Post LP Headache

On my first month in the Parkland ED, I saw multiple patients with post-lumbar puncture headaches and even iatrogenically caused one myself.  Often I found myself wondering what proven preventative measures during an LP decrease the incidence of such headaches, what could I have done better, and what literature supports treatment of post-lumbar puncture headaches in the emergency department.

Headache after LP is a very common occurrence (up to 32%) in the ED and can have detrimental consequences including subdural hematoma and seizures.  These headaches usually begin within 24-48 hours after dural puncture and are often bilateral, dull, and worse with certain head movements.  Although there are many theories on what really causes these symptoms, most agree that the unclosed hole from the punctured dura leads to a persistent leak of CSF.  It is postulated this decrease in CSF pressure and volume reduces the amount of CSF cushioning the brain and also turns on adenosine receptors (inducing cerebral vasodilatation) leading to headache.

Only five factors have proven to decrease the incidence of post-LP headache:  replacement of stylet, direction of bevel, number of puncture attempts, design of the needle, and size of the spinal needle.  A randomized prospective study with 600 patients showed that replacing the stylet when removing the needle decreased the post-LP headache incidence from 16% to 5%.  The theory behind this technique is that when withdrawing the needle without the stylet, a strand of arachnoid can be drawn through the dural defect, thus, keeping the dural “hole” open.  Replacing the stylet decreases the likelihood this happens.  The direction of the bevel also plays a part in incidence of post-LP headaches.  The thought process behind this is that you want the bevel of the needle when going through the dural fibers to separate, rather than cut the fibers.  If the fibers are cut, then a larger dural deficit is left and more CSF leaks from the subarachnoid space.  No studies have proven that more LP attempts leads to greater likelihood of headache, but the more dural fibers are damaged with multiple attempts, it is presumed there is a more persistent CSF leakage.  Spinal needles can be in 2 main forms – nontraumatic needles and cutting needles.  Although cutting needles are more likely to result in a successful tap, they are more likely to cause post-LP headache (5-25%) because the dural fibers are again cut.  The nontraumatic needles significantly decrease this poor outcome (1-11%) by a softer tip 0.5mm in front of the needle separating the fibers before the needle reaches the subarachnoid space.  Finally, the gauge of the needle is inversely proportional to the incidence of post-LP headache.  A 1996 study showed the incidence of post-LP headaches is 70% with 16-19G spinal needles, 40% with 20-22G needles, and 12% with 24-27G needles, once again showing that the size of the dural tear correlates with the incidence of post-LP headaches.  It must be noted that LPs with spinal needle gauges smaller than 22G took over 6 minutes to collect 2mL of CSF and another 6 minutes to measure CSF pressure.

It is interesting that there are several urban myths that the literature does not support in decreasing incidence of post-LP headache.  Of note, there is no evidence supporting the volume of CSF extracted, patient position after LP, use of IVF, or bed rest s/p LP.

Up to 85% of post-LP headaches resolve on their own.  Before 72 hours of symptoms, conservative treatments are encouraged including IV hydration, antiemetics, and pain medications.  After 72 hours, specific therapy aimed at replacing CSF, decreasing cerebral vasodilatation, and closing the dural puncture site might be indicated.  Blood patch is the most popular treatment for post-LP headache.  Although performed by anesthesiologists and not completed in the ED, it is important to know that a blood patch is effective 70-98% of the time.  Twenty-thirty mL of the patient’s blood is injected in the epidural space, preventing subsequent CSF leakage.  Although the literature is sparse, caffeine has been advocated for post-LP headaches.  One study demonstrated 500mg IV caffeine sodium benzoate relieved post-LP headache in 75% of the 41 participants, theoretically by decreasing cerebral vasodilatation.  IV or oral hydration has not demonstrated a decrease in post-LP headaches.

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