CNS Viral Infections Overview
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CNS Viral Infections Overview

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Questions and Answers

What is the primary mode of transmission for enteroviruses?

Hand-to-mouth contact.

Which group of enteroviruses is known to cause paralytic poliomyelitis?

Poliovirus.

What are common symptoms of enterovirus infections in children?

Respiratory infections, conjunctivitis, and hand-foot-mouth disease (HFMD).

How does the virulence of enterovirus compare to poliovirus?

<p>Enterovirus is less virulent than poliovirus.</p> Signup and view all the answers

What age group is particularly at risk for severe disease when infected with Enterovirus 71?

<p>Children under 5 years.</p> Signup and view all the answers

Which enterovirus can lead to aseptic meningitis among other conditions?

<p>Coxsackievirus.</p> Signup and view all the answers

What impact does damage to anterior horn cells have on muscle function?

<p>It affects muscle movements.</p> Signup and view all the answers

In what regions have outbreaks of Enterovirus 71 been previously reported?

<p>Asia and occasionally in Australia.</p> Signup and view all the answers

What are the key clinical features commonly associated with aseptic meningitis?

<p>The key clinical features include a triad of fever, meningism, and vomiting.</p> Signup and view all the answers

Which viruses are most commonly responsible for viral encephalitis?

<p>The most commonly diagnosed viruses are enterovirus, HSV, rabies virus, and arboviruses.</p> Signup and view all the answers

What differentiates encephalitis from meningitis?

<p>Encephalitis is the inflammation of the brain, while meningitis is the inflammation of the meninges surrounding the brain.</p> Signup and view all the answers

Identify the typical CSF findings in cases of viral meningitis.

<p>Typical CSF findings include increased mononuclear cell count and normal glucose and protein levels.</p> Signup and view all the answers

What condition is referred to when there is inflammation of both the brain and spinal cord?

<p>The condition is called encephalomyelitis.</p> Signup and view all the answers

What is acute flaccid paralysis and what can cause it?

<p>Acute flaccid paralysis is characterized by sudden onset of flaccid paralysis in one or more limbs, potentially caused by viral infections like poliovirus.</p> Signup and view all the answers

What is the significance of mononuclear pleocytosis in aseptic meningitis?

<p>Mononuclear pleocytosis indicates an inflammatory response due to a viral infection in the meninges.</p> Signup and view all the answers

List two common symptoms of viral encephalitis.

<p>Common symptoms include headache and confusion.</p> Signup and view all the answers

What is the primary mode of transmission for Japanese encephalitis virus?

<p>The virus is primarily transmitted by Culex mosquitoes.</p> Signup and view all the answers

Which animals are considered dead-end hosts for Japanese encephalitis virus?

<p>Humans are considered dead-end hosts for Japanese encephalitis virus.</p> Signup and view all the answers

What are some clinical signs of Japanese encephalitis?

<p>Clinical signs include headache, high fever, stiff neck, stupor, and may progress to paralysis and seizures.</p> Signup and view all the answers

What hypothesis suggests how JEV enters the central nervous system from the blood?

<p>The 'Trojan horse' mechanism, where JEV enters through an infected leukocyte, is a possible hypothesis.</p> Signup and view all the answers

What percentage of Japanese encephalitis survivors might experience neuropsychiatric sequelae?

<p>About 45-70% of survivors may experience neuropsychiatric sequelae.</p> Signup and view all the answers

What factors influence the overflow of JEV into domestic animals during the transmission cycle?

<p>An increase in mosquitoes during the rainy season influences the overflow of JEV into domestic animals.</p> Signup and view all the answers

What can be a consequence of in utero infection by Japanese encephalitis virus?

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

What destruction occurs in neurons due to West Nile Virus (WNV)?

<p>Anterior and posterior horn neurons are destroyed by West Nile Virus.</p> Signup and view all the answers

What percentage of hospitalized patients with Japanese Encephalitis (JE) die?

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

What are some possible neurologic sequelae in survivors of JE?

<p>Survivors of JE may experience learning difficulties, behavioral problems, and subtle neurologic signs.</p> Signup and view all the answers

What is the primary cause of herpes simplex encephalitis?

<p>Herpes simplex encephalitis is primarily caused by reactivation of an earlier infection with HSV.</p> Signup and view all the answers

How does rabies enter the central nervous system (CNS)?

<p>Rabies enters the CNS via retrograde flow in axons through sensory and motor nerves.</p> Signup and view all the answers

What are Negri bodies, and in which viral infection are they found?

<p>Negri bodies are the classic histopathologic feature of rabies infection.</p> Signup and view all the answers

Describe the prodromal phase of rabies infection.

