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Spinal needles & PDPH

Cutting versus non-cutting tips, the gauge–headache relationship, and the diagnosis and treatment of post-dural puncture headache.

The two tip designs

Feature	Dura-cutting	Dura-splitting (pencil-point)
Tissue trauma	↑ Cuts the dural fibres	↓ Parts the fibres
PDPH incidence	↑ Higher	↓ Lower
Technical ease	Easier — clearer feel, CSF at the tip	Harder — more force needed, later CSF flashback
Examples	Quincke–Babcock	Whitacre · Sprotte · Pencan · Greene
Current practice	Rarely used for elective spinals	Standard of care, especially in obstetrics

Why splitting beats cutting

Dural fibres run in multiple directions, but the elastic recoil of a split closes better than a cut edge.
The older advice to orient a Quincke bevel parallel to the long axis of the spine follows the same logic and does reduce PDPH — but it is a mitigation, not a substitute for a pencil-point needle.
An introducer is used with fine needles to prevent bending and to avoid dragging skin fragments into the CSF.

Gauge and PDPH incidence

Gauge of Quincke needle	Incidence of PDPH
22 G	36%
25 G	25%
26 G	2–12%
Finer than 26 G	<2%

Remember these are cutting-needle figures — which is exactly why they look so alarming. A 25–27 G pencil-point needle sits around 1% or below even in the highest-risk group, young obstetric patients.

The trade-off — and the limit of "finer is better"

Finer needle → less PDPH, but also slower CSF flashback, more bending and deflection, and a higher rate of technical failure.
At 29 G the spinal success rate falls: CSF may take many seconds to appear, and confirming placement becomes unreliable. The optimum is a compromise, not the smallest available needle.
25–27 G pencil-point is the usual working answer.

A caveat on the table

The 26 G row and the "finer than 26 G" row overlap awkwardly, and published figures vary widely between studies — populations, follow-up and diagnostic criteria all differ.
Learn the direction and rough magnitude — larger gauge and cutting tip mean substantially more headache — rather than defending an exact percentage in a viva.

Post-dural puncture headache

Mechanism

CSF leak through the dural defect exceeds production (about 0.35 ml/min), so CSF pressure falls.
Two consequences: traction on pain-sensitive intracranial structures (dura, vessels, cranial nerves) when upright, and compensatory cerebral vasodilatation (Monro–Kellie).
The vasodilatation explains why the headache has a throbbing, migrainous quality and why caffeine and theophylline were tried.

Clinical picture

Postural — worse within 15 minutes of sitting or standing, relieved within 15 minutes of lying flat. This is the defining feature.
Frontal, occipital or both, often radiating to the neck and shoulders.
Onset typically 24–48 hours after puncture; over 90% within 3 days.
Associated: neck stiffness, photophobia, nausea, tinnitus, hearing changes and diplopia.
Diplopia is from sixth nerve traction — it has the longest intracranial course. It is a red flag warranting definitive treatment.

Risk factor	Increases risk	Note
Needle tip	Cutting	The single biggest modifiable factor
Needle size	Larger gauge	A 17 G Tuohy accidental dural puncture gives PDPH in 50–80%
Bevel orientation	Perpendicular to the spinal axis	Applies to cutting needles only
Age	Young	Uncommon over 60 and under 10 — a favourite exam point
Sex & pregnancy	Female, pregnant	Hence the obstetric focus
Body habitus	Low BMI	Previous PDPH also predicts recurrence
Number of attempts	Multiple punctures	More holes, more leak

Differential diagnosis — do not assume PDPH

A headache that is not postural is not PDPH. Reassess.
Pre-eclampsia — check blood pressure, urine and platelets in any postpartum headache.
Subdural haematoma — intracranial hypotension stretches bridging veins. Suspect if the headache loses its postural character, becomes constant, or develops focal signs or drowsiness. This is the reason a "resolving" PDPH that changes character needs imaging, not reassurance.
Cerebral venous sinus thrombosis, meningitis, subarachnoid haemorrhage, posterior reversible encephalopathy, migraine, caffeine withdrawal, sinusitis, and simple dehydration.
Red flags: fever, neck stiffness with fever, focal neurology, seizures, altered consciousness, thunderclap onset, or loss of the postural component.

Management

Conservative — first 24–48 hours

Simple analgesia: regular paracetamol and NSAIDs. Opioids add little and cause constipation and straining.
Adequate oral or IV hydration — it does not increase CSF production, but dehydration makes everything worse.
Bed rest relieves the symptom but does not shorten the illness — and it adds thromboembolic risk, especially postpartum. Do not prescribe it as a treatment.
Avoid straining — laxatives, and avoid a Valsalva.
Caffeine gives short-lived relief through cerebral vasoconstriction; the evidence is weak and the effect is not sustained.
Explain and follow up daily. The commonest complaint in these cases is not the headache — it is not being taken seriously.

Epidural blood patch — the definitive treatment

15–20 ml of the patient's own blood, taken under strict asepsis, injected into the epidural space at or one space below the level of puncture — blood spreads preferentially cephalad.
Stop injecting when the patient reports back, buttock or leg pressure or pain.
Two mechanisms: an immediate mass/tamponade effect raising CSF pressure, then clot sealing the dural defect.
Success about 70–90%; a second patch may be needed and works in most of the remainder.
Timing: generally deferred beyond 24–48 hours, since earlier patches have a higher failure rate — but do not delay it in a patient with severe symptoms or cranial nerve signs.
Lie flat for 1–2 hours afterwards; avoid lifting and straining for 24–48 hours.
Contraindications: local or systemic sepsis, coagulopathy, patient refusal, raised ICP. In an HIV-positive patient a patch is not contraindicated.
Complications: backache (very common, usually self-limiting), a further dural puncture, infection, and rarely arachnoiditis or neurological injury.

Other options

Sphenopalatine ganglion block — transnasal local anaesthetic on a cotton applicator. Non-invasive, quick, increasingly used as a first step or while awaiting a patch.
Greater occipital nerve block.
Intrathecal catheter after an accidental dural puncture: threading and leaving the catheter for 24 hours may reduce the incidence — the evidence is mixed but the technique also provides labour analgesia and removes the risk of a second puncture. Label it unmistakably.
Epidural saline gives only transient relief.

Quick recall

Pencil-point splits, doesn't cut

25–27 G the working compromise

29 G success rate falls

17 G Tuohy PDPH 50–80%

Postural or it isn't PDPH

CN VI diplopia = red flag

Blood patch 15–20 ml, 70–90%

Young higher risk, not older

Built from your spinal needle and PDPH pages. Incidence figures for cutting needles vary considerably between published series — learn the pattern rather than the exact number.