Cerebrospinal fluid (CSF) surrounds your brain and spinal cord and provides a cushion to protect them from injury. The spinal cord and CSF are surrounded by three layers of membranes. A CSF leak occurs when there is a hole or tear in the outermost layer of these membranes (dura mater), which allows some of the fluid to escape.
There are two distinct types of CSF leaks with different symptoms, causes and treatments. These are spinal CSF leaks and cranial CSF leaks. A spinal CSF leak occurs anywhere in the spinal column. A cranial CSF leak occurs in the skull.
The most common symptom of a spinal CSF leak is a headache, while a cranial CSF leak causes symptoms such as clear fluid leaking from the nose or ear. Some CSF leaks may heal with conservative treatments such as bed rest. Many CSF leaks need a blood patch to cover the hole or surgery to repair the leak.
Symptoms vary between spinal and cranial CSF leaks.
Spinal CSF leaks
The most common symptom of a spinal CSF leak is headache. These headaches usually:
- Cause pain in the back of the head
- Improve when lying down
- Worsen when standing up
- May start or worsen with exertion (such as coughing or straining)
- Rarely, start suddenly ("thunderclap" headache)
Other symptoms of spinal CSF leaks may include:
- Neck or shoulder pain
- Ringing in the ears (tinnitus)
- Changes in hearing
- Nausea or vomiting
- Changes in vision
- Changes in cognition or behavior
Cranial CSF leaks
Cranial CSF leak symptoms may include:
- Clear, watery drainage from the nose or ear (on one side)
- Hearing loss
- A metallic taste in the mouth
Spinal CSF leaks may be caused by:
- A lumbar puncture (spinal tap)
- An epidural in the spine for pain relief, such as during labor and delivery
- An injury to the head or spine
- Bone spurs along the spine
- Abnormalities of the dura mater around the nerve roots in the spine
- Abnormal connections between dura mater and veins (CSF-venous fistulas)
- Prior surgery on the spine
Cranial CSF leaks may be caused by:
- A head injury
- Increased pressure in the brain
- Poorly functioning shunt
- Malformations of the inner ear
Sometimes CSF leaks develop after very minor events:
- Straining to have a bowel movement
- Lifting heavy objects
Sometimes a CSF leak doesn't have a known cause (spontaneous CSF leak).
Risk factors for spinal CSF leaks include:
- Having a previous surgery or procedure on or around the spine
- Connective tissue disorders such as Marfan syndrome or Ehlers-Danlos syndrome
Risk factors for cranial CSF leaks include:
- Having a previous surgery on or around the skull
- Obstructive sleep apnea
- Head trauma
- Tumor at the skull base
- Abnormalities of the skull base or inner ear
Possible complications of a cranial CSF leak that is left untreated include meningitis and air entering the spaces surrounding the brain (tension pneumocephalus).
Spinal CSF leak
Your doctor will likely start with your medical history and a physical exam. The flexibility of your joints also may be checked.
Tests to diagnose a spinal CSF leak may include:
- MRI with gadolinium. This imaging test uses a contrast agent, gadolinium, to better highlight abnormalities in the brain or spine that result from a CSF leak.
- Radioisotope cisternography. This test involves measuring the CSF pressure and then injecting a chemical into the space surrounding the spinal cord. Then, images of the area are taken several times within a 24-hour period. These images track the flow of CSF, which will be abnormal if there is an active spinal CSF leak.
- Myelography. This test is considered the gold standard for diagnosing and locating CSF leaks. It uses digital subtraction fluoroscopy, a CT or MRI scan, and a contrast dye to locate CSF leaks. It provides the most precise location of a CSF leak and helps to determine the most appropriate treatment plan.
- Spinal tap (lumbar puncture). This test involves placing a needle in the spinal column to measure the pressure of CSF inside the spinal column, though pressure is normal in more than half of patients with spinal CSF leaks.
Cranial CSF leak
Your doctor will likely start with your medical history and a physical exam, including close evaluation of your nose and ears. You may be asked to lean forward to check for any nasal discharge, which may be collected and sent to a lab for testing.
Tests to diagnose a cranial CSF leak may include:
- MRI with gadolinium. This imaging test uses a contrast agent, gadolinium, to better highlight abnormalities in the brain to locate the source of a CSF leak.
- Tympanometry. Your middle ear fluid may be tested to check for CSF.
- CT myelography. This test is considered the gold standard for diagnosing and locating CSF leaks. It uses a CT scan and a contrast dye to locate CSF leaks anywhere in the skull base. It provides the most precise location of a CSF leak and helps to determine the most appropriate treatment plan. High-resolution CT (HRCT), which provides images in even greater detail, also may be used.
Some CSF leaks improve with bed rest alone. Other CSF leaks may need treatment.
Treatments for spinal CSF leaks may include:
- Epidural blood patch. This treatment involves taking a sample of your own blood, then injecting it into the spinal canal. The blood cells form a clot, which creates a patch to cover the area where the CSF is leaking.
- Sealant. A special sealant may be used alone or mixed with your blood in the same technique described above to cover the hole and stop the CSF leak.
- Surgery. Some CSF leaks need surgery, though surgery is only performed if the other treatment options don't work and the precise site of the leak is known. There are several types of surgical treatments that repair CSF leaks. Surgery may involve repairing the CSF leak with stitches or grafts made from patches of muscle or fat.
- Trans-venous embolization. This is a new minimally invasive, catheter-based treatment for CSF-venous fistulas only that involves gluing shut the fistula from inside the culprit vein.
Some cranial CSF leaks, such as those caused by trauma, improve with conservative measures such as:
- Bed rest
- Elevating the head of the bed
- Taking stool softeners to prevent straining
Most spontaneous cranial CSF leaks require surgery.
Preparing for an appointment
After discussing your symptoms with your family doctor, he or she might refer you to a doctor trained in brain and spine conditions (neurologist, neurosurgeon, ENT) for further evaluation.
Here's some information to help you get ready for your appointment.
What you can do
Make a list of:
- Your symptoms, including any that may seem unrelated to the reason for which you scheduled the appointment, and when they began
- Key personal information, including major stresses or recent life changes
- All medications, vitamins or other supplements you take, including doses
- Questions to ask your doctor
Bring with you to the appointment recent test results and scans of your brain and spine. Take a family member or friend along, if possible, to help you remember the information you receive.
For CSF leaks, questions to ask your doctor include:
- What is likely causing my symptoms or condition?
- What tests do I need?
- Is my condition likely temporary or chronic?
- What is the best course of action?
- Would losing weight help my condition?
- I have these other health conditions. How can I best manage them together?
- Are there restrictions I need to follow?
- Should I see a specialist?
- Are there brochures or other printed material that I can have? What websites do you recommend?
Don't hesitate to ask other questions.
What to expect from your doctor
Your doctor is likely to ask you questions, including:
- Have your symptoms been continuous or occasional?
- How severe are your symptoms?
- What, if anything, seems to improve your symptoms?
- What, if anything, appears to worsen your symptoms?