Meningitis Overview Quiz
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Questions and Answers

Which condition specifically refers to inflammation of the meninges surrounding the brain?

  • Encephalitis
  • Meningoencephalitis
  • Meningitis (correct)
  • Cerebral abscess

    • What characterizes viral meningitis compared to bacterial meningitis?

  • It is generally less severe and not an emergency. (correct)
  • It is always life-threatening.
  • It leads to focal lesions in the brain.
  • It primarily affects the cerebral abscess.

    • Which of the following organisms is most commonly associated with acute meningitis?

  • Plasmodium spp.
  • Amoeba
  • Neisseria gonorrhoeae
  • Streptococcus pneumoniae (correct)

    • What type of CNS infection involves both inflammation of the meninges and the brain parenchyma?

    <p>Meningoencephalitis</p> Signup and view all the answers

    Which method of pathogen spread is common for CNS infections?

    <p>Infection through peripheral nerves</p> Signup and view all the answers

    What is the primary mechanism through which the rabies virus spreads from muscle cells to the brain?

    <p>Retrograde axonal transport</p> Signup and view all the answers

    What role does the rabies virus play in the presence of neurological effects like foaming at the mouth?

    <p>It signals transmission to the next host</p> Signup and view all the answers

    Why is it critical to treat a rabies bite immediately after potential exposure?

    <p>To allow time for the immune system to build up defenses</p> Signup and view all the answers

    What is the purpose of rabies immunoglobulin (RIG) in rabies post-exposure treatment?

    <p>To neutralize the virus locally at the bite site</p> Signup and view all the answers

    What is the typical onset period for rabies symptoms after exposure?

    <p>20-90 days</p> Signup and view all the answers

    What is the primary indication of Kernig’s sign in a patient?

    <p>Discomfort when the leg is lifted to 90 degrees</p> Signup and view all the answers

    Which organism is NOT part of the 'big 6' causative organisms for bacterial meningitis?

    <p>Candida albicans</p> Signup and view all the answers

    What differentiates acute meningitis from chronic meningitis?

    <p>Rapid onset of symptoms over hours to days</p> Signup and view all the answers

    Which symptom is NOT typically associated with acute meningitis?

    <p>Gradual nausea</p> Signup and view all the answers

    What is a distinguishing feature of viral meningitis compared to bacterial meningitis?

    <p>Slow onset over several days</p> Signup and view all the answers

    Which of the following viruses is most commonly associated with viral meningitis?

    <p>Echoviruses</p> Signup and view all the answers

    What symptom might be observed if Brudzinski’s sign is positive?

    <p>Raising of the head and neck involuntarily</p> Signup and view all the answers

    Which pathogen is a common cause of fungal meningitis?

    <p>Coccidiodes immitans</p> Signup and view all the answers

    What is the typical appearance of cerebrospinal fluid (CSF) in bacterial meningitis?

    <p>Cloudy with pus</p> Signup and view all the answers

    What effect does a bacterial meningitis infection have on glucose levels in the CSF?

    <p>Glucose levels decrease</p> Signup and view all the answers

    Which of the following conditions is NOT associated with meningitis symptoms?

    <p>Bechet’s disease</p> Signup and view all the answers

    What type of pathogens is Naegleria fowleri classified as?

    <p>Protozoa</p> Signup and view all the answers

    Which type of white blood cells predominantly infiltrate the CSF during bacterial meningitis?

    <p>Neutrophils</p> Signup and view all the answers

    What characterizes chronic meningitis?

    <p>Waxing and waning neurologic symptoms</p> Signup and view all the answers

    Which characteristic typically distinguishes the CSF appearance in bacterial meningitis?

    <p>Cloudy to purulent</p> Signup and view all the answers

    Which intervention is typically NOT needed for viral meningitis?

    <p>Antiviral medications</p> Signup and view all the answers

    What is the immediate action taken for a patient suspected of having bacterial meningitis?

    <p>Start empirical bactericidal antibiotic treatment</p> Signup and view all the answers

    In viral meningitis, why do glucose levels typically remain the same?

    <p>Viruses only replicate in living cells</p> Signup and view all the answers

    In which population is listeria particularly concerning?

    <p>Immunocompromised patients</p> Signup and view all the answers

    What supportive therapies are essential in managing viral meningitis?

    <p>Reducing inflammation and seizures</p> Signup and view all the answers

    What would a high level of neutrophils in the CSF most likely indicate?

    <p>Bacterial meningitis</p> Signup and view all the answers

    Which feature is not typical of viral meningitis compared to bacterial meningitis?

