About a third of the patients who undergo a diagnostic lumbar puncture experience headache following the procedure. The headache typically starts 24 to 48 hours after the procedure, lasts for one or two days, and is often severe enough to immobilize the patient. To lessen the risk of post-lumbar puncture headache, the American Academy of Neurology (AAN) recently recommended the use of smaller needles for diagnostic punctures. According to the AAN report, which appeared in the October 10 Neurology,angle of needle insertion, replacement of the stylet, and needle design also appear to influence the likelihood of post-lumbar puncture headache.

PATIENT RISK PROFILES

To identify risk factors that could be modified to reduce the frequency of post-lumbar puncture headache, Douglas S. Goodin, MD, and members of the American Academy of Neurology's Therapeutics and Technology Assessment Subcommittee surveyed literature dating back to 1966; the search included all definitions of post-lumbar puncture headache. From this research, they were able to identify definite demographic risk factors for such headaches, including younger age, female gender, and headache before or at the time of the lumbar puncture. Lower body weight and prior post-lumbar puncture headache were less-certain risk factors.

According to the report, patients who had headache before the procedure were not only at greater risk for post-lumbar puncture headache but their headaches usually were more severe and were longer in duration than those of patients who did not have headache prior to or during the lumbar puncture.

Post-lumbar puncture headache occurs twice as often in women as in men; in both sexes, the highest frequency is in patients between the ages of 18 and 30. Patients with small body mass index are reportedly at greater risk; therefore, young women with a small body mass index may be at greatest risk of developing post-lumbar puncture headache.

AVOIDING TECHNICAL DIFFICULTIES

The Subcommittee's report also identified a number of technical factors that may be helpful in reducing the incidence of post-lumbar puncture headache:

Needle size:When the Quincke (conventional) needle is used, the smaller the needle diameter, the less the risk of post-lumbar puncture headache. Smaller needles create a proportionally smaller tear in the dura, thus lessening the potential for leakage. According to the report, the incidence of post-lumbar puncture headache decreases as needle diameter decreases. The associated risk of post-lumbar puncture headache was 70% for a 16- to 19-gauge needle, 20% to 40% for a 20- to 22-gauge needle, and 5% to 12% for a 24- to 27-gauge needle.

The authors acknowledged that needles smaller than 20 guage may be impractical for diagnositc use, especially if large volumes of fluid are needed. When a small needle is used, the fluid rate is much slower, and it takes much longer for the opening pressure to register on the manomenter. Smaller-diameter needles are more appropriate for spinal and epidural anesthesia and myelography.

Direction of bevel:The incidence of post-lumbar puncture headache can be reduced by ensuring that the bevel of the Quincke needle is inserted parallel, not perpendicular, to the dural fibers—which run parallel to the long axis of the spine. In this orientation, the needle severs fewer dural fibers. A 50% reduction in post-lumbar puncture headache has been demonstrated in patients receiving spinal anesthesia with this technique.

Replacement of stylet before needle withdrawal:When a noncutting needle is used, reinserting the stylet before the needle is withdrawn can reduce the incidence of postprocedure headache. According to a report by Strupp and Brandt, post-lumbar puncture headache developed in only 5% of patients for whom the stylet was reinserted but in 16% of those for whom it was not replaced. The explanation is that if the stylet is not replaced, a strand of arachnoid may enter the needle with the cerebrospinal fluid and may be threaded back through the dural defect, thus causing prolonged cerebrospinal fluid leakage.

Needle design:Use of noncutting, "atraumatic" needles such as the Whitacre or Sprotte (which have a duller tip and an oval opening proximal to the tip, unlike the Quincke) has been shown in the anesthesia literature to reduce the incidence of post-lumbar puncture headache.

Potential problems and hazards of noncutting needles:Use of the Sprotte needle may require some practice. Because the needle is relatively dull, a sharp, short introducer is provided. Two thirds of the introducer must be inserted before the Sprotte needle is inserted. If the needle is not in the correct location, the direction of the introducer must be changed. The Sprotte needle can occasionally be damaged or simply inappropriate for lumbar puncture, in which case the physician may prefer to use the Quincke needle.

Other concerns:Although bed rest is a standard recommendation to stave off headache following lumbar puncture, the AAN Subcommittee report contends that there is no evidence to support such a precaution. Likewise, the practice of increasing fluid intake after lumbar puncture has no proven benefit, according to the report. The authors also believe that the volume of spinal fluid removed has no bearing on probability of post-lumbar puncture headache.

SUPPORTIVE EVIDENCE

In a similar editorial in the October 21 British Medical Journal,Drs. Michael G. Serpell and Narinder Rawal suggested two additional practices to reduce the incidence of headache following diagnostic dural puncture. Needle gauge, and therefore the incidence of subsequent headache, can be reduced by collecting fluid through aseptic aspiration using a syringe "in which 2 ml can be collected in less than a minute via a 24-gauge needle." These authors also noted that "accurate and reliable pressure measurements can be made with 25-gauge spinal needles using an aseptic transducer system."

In the same issue of the British Medical Journal,Dr. Keith W. Muir and colleagues noted another virtue of the atraumatic needle: a reduction in the need for medical intervention. According to their study, the use of atraumatic needles, rather than Quincke needles, avoided one moderate to severe headache for every four patients undergoing lumbar puncture. The researchers also noted a potential drawback of atraumatic needles—in patients with a high body mass index, their use was associated with a higher failure rate than was use of a standard needle.

RECOMMENDATIONS FOR FUTURE RESEARCH

The AAN's Therapeutics and Technology Assessment Subcommittee made several recommendations for future research toward reducing the incidence of post-lumbar puncture headache:

• Future studies of post-lumbar puncture headache should use the International Headache Society (IHS) criteria for post-lumbar puncture headache and published criteria for severity of post-lumbar puncture headache and should report the amount and depth of placement of local anesthetic.
• A random sample of neurologists should be surveyed, and those who perform at least two lumbar punctures per month should be asked to participate in a 12-month prospective study (thus solving the problems of publication and recall bias). All pertinent patient information should be recorded, and all patients should be contacted eight and 15 days after the lumbar puncture, in order to monitor the occurrence post-lumbar puncture headache.
• Two practices that perform a large number of diagnostic lumbar punctures with cutting needles and that document a greater than 10% frequency of severe post-lumbar puncture headache should be recruited to perform independent, double-blind, prospective studies of same-gauge cutting versus noncutting needles.
• More definitive studies—using contemporary techniques, current definitions of post-lumbar puncture headache, and broadly representative patient populations—are required to clarify the role of recumbency in preventing post-lumbar puncture headache.
• The neurologists should be resurveyed three years later to see if there have been any changes in the frequencies of post-lumbar puncture headache in their practices.
• If the incidence of severe headache after lumbar puncture continues to exceed 10% even after the neurologists have made appropriate changes in needle choice and insertion technique, a collaboration with anesthesiologists could identify additional technical, patient-specific, or perioperative (or peripartum) factors that may contribute to the lower frequency of post-lumbar puncture headache reported in spinal anesthesia and obstetric series.

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