Approach to Chronic Meningitis
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Direct answer
Chronic meningitis is inflammation of the meninges with symptoms lasting four weeks or more, most often caused by tuberculosis, cryptococcus, neurosyphilis, sarcoidosis or carcinomatous spread. The CSF pattern of lymphocytic pleocytosis, raised protein and low glucose narrows the list. Cytology, cryptococcal antigen and VDRL then decide between the remaining causes.
What you must remember
- Definition: meningeal symptoms lasting four weeks or more, such as headache, low-grade fever, neck stiffness, cranial nerve palsies and altered sensorium.
- Tuberculosis: the commonest infectious cause in India, with lymphocytic CSF, low glucose, high protein and a fibrin web on standing.
- Cryptococcus: classically seen in HIV with a low CD4 count, diagnosed by India ink stain and cryptococcal antigen, with opening pressure often markedly raised.
- Neurosyphilis: lymphocytic CSF with raised protein, where a positive CSF VDRL is specific but a negative result does not exclude disease.
- Sarcoidosis: a diagnosis of exclusion with lymphocytic CSF and raised protein, often with facial palsy or hilar lymphadenopathy, and serum ACE may be raised.
- Carcinomatous meningitis: leptomeningeal spread from breast, lung, melanoma or haematological malignancy, confirmed by CSF cytology.
- Opening pressure: measured at lumbar puncture and often raised in tuberculous, cryptococcal and carcinomatous meningitis, where drainage may be therapeutic.
- MRI: basal meningeal enhancement favours tuberculosis, leptomeningeal enhancement favours carcinomatous spread, and hydrocephalus is common in tuberculous disease.
Matching the CSF pattern to the cause
Chronic meningitis is worked up by matching the CSF pattern with the clinical setting, then confirming with a specific test. The table links each common cause to its typical CSF finding and confirmatory test.
| Cause | Typical CSF pattern | Confirmatory test |
|---|---|---|
| Tuberculosis | Lymphocytic, low glucose, high protein | CSF Xpert MTB/RIF, AFB stain or culture |
| Cryptococcus | Lymphocytic, low glucose, high pressure | India ink stain, cryptococcal antigen |
| Neurosyphilis | Lymphocytic, raised protein | CSF VDRL with serum treponemal test |
| Sarcoidosis | Lymphocytic, raised protein | Biopsy of non-caseating granulomas after exclusion |
| Carcinomatous | Low glucose, high protein, few cells | Repeated CSF cytology and contrast MRI |
The table is a starting point, not a verdict. A single negative test seldom ends the search, so the clinical setting and imaging are weighed together.
Worked example: a 34-year-old man with HIV and six weeks of headache and vomiting has raised opening pressure, low CSF glucose and lymphocytic pleocytosis. The India ink stain shows encapsulated yeasts, so cryptococcal meningitis is the diagnosis and raised pressure needs urgent drainage.
Where the examiner tests the approach
Questions typically give a CSF report with a clinical setting and ask for the cause.
- Trap: Calling a lymphocytic CSF viral meningitis without excluding tuberculosis. Correct: Lymphocytic CSF with low glucose and high protein is tuberculosis until proved otherwise, and it needs the full work-up.
- Trap: Treating a negative CSF cytology as excluding leptomeningeal metastasis. Correct: Cytology is positive only in a proportion of cases, so repeated sampling and contrast MRI are needed.
- Trap: Treating a negative CSF VDRL as excluding neurosyphilis. Correct: The VDRL is specific but insensitive, so a negative result does not exclude neurosyphilis when clinical suspicion is high.
- Trap: Performing lumbar puncture without checking for mass effect. Correct: Imaging comes first with focal signs or papilloedema, and opening pressure is measured at the procedure.
Frequently asked questions
What defines chronic meningitis?
Chronic meningitis is defined as meningeal inflammation with symptoms lasting four weeks or more. Its usual presentation includes headache, low-grade fever, neck stiffness and sometimes cranial nerve palsies. Tuberculosis, cryptococcosis, neurosyphilis, sarcoidosis and carcinomatous spread are the main causes.
Which CSF pattern suggests tuberculous meningitis?
Tuberculous meningitis produces lymphocytic pleocytosis, high protein and low glucose, and often a fibrin web when the fluid stands. Opening pressure is frequently raised in this condition. Confirmation uses CSF Xpert MTB/RIF, acid-fast bacilli staining or culture, and the culture result takes time.
How is cryptococcal meningitis diagnosed?
Cryptococcal meningitis is diagnosed by an India ink stain of CSF and by detecting cryptococcal antigen in CSF or serum. It classically occurs in people with HIV and a low CD4 count. Opening pressure is often markedly raised and may need repeated therapeutic drainage.
Why is CSF cytology important in carcinomatous meningitis?
CSF cytology is important in carcinomatous meningitis because it can show malignant cells that confirm leptomeningeal spread. A single sample may be negative, so repeated lumbar punctures are often needed. Contrast MRI supports the diagnosis by showing leptomeningeal enhancement.