CNS infections Flashcards
Meningitis Encephalitis I accidentally did HSV not HZV! HZV in separate set. Medsoc revision formative exam Qs
What is meningitis?
Inflammation of the arachnoid and pia mater of the meninges (inner layers of the meninges).
Where is CSF contained?
The subarachnoid space, between the arachnoid and pia mater of the meninges.
What does CSF contain?
Lymphocytes Monocytes Polymorphonucleocytes (PMNs) eg Neutrophils Proteins Glucose
What can cause meningitis other than infection?
(1. Infection (most common))
2. Autoimmune disease eg lupus
3, Intrathecal therapy (medications infected into CSF)
What is a common viral cause of meningitis?
Herpes simplex virus
Enteroviruses eg coxsackie
HIV
How do pathogens get into the meninges through direct spread?
Through skull or spinal column, usually due to anatomical defect : spina bifida (congenital) skull fracture (acquired). Pathogen may also enter through skin or nose (rarer).
How does meningitis occur by haematogenous spread?
Pathogens cross the BBB by:
Binding to surface receptors on the endothelial cells
Going through vulnerable areas - choroid plexus, damaged areas.
What could cause >100 WBCs/ml CSF and >90% PMNs?
Bacterial meninigitis eg neisseria meningitides. This is usually acute. [osmosis]
What could cause 10-1000 WBCs/ml and <20% PMNs?
Viral meningitis eg herpes simplex. This is usually acute. [osmosis]
What could cause 10-500 WBCs/ml and >50% lymphocytes?
Fungal meningitis eg cryptococcus. This is often chronic and affects immunocompromised.
What could cause 50-500 WBCs/ml and >80% lymphocytes?
TB meningitis
What happens to CSF pressure in meningitis?
Increases to >200mmH2O.
What happens to glucose concentration in meningitis?
Decreases to less than 2/3 blood glucose, because immune cells respire and use up glucose
[osmosis, medsoc]
What happens to protein levels in meningitis and why?
Increase to >50mg/dL because immune cells proliferate and synthesise proteins.
[osmosis, medsoc]
What is the most common cause of bacterial meningitis in children and teenagers?
Neisseria meningitidis, strep pneumoniae
[osmosis]
What is the most common cause of bacterial meningitis in adults and elderly people?
Strep pneumoniae, listeria monocytogenes [osmosis]
What may cause meningitis in someone with a tick bite?
Borrelia burgdorferi (causes lyme disease)
What may cause meningitis in a patient on azothiaprine?
Immunocompromised -> Fungal meningitis eg cryptococcus/ coccidiodes.
What may cause meningitis is someone who has recently returned from a hot country?
P. falciparum (malaria)
What is the most common cause of bacterial meningitis in neonates?
Group B streptococci. Also E. Coli and listeria monocytoges.
[osmosis, medsoc]
What are the main symptoms of meningitis?
Headaches
Fever
Nuchal rigidity (neck stiffness)
Photo/phonophobia
How would you differentiate meningitis from meningoencephalitis?
Encephalon (brain) involvement would cause altered mental state/ seizures.
What is Kernig’s sign?
Patient lies flat and extends one leg at 90 degrees. When extended further, it causes pain due to stretching of inflamed meninges.
What is Brudzinski’s sign?
When the patient lies supine and lifts their head, they flex their knees too, due to inflamed meninges.
How is meningitis diagnosed?
History and exam - test for Kernig’s and Brudzinski’s signs
Blood cultures to check for bacteraemia
LP - measure CSF pressure and levels of WBCs, proteins and glucose
PCR used to identify cause eg HIV/TB
What can be used to test for borrelia burgdorferi?
Western blot test
What can be used to test for malaria?
Thin blood smear [osmosis]
Why would you administer steroids before antibiotics?
If treating bacterial meningitis, steroids are administered to prevent injury to the meninges from the inflammation caused as the abx destroy the bacteria. [osmosis]
How can meningitis be prevented?
Vaccine: N. meningitidis, Mumps, disseminated TB
Prophylactic antibiotics eg if not vaccinated.
How does meningitis cause death?
Due to raised intracranial pressure.
How can you differentiate viral from bacterial meningitis?
Viral has no rash and is less severe. CSF is clear if viral, cloudy if non-viral.
Give 1 similarity and 1 difference between the CSF results for meningitis and subarachnoid haemorrhage?
In both, opening pressure and protein can be raised
In SAH CSF contains blood (xanthochromia).
Describe the management of meningitis.
Abx: cefotaxime, ceftriaxone. Add amoxicillin if immunocompromised to cover listeria.
Inform public health.
Viral - monitor
Give 3 signs of sepsis in someone with meningitis.
Joint pain Prolonged capillary refill Pallor Cold peripheries Tachycardia Tachypnoea
Describe the management of meningococcal sepsis.
ICU
Blood cultures, IV abx eg ceftriaxone
Airway support/ pre-emptive intubation
Delay LP until stable
How can meningococcal sepsis cause death?
