Week 10 - Topic 3: CNS Infections Flashcards by M00nlight Stars

What are the 3 tissue layers covering the CNS?

Meninges

1) Pia mater
2) Arachnoid mater
3) Dura mater

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What does the CNS bathe in?

CSF - cerebral spinal fluid

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What is between the dura mater and the skull?

Epidural space

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What is between the arachnoid and dura mater?

Subdural space

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What is between the pia and arachnoid mater?

Subarachnoid space

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In which space is the CSF located?

Subarachnoid space and in ventricles

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Where is CSF produced?

Choroid plexus in the ventricles

roof of 3rd and 4th ventricle and floor of lateral ventricle

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What is the purpose of CSF?

Communication of neurons and cushion in case of trauma

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True or False: CSF is normally sterile.

True

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Why are epithelial cells lining the brain’s blood vessels less permeable than blood vessels in the body?

Tight junctions = blood brain barrier

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What substances does the blood brain barrier limit access to the brain?

Invading microorganisms
Toxic substances
Ig
Complements
Abx

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Your patient has meningitis. What must you consider with regards to antibiotics dosage?

Give them maximal or “meningitis” doses to cross over to the CNS (not doses systemically)

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What are the pathways of entry for CNS infections (5) and what microorganisms are associated with each?

1) Olfactory nerve pathway (influenza, herpes simplex, polio, rabies, west nile, etc.)
2) Hematogenous pathway (arthropod borne tropical viruses like Zika)
3) Intestinal tract (polio)
4) Respiratory tract (Neisseira meningitis, Strep Group A, Haemophilus influenza type B)
5) Peripheral nerve pathway (Chicken pox, herpes simplex)

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How can one be infected with CJD prion?

Coming into contact with human brain products, dural grafts, corneal grafts, human growth hormone

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What are portals of entry for local CNS invasion?

Ears, sinuses, spine injury/defects, trauma

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What causes spongiform encephalopathy?

Prion diseases

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What does the brain damage from spongiform encephalopathy look like?

Brain looks like a sponge due to the vacuoles

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What is CSF collected in during a lumbar puncture?

Multiple sterile, screw cap containers

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True or False: If you do the aseptic sterile no touch technique, you can send the initial volume for gram stain, cell count and cultures.

False, send tube #3 or #4 bc the first tube will most likely be contaminated with skin flora.

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True or False: You use face shields during CSF culture.

False

But you use mask, sterile gloves, gowns and sterile field

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True or False: You can refrigerate CSF cultures.

False, send it to lab ASAP

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True or False: Physicians must start meningitis treatment before culture results.

True, bc meningitis can cause rapid irreversible damage

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Why must we proceed with caution when we evaluate PTs with meningitis?

Clinical findings do not reliably differentiate bacteria from other causes (ex: viruses)
Particularly true for pediatrics

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What is the difference between septic and aseptic meningitis.

Septic caused by bacteria/brain abscesses, turbid CSF, high protein/neutrophil count, low glucose

Aseptic caused by viruses /TB/fungi, cells are mainly mononuclear, moderate-high protein count, normal glucose

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What is encephalitis?

Inflammation of cerebral cortex

What is meningitis?

Inflammation of meninges

Where are abscesses usually located (3)?

1) Brain abscesses = cerebral cortex 2) Subdural abscesses = btwn dura and arachnoid 3) Epidural abscesses = outside of dura

What is myelitis?

Spinal cord inflammation

What is neuritis?

Peripheral nerve inflammation (travels up and down axons)

What is paralysis?

Peripheral nerve block: - Blocks the release of acetylcholine at the synapses - Destroys motor neurons, killing the nerves

What are the symptoms of encephalitis?

- Abnormal behaviour - Seizures, convulsions, muscle spams - Altered consciousness - Nausea, vomiting, fever

What are the symptoms of meningitis?

- Fever, irritability - Neck stiffness - Photophobia

What are symptoms of CNS infection in neonates?