<p>The prodromal phase of rabies infection includes fever, nausea, vomiting, headache, and fatigue, with possible pain at the wound site.</p> Signup and view all the answers

What is the mortality rate for neonatal herpes simplex encephalitis?

<p>The mortality rate for neonatal herpes simplex encephalitis is greater than 25%.</p> Signup and view all the answers

What factors can influence the severity of chickenpox and shingles caused by Varicella Zoster Virus (VZV)?

<p>The severity of chickenpox and shingles is influenced by age and the immune status of the individual.</p> Signup and view all the answers

What are the main neurocognitive disorders associated with HIV infection?

<p>AIDS Dementia Complex, Vacuolar Myelopathy, and Peripheral Neuropathy.</p> Signup and view all the answers

How does HIV affect the blood-brain barrier?

<p>HIV easily crosses the blood-brain barrier, facilitating infection of the nervous system.</p> Signup and view all the answers

What role do neurotoxic viral proteins play in HIV-associated neurocognitive disorders?

<p>They trigger astrocyte activation, increasing extracellular glutamate, leading to neuronal injury.</p> Signup and view all the answers

What is the effect of sustained viral replication on brain tissue?

<p>It leads to inflammation, permanent cell death, and HIV-associated neurocognitive disorders.</p> Signup and view all the answers

Why is the CNS considered a compartmentalized viral reservoir in some HIV patients?

<p>In some patients, HIV-1 variants in CSF are not found in the blood, indicating localized infection.</p> Signup and view all the answers

Study Notes

CNS Viral Infections

  • Common CNS viral infections include meningitis, encephalitis, myelitis, and paralysis.
  • Aseptic meningitis is a form of meningitis not caused by bacteria.
  • The most common cause of aseptic meningitis is viral infection, with enteroviruses being the most frequent culprits.
  • Enteroviruses can cause respiratory infections, conjunctivitis and hand-foot-mouth disease (HFMD).
  • Encephalitis is an inflammation of the brain.
  • Myelitis is an inflammation of the spinal cord.
  • Encephalitis with meningitis is called meningoencephalitis.
  • Acute flaccid paralysis (AFP) is characterized by sudden weakness in one or more limbs, which can be caused by various viral infections, including poliovirus, enterovirus 71, and other enteroviruses.
  • Anterior horn cells in the spinal cord contain motor neurons, which are crucial for transmitting brain-generated movement commands to muscles. Damage to these cells affects muscle function.

Enteroviruses

  • Enteroviruses are non-enveloped, single-stranded RNA viruses (ssRNA) belonging to the Picornaviridae family.
  • There are at least 72 serotypes of enteroviruses.
  • Enteroviruses are transmitted via hand-to-mouth contact.
  • Transmission occurs through saliva, nasal mucous, or sputum from infected individuals.

Poliovirus

  • Paralytic poliomyelitis is a rare but potentially serious complication of poliovirus infection that causes paralysis.
  • Poliovirus can also cause aseptic meningitis and febrile illness (fever).

Coxsackievirus

  • Coxsackievirus group A can cause aseptic meningitis.
  • Coxsackievirus group B can cause aseptic meningitis and encephalitis.

Echovirus

  • Echoviruses can cause aseptic meningitis.

Enterovirus

  • Enteroviruses can cause meningitis.

Enterovirus 71

  • Enterovirus 71 usually causes mild illness in adults and children.
  • Outbreaks of EV71 are associated with severe disease, including meningitis and encephalitis, particularly in young children under 5 years old.
  • EV71 has been reported in Asia for many years and occasionally in Australia.

Arboviruses

  • Arboviruses are viruses spread through the bites of infected arthropods, primarily mosquitoes and ticks.
  • Arboviruses causing encephalitis include:
    • Eastern equine encephalitis
    • Western equine encephalitis
    • La Crosse encephalitis
    • Japanese encephalitis virus (JEV)
  • Certain arboviruses are transmitted by mosquitos and can affect both humans and animals.

Japanese Encephalitis Virus (JEV)

  • JEV is a mosquito-borne flavivirus that affects the central nervous system.
  • JEV is transmitted naturally between aquatic birds by Culex mosquitoes.
  • During the rainy season, an increase in mosquitos allows the virus to spread to other animals, including pigs, and then to humans.
  • While humans are not a significant source of virus transmission, they can be considered "dead-end hosts."
  • JEV can cause a range of symptoms, from fever and headache to coma and death.
  • About 1 in 25 to 1 in 1000 infected people develop symptomatic disease.
  • About 30% of hospitalized patients with JE die.
  • Neurologic sequelae occur in about half of survivors, with about half of those experiencing difficulties such as learning disabilities, behavioral problems, and subtle neurologic signs.
  • The clinical course of JEV infection is characterized by:
    • Acute encephalitis: Symptoms include headache, high fever, stiff neck, and stupor. The disease may progress to paralysis, seizures, convulsions, coma, and death.
    • Neuropsychiatric sequelae: These occur in 45-70% of survivors.
    • In utero infection is possible, leading to abortion of the fetus.