    <p>Lower CSF protein levels</p> Signup and view all the answers

    What is a challenge in diagnosing fungal or TB meningitis?

    <p>Variable appearance of the CSF</p> Signup and view all the answers

    What is the main goal of care in encephalitis?

    <p>Symptomatic relief and management of complications</p> Signup and view all the answers

    What is a common method for a pathogen to breach the blood-brain barrier?

    <p>Retrograde axonal transport via peripheral nerves</p> Signup and view all the answers

    Which symptom is typically associated with meningitis but not with encephalitis?

    <p>Stiff neck (nuchal rigidity)</p> Signup and view all the answers

    How can pathogens in the blood utilize a 'trojan horse' mechanism to enter the central nervous system?

    <p>By being engulfed by phagocytic cells that cross the barrier</p> Signup and view all the answers

    What type of barrier protects the brain and central nervous system from pathogens?

    <p>Blood-brain barrier</p> Signup and view all the answers

    Which of the following is a key symptom of encephalitis?

    <p>Hallucinations</p> Signup and view all the answers

    What is a common symptom of chronic meningitis?

    <p>Altered sensorium</p> Signup and view all the answers

    What diagnostic procedure is most commonly used to analyze CSF for signs of infection?

    <p>Lumbar puncture</p> Signup and view all the answers

    What recent technological advancement aids in the diagnosis of CNS infections using a single CSF sample?

    <p>Multiplex PCR</p> Signup and view all the answers

    Which pathogen is NOT associated with causing chronic meningitis?

    <p>Coxiella burnetii</p> Signup and view all the answers

    Which sign is characteristic of meningeal irritation in a patient with meningitis?

    <p>Brudzinski's sign</p> Signup and view all the answers

    What is a definitive test for diagnosing Cryptococcus neoformans in the CSF?

    <p>Indian ink staining</p> Signup and view all the answers

    Increased permeability of the blood-brain barrier may occur due to which condition?

    <p>Inflammation</p> Signup and view all the answers

    What finding in CSF analysis is typical for Mycobacterium tuberculosis meningitis?

    <p>High lymphocytes and low glucose</p> Signup and view all the answers

    Which of the following clinical features differentiates viral meningitis from bacterial meningitis?

    <p>Biphasic fever</p> Signup and view all the answers

    Which of the following can act as a portal of entry for pathogens to the central nervous system?

    <p>Bite from an infected animal</p> Signup and view all the answers

    Which of the following methods can pathogens use to cross the blood-CSF barrier to cause meningitis?

    <p>Phagocytosis by immune cells</p> Signup and view all the answers

    What is the primary mode of transmission for Coxsackie virus?

    <p>Fecal-oral route</p> Signup and view all the answers

    What is the primary mode of transmission for Streptococcus pneumoniae in crowded environments?

    <p>Saliva and respiratory secretions</p> Signup and view all the answers

    What finding in cerebrospinal fluid (CSF) would indicate meningitis?

    <p>Change in microbe composition</p> Signup and view all the answers

    Which statement about chronic meningitis is accurate?

    <p>Symptoms may wax and wane over time.</p> Signup and view all the answers

    Which patient population is most at risk for severe complications from Listeria monocytogenes infection?

    <p>Elderly and immunocompromised individuals</p> Signup and view all the answers

    What is the typical treatment for fungal meningitis due to Cryptococcus neoformans?

    <p>Antifungals</p> Signup and view all the answers

    Which CNS infection is characterized by focal neurological defects?

    <p>Encephalitis</p> Signup and view all the answers

    Which bacterium is primarily responsible for meningitis in neonates?

    <p>Streptococcus agalactiae</p> Signup and view all the answers

    What is a potential consequence of increased intracranial pressure during meningitis?

    <p>Lowered mental function</p> Signup and view all the answers

    What additional condition should be checked in chronic meningitis patients due to potential opportunistic pathogens?

    <p>Cancer</p> Signup and view all the answers

    What type of bacteria is Haemophilus influenzae?

    <p>Gram negative coccobacilli</p> Signup and view all the answers

    Which pathogen is the leading cause of adult meningitis in central and southern Africa?

    <p>Cryptococcus neoformans</p> Signup and view all the answers

    What clinical feature indicates a medical emergency when associated with Neisseria?

    <p>Rash with purpuric and petechial spots</p> Signup and view all the answers

    Which CSF analysis result is indicative of viral meningitis?

    <p>Normal glucose levels</p> Signup and view all the answers

    How does viral meningitis typically present compared to bacterial meningitis?

