Tubercular Meningitis

Educational clinical summary of Tubercular Meningitis for doctors and students: definition, workup, management, and key caveats. Not a substitute for guidelines.

Maintained by Dr. Vivek Karn Review process: editorial policy

Disclaimer: This information is intended for educational purposes and as a clinical reference for healthcare professionals. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider for any health concerns or before making any decisions related to patient care. Clinical decisions must always be made based on individual patient circumstances, current clinical guidelines, and the clinician's judgment and expertise.

Tubercular Meningitis

Overview

Definition: Tubercular meningitis (TBM) is a severe form of extrapulmonary tuberculosis (TB) caused by Mycobacterium tuberculosis, involving the leptomeninges and subarachnoid space. It is characterized by inflammation, exudate formation, and vasculitis within the central nervous system, leading to potentially devastating neurological sequelae.
Epidemiology:
- Global Burden: TBM is the most common form of central nervous system (CNS) TB and accounts for approximately 5-10% of all extrapulmonary TB cases. It is a leading cause of death and disability from TB globally.
- High-Risk Populations: Predominantly affects young children (especially <5 years of age) and immunocompromised individuals, particularly those with HIV infection. Incidence is higher in regions with high TB endemicity.
- Mortality: Despite treatment, mortality rates remain high, especially in advanced stages (up to 50% in HIV-negative and higher in HIV-positive individuals).
Classification: TBM severity is commonly classified using the modified British Medical Research Council (MRC) staging system, which guides prognosis and treatment intensity:
- Stage I: Alert, oriented, no focal neurological deficits, no hydrocephalus on imaging.
- Stage II: Obtunded, confused, Glasgow Coma Scale (GCS) 11-14, or presence of focal neurological deficits (e.g., cranial nerve palsies) with or without hydrocephalus.
- Stage III: Stuporous or comatose, GCS <11, hemiplegia, or paraplegia, with or without hydrocephalus.

Pathophysiology

Mechanism:
1. Primary Infection: Initial infection with M. tuberculosis typically occurs via inhalation, leading to primary pulmonary TB.
2. Hematogenous Dissemination: Bacillemia occurs, leading to the formation of small subpial or subependymal foci (Rich foci) in the brain parenchyma or meninges.
3. Rupture of Rich Foci: Weeks to months or years later, these Rich foci may rupture into the subarachnoid space, releasing M. tuberculosis bacilli and their antigens.
4. Inflammatory Response: This triggers a robust host immune response, leading to a granulomatous inflammatory reaction in the basal meninges.
5. Exudate Formation: A thick, gelatinous exudate forms, primarily in the basal cisterns, which can entrap cranial nerves and obstruct cerebrospinal fluid (CSF) flow.
6. Vasculitis: Arteritis (particularly of the small and medium-sized arteries) is common, leading to vascular occlusion, ischemia, and cerebral infarcts.
7. Hydrocephalus: Obstruction of CSF flow at the basal cisterns or within the ventricular system (e.g., aqueductal stenosis) leads to communicating or obstructive hydrocephalus.
8. Other Lesions: Tuberculomas (intraparenchymal granulomas), miliary TB (diffuse small granulomas), and spinal arachnoiditis can also occur.
Risk Factors:
- HIV infection (strongest risk factor, increases risk by 100-fold)
- Immunosuppression (e.g., organ transplant recipients, individuals on TNF-alpha inhibitors, chemotherapy, chronic corticosteroid use)
- Malnutrition
- Diabetes mellitus
- Alcoholism
- Close contact with an individual with active pulmonary TB
- Young age (<5 years) and elderly individuals
- End-stage renal disease
- Silicosis
Protective Factors:
- BCG vaccination (offers partial protection against severe forms like TBM in children, but variable efficacy against pulmonary TB)
- Early diagnosis and adequate treatment of primary TB to prevent dissemination.
- Absence of underlying immunosuppression.
- Good nutritional status.

