Intracranial Hypotension/CSF Leak
What is Intracranial Hypotension?
Intracranial hypotension means that there is low pressure in the fluid surrounding your brain and spine. This fluid is called cerebrospinal fluid, or CSF. It flows around the brain and spine continuously, in part helping remove waste products from the brain. It is continuously made and reabsorbed by cells in the brain, and it usually kept at a fairly constant pressure.
Sometimes a leak of this CSF can occur. This can be due to a tiny hole – sometimes in the layers around the brain, but more commonly around the spine. When this happens, the CSF slowly leaks from it’s normal space around the brain. This means that the CSF in the brain is at a lower pressure than normal. This is called “intracranial hypotension”.
When this happens, the brain is not protected by it’s “bath” of fluid in the normal way, and the patient can get symptoms of CSF leak or intracranial hypotension.
“Sagging” of the brain in a patient with intercranial hypotension.
What kind of symptoms does it cause?
Intracranial hypotension most commonly causes a headache. This headache can often be quite severe, and it can go on for a long time, or become chronic. It can sometimes be so severe that it has a significant impact on the patient’s life. The headache is sometime worse when standing up – this is called a “positional headache” or sometimes a “postural headache”.
Sometimes patients will have little or no symptoms from a CSF leak, and we will only find signs of the leak on CT or MRI scans of the brain. This can happen, but it is relatively rare. There are a few telltale signs we look for on these CT or MRI scans to point towards a possible CSF leak and intracranial hypotension.
Sometimes, the brain can “slump” or sink down in the skull, lower than it normally would if the CSF pressure was normal. This can sometimes leads to chronic bleeds or haemorrhages around the brain, as when the brain slumps down it can tear small veins around the brain. When we see these signs of CSF leak on a brain MRI or CT, we will look very closely to see if there are other signs, or if a cause can be seen.
How did I get it?
There are a few various things in the spine which can cause a leak of fluid. One of the most common is when a small calcified, sharp “spur” arising from the bones and discs in the spine can make a tiny tear in the front of the sac that surrounds the spinal cord. Fluid can leak out in this way, and it can be very hard to find the hole. Sometimes a small tear can occur on the side of the spinal cord, where the nerves are leaving. Less commonly, a tiny opening called a “fistula” can happen between the sac surrounding the spine and small veins in the area. This can then form a small, persistent leak of CSF from the spinal cord into the vein – this is called a “CSF-venous fistula”. It can also be hard to diagnose.
Does it need treatment?
If you have symptoms and/or significant changes on your MRI or CT brain to indicate you have a CSF leak, we will first try and find it. If we find it, we can repair it. We generally recommend treatment of these because if the leak persists, the symptoms usually will too.
What are the ways in which it can be treated?
These CSF leaks from the spine are usually fairly easy to treat with surgery. Occasionally, we can inject something called “fibrin glue” into the area beside the leak to try and close if off. Traditionally patients with intracranial hypotension from a CSF leak were treated by something called a “blood patch”. This means taking some blood from an IV in your arm, and injecting it into the space around the spine in the hope that it will clot off and close the tear. This sometimes works, but it does not always work for every leak. We prefer to first confirm that there is a leak there and figure out what type it is, and where it is in the spine. We can then offer targeted treatment tailored to what type of leak it is.
How do they get diagnosed?
We are one of the few centres in North America with developing expertise in this area. When you are referred to our unit for workup for intracranial hypotension, you will meet Dr. Richard Farb who is our neuroradiologist with a special interest in this disease. We will talk to you about the nature of your symptoms. An MRI of the brain and spine is also performed. This is done not only to look to see are there signs of a CSF leak in the brain, but also to see if we can see fluid in spaces it shouldn’t be around the spine. This helps us try and identify the site of the leak better.
The next step is usually a myelogram. This is a specialised type of diagnostic test, and is performed as a day case using local anaesthetic. It involves performing a lumbar puncture in the x-ray dept, and measuring the pressure of the CSF around the brain and spine. We next inject some x-ray dye or contrast into the lumbar puncture needle, so that this x-ray contrast enters the sac surrounding the spine. We do this with you lying down, so that the contrast runs up along the length of the spine. This allows us to try and identify a leak of fluid around the spine. You are then transferred for a CT scan so we get a better look at the x-ray contrast around the spine, to try and get a better look at the site of the leak.
Sometimes, if we do not find the leak after one myelogram we will repeat with you lying in a different position, if we think this will help us find the leak better.
Once we’ve correctly identified the site of the leak – which we can do in quite a high percentage of cases – you are then referred for the correct type of treatment, which is usually surgery.