December, 2012
Charles A. Pilcher MD FACEP
At the 2012 ACEP Scientific Assembly, Dr. Ashley Shreves and Dr. David Newman presented statistics showing the number of lumbar punctures (LP) that must be done to find a single subarachnoid hemorrhage (SAH) in a CT negative patient with sudden onset of headache. The answer: 700.
Emergency physicians have routinely performed LP’s on patients with a so-called “thunderclap headache,” but the paradigm may need to change. Drs. Shreves and Newman suggest that “lumbar puncture should no longer be performed on patients arriving within 6 hours of the headache onset, if the CT imaging is negative.” For patients presenting later, the risks and benefits of further testing are less clear, Dr. Shreves noted. They report that large prospective studies with excellent followup show that the risks of LP outweigh the benefits.
The presentation was nicely summarized by Dr. Newman in the December issue of Emergency Physicians Monthly. He says:
For years we have been true believers that performing an LP after a negative CT increases a patient’s safety. But the numbers raise an important question: if we’re poking hundreds of backs for just one to benefit, how much safety is lost? LPs, after all, cause infections, pain, headaches, and on rare occasion serious morbidity. They also lead to false positives, which typically mean a second LP, or perhaps advanced imaging with radiation, and contrast exposure. Sometimes patients are admitted after a false positive LP and have cerebral angiography, a procedure with definite risks. And once in a blue moon someone undergoes risky neurosurgery due to a false positive, because imaging can’t discern which aneurysms were causing a headache and which are incidental… [In patients without classic symptoms], the ratio of LPs to aneurysmal SAH jumps from 700 to 1400. And for those with lower risk headaches the number is in the thousands, which helps to explain why finding an aneurysmal SAH by LP is a Ghostbusters moment.
As a result, Drs. Shreve and Newman are proposing a new algorithm for the evaluation of such headaches. In those patients without CT evidence of SAH, and who are stable and low risk, treatment of the headache and close follow-up, especially with any recurrence, is likely safer than routine performance of an LP. They suggest that about 600 of the 700 LP’s could safely be eliminated. “According to our best calculations, unless a patient has high risk headache features (syncope, stiff neck, etc.) the most beneficial approach to diagnosing SAH is a CT scan—with no LP—because the scan typically gets you well under the 1% mark,” they contend.
If the algorithm were to change – or even if it doesn’t – detailed documentation of a discussion of the risks and benefits of the path chosen from among the various options remains crucial to a satisfactory outcome for both patient and physician.
To view a video presentation of the authors’ original discussion of this topic, visit the “SmartEM” website. To read the report in EP Monthly, click here.