Clinical Presentation

Signs and Symptoms

TBM typically has a subacute onset, evolving over 2-8 weeks, though acute and chronic presentations can occur. - Cardinal Features: - Headache: Most common symptom, often severe, persistent, and progressively worsening. - Fever: Low-grade, persistent, or intermittent. - Altered Mental Status: Lethargy, confusion, irritability, apathy, progressing to stupor or coma. - Neck Stiffness: Meningismus, though can be absent, especially in young children, elderly, or severely immunocompromised patients. - Early Signs (Prodromal Stage - usually Stage I MRC): - Non-specific malaise, fatigue - Irritability, behavioral changes (especially in children) - Anorexia, weight loss - Low-grade fever - Subtle, often non-specific headache - Advanced Signs (Later Stages - usually Stage II/III MRC): - Worsening headache and fever - Progressive altered consciousness (obtundation, stupor, coma) - Focal neurological deficits: - Cranial nerve palsies (CN III, IV, VI, VII are common due to basal exudates) - Hemiparesis or hemiplegia (due to vasculitis and infarcts) - Aphasia, visual field defects - Seizures (generalized or focal) - Signs of increased intracranial pressure (ICP): Vomiting (projectile), papilledema (on fundoscopy), Cushing's triad (bradycardia, hypertension, irregular respiration – late sign). - Decorticate or decerebrate posturing. - Spinal signs (if spinal arachnoiditis is present): Radicular pain, weakness, sphincter dysfunction. - Atypical Presentations: - Acute fulminant course mimicking bacterial meningitis (less common). - Stroke-like presentation due to cerebral infarcts. - Presentation dominated by tuberculomas (mass effect, focal deficits). - Presentation without meningeal signs in young children, elderly, or severely immunocompromised. - Symptoms suggestive of space-occupying lesion (e.g., headache, seizures, focal signs) due to large tuberculomas. - Paradoxical worsening or new neurological deficits during treatment (Immune Reconstitution Inflammatory Syndrome - IRIS), especially in HIV-positive patients initiating antiretroviral therapy (ART).

Physical Examination

Inspection:
- General Appearance: Cachexia, signs of chronic illness, poor hygiene.
- Neurological Status: Level of consciousness (GCS), focal neurological deficits (e.g., hemiparesis, ptosis, strabismus).
- Signs of Increased ICP: Papilledema on fundoscopy (requires ophthalmologic exam).
- Respiratory Pattern: Cheyne-Stokes respiration (advanced stages).
Palpation:
- Neck Stiffness: Assessment of nuchal rigidity (resistance to passive neck flexion).
Special Tests:
- Kernig's Sign: Patient supine, flex hip to 90 degrees, then attempt to extend knee; pain and hamstring spasm indicate positive sign.
- Brudzinski's Sign: Patient supine, passive flexion of neck causes involuntary flexion of hips and knees.
- Cranial Nerve Examination: Detailed assessment for palsies (e.g., extraocular movements, facial symmetry).
- Motor and Sensory Examination: To detect focal deficits.
- Fundoscopy: Essential to look for papilledema (suggests increased ICP) or choroidal tubercles (pathognomonic but rare).

Diagnostic Approach

History Taking

Key Questions:
- Duration and progression of symptoms (headache, fever, mental status changes).
- Exposure history to TB (household contacts, occupational exposure).
- Past medical history of TB or latent TB infection.
- Immunosuppression status (HIV, diabetes, organ transplant, chronic steroid use, biologics).
- BCG vaccination status.
- Travel history to TB endemic areas.
- Any constitutional symptoms (weight loss, night sweats, fatigue).
Red Flags:
- Rapid neurological deterioration.
- Signs of increasing intracranial pressure (e.g., worsening headache, persistent vomiting, papilledema).
- Development of new focal neurological deficits or seizures.
- Comatose state.
- These necessitate urgent diagnostic workup and empiric treatment.

