Cerebrospinal Fluid (CSF) Leak

What is a CSF leak?

Cerebrospinal fluid surrounds the brain and spinal cord inside a sealed sac formed by the dura. The body makes about 500 ml (17 fl oz) a day, and only about 150 ml is present at any time. When fluid escapes faster than it is replaced, the volume and pressure fall and the brain sags slightly in the skull, pulling on pain-sensitive structures. That is why the headache is so strongly linked to posture.

Spinal CSF leak vs cranial CSF leak

When a spinal leak happens without a procedure, it is called spontaneous intracranial hypotension, which has its own detailed page.

Symptoms

Spinal leak

• Orthostatic headache: at the back of the head or all over, starting within minutes to hours of being upright and easing within about 15 to 30 minutes of lying flat. In long-standing leaks the pattern can blur, so the headache becomes worse in the afternoon.
• Neck pain or stiffness
• Nausea and vomiting
• Muffled hearing, ear fullness or ringing in the ears
• Dizziness, sensitivity to light, and occasionally double vision or facial numbness

Cranial leak

• A clear, thin fluid from one nostril that increases when leaning forward or straining
• A salty or metallic taste from fluid running down the back of the throat
• Fluid from the ear after a fracture, or a feeling of fluid behind the eardrum with hearing loss
• Sometimes a headache, or repeated bouts of meningitis

Causes

• Medical procedures: a post-lumbar puncture headache is the most common CSF leak. It is more likely with larger, cutting needles and accidental dural puncture during an epidural. Spinal surgery and sinus or skull base surgery also cause leaks.
• Head injury: fractures of the skull base can tear the dura. Many of these close within a week.
• Spontaneous leaks: bone spurs that pierce the dura, weak spots in nerve root sleeves and CSF-venous fistulas. Connective tissue disorders such as Ehlers-Danlos syndrome raise the risk.
• Raised brain pressure: long-term high CSF pressure, as in idiopathic intracranial hypertension, can thin the skull base and lead to a spontaneous nasal leak. These patients are often women with obesity, and the high pressure must be treated or the leak may recur after repair.

How a CSF leak is diagnosed

• Beta-2 transferrin or beta-trace protein test: a sample of the dripping fluid is checked for proteins found only in CSF. This is the most reliable way to confirm that a nasal or ear drip is CSF.
• Brain MRI with contrast: in spinal leaks it may show thickened, enhancing dura, sagging of the brain and engorged veins. It can also be normal.
• Spine imaging: MRI, CT myelography (dye injected into the spinal fluid during a CT scan) or digital subtraction myelography to find the exact leak site, including hard-to-see venous fistulas.
• High-resolution CT of the skull base: to find the bony defect in a cranial leak.
• Lumbar puncture: may show low opening pressure, though pressure is often normal in confirmed leaks.

Treatment

Conservative care

Most leaks after a lumbar puncture and many after head injury heal on their own within one to two weeks. Lying flat, drinking plenty of fluids, caffeine and simple pain relief ease symptoms while the hole seals. People with a cranial leak are asked to avoid nose blowing, straining and heavy lifting.

Epidural blood patch

A doctor injects 10 to 20 ml or more of your own blood into the epidural space near the leak. The blood presses on the dura and forms a seal. Post-lumbar puncture headaches often resolve within hours. Spontaneous leaks may need repeated or targeted patches, sometimes with fibrin glue.

Surgery and other procedures

• Surgical repair of a spinal tear or leaking cyst when patches fail.
• Transvenous embolization or surgery for CSF-venous fistulas.
• Endoscopic repair through the nose for most skull base leaks, with success rates above 90% in experienced centers.
• Treating high pressure with medicine, weight loss or a shunt when idiopathic intracranial hypertension is the cause.

Doctors often recommend the pneumococcal vaccine for people with an ongoing cranial leak because of the meningitis risk.

Complications

• Bacterial meningitis, mainly with cranial leaks
• Subdural fluid collections or bleeds from brain sagging
• Rebound high-pressure headache after a successful repair, usually temporary
• Chronic disability from untreated spinal leaks, which are often misdiagnosed as migraine or long COVID

Frequently asked questions

What does a CSF leak headache feel like?

It is usually a pressure or throbbing headache at the back of the head that starts after you sit or stand up and eases when you lie flat. It may come with neck stiffness, nausea, muffled hearing and dizziness. The link to posture is the strongest clue.

How can I tell if fluid from my nose is CSF?

CSF is thin, clear and watery, usually from one side only, and increases when you lean forward. It may taste salty. Mucus from a cold is thicker and often from both sides. Only a lab test for beta-2 transferrin can confirm it, so collect a sample in a clean container if your doctor asks.

Can a CSF leak heal on its own?

Yes, many do. Most leaks after a lumbar puncture and many after head injury seal within one to two weeks. Spontaneous spinal leaks and skull base leaks are less likely to heal without a blood patch or surgery.

Is a CSF leak dangerous?

A spinal leak is rarely life-threatening but can be disabling. A cranial leak carries a real risk of meningitis because it links the sinuses or ear to the fluid around the brain, so it usually needs repair. Fever and neck stiffness with a leak need emergency care.

How long does an epidural blood patch take to work?

For a headache after a lumbar puncture or epidural, relief often comes within minutes to hours, and one patch works for most people. Spontaneous leaks respond less predictably and may need more than one patch.