Differentials
Tuberculous meningitis
SIGNS / SYMPTOMS
History of contact, or resident in endemic area.
Symptoms and signs of pulmonary and extraneural disease.
INVESTIGATIONS
Cerebrospinal fluid (CSF) smear and culture, and nucleic acid amplification tests (NAAT).
Rapid NAATs (Xpert MTB/RIF and Xpert Ultra) are recommended by the World Health Organization as initial diagnostic tests in adults and children with signs and symptoms of extrapulmonary tuberculosis.[95] Sensitivity of 89.4% has been reported in CSF.[96]
CSF acid-fast bacilli smear has poor sensitivity in most settings.[97] Culture requires large volume for maximum sensitivity.
Bacterial meningitis
SIGNS / SYMPTOMS
Relevant exposure history.
May be difficult to distinguish clinically with symptoms and signs including meningismus, headache, myalgias, and pharyngitis.
INVESTIGATIONS
Polymerase chain reaction amplification of bacterial DNA from blood is more sensitive and specific than traditional microbiological techniques. Can aid diagnosis in patients who have already received antibiotics.
Specific serology (Borrelia burgdorferi, Brucella, Leptospira, Treponema pallidum).
Culture (Actinomyces, Nocardia, Brucella).
Viral meningitis
SIGNS / SYMPTOMS
Relevant exposure history.
May be difficult to distinguish clinically with symptoms and signs including meningismus, headache, myalgias, and pharyngitis.
INVESTIGATIONS
Serology for herpes simplex virus, varicella zoster virus, and other viruses; cerebrospinal fluid viral culture; polymerase chain reaction for enteroviruses and herpes viruses.
Non-infectious lymphocytic meningitis
SIGNS / SYMPTOMS
History, symptoms, signs suggestive of autoimmune disease, sarcoidosis, systemic lupus, Behcet's disease, carcinomatous meningitis.
Recurrent chemical meningitis may be associated with epidermoid cysts or craniopharyngioma.
INVESTIGATIONS
Head CT/MRI may demonstrate epidermoid cysts or craniopharyngioma.
Cerebrospinal fluid (CSF) cytology may demonstrate malignant cells; CSF ACE elevated in sarcoidosis.
Autoantibodies to investigate systemic manifestations.
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