Tuberculous Meningitis

Key Features

Essentials of Diagnosis

• Gradual onset of listlessness and anorexia

• Fever, headache, vomiting, and seizures common

• Cranial nerve abnormalities typical

• Tuberculous focus may be evident elsewhere

• Cerebrospinal fluid shows several hundred lymphocytes per microliter, low glucose, and high protein

General Considerations

• Caused by rupture of a meningeal tuberculoma resulting from earlier hematogenous seeding of tubercle bacilli from a pulmonary focus, or may be a consequence of miliary spread

Clinical Findings

Symptoms and Signs

• Onset usually gradual

  • With listlessness, irritability, anorexia, and fever

  • Followed by headache, vomiting, convulsions, and coma

• In older patients, headache and behavioral changes are prominent early symptoms

• Nuchal rigidity and cranial nerve palsies occur as the meningitis progresses

• Evidence of active tuberculosis elsewhere or a history of prior tuberculosis is present in up to 75% of patients

Differential Diagnosis

• May be confused with any other type of meningitis, but the gradual onset, the predominantly lymphocytic pleocytosis of the spinal fluid, and evidence of tuberculosis elsewhere often point to the diagnosis

• Chronic lymphocytic meningitis due to

  • Fungi (Cryptococcus, Coccidioides, Histoplasma)

  • Brucellosis

  • Leptospirosis

  • Syphilis

  • Lyme disease

  • HIV infection

  • Neurocysticercosis

• Carcinomatous meningitis

• Sarcoidosis

• Subdural hematoma

Diagnosis

Laboratory Tests

• The spinal fluid is frequently yellowish, with increased pressure, 100–500 cells/mcL (predominantly lymphocytes, though neutrophils may be present early during infection), high protein, and low glucose (Table 30–1)

• Acid-fast stains of cerebrospinal fluid usually are negative, and cultures also may be negative in 15–25% of cases

• Nucleic acid amplification tests allow for rapid diagnosis, although sensitivity is only 68–80%

• The tuberculin skin testing and interferon-gamma release assays do not distinguish between active and latent tuberculosis and are frequently negative in the presence of CNS infection