Laboratory Tests

Diagnosis of TBM is challenging due to non-specific symptoms and the paucibacillary nature of CSF. A combination of clinical, CSF, and imaging findings is typically required. - First-Line: - Cerebrospinal Fluid (CSF) Analysis: Obtained via lumbar puncture (LP). Crucial for diagnosis. - Opening Pressure: Often elevated (>180 mm H2O). - Appearance: Usually clear or xanthochromic, but can be turbid. - Cell Count and Differential: Pleocytosis, typically lymphocytic (lymphocyte predominance >50%), though early TBM can show neutrophil predominance. Cell count usually 100-500 cells/µL, but can be lower or higher. - Protein: Elevated, typically >100 mg/dL (often 100-500 mg/dL, can be >1000 mg/dL). - Glucose: Low (<40 mg/dL or CSF:blood glucose ratio <0.5). - CSF Acid-Fast Bacilli (AFB) Smear: Low sensitivity (10-20% for single smear, up to 40% with repeated LPs/large volumes). - CSF Adenosine Deaminase (ADA): Elevated (>6-10 U/L) in TBM; good sensitivity (70-90%) and specificity (80-90%) in endemic areas, but not definitive. - CSF GeneXpert MTB/RIF: Molecular test for M. tuberculosis DNA and rifampicin resistance. Higher sensitivity (50-70%) than AFB smear, faster than culture. WHO recommends it as the initial diagnostic test on CSF for suspected TBM. - Blood Tests: - Complete Blood Count (CBC): May show anemia, leukocytosis, or normal. - Erythrocyte Sedimentation Rate (ESR) / C-reactive protein (CRP): Often elevated. - Electrolytes: Hyponatremia (due to SIADH or cerebral salt wasting) is common. - Liver Function Tests (LFTs): Baseline for monitoring anti-TB drug toxicity. - HIV Serology: Essential in all TBM suspects due to high co-infection rates. - Confirmatory: - CSF Culture for M. tuberculosis: Gold standard for definitive diagnosis, but slow (up to 6 weeks for liquid culture, longer for solid media). Sensitivity 30-70% (increased with larger CSF volume, e.g., 5-10 mL). Drug susceptibility testing (DST) is critical. - CSF Nucleic Acid Amplification Tests (NAATs): E.g., PCR (in-house or commercial assays) for M. tuberculosis DNA. Varies in sensitivity (40-80%) and specificity, generally better than AFB smear but less sensitive than culture. GeneXpert is a type of NAAT. - Histopathology: Biopsy of meninges (rarely performed) or brain (if tuberculoma) showing granulomas with caseating necrosis and AFB. - Monitoring: - LFTs: Weekly/bi-weekly during initial phase of anti-TB treatment, then monthly, due to risk of drug-induced liver injury. - Renal Function Tests: To adjust drug dosages if needed. - Electrolytes: To monitor and manage hyponatremia. - Audiometry: Baseline and regular follow-up if streptomycin or other ototoxic drugs are used. - Ophthalmologic Exam: Baseline and monthly if ethambutol is used (for optic neuritis).

Imaging

Recommended:
- Magnetic Resonance Imaging (MRI) Brain with Gadolinium Contrast: Superior to CT for demonstrating characteristic TBM features.
  - Key Findings:
    - Basal Meningeal Enhancement: Classic finding, particularly in the basal cisterns, often with a thick, gelatinous exudate.
    - Hydrocephalus: Communicating or obstructive, with ventricular dilatation.
    - Cerebral Infarcts: Multiple, small infarcts due to vasculitis, often in the basal ganglia or internal capsule.
    - Tuberculomas: Single or multiple ring-enhancing lesions.
    - Spinal Imaging: If signs of myelopathy or radiculopathy, look for spinal arachnoiditis or tuberculomas.
- Computed Tomography (CT) Brain with Contrast: More readily available, useful for initial assessment of hydrocephalus, large tuberculomas, and infarcts. Less sensitive than MRI for subtle meningeal enhancement or small lesions.
  - Key Findings:
    - Communicating or obstructive hydrocephalus.
    - Basal cistern effacement and hyperdensity (suggesting exudate).
    - Infarcts (hypodense areas).
    - Tuberculomas (often ring-enhancing lesions).
Advanced:
- CT Angiography (CTA) / MR Angiography (MRA): To better delineate vasculitis and evaluate cerebral arterial stenosis/occlusion, especially in stroke-like presentations.

