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Flashcards in CNS infections Deck (53):
1

What can an untreated CNS infection lead to?

Brain herniation and death
Cord compression and necrosis with subsequent permanent paralysis

2

What are the different types of CNS infections?

Encephalitis
Meningitis
Meningoencephalitis
Encephalomyelitis
Epidural abscess
Neuritis
Sepsis syndrome

3

What is meningitis?

Inflammation of the meninges

4

What is encephalitis?

Inflammation of brain parenchyma

5

What are the different types of meningitis?

Acute pyogenic
Acute aseptic (viral)
Acute focal suppurative (brain abscess, subdural and extradural empyema)
TB

6

What will pyogenic meningitis show?

Thick layer of suppurative exudate covering the leptomeninges over the surface of the brain
Exudate in the basal and convexity surface

7

What will meningitis show microscopically?

Neutrophils in the subarachnoid space

8

Are neutrophils present in viral meningitis?

NO - it is aseptic

9

What is the basic treatment for bacterial meningitis

Ceftriaxone IV 2g bd
AND
Dexamethasone IV 10mg qds (3ml of 3.3mg/ml base injection)

10

What are the risk factors for listeria infection?

Over 60 years
Immunocompromised including alcohol dependency and diabetes

11

What should be added to the empirical antibiotics if there are risk factors for listeria?

Amoxicillin IV 2g hourly

12

What is used instead of ceftriaxone in penicillin allergy?

Chloramphenicol IV 25mg/kg qds

13

What is used instead of amoxicillin cover for listeria in penicillin allergy?

Co-trimoxazole IV 120mg/kg divided into 4 doses/day

14

What should be added to empirical antibiotic therapy if there has been recent travel to a country with high rates of penicillin resistant pneumococci?

Vancomycin IV aiming for a pre dose level of 15-20mg/L OR rifampicin IV/PO 600mg bd

15

What are countries with high rates of pneumococcal resistance?

Canada
China
Croatia
Pakistan
Poland
Spain
Mexico
Italy
USA
Greece
Turkey

16

Should you continue dexamethasone in the case of a confirmed meningitis that is not pneumococcus?

No - stop

17

How long should dexamethasone be given?

4 days

18

What virus commonly causes meningitis?

Enteroviruses
Coxsackie
HSV
VZV
Paromyxovirus

19

How is viral meningitis diagnosed?

Viral stool culture
Throat swab
CSF PCR

20

What is encephalitis?

Diffusely inflamed cerebral cortex

21

What are the common signs of encephalitis?

Mental status changes
Confusion
Coma
INSIDIOUS ONSET

22

What investigations are performed for encephalitis?

LP
EEG
MRI

23

What is the treatment for encephalitis?

IV aciclovir 10mg/kg 8hrly

24

What is the treatment for viral meningitis?

Early management for bacterial meningitis then when viral confirmed STOP antibiotics, antivirals and steroids if enteroviral or mumps - supportive management
If HSV or VZV then antivirals continued

25

What are CT findings that are contraindications to an LP?

Significant brain shift/ swelling
Tight basal cisterns

26

What are the CSF findings for a bacterial infection?

Opening pressure: high
Colour: cloudy
Cells: high/v high (100-50,000)
Differential: neutrophils
CSF/plasma glucose: low <40%
Protein (g/l): High >1

27

What are the normal CSF findings?

Opening pressure: 10-20 cm
Colour: clear
Cells: <5
Differential: lymphocytes
CSF/plasma glucose: 50-66%
Protein (g/l): <0.45

28

What are the CSF findings for a viral infection?

Opening pressure: normal/high
Colour: "gin" clear
Cells: Slightly increased (5-1000)
Differential: lymphocytes
CSF/plasma glucose: normal
Protein: normal-high (0.5-1.0)

29

What are the CSF findings for TB meningitis?

Opening pressure: high
Colour: cloudy/yellow
Cells: slightly increased (<500)
Differential: lymphocytes
CSF/plasma glucose: low-very low (<30%)
Protein (g/l): High-very high (1.0-5.0)

30

What are signs and symptoms of meningitis?

