CSF Leak Repair
Amber Luong, MD, PhD.
Cerebrospinal fluid (CSF) bathes the brain and is contained within a lining around the brain called the dura. These intracranial structures (structures within the brain cavity) are also separated from the sinuses by bone. When there is a hole in the dura and bone, CSF can then leak into the sinuses and cause a CSF leak. This is noticed when there is clear drainage from the nose or into the back of the throat that may occur with straining or position changes and does not improve with medications aimed at other causes of a ‘runny nose’. If it drains out of the nose, it is usually from one side. If it drains into the throat, it has been described as salty tasting. The breaks in the bone and dura can occur from an accident involving the head, a complication from sinus or brain surgery, an expected consequence of removing a tumor within the sinuses, or from anything that can increase pressures on the CSF. The increased pressure on the CSF can ultimately erode the bone separating the brain and sinuses and break through the dura (the lining of the brain). High CSF pressures can occur spontaneously without any obvious cause. Your doctor may need to do additional studies to determine the most likely cause of your CSF leak.
Read more about CSF Leaks.
Once it is confirmed that in fact the clear drainage is CSF, determining the cause of the CSF leak will determine how it should be managed. A CSF leak as a result of trauma to the head usually is managed with placement of a lumbar drain and bed rest. A lumbar drain is a small tubing placed in the back that allows drainage of small amounts of CSF. This allows diversion of the brain fluid to minimize pressure through any injured areas so that they can heal. Over 90% of these leaks will heal with this management and do not require any surgical intervention.
The other common causes of CSF leaks generally require surgical repair. For example, injury to the skull base with a CSF leak at the time of surgery often warrants an attempted repair at the time the leak is noted.
When a CSF leak develops from unexpected injury to the skull base at the time of surgery but its recognition or onset is delayed, a CT sinus is typically requested in order to identify the defect site (the site of the hole where the fluid can leak through). If the CT sinus suggests that in addition to a CSF leak there may be some brain tissue falling through the defect, then an MRI of the skull base may be indicated. On occasion, the defective skull base site may not obvious on imaging studies and the leak has to be identified in the operating room. A dye is added to the CSF via a lumbar drain (the tube in the back as described above) while the nasal cavity is examined carefully to identify the site of drainage. Once identified, then the leak can be repaired.
Finally, a significant number of CSF leaks occur spontaneously without any preceding trauma or surgery. In those cases, it is thought that increased intracranial pressures may be eroding the skull base bone which ultimately results in a CSF leak. In those situations, once a CSF leak is confirmed with appropriate laboratory studies then CT and MRI of the sinuses and skull base can be used to identify the defect site(s). Again if the leak site cannot be found on imaging studies, dye placed into the spinal fluid, which mixes with the brain fluid, can be placed at the beginning of the repair surgery to identify the leak under direct visualization.
The defect site can be repaired either from the brain or the sinus side of the skull base. Repairing a CSF leak site from the brain side requires a cut through the skull, and slight pulling of the brain away from the skull base to identify and ultimately repair the defect. These procedures are typically performed by a neurosurgeon. The failure rates of repair from the brain side are quoted as high as 25%.
More recently, repair of these bony defect sites are commonly performed from the sinus/nose side. If the defect site is clear based on pre-operative images, then the surgeon will open up those sinuses and remove bone that may obstruct the view of the defect site. This surgery is performed through the nasal cavity under the direct visualization with a small scope called an endoscope. Although generally this surgery does not involve any incisions on the face, in rare situations where the defect is within the frontal sinuses above the eyes, a small incision may be necessary to allow repair of these sites that are difficult to reach with instruments and endoscope.
If the site is not clear based on pre-operative images or if the surgeon wants confirmation of the site of the CSF leak, intraoperative fluorescein (which has a fluorescent green-yellow color) can be added to the spine fluid. Ultimately the dye will allow a way of visualizing leaking CSF while in the operating room.
Once the CSF leak site is identified, the mucosa (nasal and sinus lining) is then removed around the defect site to clearly see the bony defect. The specifics of the repair are often surgeon dependent and often influenced by the size and location of the defect. If the defect size is small, one layer placed over the defect on the sinus side may be sufficient. On the other hand, if the defect is large, then the surgeon may chose to tuck in a layer of support between the brain and the bony defect in addition to the layer on the sinus side. Once the surgeon confirms that the layers used to repair the defect have stopped the CSF leak, then various sealants or packing may be placed next to the repair site to further support the repair.
A lumbar drain may or may not be kept in place after surgery to divert CSF away from the repair site to minimize pressure. Sometimes, bed rest is recommended for a day or a few days after the repair along with other medications to minimize pressure within the brain fluid. The success rate of endoscopic CSF leak repairs ranges above 90%.
The risk of the surgery is basically similar to risk of undergoing endoscopic sinus surgery. There is a less than 1% risk of unexpected damage to nearby critical structures including the brain and optic nerve (nerve of vision). Another risk is that the leak can come back.
The benefit of the surgery is to not only stop the CSF leak, but also to remove the risk of an intracranial infection. The defect which allows CSF to drain into the sinuses can also allow bacteria (commonly found within the sinuses) to infect the brain and its surrounding tissue.
CSF leaks can occur as a complication of sinus or skull base surgery or from an accident involving the head, or develop spontaneously if CSF pressure is too high. Once the clear drainage is confirmed to be CSF, the next step is to identify the leakage site. If surgical repair is necessary, a majority of these defects can be repaired endoscopically which requires no incisions on the face or head. The success of such repairs are over 90%.
©American Rhinologic Society