Post-dural puncture headache

Why examiners ask this

Post-dural puncture headache (PDPH) is common, but the exam point is the differential: postpartum headache includes pre-eclampsia, cortical vein thrombosis, subdural hematoma and posterior reversible encephalopathy, all of which can kill. The examiner tests application of knowledge about the mechanism and blood patch, judgment about when to image, and communication with an upset patient who wants to go home with her baby.

The 60-second answer

Decision points and the "why"

• Mechanism — CSF leak lowers intracranial pressure; the brain sags onto pain-sensitive structures and compensatory venodilation (Monro-Kellie) causes the headache. Sitting worsens both.
• Red flags before treatment — a pre-eclamptic headache with hypertension, or a subdural from prolonged low CSF pressure, is missed when every postpartum headache is labeled PDPH. Loss of positional character after a long PDPH is a subdural until imaged.
• Blood patch timing — it is most effective after about 24 hours; very early patches have a higher failure rate. Success is roughly 60–80% with the first patch; I offer a second if the first fails and the diagnosis still fits.
• Contraindications — fever or bacteremia, coagulopathy, infection at the site, and refusal. For thrombocytopenia I use the same reasoning as any obstetric neuraxial procedure: 70,000 or more carries very low hematoma risk.¹ I do not patch through an active infection.
• Sphenopalatine ganglion block and drugs — I offer these as adjuncts; the evidence is weaker than for the blood patch.
• After an accidental dural puncture during labor — I can thread the catheter intrathecally as a continuous spinal, which avoids re-puncture and gives reliable analgesia, with every staff member told and the catheter clearly labeled; it has not been shown to reduce headache or blood patch rates compared with re-siting the epidural.²

The complication they will inject

Three days after a wet tap she calls back: the headache is now constant, not positional, and she has vomited twice and is confused. I tell her to come back immediately and I meet her in the emergency department. I check blood pressure, temperature and neurologic status. Loss of positional character with new neurology suggests a subdural hematoma or cerebral venous thrombosis, and the postpartum period adds eclampsia and PRES. I get urgent neurology and neuroimaging, preferably MRI with venography, and I do not perform a blood patch until the diagnosis is clear. I explain to her and her partner what we are looking for and why.

Pitfalls that cost points

• Patching every postpartum headache without a differential.
• Forgetting to check blood pressure in a postpartum headache.
• Recommending strict bed rest, which does not prevent PDPH and increases thromboembolic risk.
• Promising that one patch always works.
• Not documenting the dural puncture or not arranging follow-up.

Rapid-why

Q: Why do pencil-point needles reduce PDPH? A: They separate rather than cut dural fibers and leave a smaller hole that seals better.

Q: How does a blood patch work immediately? A: The volume compresses the thecal sac and raises CSF pressure; the clot then seals the leak.

Q: What is the incidence after an epidural needle wet tap? A: About half of parturients develop a headache (52% in a recent meta-analysis), more with a 16-gauge than an 18-gauge needle.²

Q: Why is the parturient at higher risk? A: Pregnant women have a higher PDPH risk after dural puncture;² young age, female sex, and pushing in the second stage after a puncture all increase leak and headache.

Numbers to know

Links

• Neuraxial labor analgesia and its complications, Spinal anesthesia: dosing, spread, hypotension, Epidural hematoma and abscess (coming), Pre-eclampsia and eclampsia, Disclosing a peri-procedural complication or error
• ASRA/international multisociety practice guidance on post-dural puncture headache; ASA Practice Guidelines for Obstetric Anesthesia