Aseptic meningitis

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Thanks Maria for presenting a great case. This case was a young woman presenting with acute-subacute onset headache, nausea/vomiting, nuchal rigidity with CSF studies most consistent with aseptic meningitis.

Main points:

  1. CSF analysis can be broken down into 4 groups depending on WBC (100s vs 1000s) and Glucose (normal vs low).
    • WBC 1000s & glucose low: MCC acute bacterial
    • WBC 100s & glucose low: MCC granulomatous
    • WBC 1000s & glucose normal: MCC aseptic meningitis
  2. Aseptic meningitis can be thought of as infectious (viral, fungal, bacterial, parasitic) vs noninfectious (autoimmune, meds, neoplastic).
  3. Empiric coverage for bacterial meningitis includes vancomycin (for pen-resistent S pneumo) and ceftriaxone. Ceftriaxone is dosed at 2g IV q12 for CNS penetration and S pneumo, N meningitidis, H flu.

Want to know more?

More common ddx for aseptic meningitis:

  • Viral – enterovirus, HSV2 (which can also cause a Mollaret's meningitis/ recurrent benign lymphocytic), HIV, coxsackie, arbovirus
  • Bacterial – partially treated bacterial, mycobacteria, lyme, syphilis, leptospirosis, parameningeal infection, atypicals
  • Fungal – crypto, endemic mycosis
  • Parasitic - toxoplasma, strongy
  • Autoimmune – SLE, sarcoid
  • Medications – NSAIDs, TMP-SMX, immunosupp (IVIG, azathioprine)
  • Neoplasm – leukemia, lymphoma, metastatic cancer

Rabies Virus

Rabies virus invades the peripheral nerves and moves through retrograde transport into the CNS. Rabies encephalitis can be diagnosed with a nuchal skin biopsy -> IHC and PCR. Sensitivity is about 60% in early encephalitis and 100% in the terminal stage of disease. For more info: here is a link to the CDC website and a JAMA dermatology article on this subject.

Antibiotic choice for meningitis

Empiric coverage includes vancomycin and ceftriaxone. Ampicillin for age > 50 (and consider for pregnancy and IC state). For patients with penicillin allergies, can substitute aztreonam for ceftriaxone and TMP-SMX for ampicillin. Here are IDSA guidelines for suspected bacterial meningitis. Note Figure 2 which has a nice algorithm for adults and Table 4 noting empiric antibiotics.

Ddx elevated protein in an LP sample

cocci, crypto, TB, epidural abscess