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MD4001 > Infections of the CNS > Flashcards

Infections of the CNS Flashcards

1
Q

Describe clinical features of Meningitis.

A
  • Headache, sore throat, drowsiness
  • Rapid onset fever, photophobia, neck stiffness
  • Level of consciousness progressively falls
  • Petechial or purpuric rash
  • Intravascular coagulation, endotoxaemia, shock, multi-organ failure, raised intracranial pressure.
  • Gangrene
  • Life-threatening emergency!
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2
Q

Identify a test to ensure whether or not a rash is from meningitis.

A

GLASS TEST
“Press a clear drinking glass against the rash. If the rash and marks are visible even while pressing down on the glass (non-blanching rash), seek medical help immediately.

This is a sign that the rash is petechial. Petechial rashes can result from meningitis or other serious illnesses that cause bleeding.”

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3
Q

Identify possible complications of meningitis.

A
  • Gangrene

- Purpura fulminans (of acute meningitis)- thrombotic disorder

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4
Q

Describe diagnosis of meningitis.

A

• Initial diagnosis based on symptoms (listed above)

• Other symptoms in babies:
– Tense or bulging soft spot on their head
– Refusing to feed
– Irritable when picked up, with
a high pitched or moaning cry
– A stiff body with jerky movements, or else floppy and lifeless

• To confirm, “spinal tap to collect cerebrospinal fluid (CSF)”

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5
Q

Define meningitis, encephalitis, and sepsis.

A 
• Meningitis
– Inflammation of the meninges • Encephalitis
– Inflammation of the brain 
• Sepsis
– Whole-body inflammation
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6
Q

Identify ways through which infectious agents from outwith the brain can cause infection in the brain.

A

• Blood-brain barrier (BBB)
– Breach by infectious agents causes encephalitis.

• Blood- cerebrospinal spinal fluid (CSF) barrier
– Breach by infectious agents causes meningitis.

• Direct Spread
– Sinuses
– Otitis media
– Skull fracture

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7
Q

What forms the BBB ?

A

– Created by tightly packed endothelial cells lining the blood
vessels in the brain.
– Endothelial cells mechanically supported by thin basement membrane

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8
Q

What forms the blood-CSF barrier ?

A

– Similar barrier as BBB at arachnoid membrane and in ventricles.

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9
Q

How can pathogens cross barriers protecting the brain ?

A

– Growing across and infecting cells comprising barrier
– Passive transfer in intracellular vacuoles
– Carriage across in infected white blood cells

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10
Q

What laboratory investigations

would be carried out to confirm diagnosis of meningitis ?

A 
• Blood
– culture
– NAAT
– glucose 
– FBC
– UandE
– clotting
• CSF (through lumbar puncture):
– white cell count
– Gram stain
– Ziehl-Neelsen stain 
– India ink
– NAAT
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11
Q

When is a lumbar puncture contra-indicated ?

A
  • Skin infection near the site of the lumbar puncture

- Suspicion of increased intracranial pressure due to a cerebral mass

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12
Q

Identify possible causative pathogens of meningitis.

A

BACTERIA

  • Neisseria meningitidis
  • Haemophilus influenzae
  • Streptococcus pneumoniae
  • Myobacterium tuberculosis

VIRUSES

  • Enteroviruses (echovirus, coxsackie viruses A and B, poliovirus)
  • Herpes viruses (Herpes simplex 1 and 2)
  • Paramyxovirus (complication of mumps)

FUNGI
-Cryptococcus neoformans

PROTOZOA

  • Amoebae
  • Naegleria
  • Acantoamoeba
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13
Q

NEISSERIA MENINGITIDIS

  • Condition caused
  • Classification
  • Transmission
  • Strains
A

NEISSERIA MENINGITIDIS

  • Condition caused: meningococcal disease
  • Classification: Gram negative, intracellular diplococcus, humans only, (exists as) normal microbiota of nasopharynx
  • Transmission: by droplet spread or direct contact from carriers
  • Strains: 5 (A, B, C, W135, Y)

(Also, distinct pathogenic serogroups)

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14
Q

HAEMOPHILUS INFLUENZAE

  • Classification
  • Strain
A

HAEMOPHILUS INFLUENZAE

  • Classification: Gram-negative, coccobacilli
  • Strain: Six capsular serotypes (a-f) known to cause disease, most virulant strain is H. influenzae type B (Hib)
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15
Q

STREPTOCOCCUS PNEUMONIAE

  • Classification
  • Conditions caused
A

STREPTOCOCCUS PNEUMONIAE

  • Classification: Gram positive, chains of cocci, (exists as) normal microbiota in nasopharynx
  • Conditions caused: Meningitis, pneumococcal disease, pneumonia, otitis media
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16
Q

Identify virulence factors of bacterial meningitis.

