Meningitis

Background

• Microbiology
  • Bacterial meningitis:
    • Pneumococcus (60%), meningococcus (15%), GBS (15%), H flu (7%), listeria (2%)
  • Viral meningitis
    • Echo, coxsackie, entero (85%)
    • HSV, CMV
• Pathophysiology
  • Hematogenous spread via respiratory tract
  • Contiguous spread (otitis media, sinusitis, brain abscess)

Risk Factors

1. Otitis Media
2. Sinusitis
3. Immunosuppression/splenectomy
4. Alcoholism
5. Pneumonia
6. Diabetes Mellitus
7. CSF leak
8. Endocarditis
9. Neurosurgical procedure / head injury
10. Indwelling neurosurgical device / cochlear implant
11. Malignancy

Classification

1. Acute (<24hr)
   1. Usually bacterial in origin (25%)
2. Subacute (1-7d)
   1. Viral or bacterial
3. Chronic (>7d)
   1. Viral, TB, syphilis, fungi, carcinomatous

Clinical Features

• Almost all patients present w/ at least 2 of the following:
  • Headache
  • Fever
  • Neck stiffness
  • Altered Mental Status
• Also may have:
  • Photophobia
  • Vomiting
  • Prodromal URI
  • Focal neuro sx (e.g. CN deficit)
  • Seizure (25%)
• Jolt Test (~100% Sn)
  • Have pt rapidly shake head L and R; if does not bother pt unlikely to have meningitis

Lumbar Puncture Diagnosis

Measure	Normal	Bacterial	Aseptic (Viral)	Fungal	Tuberculosis	Subarachnoid hemorrhage	Neoplastic
Appearance	Clear	Clear, cloudy, or purulent	Clear	Clear or opaque	Clear or opaque	Xanthochromia, bloody, or clear	Clear or opaque
Opening Pressure (cm H2O)	10-20	>25	Normal or elevated	>25	>25	>25	Normal or elevated
WBC Count^ (cells/µL)	0-5^	>100^	5-1000	<500	50-500	0-5 (see correction section)	<500
% PMNs		>80-90%	1-50%^^	1-50%	Early PMN then lymph		1-50%
Glucose	>60% of serum glucose	Low	Normal	Low	Low	Normal	Normal
Protein^^^ (mg/dL)	< 45	Elevated	Elevated	Elevated	Elevated	Elevated	>200
Gram Stain	Neg	Pos	Neg	India ink	Tb stain	Blood

• ^Normal or lower WBC results may be found in immunocompromised, early, or partially treated (e.g. with oral antibiotics) bacterial menintigis, and those with tuberculosis meningitis
• ^^Lymph predominance may be found in patients with early bacterial meningitis or those that have been partially treated (e.g. with oral antibiotics)
• ^^^For unexplained elevations of protein, consider encephalitis, MS, Guillian Barre

Corrections

• WBC correction (for bloody tap)
  • Simplified version (if peripheral WBC and RBC counts are within normal limits):
    • Subtract 1 WBC for every 750 RBC in CSF
  • Complex version (WBC and/or RBC not within normal limits):
    • "WBCs added" = WBC(blood) x [RBC(CSF) / RBC(blood)]
    • WBC counted/resulted - "WBCs added" = actual WBC
• Protein correction (for bloody tap)
  • For each 1000 RBC decrease protein value by 1mg/dl

DDX

1. Encephalitis
2. Brain mass
3. Brain abscess
4. SAH
5. Migraine

Work-Up

1. CBC
2. Chem
3. Blood cx
4. ?CT head: See CT Before Lumbar Puncture
5. CXR (50% of pts w/ pneumoccocal meningitis have e/o pna on CXR)
6. CSF studies
   1. Glucose and protein (Tube 1)
   2. Gram stain and culture (Tube 2)
   3. Cell count and differential (Tube 3)
   4. Special studies if indicated (HSV PCR, india ink) - Tube 2
   5. Hold (Tube 4)

Management

Acute Treatment

1. Abx
   1. Give as soon as possible (if LP performed w/in 2hr of abx CSF culture will not be affected)
   2. Guidelines
      1. Age 18-50y
         1. Ceftriaxone 2gm IV q12hr + vancomycin 15mg/kg q8-12hr
            1. (vancomycin is for resistant pneumococcus)
      2. Age >50y
         1. Ceftriaxone 2gm IV q12hr + vancomycin 15mg/kg q8-12hr + ampicillin 2gm IV q4h
            1. (Ampicillin is for listeria)
      3. CSF leak w/ history of closed head trauma
         1. Ceftriaxone 2gm IV q12hr + vancomycin 15mg/kg q8-12hr
      4. History of recent penetrating head injury, neurosurgery, CSF shunt
         1. (Ceftazidime 2gm IV q8hr or cefepime or meropenem) + vanco 25 milligrams/kg load
      5. Meningitis due to sinusitis
         1. Ceftriaxone + metronidazole
2. Dexamethasone
   1. Only give prior to or w/ first dose of abx
   2. 10mg IV q6hr x4d
3. Mannitol
   1. For marked cerebral edema
4. Acyclovir
   1. Consider for pts w/ suspected viral meningitis who present w/ neuro deficits
   2. 10mg/kg IV q8hr (Obese patients should be dosed using ideal body weight)

Prophylaxis

• For meningococcus exposure
  • Indications:
    • Household contacts
    • School or day care contacts in previous 7d
    • Direct exposure to pt's secretions (kissing, shared utensils or toothbrush)
    • Intubation without facemask
  • Meds
    • Rifampin 600mg PO BID x2d OR ceftriaxone 250mg IM x1 OR ciprofloxacin 500mg PO x1

Disposition

1. Bacterial meningitis
   1. Admit w/ droplet precautions
2. Viral meningitis
   1. Admit for empiric abx until culture results return OR
   2. Discharge w/ 24hr f/u

See Also

• Meningitis (Peds)

Source

Tintinalli, Lexicomp