    <p>Slower onset of symptoms</p> Signup and view all the answers

    Which of the following is a common symptom in acute Listeria infection?

    <p>Fever and gastrointestinal issues</p> Signup and view all the answers

    What approach is often required to treat elevated intracranial pressure in viral meningitis?

    <p>Supportive therapy with anti-inflammatories</p> Signup and view all the answers

    When does early onset Group B Streptococcus infection typically occur?

    <p>Within the first week after birth</p> Signup and view all the answers

    What is the main complication associated with untreated Streptococcus pneumoniae infections?

    <p>Meningitis and sepsis</p> Signup and view all the answers

    What is the purpose of antibiotic prophylaxis in cases of Streptococcus pneumoniae exposure?

    <p>To prevent new infections in close contacts</p> Signup and view all the answers

    What symptom profile might indicate a parasitic cause of meningitis such as Angiostrongylus cantonensis?

    <p>Eosinophil predominance in CSF</p> Signup and view all the answers

    How can Listeria monocytogenes enter the bloodstream from the gastrointestinal tract?

    <p>By penetrating the intestinal walls</p> Signup and view all the answers

    Which bacteria is known for causing meningitis in individuals with a history of alcohol abuse?

    <p>Listeria monocytogenes</p> Signup and view all the answers

    Which characteristic is unique to Neisseria compared to other meningitis-causing organisms?

    <p>Can cause a petechial rash</p> Signup and view all the answers

    Streptococcus pneumoniae is a common pathogen found predominantly in which population?

    <p>Elderly individuals over 60 years</p> Signup and view all the answers

    What key symptoms form the triad of encephalitis?

    <p>Fever, headache, and focal neurological signs</p> Signup and view all the answers

    Which viral family is the most common cause of encephalitis?

    <p>Herpesviridae</p> Signup and view all the answers

    What is the primary mode of infection for rabies to enter the CNS?

    <p>Through peripheral nerves</p> Signup and view all the answers

    What treatment should be initiated immediately upon suspicion of viral encephalitis?

    <p>Acyclovir</p> Signup and view all the answers

    What is the consequence of untreated herpes simplex virus encephalitis?

    <p>70% mortality rate</p> Signup and view all the answers

    In which part of the brain is hemorrhagic necrosis most commonly observed in herpes simplex encephalitis?

    <p>Temporal lobe</p> Signup and view all the answers

    Which symptom is more pronounced in encephalitis compared to meningitis?

    <p>Behavioral changes</p> Signup and view all the answers

    Which of the following is NOT a viral cause of encephalitis?

    <p>Toxoplasma gondii</p> Signup and view all the answers

    What is the impact of arachnoid membrane damage in viral encephalitis?

    <p>Increased inflammation</p> Signup and view all the answers

    Which virus is associated with high mortality rates in humans when coming from bats via ingestion?

    <p>Nipah virus</p> Signup and view all the answers

    What is a characteristic of non-viral causes of encephalitis?

    <p>Caused by prions or bacteria</p> Signup and view all the answers

    How do herpesviruses typically spread and cause encephalitis?

    <p>Retrograde axonal transport via nerves</p> Signup and view all the answers

    What abnormal finding might you expect in the cerebrospinal fluid (CSF) during herpes simplex encephalitis?

    <p>Presence of RBCs and WBCs</p> Signup and view all the answers

    What is a common neurological change seen in individuals recovering from herpes simplex encephalitis?

    <p>Short-term memory defects</p> Signup and view all the answers

    What is a potential complication that may arise after treatment with antihelminthic medications like albendazole?

    <p>Mass inflammatory response in the brain</p> Signup and view all the answers

    What distinguishes subdural empyema from other types of CNS infections?

    <p>It often occurs following otorhinologic infections</p> Signup and view all the answers

    Which of the following symptoms is NOT typically associated with subdural empyema?

    <p>Severe back pain</p> Signup and view all the answers

    What is an essential step in the clinical management of acute CNS infections?

    <p>Begin empirical anti-microbial therapy as soon as possible</p> Signup and view all the answers

    What is the consequence of performing a lumbar puncture in cases of subdural empyema?

    <p>Dissemination of the infection</p> Signup and view all the answers

    Which of the following risk factors is associated with the development of an epidural abscess?

    <p>Immunocompromised state</p> Signup and view all the answers

    In the context of focal CNS infections, why is imaging preferred before performing a lumbar puncture?

    <p>To avoid exacerbating an existing infection</p> Signup and view all the answers

    What characterizes an epidural abscess compared to subdural empyema?