Management

Acute Management

Prompt initiation of anti-TB treatment and corticosteroids is critical to improve outcomes. - Immediate (within hours of suspicion): - Start Empiric Anti-TB Therapy: As soon as TBM is suspected clinically, do not wait for confirmatory culture results. Delay in treatment significantly increases morbidity and mortality. - Corticosteroids: Start high-dose dexamethasone immediately in all stages of TBM, unless contraindicated. - Manage Increased ICP: Elevate head of bed to 30 degrees, gentle fluid restriction (avoid overhydration, especially if hyponatremia is present). - Stabilization: - Fluid and Electrolyte Management: Carefully monitor for hyponatremia (common, often due to SIADH) and manage appropriately with fluid restriction or hypertonic saline (3% NaCl) if severe. Avoid rapid correction to prevent osmotic demyelination syndrome. - Anticonvulsants: Administer if seizures occur (e.g., levetiracetam, phenytoin). Prophylactic anticonvulsants are not routinely recommended. - Nutritional Support: Ensure adequate caloric intake, especially in patients with altered consciousness or prolonged illness. - Symptomatic Management: Pain control for headache, fever reduction. - Emergency: - Neurosurgical Consultation: Essential for managing hydrocephalus. - External Ventricular Drain (EVD): For acute, rapidly worsening hydrocephalus and severe ICP elevation, as a temporary measure. - Ventriculoperitoneal (VP) Shunt: Definitive treatment for persistent symptomatic hydrocephalus. Timing is controversial, but usually considered after 2-4 weeks of medical therapy if hydrocephalus is worsening or not improving. - Management of Herniation: Mannitol (0.5-1.0 g/kg IV over 20-30 min) or hypertonic saline (3% NaCl, 5-10 mL/kg IV over 20-30 min) for acute brain herniation.

Chronic Management

Pharmacological:
- Anti-Tubercular Drug Regimen:
  - Standard Regimen (WHO guidelines):
    - Intensive Phase: 2 months of daily Rifampicin (R), Isoniazid (H), Pyrazinamide (Z), and Ethambutol (E) (2HRZE).
      - Dosages:
        
        Isoniazid (H): 5-10 mg/kg (max 300 mg daily)
        
        Rifampicin (R): 10-20 mg/kg (max 600 mg daily)
        
        Pyrazinamide (Z): 20-30 mg/kg (max 2000 mg daily)
        
