In this post I shall discuss a well described and not so uncommon cause of bothersome headaches–“low cerebrospinal fluid pressure headaches”. So what is low CSF pressure headache? To understand this better one needs to have a rudimentary knowledge of the anatomy of the central nervous system. The human brain is enclosed in a rigid bony skull which protects it from injury. The brain is composed of grey and white matter. The other contents of the skull include blood (carried in the arteries, veins and sinuses of the brain) and the cerebrospinal fluid (CSF). The CSF circulates around the brain and the spinal cord. So headache can occur whenever the pressure in the brain increases. Like for example the blood pressure shoots up–one complains of headache. If one suffers a bleed (hemorrhage) in the brain–patient may complain of headache. If the blood vessels of the brain go into spasm–one has headache. All this is easy to understand.
A not so uncommon cause of headache is when the pressure inside the skull suddenly drops. Think of the brain as a ball floating in a bucket of CSF. The ball (brain) feels nice and happy when it is bobbing up and down in a full bucket of CSF. Now someone drills a small hole at the bottom of the bucket so that the CSF slowly starts leaking out. As the amount of CSF in the bucket decreases and CSF pressure falls the brain is no longer bobbing. It sinks down as the CSF decreases and this puts pressure on the nerves which are at the base of the skull. So what happens next? Well the brain complains of a headache. This in a simple way is what is called low CSF pressure headache.
Low CSF pressure headache has some defining characteristics. The headache is positional–meaning it is worse when the person is standing or sitting upright and abates when he lies down. Unlike migraines patients do not complain of throbbing unilateral headache accompanied by sensitivity to bright lights and loud sounds. Low CSF pressure headache is usually holocranial (whole head), dull, aching and like I said earlier positional. The positional component to the headache is its defining characteristic.
There can be many causes that lead to low CSF pressure headache. A common iatrogenic cause is a spinal tap (also called lumbar puncture). Let me give you a classical example. Let us assume you suffer from migraines (though you may not be aware of it since it was never formally diagnosed by a doctor). One day you suffer a particularly severe and disabling headache episode (in the past you only had “minor” headaches). You end up going to the ER where the doctor orders a lumbar puncture to be carried out. Now you may ask why did the ER physician order a spinal tap in the first place. What was he looking for? Well the two most common conditions the ER physician wants to rule out is infection (meningitis) and subarachnoid hemorrhage (please see my post–thunderclap headache). So the lumbar puncture (spinal tap) is carried out by inserting the spinal tap needle into the lower part of the back. The needle pierces the dura and CSF starts flowing out. The sample is collected and sent to the lab. Soon enough the results are available and the ER physician comes back to update you. Good news the spinal fluid was clean. You do not have infection nor do you have subarachnoid hemorrhage. You just have a bad migraine attack. You are given pain medications for your headache and sent home.
You are relieved that it is nothing too serious. Next day however when you wake up you are bothered by a holocranial headache. Over the course of the next few days you realize that when you lie down the headache becomes better. It is worse when you are standing or sitting. After suffering through this for a few days two things may happen. The low CSF pressure headache may abate on its own and you are back to your good health or the low CSF pressure headache may persist and prompt a visit to your local neurologist.
The diagnosis is usually straight forward in someone who has the classical history which I have documented above. There are other less common causes of low CSF headache but I shall not dwell into that now. No special investigations are needed. The neurologist advice is rest and drink plenty of fluids (water, caffeine, juices and so forth). I at times advice my patients to sleep on their tummy for a few nights. The rationale of this advice–the CSF is leaking out of the small hole in the dura made by the spinal needle. The hole shall close on its own in a few days time. The CSF lost shall be replenished and the headache shall abate. Most of the times this advice works well. At times we prescribe the patient a pain killer containing Tylenol (acetaminophen) and caffeine.
In a few patients inspite of the above conservative treatment the headache persists. In these select patients a blood patch is extremely helpful. What is an epidural blood patch you may ask? Well we take about 10 cc of the patient’s own blood and inject into the epidural space (usually near the site where the original lumbar puncture was carried out). The blood clots and seals off the small opening in the dura. No more CSF leak and no more headache.
That is all about low CSF pressure headache for now folks. Now I too must lie down and enjoy my vacation in India. Miss my parents so it is always nice to be back home.
Nitin K Sethi, MD
Braindisease's Weblog 