Meningitis

In the patient with a non-specific febrile illness, look for meningitis, especially in patients at higher risk (e.g., immuno-compromised individuals, alcoholism, recent neurosurgery, head injury, recent abdominal surgery, neonates, aboriginal groups, students living in residence).
When meningitis is suspected ensure a timely lumbar puncture.
In the differentiation between viral and bacterial meningitis, adjust the interpretation of the data in light of recent antibiotic use.
For suspected bacterial meningitis, initiate urgent empiric IV antibiotic therapy (i.e., even before investigations are complete).
Contact public health to ensure appropriate prophylaxis for family, friends and other contacts of each person with meningitis.

General Overview

Droplet precautions (until 24h after antibiotics)
Empiric Antibiotics (do not delay beyond 1h if possible)
- 0-1mo: Ampicillin + Cefotaxime (or Ampicillin + aminoglycoside)
- >1mo: Vancomycin + 3rd gen cephalosporin (Ceftriaxone 2g IV q12h or Cefotaxime 2g IV q4-6h)
  - Vancomycin 15-20mg/kg IV q8-12h (pre 4th dose trough levels 15-20mcg/mL) + Ceftriaxone 2g IV q12h
- >50y: Add Ampicillin 2g IV q4h to cover Listeria monocytogenes
Dexamethasone 10mg q6h x 4 days if suspect S. pneumoniae (reduce mortality), or H influenzae (reduce hearing loss)
- Best to administer prior or with initial antibiotic therapy
- Consider Rifampin instead of vancomycin if bacteria not sensitive to ceftriaxone, as vancomycin may not enter CSF as well after steroids decreased inflammation
Consider Acyclovir if suspect HSV encephalitis (changes in personality, behaviour, cognition, AMS)
Consider covering for P. aeruginosa in immunocompromised with Cefepime or Meropenem 2g IV q8h
Consider covering for tuberculous and cryptococcal meningitis in immunocompromised

Do not delay treatment for investigations, increase in mortality of 13% per hour of delay

Consider delaying LP if unstable, signs of herniation, coagulopathy, overlying infection,
If no concerns or negative CT head, proceed to lumbar puncture
- CSF opening pressure (if done in left lateral decubitus)
- CSF leukocyte count, protein, glucose
- CSF culture (70-85% positive, antibiotics decreases yield by 10-20%)
- CSF Gram stain (60-90% positive with excellent specificity, yield decreases 20% if antibiotics)
  - Gram-positive rods and coccobacilli (think L monocytogenes) add Ampicillin
  - Gram-positive diplococci = pneumoccocal
  - Gram-negative diplococci = meningococcal
  - Small pleomorphic gram-negative coccobacilli = H influenzae
- CSF PCR (Meningococcal, Pneumococcal, Enteroviral, HSV, VZV)
- Consider CSF lactate and CRP to differentiate bacterial from aseptic (limited value if received antibiotic or CNS disease)

Neonates or immunocompromised may have normal CSF findings in bacterial meningitis
- Consider using Clinical Decision Rule in children
L monocytogenes may present with CSF profile similar to viral, WBC >100 and normal glucose

CBC
Electrolytes (Mild hyponatremia)
LFTs
Coags
VBG (AGMA)
Blood cultures x2 (60% positive) before first dose of antibiotics if possible
Consider
- If sexual history or substance use: serum RPR, CSF VDRL, serum HIV Ab and HIV PCR
- In children (to guide diagnosis): Serum CRP and pro-calcitonin
- Throat swab for meningococcal culture

Droplet precautions
Chemoprophylaxis to close contacts and direct exposure to respiratory secretions
- Contact public health for post-exposure prophylaxis for close contacts (7d prior to symptom onset until 24h treatment)
  - N meningititidis (>8h close contact or oral secretions)
    - Ciprofloxacin 500mg PO x1, Rifampin 600mg PO q12h x2d, Ceftriaxone 250mg IM x1
  - H influenzae (household with unvaccinated)
    - Rifampin
Vaccination (H influenzae B, Pneumococcal, N Meningitidis)
Pregnancy
- Pen G to cover GBS as indicated
- Avoid soft cheeses with unpasteurized milk, raw sprouts, melons, cold cuts, smoked seafood (Listeria monocytogenes)

References:

ESCMID guideline: diagnosis and treatment of acute bacterial meningitis. Clin Microbiol Infect. 2016 May;22 Suppl 3:S37-62. doi: 10.1016/j.cmi.2016.01.007. Epub 2016 Apr 7. http://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(16)00020-3/abstract
The UK joint specialist societies guideline on the diagnosis and management of acute meningitis and meningococcal sepsis in immunocompetent adults. J Infect. 2016 Apr;72(4):405-38. doi: 10.1016/j.jinf.2016.01.007. Epub 2016 Feb 2. http://www.journalofinfection.com/article/S0163-4453(16)00024-4/abstract
CPS. Guidelines for the management of suspected and confirmed bacterial meningitis in Canadian children older than one month of age. Paediatr Child Health 2014;19(3):141-6. http://www.cps.ca/documents/position/management-of-bacterial-meningitis
Acute bacterial meningitis in adults. CMAJ June 12, 2012 vol. 184 no. 9 First published February 13, 2012, doi: 10.1503/cmaj.111304. http://www.cmaj.ca/content/184/9/1060
Bamberger D. Diagnosis, Initial Management, and Prevention of Meningitis. Am Fam Physician. 2010 Dec 15;82(12):1491-1498. http://www.aafp.org/afp/2010/1215/p1491.html
IDSA. Practice Guidelines for the Management of Bacterial Meningitis. Clin Infect Dis (2004) 39 (9): 1267-1284. https://academic.oup.com/cid/article-lookup/39/9/1267

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