The headache may first be experienced several hours to days after the dural puncture. It is usually bifrontal and occipital and is aggravated by the upright posture and by straining. It is relieved by lying down (Chapter 85). It needs to be differentiated from aseptic meningitis, infective meningitis, cortical vein thrombosis, cerebral/epidural haematoma and tension/migraine headache.
The incidence of PDPH can be as high as 80% if puncture occurs with a 16G needle. Series have been reported suggesting that the incidence of PDPH can be reduced to almost 0% with the use of specially designed, non-cutting point, fine gauge needles. However, most recent series report incidences of 1% - 3% even with these smaller gauge needles.
The fact that not every patient has a headache after dural puncture, even with 16G needles, would indicate that the degree of inter-patient variability and difference in technique of insertion also have a profound effect on incidence.
The factors which have been identified in affecting the incidence of PDPH are the:
1. size of needle (3) - decreased incidence with smaller needles,
2. design of needle (Figure E.1) - decreased incidence with a non-cutting tip as compared with a cutting tip (3),
3. relationship of bevel to the dural fibres - decreased incidence if needle bevel is parallel to dural fibres (Chapter 63),
4. angle of puncture of the dura - less with acute angles,
5. age- most studies have shown a decreased incidence with increasing age,
6. gender - females (even after removing the bias introduced by obstetric patients)have almost double the incidence of headache when compared with males in the under 50yr age group,
7. use of Povidone-lodine skin-prep. One study showed that removal of the skin-prep decreased the incidence of PDPH,
8. formation of a burr on the tip of a needle if the lamina is encountered before dural puncture,
9. concentration of local anaesthetic solution - less with weaker solution,
10. choice of local anaesthetic agent - lignocaine > bupivacaine > tetracaine (4).
The meta-analyses performed by Halpern and Preston confirmed that there was a reduction of PDPH when a small spinal needle was used, compared with a large needle of the same type (p <0.05). In addition, PDPH was reduced with the use of non-cutting spinal needles ( p < 0.05) (3).
The designers of spinal needles have sought to minimise the incidence of PDPH while also improving speed of CSF flashback. For epidural needles the compromise is between sufficient sharpness of the tip to permit easy insertion and a degree of bluntness which will minimise the likelihood of dural puncture with a large needle (Chapter 31).
The nomenclature of needle size derives from the "Standard Wire Gauge" used to measure electrical wires. The commonly used sizes of spinal needles are 22G-27G. However, spinal needles are available in a variety of sizes from 19G-30G. The epidural needles in common use in obstetrics are 16G-18G.
The quest for a minimally damaging needle with optimal ease of insertion continues. There are a variety of needle tips and sizes available today which have a low incidence of PDPH and an acceptably low failure rate. These include the Whitacre, Greene and Sprotte needles (Chapter 59).
References:
1. Bier A Dtsch Z Chir 51:361, 1899
2. Vandam L, Dripps R. JAMA 2:586-591, 1956
4. Naulty JS et al Anesthesiology 72: 450-454, 1990