All of the adult patients with viral encephalitis hospitalized between 2011-2017 were enrolled, including 16 patients with HSV-1 encephalitis and 51 patients non-HSV-1 viral encephalitis. Determination of viruses in cerebrospinal fluid was performed by PCR tests. Female sex, hyponatremia, and abnormalities in MRI were independently associated with HSV-1 encephalitis (p < 0.05 for each). In particular, hyponatremia (< 135 mEq/L) was found in nine patients with HSV-1 encephalitis (56.3%) and 10 patients with non-HSV-1 viral encephalitis (19.6%) (p = 0.005). As serum sodium is determined easily and quickly in clinical practice, the presence of hyponatremia among patients with viral encephalitis could be helpful for the early diagnosis of HSV-1 encephalitis before cerebrospinal fluid PCR results were available. Moreover, the presence of positive finding in MRI could further support the diagnosis. This is the first study that compared the serum sodium levels among patients between HSV-1 and non-HSV-1 viral encephalitis. We thus propose the diagnostic value of hyponatremia for HSV-1 encephalitis.

The neurocritical care of tuberculous meningitis

Tuberculous meningitis is the most severe form of tuberculosis and often causes critical illness with high mortality. Two primary management objectives are reducing intracranial pressure, and optimising cerebral perfusion, while killing the bacteria and controlling intracerebral inflammation. However, the evidence base guiding the care of critically ill patients with tuberculous meningitis is poor and many patients do not have access to neurocritical care units. Invasive intracranial pressure monitoring is often unavailable and although new non-invasive monitoring techniques show promise, further evidence for their use is required. Optimal management regimens of neurological complications (eg, hydrocephalus and paradoxical reactions) and of hyponatraemia, which frequently accompanies tuberculous meningitis, remain to be elucidated. Advances in the field of tuberculous meningitis predominantly focus on diagnosis, inflammatory processes, and antituberculosis chemotherapy. However, clinical trials are required to provide robust evidence guiding the most effective supportive, therapeutic, and neurosurgical interventions for tuberculous meningitis that will improve morbidity and mortality.

Infectious encephalitis: mimics and chameleons

Click here to listen to the Podcast 'Query encephalitis' is a common neurological consultation in hospitalised patients. Identifying the syndrome is only part of the puzzle. Although historically encephalitis has been almost synonymous with infection, we increasingly recognise parainfectious or postinfectious as well as other immune-mediated causes. We must also distinguish encephalitis from other causes of encephalopathy, including systemic infection, metabolic derangements, toxins, inherited metabolic disorders, hypoxia, trauma and vasculopathies. Here, we review the most important differential diagnoses (mimics) of patients presenting with an encephalitic syndrome and highlight some unusual presentations (chameleons) of infectious encephalitis.

Genomic Analyses of Acute Flaccid Myelitis Cases among a Cluster in Arizona Provide Further Evidence of Enterovirus D68 Role

Enteroviruses frequently result in respiratory and gastrointestinal illness; however, multiple subtypes, including poliovirus, can cause severe neurologic disease. Recent biennial increases (i.e., 2014, 2016, and 2018) in cases of non-polio acute flaccid paralysis have led to speculations that other enteroviruses, specifically enterovirus D68 (EV-D68), are emerging to fill the niche that was left from poliovirus eradication. A cluster of 11 suspect cases of pediatric acute flaccid myelitis (AFM) was identified in 2016 in Phoenix, AZ. Multiple genomic analyses identified the presence of EV-D68 in the majority of clinical AFM cases. Beyond limited detection of herpesvirus, no other likely etiologies were found in the cluster. These findings strengthen the likelihood that EV-D68 is a cause of AFM and show that the rapid molecular assays developed for this study are useful for investigations of AFM and EV-D68.

Enteroviruses are a common cause of respiratory and gastrointestinal illness, and multiple subtypes, including poliovirus, can cause neurologic disease. In recent years, enterovirus D68 (EV-D68) has been associated with serious neurologic illnesses, including acute flaccid myelitis (AFM), frequently preceded by respiratory disease. A cluster of 11 suspect cases of pediatric AFM was identified in September 2016 in Phoenix, AZ. To determine if these cases were associated with EV-D68, we performed multiple genomic analyses of nasopharyngeal (NP) swabs and cerebrospinal fluid (CSF) material from the patients, including real-time PCR and amplicon sequencing targeting the EV-D68 VP1 gene and unbiased microbiome and metagenomic sequencing. Four of the 11 patients were classified as confirmed cases of AFM, and an additional case was classified as probable AFM. Real-time PCR and amplicon sequencing detected EV-D68 virus RNA in the three AFM patients from which NP swabs were collected, as well as in a fourth patient diagnosed with acute disseminated encephalomyelitis, a disease that commonly follows bacterial or viral infections, including enterovirus. No other obvious etiological causes for AFM were identified by 16S or RNA and DNA metagenomic sequencing in these cases, strengthening the likelihood that EV-D68 is an etiological factor. Herpes simplex viral DNA was detected in the CSF of the fourth case of AFM and in one additional suspect case from the cluster. Multiple genomic techniques, such as those described here, can be used to diagnose patients with suspected EV-D68 respiratory illness, to aid in AFM diagnosis, and for future EV-D68 surveillance and epidemiology.

