A 38-year-old woman undergoing emergency cesarean section under spinal anesthesia (1.8 mL of 0.5% hyperbaric bupivacaine at L3–L4) develops sudden onset of severe headache, neck stiffness, photophobia, and altered mental status 6 hours postoperatively. CSF analysis shows elevated protein (180 mg/dL), normal glucose, and pleocytosis with lymphocytic predominance. Which of the following is the MOST likely diagnosis, and what is the key distinguishing feature that differentiates it from other post-dural puncture complications?

Explanation

## Aseptic Meningitis Following Spinal Anesthesia **Clinical Presentation:** The patient presents with classic meningeal signs (headache, neck stiffness, photophobia) and altered mental status within 6 hours of spinal puncture—a timeline consistent with aseptic (chemical) meningitis rather than PDPH, which typically develops 24–48 hours post-procedure and is positional. **CSF Profile (Gold Standard):** - **Lymphocytic pleocytosis** (100–1000 cells/μL, predominantly lymphocytes) - **Elevated protein** (100–500 mg/dL) - **Normal glucose** (>40 mg/dL, CSF:serum ratio >0.4) - **Negative bacterial cultures** and Gram stain **Pathophysiology:** Aseptic meningitis post-spinal anesthesia is caused by chemical irritation of meninges from: - Detergents in local anesthetic solutions (historically methylparaben, propylparaben) - Needle trauma - Intrathecal medications (NSAIDs, antibiotics, corticosteroids if injected intrathecally) **Key Distinguishing Features:** 1. **Timing:** Onset within 6–48 hours (vs. PDPH: 24–48 hours, positional) 2. **CSF findings:** Lymphocytic pleocytosis + normal glucose (vs. bacterial meningitis: neutrophilic + low glucose) 3. **Cultures:** Always negative 4. **Self-limited course:** Resolves in 24–72 hours with supportive care **High-Yield:** The normal CSF glucose with lymphocytic pleocytosis is pathognomonic for aseptic meningitis; bacterial meningitis presents with low CSF glucose (<40 mg/dL) and neutrophilic predominance. **Clinical Pearl:** Modern preservative-free local anesthetic solutions have dramatically reduced the incidence of aseptic meningitis post-spinal anesthesia.