        Ethambutol (E): 15-25 mg/kg (max 1600 mg daily)
    - Continuation Phase: 7-10 months of daily Rifampicin (R) and Isoniazid (H) (7-10HR).
    - Total Duration: 9-12 months. Some experts recommend 12 months for all stages due to the severity of TBM. For drug-resistant TBM, duration may be 18-24 months.
  - Drug Penetration: All standard first-line drugs penetrate the CSF well, especially during meningeal inflammation.
- Corticosteroids:
  - Drug: Dexamethasone is preferred due to good CNS penetration.
  - Dosing (WHO/IDSA Guidelines):
    - Stage II/III TBM: Initial dose of 0.4 mg/kg IV daily for the first week, then 0.3 mg/kg for week 2, 0.2 mg/kg for week 3, 0.1 mg/kg for week 4. Then switch to oral dexamethasone and taper by 0.05 mg/kg/week over 3 weeks. Total duration 6-8 weeks.
    - Stage I TBM: Initial dose of 0.3 mg/kg IV daily for the first week, then 0.2 mg/kg for week 2, 0.1 mg/kg for week 3, and then taper by 0.05 mg/kg/week over 3 weeks. Total duration 6 weeks.
    - HIV-positive patients: Same regimen, but carefully monitor for paradoxical IRIS.
  - Rationale: Corticosteroids reduce inflammation, exudate formation, cerebral edema, and vasculitis, thereby reducing mortality and disability.
Non-pharmacological:
- Nutritional Support: Crucial for recovery, especially for patients with prolonged hospital stays or neurological deficits.
- Physical and Occupational Therapy: For neurological rehabilitation (motor deficits, cognitive impairment, activities of daily living).
- Speech Therapy: For dysphagia or speech impediments.
- Psychosocial Support: For patients and families dealing with chronic illness and disability.
Monitoring:
- Clinical Monitoring: Regular neurological examinations, GCS, vital signs, seizure activity, signs of increased ICP.
- Adverse Drug Reactions:
  - Hepatotoxicity: Monitor LFTs (ALT, AST, bilirubin) weekly for the first month, then monthly. If ALT/AST >3x ULN with symptoms or >5x ULN without symptoms, stop hepatotoxic drugs.
  - Peripheral Neuropathy: (Isoniazid) Administer pyridoxine (vitamin B6) 10-25 mg daily with isoniazid.
  - Optic Neuritis: (Ethambutol) Baseline and monthly visual acuity and color vision testing. Discontinue if symptoms occur.
  - Ototoxicity/Nephrotoxicity: (Streptomycin, if used for MDR-TB) Monitor audiometry and renal function.
  - Joint Pain/Gout: (Pyrazinamide) Monitor uric acid levels.
- Drug Resistance: Monitor clinical response. If poor response, re-evaluate adherence, drug levels (if available), and re-test for drug resistance.
- Follow-up Imaging: Repeat MRI/CT if clinical deterioration or to assess shunt function.

Treatment Algorithms

First-Line (Drug-Susceptible TBM):
1. Suspect TBM (based on clinical picture, CSF, imaging): Initiate empiric treatment immediately.
2. Start Dexamethasone: Based on MRC stage (see above for specific dosing).
3. Start Anti-TB Regimen:
  - Intensive Phase (2 months): Rifampicin, Isoniazid, Pyrazinamide, Ethambutol (HRZE) daily.
  - Continuation Phase (7-10 months): Rifampicin, Isoniazid (HR) daily.
4. Manage Complications: Hydrocephalus (shunting if needed), seizures, hyponatremia.
5. HIV Co-infection:
  - Initiate ART 2-8 weeks after starting anti-TB therapy in stable patients. Delaying ART reduces risk of paradoxical IRIS, but balance against risk of opportunistic infections. Consider starting ART earlier (within 2 weeks) in those with severe immunosuppression (e.g., CD4 <50 cells/µL).
Second-Line (Drug-Resistant TBM):
- Suspect resistance if patient has previous TB treatment failure, contact with drug-resistant TB, or fails to respond to first-line drugs.
- Diagnostic Confirmation: Obtain CSF culture and drug susceptibility testing (DST).
- Regimen Tailoring: Based on DST results. Multidrug-resistant (MDR) TBM and extensively drug-resistant (XDR) TBM require individualized regimens typically including:
  - Fluoroquinolones (levofloxacin or moxifloxacin, high doses)
  - Injectable agents (amikacin, capreomycin - use with caution due to toxicity and limited data for TBM)
  - Second-line oral agents (e.g., cycloserine, prothionamide, linezolid, clofazimine)
  - Newer drugs (bedaquiline, delamanid) may be considered, but CNS penetration data and clinical experience for TBM are limited.
- Duration: Typically 18-24 months or longer.
- Consultation: Always consult with a TB expert or infectious disease specialist for drug-resistant TBM.
Refractory Cases (Treatment Failures):
- Re-evaluate Diagnosis: Confirm it is TBM (consider other causes of meningitis, neurological deterioration).
- Assess Adherence: Check patient adherence to medication.
- Re-evaluate Drug Resistance: Repeat CSF culture and DST.
- Therapeutic Drug Monitoring: May be considered for drugs like rifampicin and isoniazid, if available, to ensure adequate drug levels.
- Surgical Options: Re-evaluate for hydrocephalus requiring shunting or large tuberculomas causing significant mass effect.
- IRIS: Consider paradoxical IRIS in HIV-positive patients, especially after ART initiation. May require increasing corticosteroid dose temporarily.