Headache
Vomiting
Pyrexia
Neck stiffness
Photophobia
Lethargy
Confusion
Rash

31

What is the epidemiology of community acquired bacterial meningitis?

Neonates: listeria, group B strep, e.coli
Children: Hib
Ages 10-21: neisseria meningitidis
Age >21: streptococcus pneumoniae, neisseria meningitidis
>65: streptococcus pneumoniae, listeria
Immunocompromised: listeria
Neurosurg: staphylococcus aureus, gram neg bacillus
# cribriform plate: streptococcus pneumoniae

32

What are complications of meningitis?

Purulence at base of brain and convexities of rolandic and sylvian sulcus
Exudate around CN 3 and 6
Invasion of pia = abscess
Cerebral oedema
Ventriculitis
Hydrocephalus

33

What is the pathogenesis of bacterial meningitis?

1. Nasopharyngeal colonization
2. direct extension of bacteria (sinusitis, mastoiditis, brain abscess) or across skull defects/#
3. remote foci of infection (endocarditis, pneumonia, UTI)

34

What should be looked at in the CSF?

Haematology: cell count, differential
Microbiology: gram stain, cultures
Chemistry: glucose, protein
PCR

35

Where can neisseria meningitidis (meningococcal) be found to colonize?

Throats and nasopharynx

36

What are the symptoms of neisseria meningitis due to?

Endotoxin release

37

Where can strep pneumoniae be found?

Nasopharynx

38

Who is most susceptible to pneumococcal meningitis?

Hospitalized patients
Patients with CSF skull fracture
Diabetics
Alcoholics
Asplenic
Young children

39

Which meningitis are people with a HIV count below 100 likely to get?

Cryptococcus

40

How is cryptococcus diagnosed?

India ink
Subtle neurological presentaion
Asepti picture on CSF
V high opening pressure

41

What type of bacteria is listeria?

Gram positive bacillus

42

What is the treatment for TB meningitis?

Isoniazid + rifampicin (add pyrazinamide and ethambutol)

43

Who gets TB meningitis?

Re-activation
Elderly
Previous TB on CXR
Poor yield from CSF

44

What is the treatment for cryptococcal meningitis?

IV amphotericin B and fluconazole

45

What percentage of bacterial meningitis are culture-neg?

10-15%
Pre-LP use of oral antibiotics will lower culture positivity by 30%

46

What is aseptic meningitis?

Spinal fluid that has:
Low number of WBC
Minimally elevated proteins
Normal glucose

47

What are the common causes of aseptic meningitis/encephalitis?

HSV 1 and 2
Syphilis
Listeria (occasionally)
TB
Cryptococcus
Leptospirosis
Cerebral malaria
African tick typhus
Lyme disease
Carcinomatous
Sarcoid
Vasculitis
Dural venous sinus thrombosis
Migraine
Drug: co-trimoxazole, IVIG, NSAID

48

What will HSV encephalitis look like on MRI?

Affects temporal lobes

49

What are the clinical signs of bacterial meningitis?

Fever
Stiff neck
Alteration in consciousness
Non-blanching purpuric/petichial rash

50

What is the contact prophylaxis regime?

600mg rifampicin orally 12-hourly for 4 doses or 10mg/kg orally 12 hourly for 4 doses (aged 3-11 mnths)
OR
500mg ciprofloxacin orally as a single dose for adults and children over 12

51

What vaccine are available for meningitis?

Neisseria meningitidis - men ACWY given to all school leavers
Hib
Streptococcus pneumoniae

52

What are CI to LP?

Immunocompromised state
History of CNS disease (mass lesion, stroke, focal infection)
New onset seizure
Papilloedema
Abnormal level of consciousness
Focal neurological deficit (blown pupils, ocular motility, abnormal visual fields, gaze palsy, arm or leg drift)

53

What are warning signs in meningitis?

Marked depressive conscious level (GCS <12) or a fluctuating conscious level (fall in GCS >2)
Focal neurology
Seizure before or at presentation
Shock
Bradycardia and hypertension (cushings response)
Papilloedema