CNS Viral Infections Overview

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Questions and Answers

What is the transmission route of poliovirus?

Poliovirus is transmitted via the faecal-oral route or through contaminated food or water.

What are the common symptoms associated with aseptic meningitis?

The common symptoms include a triad of fever, meningism, and vomiting.

What are the primary symptoms of poliovirus infections?

The primary symptoms include fever, headache, nausea, sore throat, and myalgia.

Describe the primary cause of viral encephalitis.

The primary cause of viral encephalitis is infection by viruses such as enterovirus, HSV, rabies virus, and arboviruses. Signup and view all the answers

How does poliovirus affect the central nervous system?

Poliovirus can invade motor neurons in the spinal cord, leading to flaccid paralysis if nervous tissue is infected. Signup and view all the answers

What percentage of polio infections leads to irreversible paralysis?

Approximately 1 in 200 infections leads to irreversible paralysis. Signup and view all the answers

Define acute flaccid paralysis (AFP) and its potential causes.

Acute flaccid paralysis (AFP) is characterized by the sudden onset of flaccid paralysis in one or more limbs, often caused by anterior horn cell infection with poliovirus or other viruses. Signup and view all the answers

What critical finding differentiates aseptic meningitis from bacterial meningitis in cerebrospinal fluid (CSF)?

Aseptic meningitis is characterized by an increased mononuclear cell count (pleocytosis) in the CSF, while bacterial meningitis shows a predominance of neutrophils. Signup and view all the answers

What is post-polio syndrome (PPS) and what percentage of survivors are affected?

Post-polio syndrome (PPS) is progressive muscle deterioration occurring in 25-50% of patients infected in childhood. Signup and view all the answers

What is the relationship between AFM and prior respiratory illness?

Most patients with Acute Flaccid Myelitis (AFM) had a mild respiratory illness or fever prior to the onset of AFM. Signup and view all the answers

Explain the difference between meningitis and encephalitis.

Meningitis is the inflammation of the meninges, while encephalitis is the inflammation of the brain itself. Signup and view all the answers

What is meningoencephalitis, and how does it occur?

Meningoencephalitis is the infection with inflammation of both the meninges and the brain, often occurring as a complication of viral infections. Signup and view all the answers

What role do enteroviruses play in the development of AFM?

Enteroviruses, particularly EV-D68, are associated with respiratory illnesses that can precede cases of AFM. Signup and view all the answers

Identify the main viral agents responsible for most cases of viral encephalitis.

The main viral agents are enteroviruses, herpes simplex virus (HSV), rabies virus, and arboviruses. Signup and view all the answers

Which age group is most commonly affected by poliovirus infections and AFM?

Both poliovirus infections and AFM predominantly affect children, with AFM being more common in those under 18. Signup and view all the answers

What are the expected clinical features for a patient with viral encephalitis?

Expected clinical features include headache, fever, confusion, and drowsiness, which may progress to convulsions and coma if severe. Signup and view all the answers

What is the natural transmission cycle of the Japanese encephalitis virus?

The virus is transmitted naturally between aquatic birds by Culex mosquitoes, then overflows into pigs and humans, who are dead-end hosts. Signup and view all the answers

Describe how Japanese encephalitis virus (JEV) spreads to the central nervous system.

JEV likely enters the CNS from the blood, facilitated by peripheral replication and viraemia, with a possible 'Trojan horse' mechanism via infected leukocytes. Signup and view all the answers

What are the common clinical signs of Japanese encephalitis?

Common signs include headache, high fever, stiff neck, stupor, and may progress to paralysis, seizures, and coma. Signup and view all the answers

What percentage of Japanese encephalitis survivors may experience neuropsychiatric sequelae?

45-70% of survivors may experience neuropsychiatric sequelae. Signup and view all the answers

What is the significance of neutralizing antibodies in preventing Japanese encephalitis?

Neutralizing antibodies are sufficient to prevent encephalitis by blocking the virus's entry into the CNS. Signup and view all the answers

What can happen in cases of in utero infection by Japanese encephalitis?

In utero infection can lead to abortion of the fetus. Signup and view all the answers

What are the possible physical complications observed in children after infection with Japanese encephalitis?

Complications can include flexion deformities and marked weakness or wasting. Signup and view all the answers

How does the prevalence of symptomatic disease in infected people with Japanese encephalitis vary?

About 1 in 25 to 1 in 1,000 infected individuals develop symptomatic disease. Signup and view all the answers

What is the mortality rate of hospitalized patients with Japanese Encephalitis (JE)?

About 30% of hospitalized patients with JE die. Signup and view all the answers

What are the common neurologic sequelae observed in survivors of JE?

Survivors often experience severe neurologic sequelae, including learning difficulties and behavioral problems. Signup and view all the answers

What percentage of herpes simplex encephalitis cases originates from initial infection with HSV?

