Cerebrospinal Fluid (CSF) Leak
Cerebrospinal Fluid Leak Overview
A cerebrospinal fluid CSF leak, or CSF leak for short, is an escape of the colorless fluid that surrounds and protects the brain from the skull and spinal cord from the thecal sac (the tough covering surrounding the spinal cord) in the spine. Cerebrospinal fluid is continuously produced in cavities in the brain called ventricles and absorbed into the bloodstream. It cushions the brain, acting as a shock absorber, and serves as a vehicle for delivering nutrients to and removing waste from the brain.
A CSF leak can occur spontaneously or after a lumbar puncture procedure. A spontaneous CSF leak can be caused by a physical trauma or it can be idiopathic, which means that a clear cause is not identified.
The loss of CSF volume causes the normally buoyant brain to sag within the skull, often resulting in headaches and other neurological symptoms.
CSF Leaks and Intracranial Hypotension
A CSF leak can cause the pressure within the skull to drop to an abnormally low level, a condition called intracranial hypotension. If spontaneous, it is referred to as spontaneous intracranial hypotension (SIH). This is diagnosed by meeting certain criteria, specifically:
- A headache that has developed around the same time that low CSF pressure or a CSF leak occurred, or
- A headache that has led to discovery the diagnosis of intracranial hypotension, along with the presence of low CSF pressure (<6cm H2O), or
- Evidence of CSF leakage on neuroimaging
People with an intracranial or lumbar shunt device that is draining too much CSF also may experience intracranial hypotension. This can often be fixed by changing the setting of the shunt in the clinic.
Cerebrospinal Fluid Leak Symptoms
The symptoms of a CSF leak can vary by person. The most common symptom is an orthostatic headache, which is a headache that worsens upon standing or being upright for a prolonged period of time and improves upon lying down. This is a pattern that is observed in the vast majority of patients with CSF leaks.
The onset of a CSF leak is usually sudden, though not in all cases. The nature of these headaches tends to be variable as well, as people can experience a headache that feels dull, throbbing, or pressure-like.
The location of the headache is most often in the back of the head, neck, and shoulders, though the pain can occur anywhere, even encompassing the entire head and face.
Other symptoms of a cerebrospinal fluid leak can include:
- Light and sound sensitivity
- Neck stiffness
- Vision changes
- Hearing changes
Cerebrospinal Fluid Leak Treatments
Depending on the cause of the leak, symptoms may resolve on their own with time and rest. Your doctor may recommend bed rest, drinking more fluids, increasing your caffeine intake, or taking pain relievers.
If your symptoms do not improve with conservative treatments, your doctor may suggest imaging and an epidural blood patch. This procedure involves injecting your own blood into the epidural space around the spinal cord to help your body heal the leak.
- If the exact site of the CSF leak is unknown, a “blind” epidural blood patch is performed
- If the site of leak is known, the epidural blood patch is considered to be “targeted”
Response to a blood patch, even in patients with known CSF leaks, can be variable. Occasionally, a person may require more than one blood patch before achieving long-term resolution of their CSF leak.
In rare cases, surgery may be needed to repair the leak.
How common is a cerebrospinal fluid leak?
CSF leaks are rare. They occur at a rate of approximately two to five cases for every 100,000 people, though this number is thought to be an underestimate.
Who gets cerebrospinal fluid leaks?
Anyone can have a cerebrospinal fluid leak, and sometimes no cause can be found. With that being said, they are more common in certain groups of people, including:
- People between the ages of 30 and 40 years
- People with connective tissue disorders like Ehlers-Danlos and Marfan syndromes
Possible causes of a CSF leak include:
- Certain head or spine surgeries
- Head or back injury
- Placement of tubes for epidural anesthesia or pain medications
- Lumbar puncture (spinal tap)
How is a cerebrospinal fluid leak diagnosed?
There are several ways to go about diagnosing a CSF leak, but the work up typically starts with an MRI of the brain with and without contrast. The addition of contrast can help visualize one of the common changes that occurs in the brain as a consequence of intracranial hypotension. After an MRI of the brain, if necessary, MRIs of the spine, a CT myelogram of the spine, or cisternography can be performed. A lumbar puncture can be performed to evaluate whether the opening pressure is lower than normal, but is often not necessary as opening pressure is often within normal limits in CSF leak. Opening pressure is measured when the dura is punctured during a CT myelogram, using a specific needle that minimizes the risk of leak at this site.