Tuberculous Meningitis

Tuberculous Meningitis: Symptoms, Causes, Types, Diagnosis, and Treatments

Tuberculosis (TB) is a global health concern, primarily known for its impact on the lungs. However, this infectious disease, caused by Mycobacterium tuberculosis, can affect various organs, including the central nervous system (CNS). One of its most severe manifestations is Tuberculous Meningitis (TBM)—a life-threatening condition characterized by inflammation of the membranes (meninges) surrounding the brain and spinal cord. Though rare compared to pulmonary TB, TBM is associated with high morbidity and mortality, especially in children and immunocompromised individuals.

This article explores tuberculous meningitis in detail, including its symptoms, causes, types, diagnostic procedures, and available treatments.

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What is Tuberculous Meningitis?

Tuberculous meningitis is a form of extrapulmonary tuberculosis where the TB bacteria spread from the lungs or other parts of the body to the brain’s meninges. It occurs when Mycobacterium tuberculosis enters the bloodstream and crosses the blood-brain barrier. This infection leads to inflammation, increased intracranial pressure, and possible damage to brain tissue.

TBM is a medical emergency. If left untreated or diagnosed late, it can result in permanent neurological damage or death. Early diagnosis and prompt initiation of therapy are crucial to improving outcomes.

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Symptoms of Tuberculous Meningitis

The clinical presentation of TBM is often nonspecific and evolves over several weeks. This slow progression frequently leads to delayed diagnosis.

Early Symptoms:

These mimic general illness and may go unnoticed:

• Low-grade fever
• Fatigue or malaise
• Loss of appetite
• Headache (mild and persistent)
• Nausea and vomiting
• Night sweats
• Weight loss

Neurological Symptoms:

As the disease progresses, neurological signs become more apparent:

• Severe headache (constant and throbbing)
• Neck stiffness or pain
• Photophobia (sensitivity to light)
• Seizures
• Altered mental status (confusion, irritability)
• Lethargy or drowsiness
• Behavioral changes
• Coma (in advanced cases)

Focal Neurological Deficits:

Depending on the affected areas, patients may develop:

• Vision problems
• Facial paralysis
• Difficulty speaking or understanding speech
• Limb weakness or paralysis
• Involuntary movements

Signs in Infants and Young Children:

• Bulging fontanel (soft spot on the head)
• High-pitched crying
• Poor feeding
• Irritability
• Developmental delay

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Causes and Risk Factors

Causative Organism:

The main pathogen is Mycobacterium tuberculosis, a slow-growing, acid-fast bacillus.

Pathophysiology:

TB bacteria from a primary infection (usually pulmonary) can spread via hematogenous dissemination. When the bacteria reach the subarachnoid space, they form Rich foci—small tubercles that rupture into the meninges, causing inflammation and fluid accumulation.

Risk Factors:

• HIV/AIDS: Immunocompromised individuals have a significantly higher risk.
• Malnutrition
• Young age (infants and toddlers)
• Elderly population
• Chronic diseases (e.g., diabetes, cancer)
• Close contact with TB patients
• Overcrowded living conditions
• Substance abuse (alcoholism, IV drug use)
• History of untreated or inadequately treated TB

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Types of Tuberculous Meningitis

TB meningitis can be classified based on clinical progression, complications, and associated pathologies.

1. Acute TB Meningitis:

• Develops within 2–3 weeks.
• Rapid onset of symptoms.
• Common in children and immunocompromised adults.

2. Chronic TB Meningitis:

• Develops over several months.
• Presents with subtle and progressive neurological decline.
• Often misdiagnosed due to vague symptoms.

3. Basal Meningitis:

• Involves inflammation around the brain’s base.
• Associated with cranial nerve palsies and hydrocephalus.

4. Spinal TB Meningitis (TB Myelitis):

• Affects the spinal cord.
• May cause back pain, limb weakness, and bowel/bladder dysfunction.

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Diagnosis of Tuberculous Meningitis

Timely diagnosis is crucial, but it’s challenging due to nonspecific symptoms and slow bacterial growth. A combination of clinical suspicion, laboratory testing, imaging, and response to therapy is often used.

1. Clinical Evaluation:

• Detailed history (travel, TB exposure, prior infections)
• Neurological examination
• Glasgow Coma Scale (GCS) to assess consciousness level

2. Cerebrospinal Fluid (CSF) Analysis:

The gold standard for diagnosis.