Cardiovascular failure.
What is encephalitis?
Inflammation of the encephalon (brain).
What would make you suspect encephalitis?
Infectious prodrome: lymphadenopathy, fever, rash etc,
followed by signs of brain involvement: odd behaviour, decreased consciousness or seizure.
History: travel or bite.
How would you differentiate encephalitis from encephalopathy?
Encephalopathy = brain malfunction or damage, eg due to hypoglycaemia (among many causes). Consider this if signs of brain involvement without infectious prodrome.
Give 3 viral causes of encephalitis
HSV-1 and 2, cytomegalovirus, Epstein-Barr virus, HIV (seroconversion), tick-borne encephalitis, measles, mumps
Give 3 non-viral causes of encephalitis
Bacterial meningitis eg n. meningitidis; TB, malaria, Lyme disease, leionella, schistosomiasis
How is encephalitis diagnosed?
- Blood cultures, serum for viral PCR, individual tests eg malaria film
- EEG - diffuse abnormalities confirms diagnosis
- Contrast CT - focal bilateral temporal lobe involvement -> HSV.
- LP - viral PCR, raised protein and lymphocytes, low glucose (as in meningitis).
Describe the management of encephalitis.
Aciclovir 14 days as empirical for HSV
Supportive therapy - may need ICU
Symptomatic tx eg phenytoin for seizures.
What family of viruses is HSV from, and do they have DNA or RNA?
Herpesviridae: Enveloped, double-stranded DNA viruses.
Which type of HSV causes more mouth and tongue infections?
1 (there is crossover)
Which type of HSV causes more genital infections?
2 (there is crossover)
How and when is HSV transmitted?
In saliva/ genital secretions. It is most contagious when virus-filled lesions are present (eg coldsore), but can be spread any time by asymptomatic shedding
How does herpes get into cells?
It goes through small gaps in the mucosa and binds to receptors on epithelial cells which then internalise the virus. This starts a lytic cycle: viral DNA is transcribed and translated by the cell, which helps form new viruses which infect neighbouring cells. They infect nearby sensory neurones and travel up the to the cell body. This starts the latent cycle.
In what two places does the herpes virus settle in the body and stay for life?
Cell bodies of sensory neurones in the face (trigeminal ganglia) and genitalia (sacral ganglia)
What causes recurrent episodes of HSV?
Triggers such as stress, skin damage and viral illnesses cause HSV to make copies of itself which go and infect epithelial cells.
What causes the unilateral distribution of herpes lesions?
The trigeminal and sacral ganglia only serve one side of the body, so the lesions only develop on the ipsilateral side as the affected ganglia.
Describe the presentation of an episode of HSV.
Prodrome: tingling or burning sensation 1-2 days before blisters.
What are the features of primary HSV infection in children?
Fever, lymphadenopathy and lesions: small, painful, fluid-filled blisters which ooze and ulcerate, and heal after a few weeks.
As well as fever, lymphadenopathy and blisters, what can HSV cause in adults?
Pharyngitis.
Describe the pattern and appearance of blisters in a recurrent episode of HSV.
Vermillion border around the lips, one side. Smaller blisters, heal in 1 week.
Describe the pattern and appearance of lesions in primary genital HSV infection.
Ulcers and pustules
Women - labia majora and minora, mons pubis, vaginal mucosa, cervix
Men - shaft of penis
What is herpetic whitlow?
Herpes infection in the finger, often occurs if finger rubs lesion. This also makes it easy to spread to the rest of the body (autoinoculation).
What is herpes gladiatorum?
Herpes infection of the trunk, extremeties and head. ‘Gladiators’ (wrestlers) have lots of skin-skin contact hence the transmission and name.
What is eczema infected with herpes called?
Eczema herpeticum.
What is keratoconjunctivitis?
Inflammation of cornea and conjunctiva. Causes pain and redness (conjunctivitis) as well as blurry vision and dendritis lesion (cornea).
What would a LP show if HSV has reached the brain or meninges?
Increased WBCs and RBCs, increased protein.
How does HSV get transmitted from mother to child?
As baby passes through infected vaginal secretions during delivery.
What patterns of illness occur in neonatal HSV infection?
- Skin, eye and mucous membranes - lesions occur 1-2 weeks after delivery
- CNS infection - lethargy, irritability and seizures 2-3 weeks after delivery.
- Disseminated infection - can follow from 1 or 2. Organ failure and sepsis.
How might HSV present in immunocompromised patients?
More frequent reactivation, more severe symptoms, unusual lesions eg in the oesophagus or lungs.
How is HSV diagnosed?
History and exam
Viral DNA using PCR
Antibody response to virus
Grow virus in culture
How is HSV treated?
Often clears up on its own
Antivirals eg acyclovir may help, best if given at start of prodrome.
If severe or life-threatening, IV antivirals are used.
