CNS infections Flashcards
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
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
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
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
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
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
What are the symptoms in meningococcal (neisseria meningitis) due to?
endotoxin
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
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
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
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
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
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
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
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
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
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)
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
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
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
Describe the clinical features of encephalitis
Insidous onset; sometimes sudden
Meningismus Stupor, coma Seizures, partial paralysis Confusion, psychosis Speech, memory symptoms
What are the investigations for encephalitis?
LP, EEG and MRI
If delay start pre-emptive aciclovir as prompt therapy improves outcomes [death]
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.
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
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
