Dr. Tigran Khachatryan, MD, PhD.

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CSF-Venous Fistula

Understanding Spontaneous Intracranial Hypotension (SIH) and CSF-Venous Fistulas

Spontaneous Intracranial Hypotension (SIH) is a condition where you experience low pressure inside your head. This happens when there is a leak of cerebrospinal fluid (CSF) from your spine. Cerebrospinal fluid is a vital fluid that surrounds and cushions your brain and spinal cord, held in place by a strong protective layer called the dura mater. If there’s a hole, tear, or weakness in this dura mater, the CSF can leak out, leading to a drop in fluid volume around your brain and spinal cord.

One increasingly recognized cause of SIH is a CSF-venous fistula. This is an abnormal connection where cerebrospinal fluid leaks directly into veins located near your spine. These fistulas were first identified in 2014. Because many doctors are not familiar with SIH, it is often misdiagnosed, causing people to suffer for a long time with incorrect treatments.

What Causes a Spinal CSF Leak?

Spontaneous Causes:

  • Pre-existing issues in your spine, such as a bone spur.
  • A natural weakness in the dura mater, often linked to genetic disorders affecting connective tissue.
  • The development of a CSF-venous fistula, where CSF drains into a vein.
  • Medical Procedures (Iatrogenic):
  • A lumbar puncture (spinal tap).
  • An epidural injection (spinal injection).
  • Spinal or other types of surgery.

Traumatic Causes:

An injury, such as from an accident.

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What Are the Symptoms?

The most common symptom of a spinal CSF leak is a headache that changes with your body position. This means the pain is usually worse when you are upright (sitting or standing) and improves when you lie down. The severity of this headache can vary greatly, from mild to very severe and disabling. Sometimes, the positional aspect of the headache can lessen or even disappear over time. However, many other symptoms can occur, including:
  • Neck pain or stiffness.
  • Nausea and vomiting.
  • Sensitivity to light and/or sound.
  • Balance problems, dizziness, or vertigo.
  • Ringing in the ears (tinnitus), or changes in hearing.
  • Profound fatigue and weakness.
  • Pain between the shoulder blades and into the upper arms.
  • Changes in vision.
  • Facial numbness, pain, or changes in taste.
  • Confusion, memory problems, or difficulty finding the right words, sometimes making patients fear they have dementia.
  • Unexplained weight loss.
These symptoms are often more severe when you are upright. Many patients find themselves significantly disabled because they cannot function normally while sitting or standing.

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What Are the Possible Complications?

While many patients recover well with appropriate treatment, there can be serious complications, though they are rare. These include:
  • Symptoms that resemble other conditions like frontotemporal dementia or Parkinson's disease.
  • Brain sagging, where the brain drops due to low fluid, potentially pressing on important nerves.
  • Spinal cord herniation, blood clots in brain veins, stupor, coma, seizures, stroke, or even death.
  • A type of bleeding in the brain called subarachnoid hemorrhage.
  • After treatment, some patients may experience rebound intracranial hypertension, which means the pressure inside the head becomes too high.
  • Ongoing symptoms and disability, even after treatment, are possible.
  • Challenges with thinking and decision-making, confirmed by brain function tests, can also occur.

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How Is It Diagnosed?

Diagnosis begins with your symptoms and involves imaging of your brain and spine. Because the condition is not widely known, and initial tests can sometimes appear normal, misdiagnosis and delayed diagnosis are common.

Key diagnostic tools include:

  • Brain MRI with contrast: This scan looks for specific signs of low CSF volume, such as fluid collections around the brain, enhancement of the brain's membranes, swollen veins, pituitary gland swelling, and brain sagging.
  • Spinal MRI: This helps guide further specialized spinal imaging.
  • Specialized Myelography Techniques: These are more advanced imaging methods used to pinpoint the exact location of the leak. They include various types of CT scans (like standard CT, dynamic CT, photon-counting CT, and conebeam CT) and digital subtraction myelography (DSM). MRI myelogram may also be used.
  • Photon-counting CT is a newer technology that can find leaks, including CSF-venous fistulas, that were previously invisible on other scans due to their hidden location near the spinal cord.
  • Digital subtraction myelography (DSM) is very important for locating CSF-venous fistulas.
Even with rapidly improving imaging techniques, sometimes a leak cannot be identified, but a negative scan doesn’t rule out the condition.

What Are the Treatment Options?

Conservative Measures:

  • Bedrest and fluids: These can help reduce symptom severity temporarily.
  • Caffeine intake: Sometimes recommended to help with symptoms.
  • Medications for nausea may be needed.

Non-Surgical Spinal Injection Procedures:

  • Epidural Blood Patch (EBP): This involves taking some of your own blood and injecting it into the space outside the dura mater in your spine. The blood clots, creating a patch that can seal the leak. These can be targeted to specific areas or performed without a precise leak location.
  • Fibrin Sealant Injection: Similar to a blood patch, but a special "glue" (fibrin sealant) is used to plug the leak.
  • These procedures may need to be repeated if the leak doesn't fully close or if symptoms return.

