A 52-year-old man undergoes spinal anesthesia for total knee replacement. During the procedure, he develops sudden onset of severe headache, neck stiffness, and photophobia within 2 hours of the block. Which is the most common cause of this complication?

Explanation

## Most Common Cause of Headache After Spinal Anesthesia **Key Point:** Post-dural puncture headache (PDPH) is the most common neurological complication of spinal anesthesia, occurring in 10–40% of cases depending on needle gauge and technique. ### Distinguishing Features of PDPH | Feature | PDPH | Meningitis | SAH | |---------|------|-----------|-----| | **Onset** | 24–48 hrs (rarely within 2 hrs) | 12–24 hrs | Immediate/sudden | | **Character** | Positional (worse upright) | Non-positional | Thunderclap | | **Associated signs** | Neck stiffness rare | Fever, neck stiffness, photophobia | Focal neuro deficit, coma | | **CSF findings** | Normal/xanthochromia | Pleocytosis, elevated protein | Blood-stained | | **Incidence** | 10–40% | <0.1% (rare) | <0.01% (very rare) | **High-Yield:** Although the clinical presentation in this case (headache + neck stiffness + photophobia) resembles meningitis, the **timing within 2 hours** and the **context of spinal anesthesia** make PDPH the most likely diagnosis. Meningitis typically develops 12–24 hours post-procedure and requires fever and CSF pleocytosis to confirm. ### Mechanism of PDPH 1. Dural puncture during spinal needle insertion 2. Leakage of CSF through the puncture site 3. Intracranial hypotension 4. Traction on pain-sensitive intracranial structures (meninges, cranial nerves) **Clinical Pearl:** PDPH is **positional** — worse when upright, better when supine. This distinguishes it from meningitis (non-positional) and SAH (constant, severe). ### Risk Factors for PDPH - **Needle gauge:** Larger gauge → higher risk (22G > 25G > 27G) - **Needle type:** Cutting bevel > pencil-point (Whitacre, Sprotte) - **Number of attempts:** Multiple punctures increase risk - **Patient factors:** Young age, female sex, low BMI, pregnancy **Mnemonic: PDPH Risk — "YOUNG LADIES"** - **Y**oung age - **O**bstetric patients - **U**nsuccessful first attempt - **N**eedle gauge (large) - **G**ender (female) - **L**arge needle - **A**ttempts (multiple) - **D**ural puncture (unintentional) - **I**ntrathecal injection - **E**arly mobilization - **S**mall BMI **Warning:** Do not confuse PDPH with meningitis. Meningitis requires fever, positive cultures, and CSF pleocytosis. PDPH is a mechanical complication, not infectious.