A
  • Anti-phagocytic polysaccharide capsule
  • Endotoxin
  • IgA protease
  • Outer membrane proteins (OMPs)
  • Pili (fimbriae)
  • All play an important role in pathogenesis
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17
Q

BACTERIAL MENINGITIS

  • Appearance
  • Cells
  • Protein
  • Glucose
  • Gram Stain
  • White Cell Count
A

BACTERIAL MENINGITIS

  • Appearance: turbid
  • Cells: polymorphs (100-2000/ul)
  • Protein: Increased (50-300 mg/dL)
  • Glucose: Reduced (0-5 mg/dL)
  • Gram Stain: Perform (result is usually Gram negative)
  • White Cell Count: Neutrophilia
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18
Q

VIRAL MENINGITIS

  • Appearance
  • Cells
  • Protein
  • Glucose
  • Gram Stain
  • White Cell Count
A

VIRAL MENINGITIS

  • Appearance: Clear
  • Cells: Lymphocytes (15-200/ul)
  • Protein: Slight increase (50-100)
  • Glucose: Normal
  • Gram Stain: N/A
  • White Cell Count: Normal
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19
Q

TUBERCULOUS MENINGITIS

  • Appearance
  • Cells
  • Protein
  • Glucose
  • Gram Stain
  • White Cell Count
A

TUBERCULOUS MENINGITIS

  • Appearance: Clear (may cobweb)
  • Cells: Lymphocytes (15-500/ul)
  • Protein: Increased (100-600 mg/dL)
  • Glucose: Reduced (0-5 mg/dL)
  • Gram Stain: Do Ziehl- Neelsen stain
  • White Cell Count: Normal
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20
Q

Which age groups are particularly at risk of pneumococcal meningitis ?

A

0 to 4 years make up majority

21
Q

What are common causative pathogens of bacterial meningitis in:

  • Neonates
  • <5 years old
  • Young adults
  • Older
  • Immunosuppressed
A

Neonates:
Escherichia coli
Group B Streptococcus
Listeria monocytogenes

<5 years old:
Neisseria meningitidis Haemophilus influenzae

Young adults:
Neisseria meningitidis

Older:
Strep pneumoniae
Listeria monocytogenes

Immunosuppressed:

  • Myobacterium tuberculosis
  • Cryptococcus neoformans
22
Q

Distinguish between early, and late onset neonatal meningitis.

A 
EARLY ONSET
• Occurs <7 days
• Infected by heavily
colonised mother
• Premature rupture of membranes
• Pretermdelivery
• 60% fatality rate
LATE ONSET
• Occurs <3 months 
• Lack of maternal antibody
• Poor hygiene in nursery 
• 20% fatality rate
23
Q

Identify possible complications of bacterial meningitis.

A
  • Sepsis
  • Intellectual deficit
  • Deafness
  • Arthritis
  • Skin necrosis
24
Q

Describe treatment for bacterial meningitis, especially:

  • Suspected meningococcal infection
  • Suspected meningococcal infection <3 months old
  • N. Meningitidis
  • H. influenzae
  • Strep. pneumoniae
  • Group B Strep
  • Gram negative bacilli
  • L. monocytogenes
A

Suspected meningococcal infection:
IV/IM Penicillin (by GP on pre-admission)
IV Ceftriaxone (on admission)

Suspected meningococcal infection <3 months old
IV Cefotaxime + amoxicillin

N. meningitidis
IV Ceftriaxone 7d

H. influenzae
IV Ceftriaxone 10d

Strep. pneumoniae
IV Ceftriaxone 14d

Group B Streptococcus
IV Cefotaxime 14d

Gram negative bacilli
IV Cefotaxime 21d

L. monocytogenes
IV Amoxicillin 21d + IV Gentamicin first 7d

25
Q

Describe prevention of bacterial meningitis.

A 
VACCINES
• MenC (meningococcal group C)
• Hib (Haemophilus influenzae type B)
• BCG (Mycobacterium tuberculosis)
• Strep. Pneumoniae (pneumonococcal)
• MenB (meningococcal group B)
• Men ACWY (quadrivalent)
26
Q

Does anyone need to be notified about this diagnosis, in bacterial meningitis ?

A

Meningococcal disease is a notifiable disease under the Public Health etc. (Scotland) Act 2008:

1) Reference Laboratories:
• Scottish Haemophilus, Legionella, Meningococcus and Pneumococcus Reference Laboratory (SHLMPRL)

2) Public Health Action:
• Public Health will identify the close contacts and arrange antibiotics. Vaccination may also be required.
• If the patient is a child at school information letters and MRF info leaflets for all school parents are arranged.