Surgical Treatment

  • For some patients, surgical repair of the dural defect is the best option. This requires precise localization of the leak.
  • In cases where other treatments have not worked (refractory SIH), surgery can be crucial. One study showed that 96% of patients who underwent surgical repair experienced significant symptom resolution or improvement.
  • Traditional surgery for CSF-venous fistulas involves procedures like laminectomy and tying off affected veins, but this typically means a hospital stay and a long recovery.

Advances in Endovascular Treatment: Transvenous Embolization for CSF-Venous Fistulas

A significant advancement in treating CSF-venous fistulas is transvenous embolization. This is a newer, less invasive procedure, first described in 2021.

How it works:

  • A specialized doctor called a neurointerventionalist, with a team of nurses and technologists, performs the procedure.
  • A tiny, flexible tube (catheter) is inserted into a large vein, usually in your groin, and guided through your body to the specific veins in your spine that are part of the CSF-venous fistula.
  • Once in place, a special liquid material called Embolic material is injected to permanently plug these abnormal veins, stopping the CSF leak.

Benefits of Embolization:

  • It's a less invasive option compared to traditional open spinal surgery.
  • Patients can often go home the same day, avoiding the need for a lengthy hospital stay and recovery associated with surgery.
  • Early studies show positive outcomes, with significant clinical improvement and resolution of symptoms like headaches in many patients.

What to Expect with Transvenous Embolization

Presurgical Preparation:

  • You will have an IV placed.
  • The groin area, where the catheter will be inserted, will be shaved and cleaned (you might be able to do the shaving yourself beforehand).
  • The groin area, where the catheter will be inserted, will be shaved and cleaned (you might be able to do the shaving yourself beforehand).
  • You'll receive moderate sedation to help you relax, though some people may remain quite awake during the procedure. General anesthesia is also an option for better comfort.
  • The doctor will numb the insertion area in your groin with a local anesthetic, which feels like a bee sting, before accessing the vein.

During the Procedure:

  • After the vein is accessed, you might feel a big, heavy pinching sensation.
  • When the plugging material (Embolic material) is injected, patient experiences vary widely.
  • Some people report little to no pain, or just pressure.
  • However, many patients describe intense, severe pain, feeling like an "elephant was sitting on them," being "strangled from the inside out," or like a "heart attack". This pain is usually brief but can be incredibly intense. Therefore, general anesthesia is recommended for most patients.

Postoperative Care and Recovery:

  • Pain at the site: It's common to have some pain at the exact spot where the embolic material was injected, which can last a few weeks. You might also have groin pain from the catheter insertion.
  • Specific pain for IVP fistulas: If your fistula was in the internal epidural venous plexus (IVP) close to the spinal cord, the pain after embolization can be severe and "shocking." Patients describe it as a "straight, hot metal rod" in their back, making it hard to breathe or stand upright, sometimes requiring strong pain medication. This intense pain can linger for weeks or even months.
  • Rebound intracranial hypertension: After the leak is sealed, the pressure inside your head might temporarily become too high. This is managed with medications.
  • Unusual odor: You might notice a strong, unpleasant smell (described as "creamed corn" or "garlic") for a few days after the procedure. This is due to how your body processes a solvent used with the embolic material, and you might not even smell it yourself.
  • You may be advised to avoid heavy lifting and activities that involve holding your breath.

When Is Treatment Indicated?

  • You experience debilitating symptoms that significantly impact your quality of life.
  • There are serious complications like coma or large subdural hematomas, requiring urgent intervention.
  • Conservative measures like bedrest and fluids are not providing enough relief, or your symptoms are severe.

Possible Challenges and Complications of Treatment:

  • Despite best efforts, some patients may still experience persistent or recurring symptoms.
  • Repeated procedures can sometimes lead to emotional distress or "medical PTSD" for some individuals.
  • The material used in embolization (Embolic material) can sometimes make it harder to see future leaks on imaging scans.
  • New leaks can sometimes develop even after a successful procedure, leading to a "whack-a-mole" scenario where new leaks appear after others are sealed.

Summary

Spontaneous intracranial hypotension (SIH), often caused by a CSF-venous fistula, is a condition resulting from low fluid pressure around the brain and spinal cord due to a leak. It commonly leads to debilitating positional headaches and a range of other neurological symptoms. Diagnosing SIH often requires specialized imaging techniques like digital subtraction myelography and photon-counting CT to pinpoint the leak. Treatment options include conservative measures, spinal injection procedures like blood patches, and surgical repair. A significant advancement in care for CSF-venous fistulas is transvenous embolization, a minimally invasive procedure where a catheter is used to plug the leaking veins. While generally effective and allowing for quicker recovery, the embolization procedure itself can sometimes be painful for some patients, and specific challenges like post-procedure pain and the possibility of new leaks can arise. Early and accurate diagnosis, followed by a tailored treatment approach, is crucial for improving outcomes and enhancing the quality of life for those affected by SIH and CSF-venous fistulas.

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