About 30% of herpes simplex encephalitis cases result from initial HSV infection. Signup and view all the answers

What is the most common presentation of Varicella Zoster Virus (VZV) in children?

The most common presentation of VZV in children is chickenpox (varicella). Signup and view all the answers

How does the rabies virus predominantly spread in the body after infection?

Rabies virus spreads via retrograde flow in axons, moving along peripheral nerves to the CNS. Signup and view all the answers

What is the classic histopathologic feature associated with rabies?

Negri bodies are the classic histopathologic feature of rabies. Signup and view all the answers

What treatment options are available for post-exposure protection against rabies?

Post-exposure protection includes recombinant antigen vaccine, human anti-sera, or monoclonal antibodies. Signup and view all the answers

What are the three clinical phases of rabies, and how do they progress?

The three phases are prodromal (fever, nausea), furious (agitation, seizures), and dumb (paralysis, stupor). Signup and view all the answers

What are the primary neurological complications associated with primary HIV disease?

The primary neurological complications include AIDS Dementia Complex, Vacuolar Myelopathy, Peripheral Neuropathy, and Meningitis. Signup and view all the answers

How does HIV-1 manage to infect the brain despite the blood-brain barrier?

HIV-1 easily crosses the blood-brain barrier, allowing it to infect neuronal cells early in the infection process. Signup and view all the answers

What role do HIV-infected macrophages and microglial cells play in neurocognitive disorders?

They release neurotoxic viral proteins that activate astrocytes, resulting in elevated glutamate levels and subsequent neuronal injury. Signup and view all the answers

What is meant by the term 'CNS compartmentalization' in the context of HIV?

CNS compartmentalization refers to instances where HIV-1 variants found in the cerebrospinal fluid (CSF) are not present in the peripheral blood, indicating a separate viral reservoir. Signup and view all the answers

What are the consequences of sustained viral replication and high viral load in relation to brain health?

Sustained viral replication and high viral load cause brain tissue inflammation, permanent cell death, and contribute to HIV-associated neurocognitive disorders. Signup and view all the answers

Study Notes

Central Nervous System Viral Infections

Most CNS viral infections are uncommon complications of common systemic infections
Viral infections are the most common cause of aseptic meningitis
Enteroviruses are the most common cause of aseptic meningitis
Typical CSF findings in various types of meningitis
There are non-infectious causes of aseptic meningitis
Clinical features of aseptic meningitis: fever, meningism, and vomiting
Encephalitis is an infection or inflammation of the brain
Myelitis is inflammation of the spinal cord
Encephalomyelitis occurs when both the brain and spinal cord are involved
Meningoencephalitis is encephalitis with meningitis
Clinical features of encephalitis: headache, fever, confusion, drowsiness; more advanced disease includes convulsions, seizures, hallucinations, memory loss, and coma
Viral encephalitis may be a direct effect of acute infection or a complication of latent disease
Most diagnosed viral encephalitis are caused by: enterovirus, HSV, rabies virus, and arboviruses
Most AFM cases are in: children over 90%
The large number of AFM cases identified in 2014 coincided with: a national outbreak of severe respiratory illness caused by EV-D68

Poliomyelitis

Polio is: an acute enteroviral infection of the spinal cord that can cause neuromuscular paralysis
Poliomyelitis is caused by: an infection of the anterior horn cells by wild or vaccine polio virus or other viruses
There are 3 poliovirus serotypes: 1-3 each with slightly different capsid proteins
Poliovirus is transmitted by: faecal-oral route, contaminated food or water
Poliovirus multiplies: in the intestine and enters the circulatory system
Paralytic disease occurs mostly in: adolescents
Poliomyelitis can cause irreversible paralysis in: 1 in 200 infections
5-10% of paralyzed persons die when: breathing muscles become immobilized
Poliovirus infects: mucosal cells in the oropharynx and the intestine
Most polio infections are short-term with mild viraemia: non-specific symptoms including fever, headache, nausea, sore throat, and myalgia
If viraemia persists, the virus spreads to: the spinal cord and brain
Invasion of motor neurons causes: flaccid paralysis
Decades later, post-polio syndrome (PPS) occurs in: 25-50% of patients infected with polioviruses in childhood

Arboviruses

Arboviruses are: viruses transmitted by arthropods (mosquitoes, ticks, etc.)
Arboviruses can cause: encephalitis, meningitis, and other neurological diseases
Examples of arboviruses: Japanese encephalitis virus (JEV), West Nile virus (WNV), Eastern equine encephalitis virus (EEEV), Western equine encephalitis virus (WEEV), La Crosse encephalitis virus (LACV)
JEV is transmitted by: Culex mosquitoes, from aquatic birds to pigs and other domestic animals, then to humans
JEV can cause: neurological disorders such as encephalitis, meningitis, and acute flaccid paralysis