Complications

TBM can lead to a wide range of severe and often irreversible complications. - Common: - Hydrocephalus: Occurs in 80-90% of patients, leading to increased ICP, headache, vomiting, and cognitive decline. - Cranial Nerve Palsies: Most commonly CN III, IV, VI (oculomotor, trochlear, abducens nerves), leading to diplopia, ptosis, and strabismus. CN VII (facial nerve) palsy also occurs. - Cerebral Infarction/Stroke: Due to vasculitis (predominantly affecting perforating arteries), leading to focal neurological deficits (e.g., hemiparesis, aphasia). - Hyponatremia: Common, usually due to SIADH. - Serious: - Severe Neurological Deficits: Persistent hemiplegia, paraplegia, blindness, deafness, cognitive impairment. - Seizures: Can lead to status epilepticus. - Spinal Arachnoiditis: Inflammation and scarring of spinal meninges, leading to myelopathy, radiculopathy, and bladder/bowel dysfunction. - Visual Impairment/Blindness: Due to optic neuropathy (compression from exudate, papilledema, or drug toxicity - ethambutol). - Endocrine Dysfunction: Hypopituitarism (rare, due to hypothalamic/pituitary involvement). - Drug Toxicity: Hepatotoxicity, peripheral neuropathy, optic neuritis, ototoxicity. - Long-term: - Neurocognitive Impairment: Memory deficits, executive dysfunction, behavioral changes. - Epilepsy: Chronic seizures. - Motor Deficits: Spasticity, gait disturbance. - Chronic Headache. - Hydrocephalus with Shunt Dependence. - Psychiatric Complications: Depression, anxiety.

Prognosis

Factors Affecting Outcome:
- Stage at Presentation: The most crucial prognostic factor. Stage I has significantly better outcomes than Stage III.
- Age: Worse prognosis in very young children (<3 years) and elderly.
- HIV Status: HIV co-infection is associated with higher mortality and more severe neurological sequelae.
- Presence of Drug Resistance: MDR/XDR TBM leads to worse outcomes.
- Delay in Treatment: Each day of delay in starting appropriate anti-TB drugs increases the risk of death or severe disability.
- Development of Complications: Hydrocephalus, stroke, seizures are associated with poorer outcomes.
- Nutritional Status: Malnutrition is a negative prognostic indicator.
Survival:
- Overall mortality rates range from 15-50%, but can be as high as 60-80% in advanced (Stage III) disease or in HIV-positive patients.
- Mortality is significantly reduced with early diagnosis and prompt, appropriate treatment, including corticosteroids.
Quality of Life:
- Significant proportion of survivors (20-50%) experience permanent neurological sequelae, impacting quality of life and requiring long-term rehabilitation.
- Children may suffer from developmental delays and learning disabilities.

Prevention

Primary Prevention:
- BCG Vaccination: While efficacy against pulmonary TB is variable, BCG provides partial protection against severe forms of TB, including TBM, particularly in young children in endemic areas. WHO recommends BCG vaccination for all infants in countries with a high incidence of TB.
- Contact Tracing and Preventive Therapy (Latent TB Infection - LTBI): Identifying and treating individuals with LTBI (especially close contacts of active TB cases) can prevent progression to active disease, including TBM.
  - Isoniazid Preventive Therapy (IPT): 6-9 months of isoniazid.
  - Shorter Regimens: 3 months of daily isoniazid and rifapentine (3HP) or 4 months of daily rifampicin (4R) are also options.
- Improved Socioeconomic Conditions and Nutrition: Addressing poverty, overcrowding, and malnutrition reduces TB transmission and progression.
Secondary Prevention:
- Early Detection and Rapid Initiation of Treatment for Active TB: Prompt diagnosis and effective treatment of pulmonary and extrapulmonary TB prevent hematogenous dissemination to the CNS.
- Active Case Finding: Screening vulnerable populations.
Tertiary Prevention:
- Management of Complications: Prompt management of hydrocephalus, seizures, and other neurological sequelae to minimize long-term disability.
- Rehabilitation: Physical, occupational, and speech therapy to improve functional outcomes and quality of life for survivors.

