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Flashcards in CNS infections Deck (25):
1

What are the 5 different classifications of CNS infections?

Acute pyogenic (bacterial) meningitis

(pyogenic – making of pus)

Acute aseptic (viral) meningitis

Acute focal suppurative infection (brain abscess,subdural and extradural empyema)

Chronic bacterial infection (tuberculosis).

Acute encephalitis is an infection of the brain parenchyma

2

Viral meningitis:
-what usually causes it?
-what are the symptoms?
-what are the investigations?
-what is the management?

Common

Late summer/ autumn

Severe headache

Enteroviruses e.g ECHO virus

Other microbes and non-infectious causes also

Diagnosis- viral stool culture, throat swab and CSF PCR

Treatment is generally supportive as self limiting

3

What are the symptoms of bacterial meningitis?

Fever, stiff neck, alteration in consciousness

Headache

Vomiting

Pyrexia

Neck stiffness

Photophobia

Lethargy

Confusion

Rash

The signs of bacterial meningitis are often absent or ‘atypical’ in the very young/old or the immunocompromised

4

What causes bacterial meningitis in:
0-3mths
3mths - 6yrs
10-21
21 onward
elderly >60yrs

0 - 3 months
Group B Streptococcus (most common cause in neonates)
E. coli
Listeria monocytogenes


3 months - 6 years
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae

10-21:
-meningococcal

21 onward
-strep. pneumonia more than meningococcal

>60:
-pneumococcal more than listeria

5

What causes a bacterial meningitis in those with:
-immunocompromised state
-basilar skull fracture
-head trauma or post neurosurgery
-CSF shunt

Immunocompromised state: S. pneumoniae, N. meningitidis, Listeria, aerobic GNR (including Ps.aeruginosa)

Basilar skull fracture: S. pneumoniae, H. influenzae, beta-hemolytic strep group A.

Head trauma or post-neurosurgery: S. aureus, S. epidermidis, aerobic GNR

CSF shunt: S. epidermidis, S. aureus, aerobic GNR, Propionibacterium acnes

6

What are the 3 pathophysiologies of bacterial meningitis?

Nasopharyngeal colonization

Direct extension of bacteria.

Parameningeal foci (sinusitis, mastoiditis, or brain abscess)

Across skull defects/fracture

From remote foci of infection

7

What are the symptoms in meningococcal (neisseria meningitis) due to?

endotoxin

8

Who is usually affected by listeria monocytogenes meningitis? what is the treatment of choice?

Neonatal and > 55 years > or immuno-suppressed especially malignancy;

Antibiotic of choice:
IV Ampicillin/amoxicillin - Ceftriaxone no value as intrinsically resistant

9

Who is usually affected by cryptococcal meningitis? what is the picture on CSF? what is the treatment?

HIV disease CD4<100

DISSEMINATED INFECTION

SUBTLE NEUROLOGICAL PRESENTATION

ASEPTIC PICTURE ON CSF

SERUM AND CSF CRYPOCOCCAL ANTIGEN

-IV amphotericin B/Flucytosine
-fluconazole

10

Pre-hospital management of meningitis:
-what are the indications for hospital admission?
-what investigations need to be done initially?

-signs of meningeal irritation
-an impaired conscious level
-a petechial rash
-who are febrile or unwell and have had a recent fit
-Any illness, especially headache, and are close contacts of patients with meningococcal infection, even if they have received a prophylactic antibiotic

Initial investigations:
-FBC, U+E, blood sugar, LFTs, CRP, clotting, blood gases
-blood culture, throat swab, clotted blood, EDTA blood for PCR

11

If you have suspicion of meningitis what is important to determine?

Whether the patient can have a lumbar puncture. If the patient has:
-immunocompromise
-history of CNS disease
-New onset seizure
-papilloedema
-altered consciousness
-focal neurological deficit
-delay in performance of diagnostic lumbar puncture

they have to have a CT head, plus blood cultures are taken and dexamethasone and IV ceftriaxone 2g BD is given
-if >55yrs add ampicillin 2g QDS to cover listeria

Then if there is a negative CT scan head can do LP

12

If there is no indication to not do a lumbar puncture on a patient who is suspected to have bacterial meningitis how is this patient manageed??

