Headaches After Spinal or Epidural Anesthesia
by William Reid Camann, MD
Q. Why and how often do headaches occur after spinal or epidural anesthesia?
A. First, a brief anatomy lesson! The average sized adult human has roughly 150ml (a little less than 8 oz or 1 cup) of a clear watery fluid, called cerebrospinal fluid (CSF) in the central nervous system, surrounding the spinal cord and brain. One of the functions of the CSF is to provide a protective layer, essentially to act as a cushion to shield the brain from the hard bony skull and to provide a soft environment for the blood vessels to supply and drain blood from the brain. There is a thin membrane surrounding the brain and spinal cord called the "dura". When there is loss of CSF for whatever reason, usually as a result of a hole in the dura, the brain tends to sag, due to loss of this protective fluid cushion. This brain sagging causes stretching in the connective tissues in the cranium, this stretching is sensed as pain, and hence the headache. Also, the loss of some CSF causes blood vessels in the brain to dilate, which can also be perceived as a painful sensation. The technical term for this kind of headache, known commonly as "spinal headache", is post-dural puncture headache, or PDPH.
When spinal anesthesia is done, a very tiny needle is placed through the dura, in the lower back, to inject the spinal medicine. Spinal needles are very small, and the hole made in the dura is also small, thus some, but very little CSF leaks out. In a few cases, (approximately 1% of the time) this leak of CSF is enough to cause a PDPH. In contrast, when an epidural is done, the dura is not punctured intentionally, as the catheter and injected medicine lies entirely outside of the dura, in the epidural space. However, sometimes, even in experienced hands, the epidural needle goes a bit too far and a hole is made in the dura. Anesthesiologists call this a "wet tap". There is a more significant leak of CSF in this case, because the epidural needle is much larger than a spinal needle. Statistics show that this happens in about 1% of cases. When a wet tap does occur with an epidural needle, the incidence of headache goes way up to about 50-70%. (In the absence of a wet tap, a PDPH is extremely rare.) In general, women tend to be more susceptible to spinal headaches, and age is important also, with younger people (e.g., less than age 40-50 or so) more likely than older to suffer this kind of headache. Hence, pregnant women are in the group at highest likelihood of experiencing this complication. So to summarize those statistics, a "wet tap" will occur in about 1% of cases, and slightly more than half of those will go on to get a headache - so the overall chance of a spinal headache after epidural anesthesia is about 1 out of 200.
Do I need to lie flat to prevent a spinal headache?
If a spinal headache occurs, the symptoms are usually worse when you are upright - sitting or standing - because gravity tends to cause the brain to sag more in this position when CSF is at a low level. Other symptoms can include visual changes (double vision or sensitivity to light), nausea, neck pain, and auditory changes, such as decreased hearing acuity. Typically, symptoms are much less when lying down. However, if you have had a spinal or epidural anesthetic, then lying down will not prevent the occurrence of the headache. In fact, studies show that early activity and ambulation (don't overdo it, though!) can help prevent the headache from occurring.
I have a history of migraines. Is my chance of a spinal headache increased?
Migraine headaches are, in part, due to dilation of the blood vessels of the brain. This is similar to a spinal headache. So, yes, it is possible that someone with a history of migraine headaches may have a higher chance of experiencing this complication. A history of migraine headaches is not necessarily a reason to avoid spinal or epidural anesthesia. However, if you then have a headache after the anesthetic, it may be a bit harder to tell if it is a true spinal headache or a migraine.
How are spinal headaches treated?
First, conservative measures are tried, such as bed rest, and analgesics, such as acetominophen, ibuprofen, naprosyn, or other pain-relieving pills. In some patients, caffeine seems to help (similar to a migraine) so strong coffee or tea or soda could be beneficial. Drinking lots of fluids is often suggested, but surprisingly, there is no research that shows this will do anything other than make you need to get up and go to the bathroom more often. Most spinal headaches go away with no treatment other than the above measures, in 2-4 days. If the headache persists, and is severe, your anesthesiologist may recommend a procedure called an epidural blood patch (EBP). In this procedure, a small amount of blood is drawn from your arm and injected into the epidural space. The blood clots, seals the hole made in the dura membrane, and the headache is relieved. The blood eventually is absorbed from the epidural space, and other than some mild to moderate backache for a few days, there are no long-term sequelae from an EBP. In the event that your anesthesiologist is not sure that the headache is a spinal headache, a consultation with a neurologist or possibly a CT or MRI scan may be done to search for other causes before doing an EBP.
The EBP is about 90% effective in relieving the headache, but in a small number of cases, the headache returns and the EBP needs to be repeated.
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