    <p>Occurs in the epidural space</p> Signup and view all the answers

    What is a common bacterial cause of epidural abscesses?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    What type of CNS infection is characterized by tissue cysts found in the brain due to egg ingestion?

    <p>Focal CNS infection from pork tapeworm</p> Signup and view all the answers

    What is a common symptom of rabid encephalitis that specifically indicates a fear of water?

    <p>Hydrophobia</p> Signup and view all the answers

    Which method does the West Nile virus use to invade the central nervous system?

    <p>Transport via macrophages</p> Signup and view all the answers

    What indicates a likely presence of West Nile virus in the area?

    <p>Groups of dead birds</p> Signup and view all the answers

    What is the most common causative agent of brain abscesses?

    <p>Bacteria</p> Signup and view all the answers

    In which patient condition is there an increased risk for developing brain abscesses?

    <p>Immunocompromised patients</p> Signup and view all the answers

    What type of imaging is preferred to diagnose focal CNS infections instead of a lumbar puncture?

    <p>CT or MRI</p> Signup and view all the answers

    Which symptom is NOT typically associated with a brain abscess?

    <p>Hydrophobia</p> Signup and view all the answers

    Which organism is specifically notorious for causing an intracerebral infection known for its 'starry night presentation'?

    <p>Toxoplasma gondii</p> Signup and view all the answers

    What is a significant predisposing factor for brain abscesses?

    <p>History of otitis media</p> Signup and view all the answers

    What role do mosquitoes play in the transmission of the West Nile virus?

    <p>They are vectors that inject the virus</p> Signup and view all the answers

    What type of organism primarily causes focal infections in the brain parenchyma that may start as cerebritis?

    <p>Bacteria</p> Signup and view all the answers

    After a brain abscess is drained, what is the next step in treatment?

    <p>Antibiotic treatment</p> Signup and view all the answers

    What is a common characteristic of abscesses seen on imaging?

    <p>Presence of a well-defined capsule</p> Signup and view all the answers

    Which of the following factors can introduce pathogens leading to brain abscess formation?

    <p>Recent head trauma</p> Signup and view all the answers

    Study Notes

    Overview of CNS Infections

    • CNS infections can be caused by a variety of pathogens, including bacteria, viruses, fungi, protozoa, and helminths.
    • Meningitis is inflammation of the meninges, the membranes surrounding the brain and spinal cord.
    • Encephalitis is inflammation of the brain parenchyma.
    • Meningoencephalitis involves both the meninges and the brain parenchyma.
    • Pathogens can invade the CNS via various routes, including insect bites, animal bites, normal flora, and reactivation of latent viruses.
    • The CNS is protected by the blood-brain barrier and the CSF-blood barrier, which prevent pathogens from entering.

    Mechanisms of Pathogen Entry

    • Pathogens can enter the CNS through anatomical defects, cranial injuries, or skin punctures.
    • Pathogens commonly infect the respiratory, gastrointestinal, and genitourinary systems and may then spread hematogenously, cross the blood-CSF barrier or the blood-brain barrier.
    • Viruses can travel via retrograde axonal transport along peripheral nerves to reach the CNS.
    • Pathogens can infiltrate the CNS through various mechanisms:
      • Trojan horse mechanism: Pathogens are engulfed by phagocytes and carried across the blood-brain barrier.
      • Transcytosis: Pathogens cross the endothelial layer of the blood-brain barrier by passing through the epithelial cells.
      • Breaching tight junctions: Increased permeability of the epithelial cell layer allows pathogens to pass through.

    Meningitis and Encephalitis Symptoms

    • Symptoms of meningitis and encephalitis can be similar and overlap.

    Meningitis

    • Fever
    • Headache
    • Stiff neck (nuchal rigidity)
    • Photophobia
    • Nausea and vomiting
    • Altered mental state
    • Kernig's sign
    • Brudzinski's sign
    • Sometimes rash (characteristic of Neisseria meningitidis infection)

    Encephalitis

    • Fever
    • Headache
    • Behavioral changes (hallucinations, speech problems, psychosis)
    • Seizures
    • Focal neurological deficits (loss of sensation, muscle weakness, paralysis)

    Diagnosis of Meningitis and Encephalitis

    • Lumbar puncture: CSF analysis for cell counts, protein and glucose levels, and microscopy/culture for pathogen identification.
    • Blood cultures: To detect bacteremia or viremia.
    • Imaging studies (MRI or CT): Primarily for encephalitis to identify focal lesions.
    • Multiplex PCR: Allows for the simultaneous detection of multiple pathogens from a single CSF sample.

