Cranial CSF Leak or CSF Rhinorrhea

This is a condition when CSF or cerebrospinal fluid leaks through the nasal cavity causing clear runny nose with no overt signs of allergy or infection.

What exactly is the issue in cranial CSF leak?

Brain and spinal cord are enclosed in 3 layers of tissue or 3 sacs (the arachnoid mater, pia mater, and the dura mater – collectively called the meninges). The dura mater being the outer most and thickest layer. Within this sac is also the CSF, bathing the spinal cord and the brain. CSF normally has no direct communication with outside. If it happens due to a leak or a crack, the CSF may start leaking outside of this sac. If it occurs in the spinal region, it causes low CSF volume or pressure and may present with headaches and number of other symptoms, a condition called Intracranial Hypotension, which is discussed in a separate post. Rarely, the leak may happen in or around the head, in which case it may be called the cranial CSF leak. In most of these cases, the CSF leaks through the nose as clear nasal secretions. Depending upon the location of the leak, it may also get into throat or the middle ear.

How is the leaking CSF differentiated from nasal secretions?

CSF leak typically causes clear-liquid secretions from one nostril while in allergies and infections, it is usually from both sides. Absence of any signs of infections or allergy also suggest an alternate diagnosis. It can also be figured out by using an 0.06% ipratropium (Atrovent) nasal spray. In case of allergy, the secretion may stop but not if there is CSF leak. Finally, a test for a protein called beta-2 transferrin can help to determine if the secretions from the nose or ear is CSF or not, which is highly specific for CSF and not found in nasal or ear secretions. About 0.5 cc of fluid is needed for the test. Another protein called beta-trace protein can also be checked but it is also present in the nasal cavity. The test can be positive if its level is too high, which suggest CSF. Some other tests like checking glucose level or the color of stain on a white paper or towel are non-specific and are not recommended in the decision-making process.

What are different causes of the cranial CSF leak?

The leading cause is trauma to the skull. There are some other conditions causing this problem where trauma is not involved. It includes idiopathic intracranial hypertension, and what is described as spontaneous CSF leak, which means a leak without any defined injury or a cause.

What test is needed to detect the site of CSF leak?

1. High Resolution CT: High -resolution CT scan without contrast of the skull base and temporal bones is usually the first test to order. Request for the high resolution must be mentioned in the order. In most cases, this test can help to localize the crack or the opening in the skull base. There are some areas of skull that are quite thin compared to the rest of the skull, and most defects are found in these areas. These areas include the cribriform plate on the roof of the nose, and sides of sphenoid sinuses. These areas can be easily injured in case of head injury. In some patients, these areas are genetically thin putting them at higher risk for a crack and opening with mild head trauma or with idiopathic intracranial HTN.

2. CT Cisternogram with intrathecal contrast: This test can help to localize the site of leak, especially in those cases where more than one area of crack is detected by the high-resolution CT.

3. MRI can help to diagnose high intracranial pressure and some related conditions.

Sometimes, when the CSF leak is confirmed by the beta-2 transferrin test, the site of leak is not detected by imaging. In such cases, based upon the location of CSF (nasal cavity or the ear), an appropriate surgical approach is taken. In those cases, CSF leak may be confirmed by a dye during the surgical procedure.

How is cranial CSF leak treated?

The treatment for a CSF leak is surgery. There are many surgical techniques that are available based upon the exact location, nature, and size of the defect. Main purpose of surgery is to stop CSF leak and its complications, and chances of meningitis. But in cases of high intracranial pressure causing or associated with a leak, the underlying condition should be treated first to avoid failure of surgical procedure.

Where may I find more information about the cranial CSF leak?

American Academy of Neurology
American Academy of Neurosurgeons.