Special Populations

Pediatric:
- Higher Incidence: Children, especially those <5 years, are disproportionately affected and have a higher risk of developing TBM after primary infection.
- Diagnosis Challenges: Atypical presentations, non-specific symptoms, and difficulty in obtaining CSF make diagnosis challenging. Clinical suspicion must be high.
- Hydrocephalus: More common and often more severe, requiring earlier neurosurgical intervention.
- Dosages: Anti-TB drug dosages are weight-based and may differ slightly from adult doses (e.g., higher mg/kg for rifampicin). Pyridoxine is crucial with isoniazid.
- Long-term Sequelae: Higher risk of severe neurological and developmental impairments.
Geriatric:
- Atypical Presentation: Symptoms may be subtle and non-specific, often without classic meningeal signs, leading to delayed diagnosis.
- Comorbidities: Often have multiple comorbidities (diabetes, chronic kidney disease) and polypharmacy, increasing risk of drug interactions and adverse drug reactions.
- Immunosuppression: Age-related immunosenescence.
- Prognosis: Worse prognosis due to delayed diagnosis and comorbidities.
Pregnancy:
- Diagnosis: LP and MRI are generally safe.
- Treatment: Standard HRZE regimen can generally be used.
  - Isoniazid, Rifampicin, Ethambutol: Considered safe in pregnancy. Pyridoxine supplementation (25-50 mg daily) is essential with isoniazid.
  - Pyrazinamide: Generally considered safe, but some reluctance in first trimester. WHO recommends its use throughout pregnancy for TB meningitis.
  - Streptomycin: Contraindicated due to risk of congenital ototoxicity (fetal deafness).
  - Newer/Second-line drugs: Use with caution, often limited data. Consult with expert.
- Corticosteroids: Dexamethasone is generally safe.
- Breastfeeding: Anti-TB drugs are secreted in breast milk, but concentrations are low and not harmful to the infant. Breastfeeding should be encouraged.
Comorbidities:
- HIV Co-infection:
  - Higher Risk of TBM: Increased incidence and more severe disease.
  - Atypical CSF: CSF parameters may be less typical (higher cell count, more protein, less glucose difference).
  - Paradoxical IRIS: A significant concern, occurring in 10-40% of co-infected patients after ART initiation. Characterized by worsening neurological symptoms or new lesions despite anti-TB treatment. Managed by continuing anti-TB drugs, short course of high-dose corticosteroids, and occasionally temporary ART interruption (rarely needed).
  - Drug Interactions: Rifampicin interaction with many antiretrovirals (especially protease inhibitors and non-nucleoside reverse transcriptase inhibitors). Dolutegravir-based regimens or rifabutin (with dose adjustment) may be preferred.
  - Mortality: Higher mortality rates.
- Diabetes Mellitus: Increased risk of TB, atypical presentations, and potential for poorer response to treatment. Careful blood glucose control is important.

