Week 10 - Topic 3: CNS Infections Flashcards
What are the 3 tissue layers covering the CNS?
Meninges
1) Pia mater
2) Arachnoid mater
3) Dura mater
What does the CNS bathe in?
CSF - cerebral spinal fluid
What is between the dura mater and the skull?
Epidural space
What is between the arachnoid and dura mater?
Subdural space
What is between the pia and arachnoid mater?
Subarachnoid space
In which space is the CSF located?
Subarachnoid space and in ventricles
Where is CSF produced?
Choroid plexus in the ventricles
roof of 3rd and 4th ventricle and floor of lateral ventricle
What is the purpose of CSF?
Communication of neurons and cushion in case of trauma
True or False: CSF is normally sterile.
True
Why are epithelial cells lining the brain’s blood vessels less permeable than blood vessels in the body?
Tight junctions = blood brain barrier
What substances does the blood brain barrier limit access to the brain?
- Invading microorganisms
- Toxic substances
- Ig
- Complements
- Abx
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)
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)
How can one be infected with CJD prion?
Coming into contact with human brain products, dural grafts, corneal grafts, human growth hormone
What are portals of entry for local CNS invasion?
Ears, sinuses, spine injury/defects, trauma
What causes spongiform encephalopathy?
Prion diseases
What does the brain damage from spongiform encephalopathy look like?
Brain looks like a sponge due to the vacuoles
What is CSF collected in during a lumbar puncture?
Multiple sterile, screw cap containers
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.
True or False: You use face shields during CSF culture.
False
But you use mask, sterile gloves, gowns and sterile field
True or False: You can refrigerate CSF cultures.
False, send it to lab ASAP
True or False: Physicians must start meningitis treatment before culture results.
True, bc meningitis can cause rapid irreversible damage
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
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
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?
