## Post-Dural Puncture Headache (PDPH) — Pathophysiology **Key Point:** PDPH is caused by **CSF leakage through the dural puncture hole**, leading to decreased CSF volume and pressure, which results in traction on pain-sensitive intracranial structures (meninges, cranial nerves). ### Mechanism of PDPH 1. **Dural puncture** creates a hole in the dura mater (and arachnoid) 2. **CSF leakage** occurs through the puncture site into the epidural space 3. **Decreased CSF pressure** reduces cushioning of the brain and spinal cord 4. **Traction on pain-sensitive structures** (meninges, cranial nerves) → headache 5. **Positional nature:** Upright posture worsens leakage; supine position relieves symptoms **High-Yield:** The hallmark of PDPH is its **positional character** — worse when sitting/standing, better when lying flat. This distinguishes it from other post-operative headaches. ### Clinical Features of PDPH | Feature | Details | | --- | --- | | **Onset** | 24–48 hours post-puncture (can be up to 7 days) | | **Character** | Frontal or occipital, throbbing or pressure | | **Positional** | Worsens within 15 min of sitting/standing; improves within 15 min of lying flat | | **Associated symptoms** | Neck stiffness, auditory symptoms (tinnitus, hearing loss), visual disturbance | | **Incidence** | 0.1–0.3% with pencil-point needles; 1–2% with cutting needles | **Clinical Pearl:** Needle design matters — pencil-point (Sprotte, Whitacre) needles have lower PDPH rates than cutting (Quincke) needles because they separate rather than cut dural fibers. **Warning:** Do not confuse PDPH with meningitis (which presents with fever, photophobia, and neck stiffness not relieved by lying flat) or vasodilation headache (which is not positional).
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