Challenges in HSV encephalitis: normocellular CSF, unremarkable CCT, and atypical MRI findings

PURPOSE

Herpes simplex virus (HSV) encephalitis continues to be the most common form of sporadic lethal encephalitis worldwide. The wide spectrum of clinical presentations and laboratory findings often poses a diagnostic challenge for physicians which might delay administration of life-saving therapy with acyclovir. Atypical presentations of HSV encephalitis have become increasingly prevalent with better diagnostic techniques and have not been well studied.

METHODS

We retrospectively evaluated all consecutive PCR-proven HSV encephalitis cases treated at the Hospital of the Ludwig-Maximilians-University in Munich, Germany from January 1, 2013 to February 28, 2018.

RESULTS

We included 18 patients with PCR-proven HSV encephalitis. The most common clinical features were altered mental status (77.8%), focal neurologic deficits (72.2%) and fever (72.2%). Remarkably, four of these patients (22.2%) had a normocellular cerebrospinal fluid (CSF) on admission. Electroencephalography and magnetic resonance imaging abnormalities were highly sensitive for HSV encephalitis independent of CSF cell count. Striking atypical findings on MRI were extensive global brain swelling and severe brainstem involvement in single patients. Of note, initial CT scans were normal in 11 out of 16 patients (68.8%). All patients were treated with acyclovir. Three patients still developed a clinical deterioration under therapy with acyclovir with one patient requiring decompressive craniotomy due to bilateral space-occupying temporal lobe hemorrhage. 94.4% of the patients survived but only 38.9% were discharged with a good clinical outcome (Glasgow Outcome Score = 5).

CONCLUSION

Atypical presentations of HSV encephalitis seem to be more common than previously thought and physicians should apply a high level of clinical suspicion and a low threshold to initiate life-saving acyclovir therapy in suspected cases.

Community-acquired acute meningitis and encephalitis: a narrative review

Meningitis and encephalitis are medical emergencies. Patients need prompt evaluation and immediate empiric therapy to reduce the likelihood of fatal outcomes and chronic neurological sequelae. Conjugate bacterial vaccines have significantly reduced the incidence of bacterial meningitis, especially in children. As the results of changes in patterns of bacterial drug sensitivity, ceftriaxone is now part of the recommended empiric treatment for bacterial meningitis and should be administered as early as possible. Neuroimaging delays the treatment of meningitis and is not needed in most cases. Adjunctive corticosteroid therapy is of benefit for many patients with meningitis and should be initiated in most adults before antibiotic therapy. Molecular testing can assist the specific diagnosis of encephalitis and should be based on the exposure history and geographic risk factors relevant to the patient, but non-infectious causes of encephalitis are also common. Empiric therapy for encephalitis should be directed at the most frequently identified infectious pathogen, herpes simplex virus type 1 (ie, intravenous aciclovir). Vaccines can protect against the major pathogens of childhood infections (measles, mumps, rubella, polio, varicella viruses), influenza viruses, and exotic pathogens that cause meningitis and encephalitis (rabies, Japanese encephalitis, dengue, yellow fever, tick-borne encephalitis viruses, Mycobacterium tuberculosis).

A Fatal Case of Herpes Simplex Encephalitis with Two False-Negative Polymerase Chain Reactions

An 88-year-old man presented with a 1-month history of altered mental status and seizures. His electrographic and imaging findings were suggestive of herpes simplex encephalitis (HSE), for which he was empirically treated with acyclovir. He underwent two lumbar punctures 3 days apart; both cerebrospinal fluid analyses tested negative for herpes simplex virus (HSV) by polymerase chain reaction (PCR). These negative results and his continued deterioration after 9 days of acyclovir therapy prompted treatment with steroids for possible autoimmune encephalitis. Shortly after the change in management, the patient died from cardiac arrest. At autopsy, his brain showed both gross and microscopic evidence of encephalitis and was positive for HSV by immunohistochemistry. This fatal case of HSE emphasizes the limitations of HSV PCR and the importance of clinical suspicion in the diagnosis and management of this disease.