Lumbar puncture yields fluid for:

• Appearance: Typically clear or slightly cloudy
• Cell count: Elevated white blood cells (predominantly lymphocytes)
• Protein: Elevated (100–500 mg/dL)
• Glucose: Decreased (often <40 mg/dL)
• ADA (Adenosine Deaminase): May be elevated

3. Microbiological Tests:

• Acid-fast bacilli (AFB) staining: Low sensitivity
• CSF culture: Gold standard but slow (up to 6 weeks)
• Nucleic Acid Amplification Test (NAAT)/PCR: Faster, detects bacterial DNA
• GeneXpert MTB/RIF: Detects TB and rifampin resistance

4. Imaging Studies:

• CT Scan: May show hydrocephalus, infarcts, or basal enhancement
• MRI Brain: More sensitive for meningeal enhancement, tuberculomas, infarctions

5. Blood Tests:

• CBC may show mild anemia or lymphocytosis.
• ESR and CRP are often elevated.
• Tuberculin skin test (TST) or Interferon Gamma Release Assays (IGRAs) support TB exposure history.

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Staging of Tuberculous Meningitis

Based on clinical severity, TBM is categorized into three stages:

Stage	Symptoms	GCS Score	Prognosis
Stage I	Non-specific symptoms, alert consciousness	15	Excellent with early treatment
Stage II	Lethargy, focal neurological signs	10–14	Moderate disability risk
Stage III	Coma, seizures, severe deficits	<10	High mortality and morbidity

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Treatment of Tuberculous Meningitis

1. Anti-Tuberculosis Therapy (ATT):

Standard TBM treatment involves a prolonged course of multiple antibiotics.

Initial Intensive Phase (2 months):

• Isoniazid (INH)
• Rifampin (RIF)
• Pyrazinamide (PZA)
• Ethambutol (EMB)

Continuation Phase (7–10 months):

• INH + RIF (± EMB if needed)

Note: TBM requires longer therapy (9–12 months) compared to pulmonary TB.

2. Adjunctive Corticosteroids:

• Dexamethasone or prednisolone helps reduce inflammation and neurological complications.
• Especially beneficial in patients with raised intracranial pressure or hydrocephalus.

3. Management of Complications:

• Hydrocephalus: May need ventriculoperitoneal (VP) shunt or external ventricular drainage
• Seizures: Antiepileptic drugs
• Hyponatremia: Managed with fluid restriction or hypertonic saline

4. Drug-Resistant TBM:

• Requires second-line anti-TB drugs (e.g., fluoroquinolones, amikacin, linezolid)
• MDR-TBM has a worse prognosis and needs individualized regimens

5. Supportive Care:

• Nutrition support
• Physiotherapy
• Cognitive rehabilitation (for patients with long-term deficits)

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Prognosis and Outcomes

The outcome of TB meningitis greatly depends on the stage at diagnosis, promptness of treatment, and host immunity.

Prognosis Factors:

• Early-stage diagnosis improves recovery.
• Infants and HIV-positive individuals have a higher risk of death.
• Neurological sequelae occur in 20–50% of survivors (e.g., hearing loss, seizures, paralysis).

Long-term Complications May Include:

• Intellectual disability
• Movement disorders
• Vision loss
• Behavioral changes

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Prevention of Tuberculous Meningitis

1. BCG Vaccination:

• Bacillus Calmette-Guérin (BCG) vaccine is given to infants in high-risk countries.
• Provides protection against severe TB forms, including TBM.

2. TB Control Programs:

• Early detection and treatment of pulmonary TB to prevent dissemination.
• DOTS (Directly Observed Therapy, Short-course) improves compliance.

3. Preventive Therapy:

• Isoniazid preventive therapy (IPT) for close contacts or high-risk groups (e.g., HIV patients).

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When to Seek Medical Attention

Prompt medical evaluation is essential if the following signs are present:

• Persistent fever with headache
• Confusion or altered mental state
• Neck stiffness
• Seizures
• Sudden neurological deficits

Early intervention can mean the difference between recovery and permanent disability.

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Conclusion

Tuberculous meningitis is a serious and often overlooked form of tuberculosis that demands immediate attention. Its nonspecific early symptoms can lead to delays in diagnosis, making awareness among healthcare providers and the general public vital. With early detection, aggressive anti-tuberculosis treatment, and supportive care, many patients can survive and recover.

However, the burden of TBM is still substantial in low-resource settings where TB is endemic. Vaccination, public health education, and robust TB control programs are essential in reducing its incidence.

Frequently Asked Questions (FAQs) About Tuberculous Meningitis

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