Viral Infections of the Central Nervous System

Bacterial and Viral Infectious Disease of the Spine

Spinal infections are a diverse group of diseases affecting different compartments of the spine with variable clinical and imaging presentations. Diagnosis of spinal infections is based on a combination of clinical features, laboratory markers, and imaging studies. Imaging plays a pivotal role in the diagnosis and management of spinal infections. The characteristic imaging manifestations of bacterial and viral infections in the spine are discussed with key teaching points emphasized.

A systematic review of brain imaging findings in neurological infection with Japanese encephalitis virus compared with Dengue virus

OBJECTIVES

Japanese encephalitis virus (JEV) and dengue virus (DENV) represent important causes of encephalitis in Asia. Brain imaging may provide diagnostic clues about the etiology of infectious encephalitis. We performed a systematic review of brain imaging findings in Japanese encephalitis (JE) and DENV neurological infection (dengue) to identify characteristic lesions.

METHODOLOGY

Five databases were searched. We included all study types and imaging techniques. Laboratory methods were categorized using diagnostic confidence levels. Imaging data were synthesized, and focal findings are presented as proportions for JE and dengue and for subgroups based on diagnostic confidence.

PRINCIPAL FINDINGS

Thalamic lesions were the most reported magnetic resonance imaging finding in both diseases but appeared to occur more often in JE (74% in 23 studies) than dengue (29.4% in 58 studies). In cases diagnosed with antigen or nucleic acid tests, thalamic lesions were reported frequently in both JE (76.5% in 17 studies) and dengue (65.2% in 23 studies).

SIGNIFICANCE

The results suggest that thalamic lesions frequently occur in both JE and dengue encephalitis. No radiological findings were found to be pathognomonic of either disease. Although brain imaging may support a diagnosis, laboratory confirmation with highly specific tests remains crucial.

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.

Japanese B Encephalitis

RNA viruses are not only reported for viral pandemics but also as important agents for emerging/re-emerging diseases. Japanese encephalitis virus (JEV) is reported to cause epidemics of encephalitis in Southeast Asia, India, Korea, China, and Indonesia. In addition, several reports show that JEV has spread to new populations beyond these geographical regions. The disease mostly affects children with a mortality rate up to 30%. In peridomestic settings, pigs are reported as amplifiers of JEV transmission and aquatic birds as maintenance hosts of the virus. The Culex mosquito is the vector for transmission of JEV. This virus is a member of the family Flaviviridae and has a single-stranded positive-sense RNA virus. Five different genotypes (G-I to G-V) of JEV have been reported. Four different kinds of vaccines have been produced to prevent JEV infection. However, there is no FDA-approved antiviral drug available for JEV. How to cite this article: Mehta A, Singh R, Mani VE, Poddar B. Japanese B Encephalitis. Indian J Crit Care Med 2021;25(Suppl 2):S171-S174.

Unusual clinical manifestations of dengue disease - Real or imagined?

The disease caused by each of the four serotypes of dengue virus (DENV) have plagued humans since last century. Symptoms of dengue virus (DENV) infection range from asymptomatic to dengue fever (DF) to severe dengue disease (SDD). One third of the world's population lives in regions with active urban DENV transmission, and thousands of serologically naïve travelers visit these areas annually, making a significant portion of the human population at risk of being infected. Even though lifelong immunity to the homotypic serotype is achieved after a primary DENV infection. Heterotypic DENV infections may be exacerbated by a pre-existing immune memory to the primary infection and can result in an increased probability of severe disease. Not only, age, comorbidities and presence of antibodies transferred passively from dengue-immune mother to infants are considered risk factors to dengue severe forms. Plasma leakage and multiple organ impairment are well documented in the literature, affecting liver, lung, brain, muscle, and kidney. However, unusual manifestation, severe or not, have been reported and may require medical attention. This review will summarize and discuss the increasing reports of unusual manifestations in the clinical course of dengue infection.

Pediatric West Nile Virus-Associated Neuroinvasive Disease: A Review of the Literature

Over the past two decades, West Nile virus has become the most common arbovirus in North America, leading to several outbreaks and infecting thousands of people. Mosquitos help transmit the virus in the majority of cases, but transmission occurs via blood transfusions, organ transplantation, and possibly pregnancy and breastfeeding. While most infected patients experience mild to no symptoms, thousands of West Nile virus-associated neuroinvasive cases have been reported in the United States, with over 700 cases occurring in children from 2003 to 2016. Neuroinvasive disease presents as meningitis, encephalitis, or acute flaccid paralysis, and carries a high likelihood of poor outcome, including severe neurological disability or death. To date, no pharmacologic treatment has proven effective. Therapeutic clinical trials have not been successfully completed due to the sporadic nature of viral outbreaks and resultant poor study enrollment. Although older age and chronic disease are risk factors for neuroinvasive West Nile virus disease in adults, the specific factors that influence the risk in pediatric populations have not been fully elucidated. This review summarizes the most recent literature regarding West Nile virus-associated neuroinvasive disease, especially as it pertains to the pediatric population. Moreover, the review describes the epidemiology, clinical, laboratory, and radiographic findings, and outlines the various therapies that have been trialed and potential future research directions.