Herpes Simplex Virus (HSV)

  • HSV is an enveloped, double-stranded DNA virus (dsDNA) belonging to the Herpesviridae family.
  • HSV can cause a variety of infections, including:
    • Acute gingivostomatitis
    • Herpes labialis (cold sores)
    • Herpetic whitlow (infection of the finger)
    • Ocular herpes (infection of the eye)
    • Genital herpes
    • Neonatal herpes
    • Meningitis
    • Encephalitis
  • HSV encephalitis is responsible for about 10% of all encephalitis cases.
  • About 30% of HSV encephalitis cases result from an initial infection, while the majority are caused by reactivation of a prior infection.
  • HSV encephalitis can manifest as neonatal HSVE (with a >25% mortality rate) or focal disease following HSV reactivation (with a 70% mortality rate in the absence of treatment).

Varicella Zoster Virus (VZV)

  • VZV is an enveloped, double-stranded DNA virus (dsDNA) belonging to the Herpesviridae family.
  • VZV causes varicella (chickenpox) during primary infection, typically a self-limiting illness in children. However, it can cause significant morbidity and mortality in other age groups and immunocompromised individuals.
  • VZV reactivation leads to herpes zoster (shingles), which primarily affects the elderly or immunocompromised.
  • VZV can also cause encephalitis in immunocompromised patients.

Rabies

  • Rabies is an enveloped, single-stranded RNA virus (-) ssRNA belonging to the Rhabdoviridae (Lyssavirus) family.
  • Rabies is spread through the bite of an infected animal, often through the salivary contamination of mucous membranes or aerosols.
  • The virus replicates in muscle tissue and then moves along peripheral nerves into the central nervous system (CNS) through retrograde axonal transport.
  • Once the virus enters the nerves, it becomes inaccessible to the host's immune defenses.
  • The infection cycle is completed when the virus replicates in the salivary glands.
  • The incubation period for rabies can range from weeks to up to two years, with shorter periods in children and for bites to the head or neck.
  • Clinical phases of rabies include:
    • Prodromal phase: Fever, nausea, vomiting, headache, fatigue, pain, burning, tingling sensations at the site of the wound.
    • Furious phase: Agitation, disorientation, seizures, twitching, hydrophobia.
    • Dumb phase: Paralysis, disorientation, stupor.
    • Coma phase: Ultimately leading to death in almost all cases.
  • Post-exposure vaccination with recombinant antigen, human antisera, or monoclonal antibodies (Mabs) can provide protection if administered before the onset of symptoms.

HIV and the Nervous System

  • HIV enters the nervous system early in infection and may cause symptoms immediately or later in life.
  • HIV easily crosses the blood-brain barrier.
  • Primary HIV disease can lead to:
    • AIDS Dementia Complex (brain)
    • Vacuolar Myelopathy (spinal cord)
    • Peripheral Neuropathy (nerve)
    • Meningitis (acute or chronic)
  • Sustained viral replication and a high viral load are associated with brain tissue inflammation, permanent cell death, and HIV-associated neurocognitive disorders (HAND).
  • HIV-1 variants in the cerebrospinal fluid (CSF) may not be present in the blood, suggesting that the CNS may be a compartmentalized viral reservoir.

HIV-associated Neurocognitive Disorders (HAND)

  • HAND encompass a spectrum of neurocognitive impairments associated with HIV infection, ranging from mild cognitive impairment to severe dementia.
  • The neuropathogenic mechanisms contributing to HAND include:
    • Release of neurotoxic viral proteins from HIV-infected macrophages and microglial cells that trigger astrocyte activation and increased glutamate release.
    • Reduced glutamate uptake, leading to elevated extracellular glutamate levels and neuronal bioenergetic disturbances. This can lead to aberrant synapto-dendritic pruning and neuronal injury.
    • Systemic inflammation and microbial translocation products activate microglia, increasing the production of chemokines and cytokines that contribute to neuronal injury.

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Viral Infections of the CNS PDF

Description

This quiz covers essential information about common CNS viral infections such as meningitis, encephalitis, myelitis, and acute flaccid paralysis. It highlights the role of enteroviruses, including their effects on the body and potential complications. Test your knowledge on the causes and characteristics of these viral infections.

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