Diagnostic Considerations
Tuberculous meningitis (TBM) continues to pose a diagnostic problem. A high index of clinical suspicion is absolutely essential. TBM should be a strong consideration when a patient presents with a clinical picture of meningoencephalitides, especially in high-risk groups, including persons with malnutrition, those who abuse alcohol or drugs, homeless persons, people in correctional facilities, residents of long-term care facilities, and patients with known HIV infection.
Diagnostic confusion often exists between TBM and other meningoencephalitides, in particular partially treated meningitis. Acid-fast bacilli are seen in only approximately 25% of cerebrospinal fluid (CSF) smears. CSF culture is time-consuming and seldom yields positive results. The sensitivities of many of the new tests are still under study, and these tests may not become generally available for some time; when they do, they are likely to prove costly.
In one study, 5 features independently predicted the diagnosis of TBM:
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Prodromal stage lasting 7 days or longer
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Optic atrophy on fundal examination
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Focal deficit
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Abnormal movements
CSF leukocytes comprising less than 50% polymorphonuclear leukocytes
Validation of these criteria on another set of 128 patients revealed a sensitivity of 98.4% if at least one feature was present and a specificity of 98.3% if 3 or more were present. This simple rule is useful for physicians working in regions where TB is prevalent.
TBM must be differentiated not only from other forms of acute and subacute meningitis but also from conditions such as viral infections and cerebral abscess. The radiological differential diagnosis includes cryptococcal meningitis, cytomegalovirus encephalitis, sarcoidosis, meningeal metastases, and lymphoma.
TB of any form is a notifiable disease in the United States. Mandatory notification of the appropriate health department is the responsibility of the physician who makes the diagnosis.
Other problems to be considered
TBM should be considered in the differential diagnosis in any patient presenting with fever and a change in sensorium. Other problems to be considered include the following:
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Infections: Fungal (cryptococcal, histoplasmosis, actinomycetic, nocardiasis, Arachnia infection, candidiasis, coccidiosis); spirochetal (Lyme disease, syphilis, leptospirosis); bacterial (partially treated bacterial meningitis, brain abscess, listeriosis, Neisseria species infection, tularemia); brucellosis; parasitic (cysticercosis, acanthamebiasis, angiostrongylosis, toxoplasmosis, trypanosomiasis); and viral (herpes, mumps, retrovirus, enterovirus [in hypogammaglobulinemics])
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Acute hemorrhagic leukoencephalopathy
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Behçet disease
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Chemical meningitis
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Chronic benign lymphocytic meningitis
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Neoplastic: metastatic, lymphoma
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Systemic lupus erythematosus
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Vascular: Multiple emboli, subacute bacterial endocarditis, sinus thrombosis
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Vasculitis: Isolated central nervous system (CNS) angiitis, systemic giant cell arteritis, Wegener granulomatosis, polyarteritis nodosa, noninfectious granulomatosis, lymphomatoid granulomatosis
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Vogt-Koyanagi-Harada syndrome
Differential Diagnoses
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Tuberculoma is the round gray mass in the left corpus callosum. The red meninges on the right are consistent with irritation and probable meningeal reaction to tuberculosis. Courtesy of Robert Schelper, MD, Associate Professor of Pathology, State University of New York Upstate Medical University.
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MRI of the brain in a patient with TBM and concurrent AIDS (with 8 CD4 cells/mL). The patient's history includes previous interstitial pneumonia, pericarditis, adnexitis, and a positive result on the Mantoux test. His recent history includes fever, headache, strabismus, diplopia, and cough. Laboratory studies revealed hyponatremia. CSF findings strongly suggested a diagnosis of tuberculous meningitis, and culture results were positive for Mycobacterium tuberculosis. The MRI shows the presence of exudates, in and over the sellar seat, with parasellar extension to the left, with irregular margins, marked heterogenous enhancement, and compression of the optic chiasm and third ventricle. Presence of nodular areas with marked enhancement of basal cisterns is an expression of basilar leptomeningeal involvement. This patient died after 2 months of inadequate antituberculosis therapy (due to poor compliance). Courtesy of Salvatore Marra, AIDS Imaging (http://members.xoom.it/Aidsimaging).
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Fluorochrome for tuberculosis. Fluorescent staining procedures are used with auramine O or auramine-rhodamine as the primary fluorochrome dye. After decolorization with an acid-alcohol preparation, the smear is counterstained with acridine orange or thiazine red and scanned at a lower magnification with a 25X dry objective fluorescent microscope. Acid-fast bacilli appear as yellow-green fluorescent thin rods against a dark background. Courtesy of Robert Schelper, MD, Associate Professor of Pathology, State University of New York Upstate Medical University.
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Hematoxylin and eosin stain showing caseation in tuberculosis. Courtesy of Robert Schelper, MD, Associate Professor of Pathology, State University of New York Upstate Medical University.
Tables
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- Overview
- Presentation
- DDx
- Workup
- Approach Considerations
- Serum and Urine Chemistry Studies
- Tuberculin Skin Testing
- Lumbar Puncture
- Dot-immunobinding assay
- Chest Radiography
- Brain and Spinal Imaging
- Angiography
- Electroencephalography
- Brainstem Auditory Evoked Response Testing
- Use of Neurochemical Markers
- Histologic Findings
- Show All
- Treatment
- Medication
- Media Gallery
- References