    Clinical Approach

    • Obtain a thorough history, including:
      • Headache, fever, intermittent symptoms
      • Systemic or febrile features
      • Signs of raised intracranial pressure
      • Altered mental state
      • Neurological symptoms
      • Rash
      • Infectious contact
      • Travel history
      • Chronic infections
    • Conduct a comprehensive physical exam, including:
      • Fever
      • Neck stiffness
      • Confusion
      • Speech
      • Motor/sensory function
      • Rash
      • Fontanelle in infants

    Meningitis Signs

    • Kernig’s sign: Pain and resistance with passive extension of the leg at 90 degrees.
    • Brudzinski’s sign: Flexion of the hips and knees when the patient's neck is flexed.

    Types of Meningitis

    Bacterial Meningitis

    • Medical emergency.
    • Major causative organisms:
      • Streptococcus pneumoniae
      • Neisseria meningitidis
      • Haemophilus influenzae
      • Listeria monocytogenes
      • Streptococcus agalactiae (Group B Strep - GBS)
      • Escherichia coli
      • Staphylococcus aureus (less common)
    • Characterized by rapid onset and severe symptoms.
    • Often results in cloudy CSF with pus and bacterial identification via microscopy and culture.

    Viral Meningitis

    • Less severe, slower onset (3-10 days).
    • Most common causes:
      • Enteroviruses (echoviruses and coxsackieviruses)
      • Herpesviridae (HSV, VZV, CMV)
      • HIV
      • Arboviruses
      • Measles, mumps, and rubella
    • CSF usually clear with limited neutrophils.
    • Often called aseptic meningitis.

    Fungal Meningitis

    • Common in immunocompromised individuals.
    • Causes:
      • Cryptococcus neoformans
      • Coccidiodes immitans
    • Chronic presentation with a gradual onset of symptoms over weeks.

    Protozoal and Helminthic Meningitis

    • Extremely rare but can be deadly.

    • Naegleria fowleri (amoeba): Enters the CNS through the olfactory bulb, causing rapidly fatal meningoencephalitis.

    • Angiostrongylus cantonensis (rat lungworm): Causes eosinophilic meningitis, often through the ingestion of infected snails or slugs.

    Other Causes of Meningitis

    • Chronic meningitis can also be caused by:

      • Mycobacterium tuberculosis
      • Treponema pallidum (neurosyphilis)
      • Borrelia burgdorferi (Lyme disease)

    • Non-infectious causes of meningitis include:

      • Cancers
      • Drug effects
      • Head trauma

    Septic vs. Aseptic Meningitis

    • Septic meningitis: Usually bacterial, results in cloudy CSF with pus.
    • Aseptic meningitis: Usually viral, fungal, or non-infectious, results in clear CSF with few inflammatory cells.

    Acute vs. Chronic Meningitis

    • Acute meningitis: Rapid onset over hours to days, usually caused by bacteria or viruses.
    • Chronic meningitis: Gradual onset over weeks, often associated with immunocompromised individuals, and caused by fungi, mycobacterium tuberculosis, or treponema pallidum.

    Key Bacterial Causes of Acute Meningitis

    Streptococcus pneumoniae

    • Gram-positive cocci.
    • Normal URT flora, opportunistic pathogen.
    • Can invade CNS via pneumonia, otitis media, mastoiditis, sinusitis, or endocarditis.
    • Causes meningitis in all age groups, particularly in elderly and young children.
    • Mortality rate varies but can be high.

    Neisseria meningitidis

    • Gram-negative cocci.
    • Normal nasopharyngeal flora, but can be pathogenic.
    • Spread through close contact, often seen in outbreaks.
    • Can cause rash, fever, and other symptoms.
    • High mortality rate if untreated.

    Haemophilus influenzae

    • Gram-negative coccobacilli.
    • Normal URT flora.
    • Common cause before Hib vaccine, now less frequent.
    • Mortality rate around 3-6%.

    Listeria monocytogenes

    • Gram-positive rod.
    • Foodborne pathogen
    • Prevalent in food-processing environments.
    • Causes meningitis in immunocompromised individuals, pregnant women, neonates, and elderly adults.
    • High mortality rate.

    Streptococcus agalactiae (Group B Strep - GBS)

    • Gram-positive cocci in short chains.
    • Normal GI and vaginal flora.
    • Primarily causes meningitis in neonates.
    • Can be acquired in utero, during labor, or shortly after birth.
    • Treatable with antibiotics.