Viral and Prion Infections of the Central Nervous System: Radiologic-Pathologic Correlation: From the Radiologic Pathology Archives

Viral infections of the central nervous system (CNS) range in clinical severity, with the most severe proving fatal within a matter of days. Some of the more than 100 different viruses known to affect the brain and spinal cord are neurotropic with a predilection for producing CNS infection. The host response to viral infection of the CNS is responsible for the pathophysiology and imaging findings seen in affected patients. Viral CNS infections can take the form of meningitis, encephalitis, encephalomyelitis, or, when involving the spinal cord and nerve roots, encephalomyeloradiculitis. In 1982, an infectious particle termed a prion that lacked nucleic acid and therefore was not a virus was reported to produce the fatal neurodegenerative disease Creutzfeldt-Jakob disease and related disorders. These prion diseases produce characteristic neuroimaging findings that are distinct from those seen in most viral infections. The clinical and imaging findings associated with viral CNS infection are often nonspecific, with microbiologic analysis of cerebrospinal fluid the most useful single test allowing for diagnosis of a specific viral infection. This review details the spectrum of viral CNS infections and uses case material from the archives of the American Institute for Radiologic Pathology, with a focus on the specific clinical characteristics and magnetic resonance imaging features seen in these infections. Where possible, the imaging features that allow distinction of these infections from other CNS inflammatory conditions are highlighted.

Case Report: Zika Virus Meningoencephalitis and Myelitis and Associated Magnetic Resonance Imaging Findings

Zika virus (ZIKV) has a wide clinical spectrum of associated neurologic disease including microcephaly and Guillain-Barre syndrome but, despite its known neurotropism, ZIKV meningoencephalitis and myelitis have been rare complications. We describe a case of ZIKV meningoencephalitis and probable myelitis and its associated magnetic resonance imaging findings that rapidly resolved during recovery in a previously healthy adult.

Combining reverse-transcription multiplex PCR and microfluidic electrophoresis to simultaneously detect seven mosquito-transmitted zoonotic encephalomyelitis viruses

Several mosquito-transmitted viruses are causative agents for zoonotic encephalomyelitis. Rapid identification of these viruses in mosquito populations is an effective method for surveying these diseases. To detect multiple mosquito-transmitted viral agents, including West Nile virus, Saint Louis encephalitis virus, Venezuelan equine encephalomyelitis virus, Western equine encephalomyelitis virus, Eastern equine encephalomyelitis virus, Highlands J virus and Japanese encephalitis virus, an assay using multiplex reverse-transcription PCR combined with microfluidic electrophoresis was developed and evaluated. Tailed nested primers were used in the assay to amplify specific viral genomic segments, and products with specific length were further analyzed by using a microfluidic electrophoresis chip. The assay exhibited good specificity and analytical sensitivity (10(2) copies/µL). This technology can be helpful in the quarantine and surveillance of exotic encephalomyelitis viruses which are transmitted by mosquitoes.

Epidemiological features of viral encephalitis in Cangzhou of China with use of multiplex RT-PCR for five RNA viruses

OBJECTIVE

With use of multiplex RT-PCR testing the five RNA viruses associated with viral encephalitis, the aim of research is to find out the epidemiological features of viral encephalitis in Cangzhou of China.

METHODS

Patients hospitalized in Cangzhou central hospital with the diagnosis of viral encephalitis from January 2010 to December 2012 were retrospectively analyzed. The sensitivity and specificity of multiplex RT-PCR was compared with ELISA through testing CSF samples of enterovirus (EVs), Japanese encephalitis virus (JEV), mumps virus (MUV), measles virus (MV) and rubella virus (RV).

RESULTS

Disease incidence of viral encephalitis in Cangzhou of China was 18.6 per 100 thousand, and the main pathogen focused on EVs, MUV, JEV, MV and RV, which positive rate were 27.8%, 14.4%, 12.2%, 6.7% and 3.3% respectively. The sensitivity and specificity were all higher than ELISA.

CONCLUSION

The most common pathogens responsible for viral encephalitis in Cangzhou, Hebei province, China, were EVs, and the multiplex RT-PCR was a rapid, sensitive, accurate method of testing the viruses responsible for causing these illnesses.

Imaging in Neurologic Infections II: Fungal and Viral Diseases

Infections of the nervous system have a significant impact on global mortality and morbidity. These infections are medical emergencies that are frequently diagnostically challenging. Incorporation of neuroimaging can be essential for early diagnosis and initiation of proper treatment. In this second part of this two-part review, we focus on diagnostic imaging features of selected fungal and viral nervous system infections.

Viral encephalitis in the ICU

Viral encephalitis causes an altered level of consciousness, which may be associated with fever, seizures, focal deficits, CSF pleocytosis, and abnormal neuroimaging. Potential pathogens include HSV, VZV, enterovirus, and in some regions, arboviruses. Autoimmune (eg, anti-NMDA receptor) and paraneoplastic encephalitis are responsible for some cases where no pathogen is identified. Indications for ICU admission include coma, status epilepticus and respiratory failure. Timely initiation of anti-viral therapy is crucial while relevant molecular and serological test results are being performed. Supportive care should be directed at the prevention and treatment of cerebral edema and other physiological derangements which may contribute to secondary neurological injury.