MENINGITIS

Etiology:

1. Bacterial:
1. The bacterial prevalence varies.  In adult population  the organisms are:    S. pneumoniae  > N. meningitides > H. influenza   but also consider special  conditions suggesting Listeria, S. aureus, G (-), TB.
    
2. Age, previous otitis, pneumonia, sinusitis, CA, DM,C5 deficiency, CNS surgery, asplenic pt are clues for possible organisms.
    
3. Mycoplasma, Rickettsiae, Leptospirosis, Lyme, syphilis can also be implicated as organism.
    
4. E. Coli, Klebsiella, Pseudomonas can be causative s/p brain or GU surgery.
    
5. S. aureus is suspected in DM or s/p brain surgery.  S. epidermidis is suspected in a pt with a shunt.   Listeria - in age extremes, immunocompromised,  and pts on steroids.
    
2. Viral (aseptic):
1. Echovirus, herpes, coxsackie, mumps, varicella.
    
3. Fungal & Protozoal:
1. Cryptococcus, Coccidoidomycosis, Toxoplasmosis.
4. Other:
1. Chemical  & Neoplatic:  Possibilities include meningeal carcinomatosis, leukemia, CVA, chemotherapy, lead, vaccines, sarcoid, and NSAID  overdose.

1. Increase in WBC with L shift (for bacterial) or lymphocytosis (for  viral).
    
2. CT should precede LP if  you suspect brain abscess or bleed, and if  exam of fundi is suggestive of increased ICP. CT or LP should NOT delay the treatment.
    
3. Example of LP fluid analysis:
    
• Tube #1: Cell count (if traumatic tap, RBC's should be coming down),
   
• Tube #2: glucose, protein
   
• Tube #3: Gram stain, C&S
   
• Tube #4: Special studies such as latex, India Ink, VDRL, AFB, AG for S. pneumoniae, N.meningitides, H. influenza

	Pressure	Cells & Type	Glucose	Protein	Appearance
Normal	100-200mg/HG	0-3 L	50-100	20-45	Clear
Bacterial	­­	500-5000 PMN*	¯¯	100 mg/dL	Cloudy
Viral	N/­	100-2000L **	N	N/­	Clear/Cloudy
Fungal	­	Monoctes	¯	­	Clear/Cloudy
TB	N/­	100-800L **	¯	­	Cloudy
Lyme	N/­	0-500 L	N	N/­	Clear/Cloudy
Guillan-Barre	N	0-100L	N	>100mg/dL	Clear/Cloudy

In addition to above test one should order India Ink or Acid fast if Cryptococcal or TB meningitis,  respectively, is suspected.

*Early bacterial meningitis or partially  treated bacterial meningitis can assume "aseptic" presentation and  present with < 1000 WBC of  lymphocytic predominance.

**Both Viral and TB meningitis in early stages may have PMN predominance and look "bacterial".

Treatment:

1. Must be started within 1 hour if bacterial meningitis is suspected.
    
2. There is always possibility of obtaining latex agglutination test to detect bacterial Ag even after starting pt on antbx.
    
3. Pt should be isolated until detection of pathogen or until treatment covering N. meningitidis is instituted x 24 hours. Bacteria other  than  N.meningitidis do not require isolation.
    
• Viral: supportive treatment (unless herpes is suspected).  Viral meningitis requires no   admission since care is only supportive. Yet, since it is  difficult to distinguish early bacterial from viral, it is prudent to admit pt for systemic antbx until  culture results are available.
   
• S. pneumoniae, N. meningitidis, H. influenza can be all treated with a 3d generation cephalosporin such as Ceftriaxone 2 gr. IV q 12 h.  Ampicillin 2 gr. IV q 4 h is no longer used because of resistance.  Vacomycin is added to cover resistant S. pneumoniae.
   
• S. aureus, S. epidermidis -Vancomycin 1 gr. IV q 12 h.
   
• G (-) - Ceftriaxone 2 gr. IV q 12 h,
   
• Pseudomonas- Ceftazidime 2 gr. IV q 8 h + aminoglycoside.
   
• Listeria- Ampicillin 2 gr. IV q 4 h
   
• TB - INH+Rifampin + Pyrazinamide
   
• Fungal- Amphothericin B
   
• Cryptococcus- Amphotericin B +/- 5-flucytosine.  Fluconazole may be used for mild cases and for suppressive treatment.
   
• Prophylaxis is indicated for people in close contact such as family members, care takers, and medical personnel that provided airway support. Prophylaxis is needed only for N.meningitidis and H. influenza and is treated with Rifampin 600 mg PO bid x 2 d or Cipro 500 mg PO x 1 dose.

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