ST. PAUL, MINN, AND GLASGOW, SCOTLAND--Nearly a third or more of patients who undergo a diagnostic lumbar puncture experience headache following the procedure. Headache onset typically occurs 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.[1] According to the AAN report, 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 possible risk factors that could be modified in order to reduce the frequency of post-lumbar puncture headache, Douglas S. Goodin, MD, and members of the AAN's Therapeutics and Technology Assessment Subcommittee conducted a retrospective literature survey dating back to 1966; the search included all definitions of post-lumbar puncture headache. From this research the investigators 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 previous 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 were usually more severe and longer in duration than those of patients without 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 between the ages of 18 and 30. It has been reported that patients with small body mass index are at greater risk; therefore, younger 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 using the Quincke (conventional) needle, 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 with higher gauge needles. Indeed, the researchers reported that a 16- to 19-gauge needle has an associated post-lumbar puncture headache rate of 70%; 20- to 22-gauge needles have an associated headache rate of 20% to 40%, and 24- to 27-gauge needles are associated with a 5% to 12% likelihood of post-lumbar puncture headache.

The authors acknowledged that for diagnostic use, it may not be practical to use a needle smaller than 20 gauge for withdrawal of large volumes of fluid, as the flow rate would be too slow and the time for transduction of the opening pressure using the manometer may be too long. 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. Remember: the dural fibers run parallel to the long axis of the spine; insertion of the bevel at this angle severs fewer fibers in the dura than does perpendicular insertion. A 50% reduction in post-lumbar puncture headache has been demonstrated in patients receiving spinal anesthesia with this technique.

Replacing stylet before withdrawing the needle: When a noncutting needle is used, the postprocedure headache incidence can be lowered if the stylet is reinserted before the needle is withdrawn.

According to a report by Strupp and Brandt,[2] post-lumbar puncture headache developed in only 5% of patients in whom the stylet was reinserted but in 16% of those in whom it was not replaced. The explanation is that a strand of arachnoid may enter the needle with the cerebrospinal fluid and may be threaded back through the dural defect, 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 below the tip, unlike the Quincke), has been shown in the anesthesia literature to reduce the incidence of post-lumbar puncture headache. Evidence from studies of diagnostic lumbar is less clear, primarily because the studies of this issue are inadequate.

Potential problems and hazards of noncutting needles: Use of the Sprotte needle requires some practice. Because the needle is relatively dull, a sharp, short introducer is provided with the needle. 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 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. In addition, the researchers believe that the volume of spinal fluid removed had no bearing on probability of post-lumbar puncture headache.

SUPPORTIVE EVIDENCE

In a similar editorial in the BMJ, Drs. Michael G. Serpell and Narinder Rawal suggested two additional practices to reduce the incidence of headache following diagnostic dural puncture.[3] Needle gauge, and therefore rate of 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 BMJ, Dr. Keith W. Muir and colleagues noted another virtue of the atraumatic needle: a reduction in the need for medical intervention.[4] 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 slight detraction to the appeal of the atraumatic needle--in patients with a high body mass index, its use was associated with a higher failure rate than was use of a standard needle.

--Heidi W. Moore

References
1. Evans RW, Armon C, Frohman EM, Goodin DS. Assessment: prevention of post-lumbar puncture headaches: report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology. 2000;55:909-914.
2. Strupp M, Brandt T. Should one reinsert the stylet during lumbar puncture? N Engl J Med. 1997;336:1190.
3. Serpell MG, Rawal N. Headaches after diagnostic dural punctures. Smaller, atraumatic needles and protocols for early treatment should reduce morbidity. BMJ. 2000;321:973-974.
4. Thomas SR, Jamieson DRS, Muir KW. Randomised controlled trial of atraumatic versus standard needles for diagnostic lumbar puncture. BMJ. 2000;321:986-990.

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