Meningitis

Causes

Appropriate Tests

 

Cerebrospinal fluid examination - microscopy and culture; Protein, Glucose (compared with plasma glucose), India ink preparation, Cryptococcal Ag if the CSF cell count is abnormal and/or if patient has HIV infection; cytology to identify eosinophils and malignant cells, if appropriate.

Blood culture.

Bacterial, especially

 

  • Neisseria meningitidis

See Neisseria meningitidis (meningococcus).

  • Streptococcus pneumoniae
See Streptococcus pneumoniae (pneumococcus)
  • Haemophilus influenzae (now rare)

See Haemophilus influenzae infection

  • Mycobacterium tuberculosis

Mycobacteria testing - CSF.

See Mycobacterial infection

  • Listeria monocytogenes

See Listeriosis

In neonates

Gastric aspirate, Ear swabs - Gram stain and culture.

  • Group B streptococci

 

  • Escherichia coli

 

Viral 

Often termed 'aseptic meningitis'.

Investigation is usually only of value in outbreaks or epidemics, to determine the specific virus responsible.

CSF, faeces, Throat swab, nasopharyngeal aspirate - Virus detection by NAA, culture as appropriate.

  • Enteroviruses

 

  • Herpes simplex virus type 1&2

See Herpes simplex virus infection

  • Mumps virus

 

Fungal, especially

 

  • Cryptococcus neoformans

See Cryptococcal infection

Protozoal

CSF microscopy (including phase contrast for motile trophozoites).

  • Naegleria fowleri

 

Helminthic

CSF microscopy (including cytology for eosinophils).

  • Angiostrongylus sp

 

Malignancy

CSF microscopy (including Cerebrospinal fluid cytology).

  • Disseminated carcinoma

 

  • Acute leukaemia

 

  • Lymphoma (non-Hodgkin)