CNS Infections and Microbiology

Question 1

what are the classifications of CNS infections

Answer 1

• acute pyogenic (bacterial) meningitis
• aseptic (viral) meningitis
• focal infection (e.g. brain abscess, subdural and extradural empyema)
• chronic bacterial infection (TB)

Question 2

what is acute encephalitis an infection of

Answer 2

brain parenchyma

Question 3

what should your Ddx be in a patient with fever and altered mental status

Answer 3

Encephalitis 
Meningitis
Meningoencephalitis
Encephalomyelitis
Severe sepsis syndrome due to infection elsewhere

Question 4

viral meningitis is very rare - true or false

Answer 4

false

- it is very common, particularly in the late summer/autumn

Question 5

who most commonly gets viral meningitis

Answer 5

children

Question 6

what causes viral meningitis

Answer 6

enteroviruses e.g. ECHO virus, coxsackie virus

Question 7

Ix for viral meningitis

Answer 7

Viral Stool culture
Throat Swab
CSF PCR

Question 8

Tx for viral meningitis

Answer 8

Supportive

self-limiting

Question 9

what is the expected CSF results of someone with viral meningitis

Answer 9

CSF WCC raised, predominantly lymphocytes
CSF protein normal or slightly raised
CSF glucose normal

Question 10

what is the most common cause of viral encephalitis

Answer 10

Herpes simplex

but also varicella zoster, CMV, HIV, measles

Question 11

what are the symptoms of encephalitis

Answer 11

Insidous onset; sometimes sudden 
Meningismus
Stupor, coma
Seizures, partial paralysis
Confusion, psychosis
Speech, memory symptoms

Question 12

what is Meningismus

Answer 12

a set of symptoms similar to those of meningitis but not caused by meningitis
e.g. neck stiffness, headache, photophobia

Question 13

in children older than 3 months and in adults, what form of HSV causes encephalitis and where does it affect

Answer 13

HSV-1

localised to the temporal and frontal lobes

Question 14

in neonates, what HSV causes encephalitis and where does it affect

Answer 14

HSV-2
(acquired at time of delivery)
generalised brain involvement

Question 15

what virus should be considered in the immunodeficient

Answer 15

CMV

Question 16

what must be considered in patients when identifying the bacterial cause of meningitis

Answer 16

age and risk factors

Question 17

what bacteria commonly cause bacterial meningitis in neonates

Answer 17

listeria
group B streptococci
E. coli

Question 18

what bacteria commonly cause bacterial meningitis in children

Answer 18

H. influenza

Question 19

what bacteria commonly cause bacterial meningitis in 10 to 21 y/o

Answer 19

meningococcal

Question 20

what bacteria commonly cause bacterial meningitis in > 21y/o and elderly

Answer 20

pneumococcal

Question 21

what bacteria is suspect in immunocompromised patients

Answer 21

listeria
S.pneumoniae
N.meningitidis

Question 22

what bacteria is suspect in patients who have had neurosurgery or opened head trauma

Answer 22

staph aureus

staph epidermidis

Question 23

if the patient has a fracture of the cribriform plate, what bacteria is suspected

Answer 23

pneumococcal

H. influenzae

Question 24

what is the 3 ways that bacteria can enter the brain

Answer 24

1 - nasopharyngeal colonisation (of pneumococcus commonly)
2 - direct extension of bacteria (e.g. brain abscess, skull fracture)
3 - from remote foci of infection (e.g. pneumonia, UTI, endocarditis)

Question 25

what does Neisseria Meningitis cause in immunocompromised patients

Answer 25

meningococcal meningitis

Question 26

what causes the symptoms in meningococcal meningitis and what would you expect to find in the CSF

Answer 26

endotoxin leukocytes

Question 27

what is the appearance of listeria and who is commonly affected by it

Answer 27

gram positive bacilli neonatal and elderly immunocompromised

Question 28

what is suggestive of Tuberculous meningitis

Answer 28

- elderly patient with Hx of TB - non specific ill health - poor yield from CSF

Question 29

Tx for Tuberculous meningitis

Answer 29

Isoniazid + rifampicin | add pyrazinamide + ethambutol

Question 30

triad of bacterial meningitis

Answer 30

fever stiff neck altered consciousness

Question 31

who are signs of bacterial meningitis often absent or atypical in

Answer 31

The very young The very old The immunocompromised

Question 32

when should a LP never be done

Answer 32

if confirmed or suspected raised ICP

Question 33

what is important to note in a LP result in bacterial meningitis

Answer 33

false negative around 10-15%. Pre-LP use of antibiotics may low the positivity of culture.

Question 34

what are CSF results predictive of bacterial meningitis

Answer 34

``` WBC Count >2,000 Neutrophils > 1180 Protein > 220 mg/dl Glucose < 34 mg/dl Glu (CSF/serum) <0.23 cloudy appearance ```

Question 35

what is aseptic meningitis

Answer 35

non-pyogenic bacterial meningitis

Question 36

what is the features of CSF in aseptic meningitis

Answer 36

low number of WBC minimally elevated protein normal glucose

Question 37

who should undergo a CT BEFORE a lumbar puncture

Answer 37

``` Immunocompromised Hx of CNS disease New Onset seizure Papilloedema Abnormal level of consciousness Focal neurologic deficit ```

Question 38

what are signs of a focal neurological deficit

Answer 38

non reactive pupils, abnormal visual fields, arm or leg drift

Question 39

what are warning signs in bacterial meningitis

Answer 39

``` 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 Papilloedema ```

Question 40

what is the empirical antibiotic therapy in bacterial meningitis

Answer 40

IV Ceftriaxone 2g bd If penicillin allergic: IV Chloramephenicol 25mg/kg 6-hourly with Vancomycin IV 500mg 6-hourly

Question 41

what is added is listeria is suspected in bacterial meningitis treatment

Answer 41

IV Ampicillin/Amoxicillin If penicillin allergic: IV Co-trimoxazole (alone)

Question 42

what should be Given to all patients suspected of bacterial meningitis before or with first dose of antibiotics

Answer 42

IV Dexamethasone

Question 43

what bacterias which cause bacterial meningitis have vaccines

Answer 43

Neisseria meningitidis Haemophilus influenzae Streptococcus pneumoniae

Question 44

how is Group B strep meningitis is neonates treated

Answer 44

benzylpenicillin and gentamicin

Question 45

what can be given as prophylaxis to family members with patients with meningococcal meningitis

Answer 45

Rifampicin/Ciprofloxacin