    Protozoa and Helminths

    • Naegleria fowleri: Amoeba found in warm, stagnant water that can enter the CNS through the olfactory bulb, causing meningoencephalitis.
    • Angiostrongylus cantonensis (Rat lungworm): Nematode larvae that enter the CNS through the ingestion of infected snails or slugs.

    Treatment

    • Bacterial meningitis: Immediate treatment with antibiotics is required.
    • Viral meningitis: Supportive therapy to manage symptoms.
    • Fungal meningitis: Antifungal therapy is essential.
    • Protozoal and helminthic meningitis: Treatment depends on the specific pathogen.

    Prevention

    • Vaccination: Hib vaccine for Haemophilus influenzae and vaccines for common serogroups of Neisseria meningitidis.
    • Proper sanitation and hygiene: Prevent foodborne exposures to Listeria monocytogenes and other pathogens.
    • Prophylactic antibiotics: For close contacts of individuals with Neisseria meningitidis infections.
    • Avoid contact with contaminated water: To prevent Naegleria fowleri infection.

    Chronic Meningitis

    • Gradual onset of neurological symptoms and signs lasting longer than 4 weeks, sometimes for months or years.
    • Chronic symptoms include mild fever, headache, altered sensorium, and meningismus.
    • Symptoms may fluctuate, improving for a period before returning or worsening.
    • Can be caused by infections, cancer, trauma, or medications.
    • It's crucial to check for HIV and immune deficiency as it can lead to unusual pathogens.
    • Common causes include Mycobacteria, Spirochetes, Fungi, and opportunistic infections.
    • Mycobacterium tuberculosis can cause chronic meningitis after a primary TB infection.
    • Cryptococcus neoformans is a leading cause of meningitis in HIV patients in central and southern Africa.
    • Fungal meningitis requires antifungal treatment.
    • Viral meningitis is the most prevalent type of acute meningitis.
    • It is less dangerous than bacterial meningitis and often resolves on its own with supportive therapy.
    • Enteroviruses, including echoviruses and coxsackievirus, are common causes of viral meningitis.
    • Coxsackie virus can cause hand foot and mouth disease.

    Encephalitis

    • Encephalitis is an acute inflammation and infection of the brain parenchyma.
    • Pathogens reach the brain via the bloodstream, crossing the blood-brain barrier, or through peripheral nerves.
    • Key triad of symptoms includes fever, headache, and focal neurological signs (e.g., mental state changes, seizures, speech disturbances, hemiparesis).
    • Viral encephalitis accounts for 85% of cases globally.
    • Herpesviridae (HSV, VZV, CMV, EBV), particularly HSV, are common causes.
    • Other causes include rabies, enteroviruses, mumps, HIV, arboviruses (West Nile, Zika, JEV), Hendra, Nipah, and non-viral agents like Listeria, rickettsia, bartonella, toxoplasma, and prions.
    • HSV encephalitis is the most common worldwide and presents with acute disease and worsening symptoms over a week.

    Herpes Simplex Encephalitis

    • HSV-1 usually causes cold sores and HSV-2 is an STI.
    • Reactivated HSV can travel from nerve ganglia to the temporal lobe of the brain via retrograde axonal transport.
    • This can lead to meningoencephalitis, encephalitis, and haemorrhagic necrosis of the brain.
    • If left untreated, there is a 70% mortality rate.
    • Treatment with acyclovir, an antiviral, reduces mortality to 20%, but some patients may experience long-term memory impairments.
    • MRI/CT scans can reveal temporal lobe involvement.

    Rabies

    • Rabies is a fatal viral infection spread through animal bites or scratches.
    • The virus spreads from muscle cells to peripheral nerves and then to the CNS.
    • The onset of symptoms occurs 20-90 days after exposure.
    • Prompt treatment with rabies vaccine and rabies immunoglobulin (RIG) injected at the bite site significantly increases survival chances.

    Meningitis CSF Results

    • CSF analysis is crucial in diagnosing meningitis.
    • Increased opening pressure, neutrophils, and protein levels suggest bacterial meningitis.
    • Increased T lymphocytes and reduced glucose levels indicate viral, fungal, or TB meningitis.
    • Cloudy CSF suggests bacterial infection, while viral meningitis is associated with clear CSF.
    • Fungal or TB meningitis can have both clear and cloudy CSF, requiring Indian ink or acid-fast staining to determine the cause.

