Skip to Main Content

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


  • 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).

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.