3) Public Awareness:
• The public should be aware of the key signs and symptoms and to seek urgent medical advice if concerned.

27
Q

What is a notifiable diseases ?

A
  • Any disease that is required by law to be reported to government authorities
  • Allows the authorities to monitor the disease
  • Provides early warning of possible outbreaks

E.g. acute meningitis

28
Q

How many cases, and deaths due to meningococcal meningitis worldwide ? Which environments is it most prevalent in ?

A
  • Approx. 500,000 cases (50,000 deaths) worldwide

* Endemic in temperate climates. Endemic and epidemic in sub-Saharan Africa

29
Q

Define meningitis belt.

A

4 African countries reported 88, 000 suspected cases

30
Q

Which meninigitis serogroup has been responsible for most infectionsin Scotland ?

A

Group B (Group C also used to be responsible for a large amount of infections, but Group C vaccine was introduced in 2000)

31
Q

VIRAL v BACTERIAL MENINGITIS

  • More severe form
  • More common form
A

VIRAL v BACTERIAL MENINGITIS

  • More severe form: bacterial
  • More common form: viral
32
Q

Describe diagnosis of viral meningitis.

A
  • NAAT is a valuable diagnostic tool

* Identify in faeces, urine, CSF, serology

33
Q

Describe treatment for viral meningitis.

A
  • No specific treatment
  • Aciclovir (if herpes virus)
  • Use of vaccination (if poliovirus)
34
Q

Describe clinical features, diagnosis, and treatment of Tuberculous Meningitis.

A

TUBERCULOUS MENINGITIS

-Clinical: Usually develops when Rich focus discharges contents in sub-arachnoid space
-Diagnosis:
• Acid-fast bacilli in CSF smear
• NAAT and culture from CSF
-Treatment:
• Treated with rifampicin, isonazid, pyrazinamide, ethambutol
• Vaccination with BCG

35
Q

Which other condition is tuberculous meningitis often associated with ?

A

Frequently associated with miliary TB

36
Q

Which group of pathogens usually cause encephalitis ? How do these pathogens gain access to the CNS ?

A

Usually viral in origin

• Viruses gain access to CNS via blood or neurons

37
Q

Identify the main kinds of encephalitis.

A

• Primary encephalitis
– First exposure to virus results in virus directly affecting brain / spinal cord
• Secondary encephalitis
– Virus first infects another part of body, then affects CNS when reactivated

38
Q

Identify common causative pathogens of encephalitis.

A
  • Cerebral malaria (Plasmodium sp.)
  • Toxoplasma gondii
  • Rabies
  • Lyme disease (Borrelia burgdorferi)
  • Herpes simplex virus
39
Q

Identify signs of cerebral dysfunction, and an example of condition which may cause these.

A 
ENCEPHALITIS
– Abnormal behaviour
– Seizures
– Altered consciousness 
– Nausea
– Vomiting
– Fever
40
Q

Identify a possible complication of encephalitis.

A

Brain Abscess

41
Q

Describe formation of brain abscesses as a result of encephalitis.

A
  • Begin as diffuse inflammation of brain matter progressing to focal lesion
  • Arise from pia mater suppuration
42
Q

How is brain abscess diagnosed ?

A
  • Visualised by MRI or CT scans

* Diagnosed by culture from aspirated pus

43
Q

Identify predisposing factors to brain abscess.

A

• Predisposing factors
– Otitis media
– Mastoiditis
– Sinusitis

44
Q

Identify pathogens associated with brain abscesses.

A

• Oral-nasopharyngeal microbiota
– Aerobic (S. aureus, Strep. milleri)
– Anaerobic (Bacteroides sp., Fusobacterium sp.)

• Immunocompromised (eg. HIV, transplantation)
– Protozoa (Toxoplasma gondii)
– Fungi (Candida sp., Nocardia sp., Aspergillus sp.)

45
Q

What are Transmissible Spongiform Encephalopathies ?

A

Prion diseases

46
Q

Which living beings do TSEs affect ?

A

• Affects humans…
– Creutzfeldt-Jakob disease (CJD)
– New variant Creutzfeldt-Jakob disease (nvCJD)

• …and animals
– Bovine Spongiform Encephalopathy (BSE)
– Kuru
– Scrapie

47
Q

What is the mechanism of action of rabies for infection of the CNS ?

A

Interference with function of infected nerve cells

48
Q

What is the mechanism of action of poliomyelitis for infection of the CNS ?

A

Direct damage to nerve cells

49
Q

What is the mechanism of action of botulism, tetanus for infection of the CNS ?

A

Release of neurotoxins released at a distant site

MD4001 (74 decks)

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