    Clinical Management of Meningitis

    • Bacterial meningitis: requires immediate treatment with broad-spectrum bactericidal antibiotics.
    • Viral meningitis: managed with supportive therapy, including anti-inflammatories, anti-epileptics, and anti-pyretics.
    • Fungal, protozoal, or helminthic meningitis: treated with specific antimicrobials depending on the pathogen.
    • Supportive therapies include fever reduction, seizure prevention, and reducing inflammation and intracranial pressure.

    Learning Outcomes

    • Understand the clinical features, outcomes, and causative agents of encephalitis and focal CNS infections.
    • Recognize the diverse range of viruses responsible for encephalitis.
    • Relate different types of microbes (bacteria, protozoa, helminths) to focal CNS infections.
    • Learn how encephalitis and focal CNS infections are diagnosed and managed.

    Rabies

    • Rabid encephalitis presents with behavioural changes, hallucinations, hypersexuality, outbursts, excessive salivation, hydrophobia, convulsions, fever, coma, and death.
    • All of these symptoms present in dogs and make it more likely for the virus to be transmitted.
    • Rabies is endemic in many locations. Vaccinations are recommended before travelling to endemic regions, and immediate treatment is crucial when exposed.

    Arboviruses

    • West Nile virus is an arbovirus that is transmitted through mosquito injection.
    • The virus travels from the lymph nodes to the spleen before crossing the blood-brain barrier to cause encephalitis.
    • The virus can enter the brain via macrophages, effectively using them as a "Trojan horse."
    • The virus can also cross the blood-brain barrier through tight junctions, causing encephalitis.
    • There is no vaccine for West Nile virus.
    • Prevention measures include removing sick or dead birds and controlling mosquitoes.
    • Common signs of West Nile virus are dead bird sightings. Birds act as reservoir hosts for the virus and can die as a result.
    • Personal protection measures against mosquito bites are essential: long sleeves, long pants, and mosquito repellent.
    • Once the virus is in the central nervous system (CNS) it infects neurons and causes significant damage, leading to encephalitis symptoms.

    Focal CNS Infections

    • Focal infections in the brain parenchyma may begin as cerebritis (inflammation of the cerebrum), potentially caused by worms, protozoa, parasites, or other pathogens.
    • Brain abscesses develop from cerebritis, usually caused by bacteria, as pus collects at the infection site and becomes surrounded by a well-vascularized capsule.
    • Brain abscesses can be observed as circular structures on CT and MRI scans, indicating the location of the pus collection.
    • The capsule surrounding the abscess prevents the infection from spreading.
    • Brain abscesses carry a high mortality rate (20%) if untreated.
    • Imaging is the preferred diagnostic method for suspected brain abscesses, due to the clarity of detection on CT/MRI scans.
    • The most common cause of brain abscesses is bacteria, followed by fungal and protozoal/helminth infections.
    • Most infections originate from normal flora in the body.
    • Brain abscesses can also be caused by surgical procedures or dental work.
    • Polymicrobial (multiple bacteria) brain abscesses are possible, often due to normal flora or trauma.
    • Significant neurological damage can occur (20% to 70%) leading to sequelae (long-term effects).

    Predisposing Factors For Brain Abscesses

    • Infections located elsewhere in the body can spread into the bloodstream and reach the brain:
      • Otitis media (middle ear infection)
      • Sinusitis (inflammation of the sinuses)
      • Dental sepsis (infected teeth)
      • Lung abscesses
      • Bacterial endocarditis (infection of the heart valves)
    • Neurosurgical procedures
    • Infections of CNS device shunts
    • Recent head trauma
    • Congenital heart disease
    • Immunosuppression (cancer patients, transplant recipients, HIV)
    • Low CD4 counts in HIV-infected individuals.
    • Example: Rebecca Dalton's case - a tooth abscess was resolved, but a brain abscess developed requiring surgery.

    Symptoms of Brain Abscess

    • Headache
    • Focal neurological deficits – vary depending on the abscess location.
    • Seizures
    • Stroke syndrome (due to pressure)

    Treatment of Brain Abscess

    • Initial empirical antibiotic treatment followed by specialization based on blood and drainage cultures and microbial analyses.
    • Depending on size and symptoms, corticosteroids may be used to reduce pressure and cerebral edema.
    • Drainage procedures are common to remove pus and alleviate pressure.

