Introduction
A hole or tear in the thick sac that covers the brain and spinal cord will cause the fluid around the brain to leak out. This fluid is known as “cerebrospinal fluid” but is often called “CSF” for short. Drainage of CSF into the sinuses can result in many problems—these range from annoying nasal drip (“CSF rhinorrhea”) to severe brain infection.
Background
CSF is a clear mixture of water, salts, sugar, proteins, and other materials. CSF is made in a special part of the brain and flows around the brain and spine, providing a cushion and helping to get rid of waste. Adults make about 1/2 of a liter of CSF each day, and at any time, about 3-5 ounces are moving around the brain and spine.
Causes
Different things can cause CSF leaks in adults. Sometimes, they have specific causes like trauma, surgery, or tumors. Other CSF leaks happen without any obvious trigger and are called “spontaneous” CSF leaks.
Trauma
Injuries cause 90% of all CSF leaks. CSF leaking out of the nose after trauma is usually seen within 48 hours of the injury but can sometimes take longer to start. Most will heal with bed rest and other conservative treatments, but surgery may be needed if the leak doesn’t stop.
Surgical Trauma
Injury to the lining of the brain can happen during sinus or skull surgery. If a leak is seen during surgery, it is best to fix it right away.
Tumor-related CSF Leak
Benign (not cancerous) tumors in the nose, sinuses, and brain rarely cause CSF leaks. Aggressive tumors and cancers can sometimes eat away at the bone between the brain and sinuses, known as the “skull base”. When this happens, CSF can leak out through the nose. Surgery to remove aggressive tumors can lead to a CSF leak that is fixed at the same time.
Spontaneous CSF Leaks
Spontaneous CSF leaks happen when there is no trauma, surgery, or tumor that causes the leak. The most common cause of spontaneous CSF leaks is the pressure around the brain being too high. This is known as “elevated intracranial pressure”, or high “ICP”, and can be caused by many things. The high pressure around the brain slowly wears away at the bone of the skull base, causing it to be thin or missing. Sometimes, a part of the lining of the brain (“meningocele”) or even brain tissue (“encephalocele”) can stick out through the hole in the sinus or nose. A CSF leak happens when the lining eventually tears. Surgery is often needed to fix spontaneous CSF leaks, but unless high brain pressures are controlled, there is a risk of having another leak.
History
CSF leaks usually show up as clear, watery drainage from one side of the nose. The drip may happen all of the time or may stop and start with straining or bending over. Patients may have a strange metal or salty taste. Many patients with spontaneous CSF leaks may be incorrectly treated for allergies or sinus infections. A history of head injury, head or brain surgery, or previous brain infection can suggest a diagnosis of CSF leak. Patients with high ICP may also notice headaches, blurry vision, and ringing in the ears. Spontaneous CSF leaks can happen in all different types of people but are most common in middle-aged women who are overweight.
Diagnosis
Several lab and imaging tests can help diagnose a CSF leak.
Laboratory (“Lab”) Tests
Proteins are building blocks of the human body, and a protein called “beta-2 transferrin” is found in CSF fluid but not in mucus. A sample of nasal drainage can be sent to the lab to look for this protein. Beta-2 transferrin is very accurate and the best lab test for diagnosing a CSF leak.
Imaging
Different kinds of imaging can be used to help diagnose CSF leaks. A detailed CT scan is often the first choice and is very good at showing holes, tumors, or other problems in the skull that can cause CSF to drip through the nose. CT scans are very good at showing bone but not as good for looking at soft tissue and fluids. Your doctor may also order an MRI, which uses strong magnets to create pictures that can better show fluid or brain tissue coming through a hole in the bone. MRI is also beneficial for the diagnosis of tumors.
Occasionally, special tests known as “cisternograms” may be needed to determine if a CSF leak is happening. A doctor can put one of several different dyes into the CSF through a small needle in the lower back. This dye will flow up to the fluid around the brain, and if it leaks through the nose, it can be seen on CT, MRI, or a special test that involves cotton patties put in the nose. Other dyes such as “fluorescein” can be seen with the naked eye and can be used with small cameras to find where CSF is leaking.
Summary
There are many causes of CSF leaks, and diagnosis can involve talking with your doctor, lab tests, and imaging studies. If a CSF leak is happening, your doctor will discuss a treatment plan that may include surgery. Untreated CSF leaks can lead to serious and even life-threatening infections of the brain lining, known as “meningitis.”