Japanese Encephalitis

JEV is: an important cause of viral encephalitis in Asia and the Pacific
JEV is a flavivirus that is transmitted by: mosquitoes
JEV is spread by: Culex mosquitoes, initially from aquatic birds to pigs and other domestic animals, then to humans
The nervous system is the main target of JEV: the virus enters the CNS through the bloodstream and infects neurons
JEV can cause: severe encephalitis, leading to coma and death
About 1 in 25 - 1:1000 infected people develop: symptomatic disease
Around 30% of hospitalized patients with JE die: about half of survivors have severe neurologic sequelae
About half of those classed with “good recovery” have: subtle neurologic sequelae such as learning difficulties, behavioral problems, and subtle neurologic signs

Herpes Simplex Virus

HSV is*: an enveloped dsDNA virus that belongs to the Herpesviridae family
HSV can cause: a range of infections including gingivostomatitis, herpes labialis, herpetic whitlow, ocular herpes, genital herpes, neonatal herpes, meningitis, and encephalitis
HSV encephalitis is responsible for: about 10% of all encephalitis cases
About 30% of encephalitis cases result from: initial infection with HSV
The majority of HSV encephalitis cases are caused by: reactivation of an earlier infection
HSV encephalitis can present as: neonatal HSVE (mortality rate >25%), or as focal disease following HSV reactivation (mortality 70% in the absence of treatment)

Varicella Zoster Virus

VZV is: an enveloped dsDNA genome virus that belongs to the Herpesviridae family
VZV causes: varicella (chickenpox) following primary infection and herpes zoster (shingles) following reactivation of VZV in sensory nerve ganglia
Varicella is a self-limiting disease of children: morbidity and mortality can occur in other age groups and those who are immunocompromised
Herpes zoster is most common in: the elderly or immunocompromised
VZV can cause encephalitis in: immunocompromised patients

Rabies

Rabies is caused by: an enveloped (-) ssRNA, bullet-shaped virus that belongs to the Rhabdoviridae (Lyssavirus) family
Rabies is spread by: the bite of an infected animal, salivary contamination of mucous membranes, or aerosols
The virus replicates first in: muscle, then moves along peripheral nerves to the CNS via retrograde flow in axons (typically via sensory and motor nerves at the site of the initial infection)
Once the virus enters the nerves it is not: accessible to the host immune defenses
The infection cycle is completed when: the virus replicates in the salivary glands
The incubation period can range from: several weeks to up to 2 years
Clinical phases of rabies: prodromal, furious, dumb, and coma
The prodromal phase includes symptoms: fever, nausea, vomiting, headache, fatigue and pain, burning, tingling sensations at the site of the wound
The furious phase includes symptoms: agitation, disorientation, seizures, twitching, hydrophobia
The dumb phase includes symptoms: paralysis, disorientation, and stupor
Progression to the Coma phase results in: death in ~ 100% of patients
Vaccines can be given post-exposure for protection, but must be given before symptoms arise

HIV and the Nervous System

HIV enters the nervous system early: at the time of initial infection, and may immediately cause symptoms or may remain asymptomatic for a lifetime
HIV easily crosses: the blood-brain barrier
Primary HIV disease can lead to: AIDS Dementia Complex (brain), Vacuolar Myelopathy (spinal cord), Peripheral Neuropathy (nerves), Meningitis (acute or chronic)
Sustained viral replication and high viral load are associated with: brain tissue inflammation, permanent cell death, and HIV-associated neurocognitive disorders (HAND)
HIV variants in CSF are not found in blood: the CNS is a compartmentalized viral reservoir

HIV-associated Neurocognitive Disorders

HIV-associated neurocognitive disorders (HAND) are: a spectrum of neurocognitive impairments that can occur in people living with HIV.
HAND can range in severity from: mild cognitive impairment to HIV-associated dementia
The pathogenesis of HAND is complex and includes: various mechanisms including direct viral infection of neurons, inflammation, and immune activation
HIV-infected macrophages and microglial cells release neurotoxic viral proteins that: trigger astrocyte activation, which results in increased glutamate release and reduced glutamate uptake
Elevated extracellular glutamate levels cause: neuronal bioenergetic disturbances that lead to aberrant synapto-dendritic pruning and neuronal injury
Systemic inflammation and microbial translocation products lead to: microglial activation and increased production of chemokines and cytokines that contribute to neuronal injury.

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Description

This quiz explores the various viral infections of the central nervous system (CNS), including their clinical features and common causes. Topics include aseptic meningitis, encephalitis, myelitis, and the clinical manifestations associated with these conditions. Test your knowledge on the different types of CNS viral infections and their management.