Respiratory distress | Poor feeding

What does the inflammation from CNS do to CSF?

Slows its normal flow which can increase ICP and cause headaches, vomiting, nausea while leading to loss of function of infected nerve cells and damage

What is the most common complication of bacterial meningitis?

Deafness

How does bacterial meningitis reach the ear?

Subarachnoid space > cochlear aqueduc > inner ear

How does bacterial meningitis lead to deafness?

The presence of bacteria in the inner ear activate the complement cascade which triggers vigorous inflammatory response and damages the cochlear

What is the treatment for bacterial meningitis that may lead to deafness?

Steroids and anti-inflammatories

How does poliovirus infect the CNS orally?

Ingested orally, enters the lymphatic system to the blood

What are the 3 phases of a CSF?

1) Meningitic phase (infects meninges) 2) Encephalitic phase (crosses the pia mater to infect cortex) 3) Paralysis (infarcts, abscesses and damage)

What are signs of Neisseria meningitis infection (usually infects via the respiratory route)?

Small purple petechia on skin

What are the signs of a CNS infection via a respiratory route?

High opening pressure of CSF (>180 mm water) High WBC count Low glucose <45 mg/dL High protein >45 mg/dL

What type of bacteria will we usually find in a CNS infection via the respiratory route?

Neisseria meningitis | Gram - diplococcus

What viruses can infect the local peripheral nerves and colonize the dorsal root gangla?

Herpes simplex virus (HSV) | Varicella-Zoster virus (VZV)

What microorganisms can travel up sensory neurons or motor axons to colonize the brain?

Rabies, tetanus, HSV, VZV

What are the symptoms of a CNS infection locally on the peripheral nerves?

Pain and lesions

Why do we have CNS shunts?

To treat hydrocephalus by draining the CSF fluid in another part of the body

What are the 4 types of CNS shunts?

1) Ventriculo-peritoneal (VP) shunt: peritoneal cavity 2) Ventriculo-atrial (VA) shunt: R atrium of heart 3) Ventriculo-pleural (VPL) shunt: pleural cavity 4) Lumbar-perioneal (LP) shubt: peritoneal cavity

What are the 3 parts of a CNS shunt?

1) Tube that goes into the fluid build up ventricle 2) Valve that controls how much fluid drains out 3) Tube that comes out of the valve and into another part of the body

How do you prevent shunt infections when handling them?

Aseptic sterile no touch technique + disinfection of ports

What causes shunt infections?

Skin flora

What are the symptoms of shunt infections?

Same to hydrocephalus (headaches, nausea, double vision, altered consciousness)

How should an externalized ventricular drain be positioned?

The transducer must be aligned to PT's auditor meatus or tragus when lying down --> Realign EVD if PT moves so it is horizontal to ventricles

What does an EVD do?

Allow drainage of CSF from ventricles to an external closed system

How do you call an infection EVD-related?

Ventriculitis

True or False: You must use a sterile vented-cap every time you zero the transducer.

False, it is a sterile dead-end cap

Can you do CSF cultures from EVDs to limit PT exposure to multiple procedures?

No, risk of contamination | Better to do lumbar tap

You are about to switch from EVD monitoring to drainage. Do you use a clamp or a 3 way tap?

Clamp!

What must you label on the EVD itself?

Label on the clamp that this is an EVD, so it is not mistaken for a CVL lumen

What must you report to the neurosurgeon ASAP?

CSK leakage, as it is port of entry for bacteria

How do you prevent non-device associated CNS infections (3)?

1) Vaccines (polio, varicella, meningitis, tetanus, TB) 2) Screen blood donors 3) Appropriate neurosurgical and ophthalmic instrument management

What do PIV, CVL, CAUTI and EVD devices all have in common?

They are made out of plastic and are more prone to blood stream infections.

What must a nurse question (3) when confronted with a catheters, IV or EVDs?

1) Does the patient still need it? 2) Why does the patient have the plastic? 3) Is it being maintained using best IPC practice bundles?