Blood cultures and lumbar puncture THEN dexamethasone and IV ceftriaxone 2g BD is given
-if >55yrs add ampicillin 2g QDS to cover listeria

13

What are the typical CSF findings in a viral meningits?
-cells
-gram stain for bacteria
-bacterial antigen detection
-protein (0.1-0.4)
-glucose (2.3-4.5)

cells: Lymphocytes

gram stain for bacteria: negative

bacterial antigen detection: negative

protein (0.1-0.4): normal or slightly high

glucose (2.3-4.5): normal

14

What are the typical CSF findings in a bacterial meningits?
-cells
-gram stain for bacteria
-bacterial antigen detection
-protein (0.1-0.4)
-glucose (2.3-4.5)

cells: polymorphs

gram stain for bacteria: positive

bacterial antigen detection: positive

protein (0.1-0.4): high

glucose (2.3-4.5): less than 70% of blood glucose

15

What are the typical CSF findings in a TB meningits?
-cells
-gram stain for bacteria
-bacterial antigen detection
-protein (0.1-0.4)
-glucose (2.3-4.5)

cells: lymphocytes

gram stain for bacteria: positive or negative

bacterial antigen detection: positive

protein (0.1-0.4): high or very high

glucose (2.3-4.5): less than 60% of blood glucose

16

If the CSF findings are consistent with a bacterial meningitis what is done?

gram stain:
-if this is negative give dexamethasone and empical abiotics
-if this is positive give dexamethasone and targeted abiotic therapy

17

What is the recommendations on steroid use in meningitis?

Give to all patients suspected of bacterial meningitis (10mg iv 15-20 min before or with the first dose of antibiotic and then every 6 hours for 4d)

18

If a patient is penicillin allergic what is the empiric treatment for bacterial meningitis?

If there is a clear history of anaphylaxis to beta-lactams give chloramphenicol iv 25 mg/kg 6-hourly with vancomycin iv 500 mg 6-hourly or 1g 12-hourly.

If listeria suspected and penicillin allergy co-trimoxazole alone has been used successfully for this infection

19

Describe the contact prophylaxis regimens for bacterial meningitis:
-adults and children over 12
-children under 12

Adults and children over 12:
-600mg PO rifampicin 12hrly 4 doses
-500mg ciprofloxacin single dose PO
-250mg ceftriaxone IM single dose

Children under 12:
-10mg/kg PO rifampicin (3mths-<12yrs) 4 doses
-125mg IV ceftriaxone

20

What is important to caution patients who are taking rifampicin?

Specific warnings about reduced efficacy of oral contraceptives, red colouration of urine and staining of contact lenses should be given

21

Describe the clinical features of encephalitis

Insidous onset; sometimes sudden

Meningismus

Stupor, coma

Seizures, partial paralysis

Confusion, psychosis

Speech, memory symptoms

22

What are the investigations for encephalitis?

LP, EEG and MRI

If delay start pre-emptive aciclovir as prompt therapy improves outcomes [death]

23

What is seen on MRI for encephalitis?

Inflamed portion of the temporal lobe, involving the uncus and adjacent parahippocampal gyrus, in brightest white on MR.

24

What viruses cause encephalitis?

-Herpes simplex in young people
-varicella zoster in older people
-Other viruses: CMV, HIV, Measles
-Travel related e.g West Nile, Japanese B encephalitis, Tick Borne Encephalitis
-Occupational related: Rabies

25

What is the management of a patient who looks clinically suspicious of encephalitis?

after ABCDE
-either immediate LP
-if contraindication do CT first
IF DELAY OF MORE THAN 6 HRS FOR EITHER GIVE IV ACYCLOVIR

if CSF indicates encephalitis (viral picture) IV acyclovir and MRI

If CSF does not indicate encephalitis repeat LP and MRI

Then if VZV or HSV confirmed IV acyclovir 14days
-21days if immunosuppressed or 3mths-12yrs