    Focal Infection Caused By Protozoa

    • Toxoplasma gondii (also known as "toxo") is a common intracellular parasite.
    • Most people have been exposed to Toxoplasma, particularly those who have cats.
    • Pregnant women are advised to avoid cleaning cat litter to prevent exposure to oocysts (parasite eggs).
    • Toxoplasma gondii can be contracted by ingesting undercooked meat containing cysts that hatch in the digestive system and can travel to the brain.
    • The infection can form walled-off areas in the brain.
    • Immunocompromised individuals are more susceptible to toxoplasmosis infection.
    • Late-stage HIV infections can exhibit "starry night presentation" on brain imaging, indicating multiple walled-off cysts.

    Taeniasis (Pork Tapeworm Infection)

    • Taeniasis is caused by the pork tapeworm.
    • Infection occurs by consuming undercooked pork meat containing oncospheres (parts of the tapeworm's life cycle).
    • The scolex (head) of the tapeworm attaches to the small intestine and grows into a large worm.
    • Eggs released by the worm are excreted in feces.
    • Ingesting these eggs can lead to infection in humans.
    • Embryos from the eggs can migrate to muscle tissue and the brain, forming cysts.

    Treatment of Taeniasis

    • Antihelminthic medications (e.g., albendazole) kill the worms but can trigger a massive immune response that may worsen inflammation in the brain.
    • Corticosteroids (e.g., dexamethasone) may be needed to manage inflammation.
    • Anticonvulsant medications may be necessary to manage seizures.
    • Surgical removal of worms is possible in cases with limited infestation.

    Subdural Empyema

    • Subdural empyema is a collection of pus in the space between the dura mater and arachnoid mater.
    • It can occur in individuals with lung or heart infections.
    • Subdural empyemas appear as high-signal regions on CT scans.
    • These are not walled-off.
    • The most frequent cause (50-80%) is otorhinologic infections (ears or nasopharynx) that spread to the brain.
    • Trauma can also introduce microbes and contribute to subdural empyema.
    • Lumbar punctures are contraindicated as they might increase the risk of infection spreading.
    • Causes include:
      • Streptococcus
      • Staphylococcus
      • Gram-negative bacilli
      • Anaerobic bacteria
    • Symptoms:
      • Fever
      • Altered mental state
      • Seizures
      • Headache
      • Hemiparesis
      • Vomiting
    • Subdural empyemas can be polymicrobial (multiple bacteria).
    • High mortality rate even with treatment (10-20%).

    Treatment of Subdural Empyema

    • Medical emergency, requires prompt intervention.
    • Urgent decompression and surgical drainage
    • Aggressive antibiotic treatment

    Epidural Abscess

    • Collection of pus in the epidural space, the area between the dura mater and the vertebral column.
    • Typically caused by bacteria, most commonly Staphylococcus aureus, often from normal flora.
    • Risk factors: immunocompromised individuals, HIV, recent spinal surgery, or trauma.
    • Lumbar punctures are contraindicated due to the risk of spreading infection, as they can push the infection into the cerebrospinal fluid (CSF) and meninges.
    • Pressure on the spinal cord can lead to neurological deficits: radiculopathy (nerve compression), paralysis.
    • Fatal if left untreated.

    Treatment of Epidural Abscess

    • Urgent aggressive antibiotic therapy.
    • Urgent decompression (surgical intervention to relieve pressure).

    Clinical Management Of Encephalitis And Focal CNS Infections

    • Immediate assessment and treatment are crucial for the best chance of survival.
    • Differentiation between meningitis, encephalitis, and focal CNS infections is essential.
    • Focal neurological signs indicate direct brain tissue injury, warranting prompt attention.
    • Imaging (CT/MRI) should be performed before lumbar puncture, if applicable.
    • Identifying the pathogen responsible is critical: MCS (microbial cultures), drainage analysis, blood cultures, PCR, serology.
    • Empiric antimicrobial therapy is initiated immediately, followed by adjustment based on identified pathogens (antibiotics, antivirals, antiparasitics, antifungals).
    • Anti-inflammatory and anti-seizure medication may be required to reduce inflammation and protect the patient.
    • Surgical intervention (drainage, removal) may be necessary in some cases.

    Summary:

    • Encephalitis involves inflammation of the brain's white matter.
    • Infections can be diffuse (e.g., HSV) or focal due to parasites or worms.
    • CT/MRI play a crucial role in diagnosing brain infections.
    • Lumbar puncture may be needed but is generally not the first choice.
    • Clinician management depends on the infectious agent involved.
    • Timely treatment is paramount due to the high risk of mortality.

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    Test your knowledge on meningitis, focusing on its causes, symptoms, and distinctions between viral and bacterial forms. This quiz covers key aspects of central nervous system infections and their pathogens. Perfect for students studying neurology or infectious diseases.

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