MENINGITIS MIRAGE

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The term "Meningitis Mirage" refers to conditions that mimic meningitis—patients present with classic meningitis symptoms (e.g., fever, headache, neck stiffness, altered mental status, elevated inflammatory markers), but the underlying cause is non-infectious.

Here are the major causes of a meningitis mirage, organized by category:

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🧬 1. Autoimmune/Inflammatory Causes

These are some of the most important mimics.

• Neuropsychiatric lupus (SLE)

• Sarcoidosis (Neurosarcoidosis)

• Vasculitis (e.g., primary CNS vasculitis)

• Behçet's disease

• Autoimmune encephalitis

  • Anti-NMDA receptor encephalitis

• IgG4-related disease

• Aseptic meningeal inflammation in Still’s disease or rheumatoid arthritis

🧠 These often involve CSF pleocytosis and imaging changes but no infectious agent.

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💊 2. Drug-Induced Aseptic Meningitis

Certain medications can trigger inflammatory reactions in the meninges:

• NSAIDs (especially ibuprofen)

• IVIG (intravenous immunoglobulin)

• Antibiotics (e.g., trimethoprim-sulfamethoxazole, ciprofloxacin)

• Monoclonal antibodies (e.g., infliximab, etanercept)

🩺 Mechanism is usually hypersensitivity or direct irritation.

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🧠 3. Neoplastic/Paraneoplastic Syndromes

Tumors or paraneoplastic syndromes can mimic meningitis:

• Carcinomatous meningitis (leptomeningeal metastases)

• Primary CNS lymphoma

• Paraneoplastic encephalitis or meningitis

⚠️ May present with elevated CSF protein, lymphocytic pleocytosis, and cranial nerve involvement.

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🧪 4. Post-Infectious or Para-Infectious Syndromes

Immune-mediated syndromes after infection:

• ADEM (Acute disseminated encephalomyelitis)

• Post-viral autoimmune meningitis

• Mollaret’s meningitis (recurrent aseptic, possibly viral)

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🔩 5. Systemic Illness with CNS Involvement

• Thyroid storm

• Uremic encephalopathy

• Hypertensive encephalopathy

• Heat stroke

🌡️ These may trigger fever, AMS, or neck stiffness—mimicking meningitis.

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🩸 6. Subarachnoid Hemorrhage (SAH)

• Presents with sudden severe headache, neck stiffness, photophobia.

• CSF may show xanthochromia or RBCs, mimicking meningitis.

🔍 CT scan and LP distinguish SAH from meningitis.

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🧠 7. Migraine with Meningeal Irritation

• Severe basilar migraines or status migrainosus can mimic meningitis:

  • Headache, photophobia, nausea, nuchal rigidity

  • Sometimes with mild CSF pleocytosis

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🧬 8. Genetic/Periodic Fever Syndromes

• Familial Mediterranean Fever (FMF)

• TRAPS (TNF Receptor-Associated Periodic Syndrome)

🔥 Can present with episodic fever, meningismus, elevated inflammatory markers—often in younger patients.

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🔍 Summary Table

Category	Example Conditions
Autoimmune	Lupus, vasculitis, sarcoidosis
Drug-induced	NSAIDs, IVIG, antibiotics
Neoplastic	Carcinomatous meningitis, lymphoma
Post-infectious	ADEM, Mollaret's
Systemic illness	Uremia, thyroid storm
Hemorrhage	Subarachnoid hemorrhage
Neurologic	Basilar migraine
Genetic	Familial Mediterranean Fever

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Would you like a diagnostic algorithm, comparison chart with infectious meningitis, or guidance on when to consider each cause?