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Block 6 > 10.3 CNS infections > Flashcards

10.3 CNS infections Flashcards

1
Q

What is the role of the BBB

A

form a continuous barrier between the blood and brain that restricts transport of ions, molecules, cells and pathogens

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2
Q

What forms the BBB?

A

Enodthelium lining the brain capillaries

  • Intracellular tight junctions
  • Limited pinocytic activity
  • Basement membrane and astrocyte foot processes
  • Specific carrier and transport systems
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3
Q

Where is CSF produced?

A

Choroid plexus in the ventricles of the brain

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4
Q

What is the normal flow of CSF

A

Lateral ventricles - third ventricle via intraventricular foramina of munro - fourth ventricle via aqueduct of sylvius - subarachnoid space via foramen of megendie

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5
Q

What forms the choroid plexus?

A

Capillaries separated from the ventricles by choroid epithelial cells (continuous with ependymal cells of the ventricles)

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6
Q

what prevents pathogen entry into CSF?

A

Tight junctions between the choroidal epithelial cells

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7
Q

Where are the potential sites for infection in the brain?

A

Meningitis: inflammation of meninges
Encephalitis: inflammation of the brain
Myelitis: inflammation of the spinal cord
Focal lesions/abcesses

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8
Q

What are the mechanisms of pathogen entry to the brain?

A

Physical pathway
Haematogenous
Peripheral nerve
Olfactory nerve

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9
Q

What is the physical pathway for pathogens?

A

BBB/BCB damaged by congenital defect, trauma or surgery, extensions from bone

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10
Q

What are the two kinds of haemogenous entry of pathogens?

A

Primary: blood infection after entry to the body usually from respiratory tract (neisseria meningiditis, viaral, fungal, bacterial)

Secondary to blood infection from primary focus elsewhere (pneumonia, endocarditis)

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11
Q

What is the peirpheral nerve entry to the brain?

A

Travel up an affected nerve to the brain - olfactory common as it doesn’t have to travel far

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12
Q

What is the presentation of meningitis?

A

Photophobia, neck stiffness, headache and fever

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13
Q

What symptoms suggest a cause other than meningitis?

A

Confusion, seizures, neurological deficitis

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14
Q

What are the extraneural symptoms of meningitis?

A

Rash, pneumonia, sinusitis, otitis media

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15
Q

What is the fatal form and most common form of meningitis?

A

Bacterial: FATAL without antibiotics
Viral: most common but usually self limiting

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16
Q

What is the gram stain, risks and associations of strep pneumoniae meningitis?

A

Gram + dipolococci

Risks: hyposplenism,

17
Q

What is the gram stain, risks and associations of Neisseria meningitides?

A

Gram - diplococci

Risks:

18
Q

What is the gram stain, risks and associations of listeria monocytogenes?

A

Gram + bacillus

Risks: immunosuppressed (T cell def.), pregnancy and neonates

Associated: Subacute, history of unpast daisy, deli meat, raw salads

19
Q

What is the gram stain, risks and associations of Group B strep?

A

Gram + cocci in chains

Risks: neonates

Associations: Maternal colonisaton and chorioamniotitis

20
Q

What is the gram stain, risks and associations of mycobacterium tuberculosis

A

Risks: TB exposure in past, immunosuppressed

Associated: subacute-chronic presentation, tuberculomas

21
Q

What are the common causes of viral meningitis and how do you treat it?

A

Enterovirus, Herpes simplex 2, varicella zoster, primary HIV

usually self limiting

22
Q

What are the common causes of fungal meningitis?

A 
Cryptococcus neoformans 
Cryptococcus gatii (red river gums)
23
Q

What are the common bacterial causes of meningitis?

A

Listeria monocytogenes

Mycoplasma pneumoniae

24
Q

What is usually the cause of spinal epidural abscess and what is it?

A

Staph aureus
Collection of pus between the outermost layer of meninges and the vertebral column
EMERGENCY

25
Q

Why is a spinal epidural abscess and emergency?

A

Can cause irreversible para/quadriplegia due to cord compression or infarction

26
Q

What do you do to diagnose CNS infection?

A 
Clinical history (inc exposure) 
Imaging (encepahalitis, brain abscess, epidural abscess) 
EEG (encephalitis) 
Lumbar puncture (CSF analysis) 
Blood cultures 
Tissue biopsy
27
Q

What do you measure on lumbar puncture?

A

Opening pressure
MCS microscopy (cell count +/- gram stain), culture, sensitivity
Protein
Glucose

Block 6 (48 decks)

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