Incidence of Spinal Headache
A spinal headache, also known as a post-dural puncture headache (PDPH), is the most common complication of epidural, spinal, or combined spinal-epidural (CSE) anesthesia. A spinal headache happens as a result of a hole being accidentally made in the membrane that separates the epidural and spinal space (the dura) with a large needle. This is called a wet tap or accidental dural puncture (as opposed to the intentional dural puncture that happens with a much smaller needle when a spinal or CSE is performed). The incidence of wet tap is about 0.5-1% anytime a needle is placed in your back for regional anesthesia (the general term for epidural, spinal, and CSE). The risk of wet tap and resulting headache are the same no matter what form of regional anesthesia you have.
How does a wet tap cause a spinal headache?
We are going to use an analogy to explain how a wet tap causes this unique type of headache. Imagine that your spinal area is a water balloon (the oblong kind you make balloon animals out of). Your brain and spinal cord are a pencil (eraser is brain, pencil is the spinal cord) that is attached to the inside top of the water balloon where you have tied the knot. When the epidural was placed, a hole was made in the water balloon that is big enough that it doesn’t close over right away which results in fluid leaking out. That fluid in the water balloon is spinal fluid which your body makes every day. However, there is a maximal limit to the amount of spinal fluid that your body can make in a 24 hour period so the leak outpaces your body’s ability to make spinal fluid and the water level in your balloon drops. What that means is that whenever you are upright, the pencil (your brain) sags because it is not being held up by as much fluid. This puts tension on the brain and creates that throbbing headache. Whenever you lay down, the force on the pencil is in a different direction and it is no longer being pulled down. This is a rather simplistic way of explaining why a spinal headache is positional in nature (worse when upright and better when laying flat).
Treating a spinal headache
A spinal headache can last for a week or more and can be very difficult for a new mother to handle, given the demands of caring for your infant. Obviously laying flat improves the pain but this is often not a practical solution. Medications such as caffeine (in IV or pill form) or sumatriptan (Imitrex) have been shown to help improve headache symptoms but have not been fully evaluated. The gold-standard for treating a spinal headache is a procedure call an epidural blood patch. During an epidural blood patch, we draw blood from you in a sterile manner and inject it into your epidural space. The process is similar to a labor epidural with the additional blood draw. An epidural blood patch seems to work in a couple of ways.
- It squeezes your balloon (spinal sac) making it smaller which raises the fluid level. At the back of the epidural space is a very tough fibrous band which does not move. By comparison, the spinal sac is squishy so anything injected into the epidural space will tend to compress the spinal sac. This is just like squeezing a half-empty water balloon – the fluid level will rise. Often, this results in instant cure of spinal headache symptoms. We are limited in how much fluid we can put in at a time (there are nerves back there that we don’t want to compress) so sometimes we are not able to bring the fluid level all the way back up and symptoms only improve at first.
- One of the jobs of your blood in your body is to find broken places and try to heal them. The first step in this is that little platelets in your blood stick together at the edges of damaged tissue. Your blood will do the same thing to the hole in your spinal sac and essentially form a cork that will plug the hole and the leak. If you only get partial relief of your headache at first, over 12-24 hours your balloon will fill up with fluid again and the headache will go away.
Epidural blood patches are remarkably effective with 75% of people getting complete relief of symptoms, 18% getting partial relief, and only 7% getting no relief. This procedure involves the same risks as a labor epidural and you will probably experience some back discomfort during the procedure and for a few hours after the procedure. This is because blood is irritating to tissues – remember how bruises hurt?
We perform epidural blood patches on Labor and Delivery. We usually require you to lay flat for an hour after the procedure and then you are discharged home. Occasionally a spinal headache will return after a successful blood patch. We think this happens if the platelet cork is displaced from the hole in the spinal sac. If the headache is severe, a repeat blood patch is usually offered.
If you are concerned that you may have a spinal headache, contact us to be evaluated.