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Infection, Central Nervous System

For further information, see CMDT Part 30-04: Infections of the Central Nervous System

Key Features

Essentials of Diagnosis

  • Central nervous system (CNS) infection is a medical emergency

  • Immediate diagnostic steps must be instituted to establish the specific cause

General Considerations

  • Infections can be caused by almost any infectious agent, including

    • Bacteria

    • Mycobacteria

    • Fungi

    • Spirochetes

    • Protozoa

    • Helminths

    • Viruses

ETIOLOGIC CLASSIFICATION

  • CNS infections can be divided into several categories that are readily distinguished by cerebrospinal fluid (CSF) examination as the first step toward diagnosis (Table 30–1)

  • Purulent meningitis

    • 18–50 years: Streptococcus pneumoniae, Neisseria meningitidis

    • > 50 years: S pneumoniae, N meningitidis, Listeria monocytogenes, gram-negative bacilli

    • Impaired cellular immunity: L monocytogenes, gram-negative bacilli, S pneumoniae

    • Postsurgical or posttraumatic: Staphylococcus aureus, S pneumoniae, gram-negative bacilli

  • Chronic meningitis

    • Mycobacterium tuberculosis or atypical mycobacteria

    • Fungi: Cryptococcus, Coccidioides, Histoplasma

    • Spirochetes: Treponema pallidum, Borrelia burgdorferi

    • Other: brucellosis, HIV infection

  • Aseptic meningitis

    • Mumps

    • Herpes simplex virus, coxsackievirus, echoviruses

    • Infectious mononucleosis

    • Leptospirosis, syphilis, Lyme disease

    • Drug-induced aseptic meningitis (eg, from nonsteroidal anti-inflammatory agents, sulfonamides and certain monoclonal antibodies)

  • Encephalitis

  • Partially treated bacterial meningitis

  • Neighborhood reaction

  • Noninfectious meningeal irritation

  • Brain abscess

  • Health care–associated meningitis

    • May result from invasive neurosurgical procedures (eg, craniotomy, internal or external ventricular catheters, external lumbar catheters), complicated head trauma, or hospital-acquired bloodstream infections

    • Outbreaks have been associated with contaminated epidural or paraspinal corticosteroid injections

    • Microbiology is generally distinct from community-acquired meningitis, with the following playing a larger role:

      • Gram-negative organisms (eg, Pseudomonas), S aureus, and coagulase-negative staphylococci

      • Mold and fungi (Exserohilum rostratum and Aspergillus fumigatus) in outbreaks associated with contaminated corticosteroids

Table 30–1.Typical cerebrospinal fluid findings in various central nervous system diseases (listed in alphabetical order after Normal).
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Table 30–1. Typical cerebrospinal fluid findings in various central nervous system diseases (listed in alphabetical order after Normal).
Diagnosis Cells/mcL Glucose (mg/dL) Protein (mg/dL) Opening Pressure
Normal 0–5 lymphocytes 45–851 15–45 70–180 mm H2O
Aseptic meningitis, viral meningitis, or meningoencephalitis2 25–2000 (0.025–2.0 × 109/L), mostly lymphocytes3 Normal or low High (> 50) Slightly elevated
Granulomatous meningitis (mycobacterial, fungal)3 100–1000 (0.1–1.0 × 109/L), mostly lymphocytes3 Low (< 45) High (> 50) Moderately elevated
“Neighborhood reaction”4 Variably increased Normal Normal or high Variable
Purulent meningitis (bacterial)5 community-acquired 200–20,000 (0.2–20 × 109/L) polymorphonuclear neutrophils Low (< 45) High (> 50) Markedly elevated
Spirochetal meningitis 100–1000 (0.1–1.0 × 109/L), mostly lymphocytes3 Normal High (> 50) Normal to slightly elevated

1Cerebrospinal fluid glucose must be considered in relation to blood glucose level. Normally, cerebrospinal fluid glucose is 20–30 mg/dL lower than blood glucose, or 50–70% of the normal value of blood glucose.

2Viral isolation from cerebrospinal fluid early; antibody ...

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