Clinical Pearls

Diagnostic:
- High Index of Suspicion: TBM is a great mimicker. Consider it in any patient with subacute headache, fever, and altered mental status, especially in endemic areas or with risk factors.
- Don't Wait: If TBM is suspected, initiate empiric anti-TB treatment and corticosteroids immediately, even before definitive diagnostic confirmation.
- CSF Analysis is Key: Perform LP (if not contraindicated by raised ICP with mass effect). Remember that CSF findings can be atypical, especially early or in immunocompromised patients.
- Imaging Essential: MRI with contrast is superior to CT. Look for basal meningeal enhancement, hydrocephalus, and infarcts.
- GeneXpert on CSF: A crucial rapid diagnostic tool. Increased sensitivity with larger CSF volumes (e.g., >5 mL).
Treatment:
- Duration Matters: Emphasize treatment duration of 9-12 months for drug-susceptible TBM. Adherence is paramount.
- Corticosteroids are Lifesaving: Dexamethasone improves survival and reduces neurological disability. Do not skip or underdose.
- Manage Complications Actively: Aggressively manage hydrocephalus (neurosurgical consultation) and hyponatremia.
- Monitoring is Critical: Closely monitor for drug side effects (hepatotoxicity, optic neuritis, neuropathy) and clinical response.
Pitfalls:
- Delay in Diagnosis and Treatment: The single biggest factor for poor outcomes.
- Missing Drug Resistance: Failure to consider drug resistance can lead to treatment failure. Obtain DST whenever possible.
- Stopping Corticosteroids Too Early: Can lead to rebound inflammation.
- Aggressive Fluid Resuscitation in Hyponatremia: Can worsen cerebral edema, especially if SIADH is the cause.
- Attributing Neurological Deterioration Solely to TB: Always consider other causes like drug toxicity, stroke, IRIS, or shunt malfunction.
- Underestimating Long-term Disability: Many survivors will require significant rehabilitation.

Recent Updates

Guidelines:
- WHO Guidelines (2022): Re-emphasize the role of GeneXpert MTB/RIF and its newer iteration (GeneXpert Ultra) on CSF as initial diagnostic tests. Continue to recommend corticosteroids in all stages of TBM. Recommendations on shorter regimens for drug-susceptible TB generally do not apply to TBM; longer durations (9-12 months) remain standard.
- IDSA Guidelines: Consistent with WHO recommendations regarding diagnosis and treatment.
Evidence:
- Optimizing Drug Dosing: Ongoing research into higher doses of rifampicin (e.g., 35 mg/kg daily) to improve CNS penetration and outcomes for TBM, but not yet standard of care.
- Newer Anti-TB Drugs: Bedaquiline and delamanid are being evaluated for use in drug-resistant TBM, but data on CNS penetration and efficacy specific to TBM are still emerging.
Controversies:
- Optimal Timing of ART in HIV-TBM: While 2-8 weeks is generally recommended, some advocate earlier ART (within 2 weeks) for severe immunosuppression, balancing the risk of IRIS with benefits of ART. Individualized approach is often needed.
- Role of Adjunctive Therapy: E.g., aspirin for reducing vasculitic complications, although evidence is limited and not routinely recommended.
- Duration of Treatment: While 9-12 months is standard, some severe cases might benefit from longer durations, but clear evidence is lacking.

Key References

Guidelines:
- World Health Organization (WHO) Guidelines for the programmatic management of drug-resistant tuberculosis (2020 update) and other TB guidelines (e.g., on TBM, HIV/TB co-infection).
- Infectious Diseases Society of America (IDSA) Clinical Practice Guidelines for the Diagnosis and Treatment of Tuberculosis (2016 and subsequent updates).
Studies:
- Thwaites, G. E., et al. "Dexamethasone for the treatment of tuberculous meningitis in adolescents and adults." New England Journal of Medicine 357.17 (2007): 1731-1741. (Landmark trial on steroids in TBM).
- Marlowe, E. M., et al. "Detection of Mycobacterium tuberculosis in cerebrospinal fluid by real-time PCR in tuberculous meningitis." Journal of Clinical Microbiology 48.7 (2010): 2523-2528.
- Long, R., et al. "Optimal timing of antiretroviral therapy initiation in HIV-infected adults with newly diagnosed tuberculous meningitis: an open-label, randomized, controlled trial." Annals of Internal Medicine 164.8 (2016): 515-524.
Reviews:
- Donnelly, K. G., et al. "Tuberculous Meningitis: A Review of Pathophysiology, Diagnosis, and Treatment." Journal of Clinical Microbiology 58.7 (2020): e01977-19.
- Thwaites, G. E., et al. "Tuberculous meningitis." The Lancet 367.9529 (2007): 1709-1721.